Heat resistant composite structure for shuttle applications (Ryton-B)

NASA Technical Reports Server (NTRS)

1972-01-01

A program was undertaken to characterize Ryton-B resin, develop graphite filament prepregs, undirectional laminates and determine the strength and heat resistance of the composite system. Through the use of a water soluble resin binder, high quality prepreg tape, three inches wide with 4 tows of HM-S were produced. The tape laminated to 0.00175 inch per ply. A wide range of properties in the cured resin and laminate were found using different curing conditions. The thermal stability and strength of molded laminates appears to be very dependent upon the cure cycle used for polymerization.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cole, K.C.; Noel, D.; Hechler, J.-J.

Samples of Narmco Rigidite 5208/WC3000 carbon-epoxy composite prepreg were exposed to ambient temperature and 50 percent relative humidity for different periods up to 66 days. The aging has a significant effect on prepreg physical properties such as tack, volatiles content, and gel time. A set of four-ply laminates made from aged prepreg was subjected to tensile testing, ultrasonic inspection, and optothermal inspection. No relationship could be discerned between laminate properties and prepreg aging time. However, variations in panel homogeneity were observed, and these correlated with thermal diffusivity and tensile modulus measurements, but not with ultimate tensile strength or elongation. Amore » set of six-ply laminates was used to measure compressive properties, interlaminar shear strength, and physical properties. These panels also showed variations in porosity, again unrelated to aging, but in addition, the fiber-resin ratio was observed to decrease with aging time. Both factors were found to affect mechanical properties. The implications concerning the importance of monitoring the aging by physicochemical methods are discussed. 30 refs.« less

Morphological and mechanical analyses of laminates manufactured from randomly positioned carbon fibre/epoxy resin prepreg scraps

NASA Astrophysics Data System (ADS)

Souza, Christiane S. R.; Cândido, Geraldo M.; Alves, Wellington; Marlet, José Maria F.; Rezende, Mirabel C.

2017-10-01

This study aims to contribute to sustainability by proposing the reuse of composite prepreg scrap as an added value from discards. The research evaluates the microstructure and mechanical properties of laminates processed by the reuse of uncured carbon fibre/F155-epoxy resin prepreg scraps, waste from the ply cutting area of an aeronautical industry. The composite scraps were used as collected and were randomly positioned to produce laminates to be cured at an autoclave. The mechanical characterization shows a decrease of 39% for the compression property due to the discontinuous fibres in the laminate and an increase of 34% for the interlaminar shear strength, when compared to continuous fibre laminates. This increase is attributed to the higher crosslink density of the epoxy resin, as a result of the cure temperature used in autoclave (60 °C higher than suggested by supplier) and also to the randomly positioned scraps. Microscopic analyses confirm the consolidation of laminates, although show resin rich areas with different sizes and shapes attributed to the overlapping of the scraps with different sizes and shapes. These resin rich areas may contribute to decrease the mechanical properties of laminates. The correlation between mechanical and morphological results shows potential to be used on non-critical structural application, as composite jigs, contributing to sustainability.

Solventless LARC-160 Polyimide Matrix Resin. [applied for use in aerospace engineering

NASA Technical Reports Server (NTRS)

Stclair, T. L.; Jewell, R. A.

1978-01-01

The addition polyimide, LARC-160, which was originally synthesized from low cost liquid monomers as a laminating resin in ethanol, was prepared as a solventless, high viscosity, neat liquid resin. The resin was processed by hot-melt coating techniques into graphite prepreg with excellent tack and drape. Comparable data on graphite reinforced laminates made from solvent-coated and various hot-melt coated prepreg were generated. LARC-160, because of its liquid nature, can be easily autoclave processed to produce low void laminates. Liquid chromatographic fingerprints indicate good reaction control on resin scale ups. Minor changes in monomer ratios were also made to improve the thermal aging performance of graphite laminates.

Tackifier for addition polyimides containing monoethylphthalate

NASA Technical Reports Server (NTRS)

St.clair, T. L.; Butler, J. M. (Inventor)

1981-01-01

An improvement of addition polyimides wherein an essentially solventless, high viscosity laminating resin is synthesized from low cost liquid monomers is disclosed. The improved process takes advantage of a reactive, liquid plasticizer such as monoethylphthalate (MEP) which is used in lieu of an alcohol solvent, and helps solve a major problem of maintaining good prepreg tack and drape, or the ability of the prepreg to adhere to adjacent plies and conform to a desired shape during the layup process. This improvement results in both longer life of the polymer prepreg and the processing of low void laminate and appears to be applicable to all addition polyimide systems.

Flow properties of a series of experimental thermoplastic polymides

NASA Technical Reports Server (NTRS)

Burks, H. D.; Nelson, J. B.; Price, H. L.

1981-01-01

The softening temperature to degradation temperature range of the polymers was about 440 to 650 K. All of the polymers retained small amounts of solvent as indicated by an increase in T(sub g) as the polymers were dried. The flow properties showed that all three polymers had very high apparent viscosities and would require high pressures and/or high temperatures and/or long times to obtain adequate flow in prepregging and molding. Although none was intended for such application, two of the polymers were combined with carbon fibers by solution prepregging. The prepregs were molded into laminates at temperatures and times, the selection of which was guided by the results from the flow measurements. These laminates had room temperature short beam shear strength similar to that of carbon fiber laminates with a thermosetting polyimide matrix. However, the strength had considerable scatter, and given the difficult processing, these polymides probably would not be suitable for continuous fiber composites.

Bismaleimide resins for flame resistant honeycomb sandwich panels

NASA Technical Reports Server (NTRS)

1978-01-01

A 60 kg batch of Resin M751 was produced in pilot plant scale. The resin was delivered to the prepreg company as an NMP solution. 100 kg of glass-fabric prepregs were fabricated. Prepreg characteristics and curing cycles for laminate fabrication were provided. A new batch of Resin M756 (Code M756 - 2) was synthesized.

3D modeling of squeeze flow of unidirectionally thermoplastic composite inserts

NASA Astrophysics Data System (ADS)

Ghnatios, Chady; Abisset-Chavanne, Emmanuelle; Binetruy, Christophe; Chinesta, Francisco; Advani, Suresh

2016-10-01

Thermoplastic composites are attractive because they can be recycled and exhibit superior mechanical properties. The ability of thermoplastic resin to melt and solidify allows for fast and cost-effective manufacturing processes, which is a crucial property for high volume production. Thermoplastic composite parts are usually obtained by stacking several prepreg plies to create a laminate with a particular orientation sequence to meet design requirements. During the consolidation and forming process, the thermoplastic laminate is subjected to complex deformation which can include intraply and/or interply shear, ply reorientation and squeeze flow. In the case of unidirectional prepregs, the ply constitutive equation, when elastic effects are neglected, can be modeled as a transversally isotropic fluid, that must satisfy the fiber inextensibility as well as the fluid incompressibility. The high-fidelity solution of the squeeze flow in laminates composed of unidirectional prepregs was addressed in our former works by making use of an in-plane-out-of-plane separated representation allowing a very detailed resolution of the involved fields throughout the laminate thickness. In the present work prepregs plies are supposed of limited dimensions compared to the in-plane dimension of the part and will be named inserts. Again within the Proper Generalized Decomposition framework high-resolution simulation of the squeeze flow occurring during consolidation is addressed within a fully 3D in-plane-out-of-plane separated representation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crabtree, D.J.

Three types of boron/epoxy prepreg tape were prestressed to fracture weak sites along the fiber by winding over 0.3- to 0.6-inch diameter rollers prior to lamination. The prestressed prepreg was then laminated, and design allowable testing was conducted to determine if mechanical strength properties are increased and data scatter is reduced by prestressing. The types of prepreg studied were standard 'Rigidite' 5505/4 prepreg, carbon substrate boron fiber prepreg, and a prepreg made from 'defect' tungsten substrate boron that was manufactured in a high-speed, low-cost, production process. The strength of angleply composites of both 'Rigidite' 5505/4 and carbon substrate boron compositesmore » were unaffected by prestressing. A study was made to determine if prepreg costs could be reduced by manufacturing low-cost 'defect' boron fiber and prestressing it to improve its properties. The results of this study were inconclusive. The test results show prestressing marginally improved some composite properties while others were reduced. On 'Rigidite' 5505/4 unidirectional composites, fatigue strength was significantly improved by prestressing, while longitudinal tensile strength was reduced at room temperature and 350 F. On unidirectional carbon substrate boron composites, the longitudinal tensile strength at room temperature and 350F was increased with attendant variability, while fatigue strength at high stress levels was reduced but not affected at low stress levels.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

May, C.A.; Breitigam, W.; Bauer, R.S.

The laminates that are used to prepare advanced composite parts generally require curing at high temperature and pressure, and their raw material shelf lives are limited. The epoxy resin systems that the authors describe here offer the potential of extended shelf life while curing at relatively low temperatures with a method the authors call rapid thermoset processing (RTP). A laminate is formed by stacking the prepreg in a pre-determined manner as required by the end product configuration. The prepreg is then bagged by placing it in a sealed envelope of a heat-resistant film, which is subsequently bonded to a metalmore » surface (the tool) with a heat-resistant vacuum bag putty. The bag has an access hole through which vacuum can be applied to the prepreg stack, facilitating removal of air and other volatiles. This assembly is then heated under vacuum and pressure in an autoclave, the resin melts, and any excess air or volatile matter bleeds from the configuration, resulting in the required dense, void-free laminate.« less

Analytical and Experimental Characterization of Thick-Section Fiber-Metal Laminates

DTIC Science & Technology

2013-06-01

individual metal layers as loading increases. The off-axis deformation properties of the prepreg layers were modeled by using equivalent constraint models...the degraded stiffness of the prepreg layer is found. At each loading step the stiffness properties of individual layers are calculated. These...predicts stress-strain curves on-axis, additional work is needed to study the local interactions between metal and prepreg layers as damage occurs in each

Detection of layup errors in prepreg laminates using shear ultrasonic waves

NASA Astrophysics Data System (ADS)

Hsu, David K.; Fischer, Brent A.

1996-11-01

The highly anisotropic elastic properties of the plies in a composite laminate manufactured from unidirectional prepregs interact strongly with the polarization direction of shear ultrasonic waves propagating through its thickness. The received signals in a 'crossed polarizer' transmission configuration are particularly sensitive to ply orientation and layup sequence in a laminate. Such measurements can therefore serve as an NDE tool for detecting layup errors. For example, it was shown experimentally recently that the sensitivity for detecting the presence of misoriented plies is better than one ply out of a 48-ply laminate of graphite epoxy. A physical model based on the decomposition and recombination of the shear polarization vector has been constructed and used in the interpretation and prediction of test results. Since errors should be detected early in the manufacturing process, this work also addresses the inspection of 'green' composite laminates using electromagnetic acoustic transducers (EMAT). Preliminary results for ply error detection obtained with EMAT probes are described.

National Transonic Facility Fan Blade prepreg material characterization tests

NASA Technical Reports Server (NTRS)

Klich, P. J.; Richards, W. H.; Ahl, E. L., Jr.

1981-01-01

The test program for the basic prepreg materials used in process development work and planned fabrication of the national transonic facility fan blade is presented. The basic prepreg materials and the design laminate are characterized at 89 K, room temperature, and 366 K. Characterization tests, test equipment, and test data are discussed. Material tests results in the warp direction are given for tensile, compressive, fatigue (tension-tension), interlaminar shear and thermal expansion.

Static and Dynamic Behavior of High Modulus Hybrid Boron/Glass/Aluminum Fiber Metal Laminates

NASA Astrophysics Data System (ADS)

Yeh, Po-Ching

2011-12-01

This dissertation presents the investigation of a newly developed hybrid fiber metal laminates (FMLs) which contains commingled boron fibers, glass fibers, and 2024-T3 aluminum sheets. Two types of hybrid boron/glass/aluminum FMLs are developed. The first, type I hybrid FMLs, contained a layer of boron fiber prepreg in between two layers of S2-glass fiber prepreg, sandwiched by two aluminum alloy 2024-T3 sheets. The second, type II hybrid FMLs, contained three layer of commingled hybrid boron/glass fiber prepreg layers, sandwiched by two aluminum alloy 2024-T3 sheets. The mechanical behavior and deformation characteristics including blunt notch strength, bearing strength and fatigue behavior of these two types of hybrid boron/glass/aluminum FMLs were investigated. Compared to traditional S2-glass fiber reinforced aluminum laminates (GLARE), the newly developed hybrid boron/glass/aluminum fiber metal laminates possess high modulus, high yielding stress, and good blunt notch properties. From the bearing test result, the hybrid boron/glass/aluminum fiber metal laminates showed outstanding bearing strength. The high fiber volume fraction of boron fibers in type II laminates lead to a higher bearing strength compared to both type I laminates and traditional GLARE. Both types of hybrid FMLs have improved fatigue crack initiation lives and excellent fatigue crack propagation resistance compared to traditional GLARE. The incorporation of the boron fibers improved the Young's modulus of the composite layer in FMLs, which in turn, improved the fatigue crack initiation life and crack propagation rates of the aluminum sheets. Moreover, a finite element model was established to predict and verify the properties of hybrid boron/glass/aluminum FMLs. The simulated results showed good agreement with the experimental results.

Development of failure criterion for Kevlar-epoxy fabric laminates

NASA Technical Reports Server (NTRS)

Tennyson, R. C.; Elliott, W. G.

1984-01-01

The development of the tensor polynomial failure criterion for composite laminate analysis is discussed. In particular, emphasis is given to the fabrication and testing of Kevlar-49 fabric (Style 285)/Narmco 5208 Epoxy. The quadratic-failure criterion with F(12)=0 provides accurate estimates of failure stresses for the Kevlar/Epoxy investigated. The cubic failure criterion was re-cast into an operationally easier form, providing the engineer with design curves that can be applied to laminates fabricated from unidirectional prepregs. In the form presented no interaction strength tests are required, although recourse to the quadratic model and the principal strength parameters is necessary. However, insufficient test data exists at present to generalize this approach for all undirectional prepregs and its use must be restricted to the generic materials investigated to-date.

Processing Science of Epoxy Resin Composites

DTIC Science & Technology

1984-01-15

3 2.2 LAMINATE FABRICATION 30 2.2.1 Baseline Laminate Fabrication 30 2.2.2 Large Laminate Fabrication 36 2.3 DIFFUSIVITY AND SOLUBILITY...Thick Laminate 42 28 Baseline Cure Cycle With Specimen Advancement Levels 45 29 Composite Panel Fabrication 47 30 Composite Panel Fabrication 48 31...first change was the elimination of the different 1 resin formulations and concentration on the normal or baseline 5208/T300 prepreg as produced by

Design and Manufacture of Conical Shell Structures Using Prepreg Laminates

NASA Astrophysics Data System (ADS)

Khakimova, Regina; Burau, Florian; Degenhardt, Richard; Siebert, Mark; Castro, Saullo G. P.

2016-06-01

The design and manufacture of unstiffened composite conical structures is very challenging, as the variation of the fiber orientations, lay-up and the geometry of the ply pieces have a significant influence on the thickness imperfections and ply angle deviations imprinted to the final part. This paper deals with the manufacture of laminated composite cones through the prepeg/autoclave process. The cones are designed to undergo repetitive buckling tests without accumulating permanent damage. The aim is to define a process that allows the control of fiber angle deviations and the removal of thickness imperfections generated from gaps and overlaps between ply pieces. Ultrasonic scan measurements are used to proof the effectiveness of the proposed method.

Improved compression molding technology for continuous fiber reinforced composite laminates. Part 2: AS-4/Polyimidesulfone prepreg system

NASA Technical Reports Server (NTRS)

Baucom, Robert M.; Hou, Tan-Hung; Kidder, Paul W.; Reddy, Rakasi M.

1991-01-01

AS-4/polyimidesulfone (PISO2) composite prepreg was utilized for the improved compression molding technology investigation. This improved technique employed molding stops which advantageously facilitate the escape of volatile by-products during the B-stage curing step, and effectively minimize the neutralization of the consolidating pressure by intimate interply fiber-fiber contact within the laminate in the subsequent molding cycle. Without the modifying the resin matrix properties, composite panels with both unidirectional and angled plies with outstanding C-scans and mechanical properties were successfully molded using moderate molding conditions, i.e., 660 F and 500 psi, using this technique. The size of the panels molded were up to 6.00 x 6.00 x 0.07 in. A consolidation theory was proposed for the understanding and advancement of the processing science. Processing parameters such as vacuum, pressure cycle design, prepreg quality, etc. were explored.

Effects of Processing Parameters on the Forming Quality of C-Shaped Thermosetting Composite Laminates in Hot Diaphragm Forming Process

NASA Astrophysics Data System (ADS)

Bian, X. X.; Gu, Y. Z.; Sun, J.; Li, M.; Liu, W. P.; Zhang, Z. G.

2013-10-01

In this study, the effects of processing temperature and vacuum applying rate on the forming quality of C-shaped carbon fiber reinforced epoxy resin matrix composite laminates during hot diaphragm forming process were investigated. C-shaped prepreg preforms were produced using a home-made hot diaphragm forming equipment. The thickness variations of the preforms and the manufacturing defects after diaphragm forming process, including fiber wrinkling and voids, were evaluated to understand the forming mechanism. Furthermore, both interlaminar slipping friction and compaction behavior of the prepreg stacks were experimentally analyzed for showing the importance of the processing parameters. In addition, autoclave processing was used to cure the C-shaped preforms to investigate the changes of the defects before and after cure process. The results show that the C-shaped prepreg preforms with good forming quality can be achieved through increasing processing temperature and reducing vacuum applying rate, which obviously promote prepreg interlaminar slipping process. The process temperature and forming rate in hot diaphragm forming process strongly influence prepreg interply frictional force, and the maximum interlaminar frictional force can be taken as a key parameter for processing parameter optimization. Autoclave process is effective in eliminating voids in the preforms and can alleviate fiber wrinkles to a certain extent.

Differential Curing In Fiber/Resin Laminates

NASA Technical Reports Server (NTRS)

Webster, Charles N.

1989-01-01

Modified layup schedule counteracts tendency toward delamination. Improved manufacturing process resembles conventional process, except prepregs partially cured laid on mold in sequence in degree of partial cure decreases from mold side to bag side. Degree of partial cure of each layer at time of layup selected by controlling storage and partial-curing temperatures of prepreg according to Arrhenius equation for rate of gel of resin as function of temperature and time from moment of mixing. Differential advancement of cure in layers made large enough to offset effect of advance bag-side heating in oven or autoclave. Technique helps prevent entrapment of volatile materials during manufacturing of fiber/resin laminates.

Toughening of PMR composites by semi-interpenetrating networks

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Srinivansan, K.

1991-01-01

Polymerization of monomer reactants (PMR-15) type polyimide and RP46 prepregs were drum wound using IM-7 fibers. Prepregging and processing conditions were optimized to yield good quality laminates with fiber volume fractions of 60 percent (+/- 2 percent). Samples were fabricated and tested to determine comprehensive engineering properties of both systems. These included 0 deg flexure, short beam shear, transverse flexure and tension, 0 deg tension and compression, intralaminar shear, short block compression, mode 1 and 2 fracture toughness, and compression after impact properties. Semi-2-IPN (interpenetrating polymer networks) toughened PMR-15 and RP46 laminates were also fabricated and tested for the same properties.

Development of LaRC 160/NR150B2 polyimide graphite hybrid composites. [for shuttle applications

NASA Technical Reports Server (NTRS)

Maximovich, M. G.; Bergren, O.; Lockerby, S.

1980-01-01

A method for co-curing NR150B2 and LaRC 160 prepregs into hybrid composites was developed. The processing characteristics and the properties of the hybrid composites were compared with those of laminates fabricated from the individual component prepregs. Resin forms were selected and optimized and a new NR150 formulation was investigated. The new formulation greatly facilitated the processing and the performance of this system. Quality control techniques were evaluated and developed, high quality laminates were fabricated from both individual resin systems, and hybrid laminates were successfully co-cured. Optimum hybrid forms were investigated and several novel approaches were explored. An optimum hybrid system was developed that utilizes a LaRC curing schedule but shows no degradation of mechanical properties after aging 500 hr in air at 260 C.

Low pressure process for continuous fiber reinforced polyamic acid resin matrix composite laminates

NASA Technical Reports Server (NTRS)

Druyun, Darleen A. (Inventor); Hou, Tan-Hung (Inventor); Kidder, Paul W. (Inventor); Reddy, Rakasi M. (Inventor); Baucom, Robert M. (Inventor)

1994-01-01

A low pressure processor was developed for preparing a well-consolidated polyimide composite laminate. Prepreg plies were formed from unidirectional fibers and a polyamic acid resin solution. Molding stops were placed at the sides of a matched metal die mold. The prepreg plies were cut shorter than the length of the mold in the in-plane lateral direction and were stacked between the molding stops to a height which was higher than the molding stops. The plies were then compressed to the height of the stops and heated to allow the volatiles to escape and to start the imidization reaction. After removing the stops from the mold, the heat was increased and 0 - 500 psi was applied to complete the imidization reaction. The heat and pressure were further increased to form a consolidated polyimide composite laminate.

X-HALE: The Development of a Research Platform for the Validation of Nonlinear Aeroelastic Codes

DTIC Science & Technology

2011-03-01

general, whenever the number of plies or the laminate direction is specifically modified or selected for a composite aircraft, the aircraft’s design is...cm 35 X-HALE’s wings are composed primarily of Hexcel E-Glass 120/F155 prepreg fabric and Rohacell Foam. Hexcel E-Glass 120/F155 prepreg

Processing and Properties of a Phenolic Composite System

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung; Bai, J. M.; Baughman, James M.

2006-01-01

Phenolic resin systems generate water as a reaction by-product via condensation reactions during curing at elevated temperatures. In the fabrication of fiber reinforced phenolic resin matrix composites, volatile management is crucial in producing void-free quality laminates. A commercial vacuum-bag moldable phenolic prepreg system was selected for this study. The traditional single-vacuum-bag (SVB) process was unable to manage the volatiles effectively, resulting in inferior voidy laminates. However, a double vacuum bag (DVB) process was shown to afford superior volatile management and consistently yielded void-free quality parts. The DVB process cure cycle (temperature /pressure profiles) for the selected composite system was designed, with the vacuum pressure application point carefully selected, to avoid excessive resin squeeze-outs and achieve the net shape and target resin content in the final consolidated laminate parts. Laminate consolidation quality was characterized by optical photomicrography for the cross sections and measurements of mechanical properties. A 40% increase in short beam shear strength, 30% greater flexural strength, 10% higher tensile and 18% higher compression strengths were obtained in composite laminates fabricated by the DVB process.

Effect of Polymer Form and its Consolidation on Mechanical Properties and Quality of Glass/PBT Composites

NASA Astrophysics Data System (ADS)

Durai Prabhakaran, R. T.; Pillai, Saju; Charca, Samuel; Oshkovr, Simin Ataollahi; Knudsen, Hans; Andersen, Tom Løgstrup; Bech, Jakob Ilsted; Thomsen, Ole Thybo; Lilholt, Hans

2014-04-01

The aim of this study was to understand the role of the processing in determining the mechanical properties of glass fibre reinforced polybutylene terephthalate composites (Glass/PBT). Unidirectional (UD) composite laminates were manufactured by the vacuum consolidation technique using three different material systems included in this study; Glass/CBT (CBT160 powder based resin), Glass/PBT (prepreg tapes), and Glass/PBT (commingled yarns). The different types of thermoplastic polymer resin systems used for the manufacturing of the composite UD laminate dictate the differences in final mechanical properties which were evaluated by through compression, flexural and short beam transverse bending tests. Microscopy was used to evaluate the quality of the processed laminates, and fractography was used to characterize the observed failure modes. The study provides an improved understanding of the relationships between processing methods, resin characteristics, and mechanical performance of thermoplastic resin composite materials.

Off-Axis Ratcheting Behavior of Unidirectional Carbon/Epoxy Laminate under Asymmetric Cyclic Loading at High Temperature

DTIC Science & Technology

2011-11-01

ply unidirectional carbon/epoxy laminates [0]12 were fabricated from the prepreg tape of P3252-20 (TORAY). They were laid up by hand and cured in...Off-Axis Ratcheting Behavior of Unidirectional Carbon/Epoxy Laminate under Asymmetric Cyclic Loading at High Temperature Takafumi Suzuki 1 and...Development of an engineering model for predicting the off-axis ratcheting behavior of a unidirectional CFRP laminate has been attempted. For this purpose

Impact Damage Detection of Toughened CFRP Laminates with Time Domain Reflectometry

DTIC Science & Technology

2013-01-30

detect damage of the CFRP structures. 3. Experiments Material used for the experiments is IM600/133 highly toughened CFRP prepreg produced by Toho...Tenux Co. Ltd. The long specimen shown in Fig. 5 is made from the prepreg . The cure condition is 180°C×0.7MPa×2h. The specimen’s stacking sequence

A theoretical study of resin flows for thermosetting materials during prepreg processing

NASA Technical Reports Server (NTRS)

Hou, T. H.

1984-01-01

A flow model which describes the process of resin consolidation during prepreg lamination was developed. The salient features of model predictions were explored. It is assumed that resin flows in all directions originate from squeezing action between two approaching adjacent fiber/fabric layers. In the horizontal direction, a squeezing flow between two nonporous parallel plates is analyzed, while in the vertical direction a poiseuille type pressure flow through porous media is assumed. Proper force and mass balance was established for the whole system which is composed of these two types of flow. A flow parameter, CF, shows to be a measure of processibility for the curing resin. For a given external load-F the responses of resin flow during prepreg lamination, as measured by CF, are categorized into three regions: (1) the low CF region where resin flows are inhibited by the high chemoviscosity during initial curing stages; (2) the median CF region where resin flows are properly controllable; and (3) the high CF region where resin flows are ceased due to fiber/fabric compression effects. Resin losses in both directions are calculated. Potential uses of this model and quality control of incoming prepreg material are discussed.

Evaluation of failure criterion for graphite/epoxy fabric laminates

NASA Technical Reports Server (NTRS)

Tennyson, R. C.; Wharram, G. E.

1985-01-01

The development and application of the tensor polynomial failure criterion for composite laminate analysis is described. Emphasis is given to the fabrication and testing of Narmco Rigidite 5208-WT300, a plain weave fabric of Thornel 300 Graphite fibers impregnated with Narmco 5208 Resin. The quadratic-failure criterion with F sub 12=0 provides accurate estimates of failure stresses for the graphite/epoxy investigated. The cubic failure criterion was recast into an operationally easier form, providing design curves that can be applied to laminates fabricated from orthotropic woven fabric prepregs. In the form presented, no interaction strength tests are required, although recourse to the quadratic model and the principal strength parameters is necessary. However, insufficient test data exist at present to generalize this approach for all prepreg constructions, and its use must be restricted to the generic materials and configurations investigated to date.

Fabrication of CFRP/Al Active Laminates

NASA Astrophysics Data System (ADS)

Asanuma, Hiroshi; Haga, Osamu; Ohira, Junichiro; Takemoto, Kyosuke; Imori, Masataka

This paper describes fabrication and evaluation of the active laminate. It was made by hot-pressing of an aluminum plate as a high CTE material, a unidirectional CFRP prepreg as a low CTE material and an electric resistance heater, a KFRP prepreg as a low CTE material and an insulator between them, and copper foils as electrodes. In this study, fabricating conditions and performances such as curvature change and output force were examined. Under optimized fabricating conditions, it became clear that 1) the curvature of the active laminate linearly changes as a function of temperature, between room temperature and its hot pressing temperature without hysteresis by electric resistance heating of carbon fiber in the CFRP layer and cooling, and 2) the output force against a fixed punch almost linearly increases with increasing temperature during heating from 313K up to around the glass transition temperature of the epoxy matrix.

Fatigue damage development of various CFRP-laminates

NASA Technical Reports Server (NTRS)

Schulte, K.; Baron, CH.

1988-01-01

The chronic strength and fatigue behavior of a woven carbon-fiber reinforced laminate in a balanced eight-shaft satin weave style was compared to nonwoven laminates with an equivalent cross-ply layup. Half the fibers were arranged in the direction of the load and the other half perpendicular to it. Two types of nonwoven laminates consisting of continuous fibers and aligned discontinuous fibers, both produced from carbon fiber prepregs, were studied. The cross-ply laminate with continuous fiber showed the best characteristics with regard to both static strength and fatigue. The similarities and differences in damage mechanisms in the laminates are described.

Development of High Performance CFRP/Metal Active Laminates

NASA Astrophysics Data System (ADS)

Asanuma, Hiroshi; Haga, Osamu; Imori, Masataka

This paper describes development of high performance CFRP/metal active laminates mainly by investigating the kind and thickness of the metal. Various types of the laminates were made by hot-pressing of an aluminum, aluminum alloys, a stainless steel and a titanium for the metal layer as a high CTE material, a unidirectional CFRP prepreg as a low CTE/electric resistance heating material, a unidirectional KFRP prepreg as a low CTE/insulating material. The aluminum and its alloy type laminates have almost the same and the highest room temperature curvatures and they linearly change with increasing temperature up to their fabrication temperature. The curvature of the stainless steel type jumps from one to another around its fabrication temperature, whereas the titanium type causes a double curvature and its change becomes complicated. The output force of the stainless steel type attains the highest of the three under the same thickness. The aluminum type successfully increased its output force by increasing its thickness and using its alloys. The electric resistance of the CFRP layer can be used to monitor the temperature, that is, the curvature of the active laminate because the curvature is a function of temperature.

Hot forming of composite prepreg: Numerical analyses

NASA Astrophysics Data System (ADS)

Guzman-Maldonado, Eduardo; Hamila, Nahiène; Boisse, Philippe; El Azzouzi, Khalid; Tardif, Xavier; Moro, Tanguy; Chatel, Sylvain; Fideu, Paulin

2017-10-01

The work presented here is part of the "FORBANS" project about the Hot Drape Forming (HDF) process consisting of unidirectional prepregs laminates. To ensure a fine comprehension of this process a combination strategy between experiment and numerical analysis is adopted. This paper is focused on the numerical analysis using the finite element method (FEM) with a hyperelastic constitutive law. Each prepreg layer is modelled by shell elements. These elements consider the tension, in-plane shear and bending behaviour of the ply at different temperatures. The contact/friction during the forming process is taken into account using forward increment Lagrange multipliers.

Integrated Printed Circuit Board (PCB) Active Cooling With Piezoelectric Actuator

DTIC Science & Technology

2012-09-01

The cooler substrate is a laminated multilayer FR-4 substrate. Individual layers are patterned to support the active element, form a resonant...prepreg epoxy. Individual FR-4 lamina were mechanically machined to pattern each layer. The layers were aligned, stacked, and laminated to form the... laminated with 70/30 copper-nickel alloy or 80/20 nickel-chrome alloy and patterned by means of photolithographic techniques and wet etching in a ferric

Numerical investigation of the effect of delaminations on fracture characteristics of glare

NASA Astrophysics Data System (ADS)

Bhat, Sunil; Narayanan, S.

2013-10-01

A finite element examination of the effect of delaminations on fracture characteristics of fibre metal laminate (Glare), by comparing energy release rates of normal cracks in laminates with and without delaminations, is presented in the paper. Glare comprising thin cracked 2024-T3 aerospace aluminum alloy layers alternately bonded with E-glass fibre based composite prepregs is considered for the analysis. Delaminations are modeled with interface cohesive elements. Energy release rates of normal cracks in laminates with delaminations are found to be higher than those in the laminates without delaminations.

Effect of laminate edge conditions on the formation of microvoids in composite laminates

NASA Astrophysics Data System (ADS)

Anderson, J. P.; Altan, M. C.

2015-05-01

Manufacturing defects such as microvoids are common in thermoset composite components and are known to negatively affect their strength. The resin pressure developed in and the resin flow out from the laminates during cure have been reported to be the primary factors influencing the final void content of a composite component. In this work, the effect of laminate edge conditions during the cure process on the formation of microvoids was experimentally investigated. This was achieved by fabricating eight-ply laminates from TenCate® BT250/7781 prepreg in a hot-press at a constant cure pressure of 170 kPa while limiting the laminate perimeter available for resin flow by 0%, 25%, 50%, 75%, and 100%. The individual plies of these five laminates were conditioned at 99% relative humidity before curing to maximize the moisture present in the lay-up before fabrication. The presence of moisture in the lay-ups was expected to promote void formation and allow the effect of restricting flow at the edges of a laminate to be better identified. The restriction of resin outflow was found to cause the average characteristic void diameter to decrease by 17% and void content to rise by 33%. This phenomenon was identified to be a result of the outflow restriction increasing the number of voids trapped within the laminate and indicates that for laminates cured at low pressures resin outflow is the dominant mechanism for void reduction.

Development of active CFRP/metal laminates and their demonstrations in complicated forms

NASA Astrophysics Data System (ADS)

Asanuma, H.; Nakata, T.; Tanaka, T.; Imori, M.; Haga, O.

2006-03-01

This paper describes development of high performance CFRP/metal active laminates and demonstrations of them in complicated forms. Various types of the laminates were made by hot-pressing of an aluminum, aluminum alloys, a stainless steel and a titanium for the metal layer as a high CTE material, a unidirectional CFRP prepreg as a low CTE/electric resistance heating material, a unidirectional KFRP prepreg as a low CTE/insulating material. The aluminum and its alloy type laminates have almost the same and the highest room temperature curvatures and they linearly change with increasing temperature up to their fabrication temperature. The curvature of the stainless steel type jumps from one to another around its fabrication temperature, whereas the titanium type causes a double curvature and its change becomes complicated. The output force of the stainless steel type attains the highest of the three under the same thickness. The aluminum type successfully increased its output force by increasing its thickness and using its alloys. The electric resistance of the CFRP layer can be used to monitor the temperature, that is, the curvature of the active laminate because the curvature is a function of temperature. The aluminum type active laminate was made into complicated forms, that is, a hatch, a stack, a coil and a lift types, and their actuation performances were successfully demonstrated.

An Experimental Study of the Influence of in-Plane Fiber Waviness on Unidirectional Laminates Tensile Properties

NASA Astrophysics Data System (ADS)

Zhao, Cong; Xiao, Jun; Li, Yong; Chu, Qiyi; Xu, Ting; Wang, Bendong

2017-12-01

As one of the most common process induced defects of automated fiber placement, in-plane fiber waviness and its influences on mechanical properties of fiber reinforced composite lack experimental studies. In this paper, a new approach to prepare the test specimen with in-plane fiber waviness is proposed in consideration of the mismatch between the current test standard and actual fiber trajectory. Based on the generation mechanism of in-plane fiber waviness during automated fiber placement, the magnitude of in-plane fiber waviness is characterized by axial compressive strain of prepreg tow. The elastic constants and tensile strength of unidirectional laminates with in-plane fiber waviness are calculated by off-axis and maximum stress theory. Experimental results show that the tensile properties infade dramatically with increasing magnitude of the waviness, in good agreement with theoretical analyses. When prepreg tow compressive strain reaches 1.2%, the longitudinal tensile modulus and strength of unidirectional laminate decreased by 25.5% and 57.7%, respectively.

Preparing polymeric matrix composites using an aqueous slurry technique

NASA Technical Reports Server (NTRS)

Johnston, Norman J. (Inventor); Towell, Timothy W. (Inventor)

1993-01-01

An aqueous process was developed to prepare a consolidated composite laminate from an aqueous slurry. An aqueous poly(amic acid) surfactant solution was prepared by dissolving a poly(amic acid) powder in an aqueous ammonia solution. A polymeric powder was added to this solution to form a slurry. The slurry was deposited on carbon fiber to form a prepreg which was dried and stacked to form a composite laminate. The composite laminate was consolidated using pressure and was heated to form the polymeric matrix. The resulting composite laminate exhibited high fracture toughness and excellent consolidation.

The development and evaluation of an alternative powder prepregging technique for use with LaRC-TPI/graphite composites

NASA Technical Reports Server (NTRS)

Ogden, Andrea L.; Hyer, Michael W.; Wilkes, Garth L.; Loos, Alfred C.; St.clair, Terry L.

1991-01-01

An alternative powder prepregging method for use with LaRC-TPI (a thermoplastic polyimide)/graphite composites is investigated. The alternative method incorporates the idea of moistening the fiber prior to powder coating. Details of the processing parameters are given and discussed. The material was subsequently laminated into small coupons which were evaluated for processing defects using electron microscopy. After the initial evaluation of the material, no major processing defects were encountered but there appeared to be an interfacial adhesion problem. As a result, prepregging efforts were extended to include an additional fiber system, XAS, and a semicrystalline form of the matrix. The semicrystalline form of the matrix was the result of a complex heat treating cycle. Using scanning electron microscopy (SEM), the fiber/matrix adhesion was evaluated in these systems relative to the amorphous/XAS coupons. Based on these results, amorphous and semicrystalline/AS-4 and XAS materials were prepregged and laminated for transverse tensile testing. The results of these tests are presented, and in an effort to obtain more information on the effect of the matrix, remaining semicrystalline transverse tensile coupons were transformed back to the amorphous state and tested. The mechanical properties of the transformed coupons returned to the values observed for the original amorphous coupons, and the interfacial adhesion, as observed by SEM, was better than in any previous sample.

Induction Bonding of Prepreg Tape and Titanium Foil

NASA Technical Reports Server (NTRS)

Messier, Bernadette C.; Hinkley, Jeffrey A.; Johnston, Norman J.

1998-01-01

Hybrid structural laminates made of titanium foil and carbon fiber reinforced polymer composite offer a potential for improved performance in aircraft structural applications. To obtain information needed for the automated fabrication of hybrid laminates, a series of bench scale tests were conducted of the magnetic induction bonding of titanium foil and thermoplastic prepreg tape. Foil and prepreg specimens were placed in the gap of a toroid magnet mounted in a bench press. Several magnet power supplies were used to study power at levels from 0.5 to 1.75 kW and frequencies from 50 to 120 kHz. Sol-gel surface-treated titanium foil, 0.0125 cm thick, and PIXA/IM7 prepreg tape were used in several lay-up configurations. Data were obtained on wedge peel bond strength, heating rate, and temperature ramp over a range of magnet power levels and frequencies at different "power-on" times for several magnet gap dimensions. These data will be utilized in assessing the potential for automated processing. Peel strengths of foil-tape bonds depended on the maximum temperature reached during heating and on the applied pressure. Maximum peel strengths were achieved at 1.25kW and 8OkHz. Induction heating of the foil appears to be capable of good bonding up to 10 plies of tape. Heat transfer calculations indicate that a 20-40 C temperature difference exists across the tape thickness during heat-up.

Polyimide-glass multilayer printed wiring boards

NASA Astrophysics Data System (ADS)

Lula, J. W.

1984-07-01

Multilayer printed wiring boards (PWBs) from a polyimide/glass reinforced copper clad laminate and prepreg were manufactured. A lamination cycle and innerlayer copper surface treatment that gave satisfactory delamination resistance at soldering temperatures were developed. When compared to similar epoxy/glass multilayer PWBs, the polyimide PWBs had higher thermal stability, greater resistance to raised lands, fewer plating voids, less outgassing, and adhesion that was equivalent to urethane foam encapsulants.

The mechanical behavior of GLARE laminates for aircraft structures

NASA Astrophysics Data System (ADS)

Wu, Guocai; Yang, J.-M.

2005-01-01

GLARE (glass-reinforced aluminum laminate) is a new class of fiber metal laminates for advanced aerospace structural applications. It consists of thin aluminum sheets bonded together with unidirectional or biaxially reinforced adhesive prepreg of high-strength glass fibers. GLARE laminates offer a unique combination of properties such as outstanding fatigue resistance, high specific static properties, excellent impact resistance, good residual and blunt notch strength, flame resistance and corrosion properties, and ease of manufacture and repair. GLARE laminates can be tailored to suit a wide variety of applications by varying the fiber/resin system, the alloy type and thickness, stacking sequence, fiber orientation, surface pretreatment technique, etc. This article presents a comprehensive overview of the mechanical properties of various GLARE laminates under different loading conditions.

Experimental study of optical fibers influence on composite

NASA Astrophysics Data System (ADS)

Liu, Rong-Mei; Liang, Da-Kai

2010-03-01

Bending strength and elasticity modulus of composite, with and without embedded optical fibers, were experimentally studied. Two kinds of laminates, which were denoted as group 1 and group 2, were fabricated from an orthogonal woven glass/epoxy prepreg. Since the normal stress value becomes the biggest at the surface of a beam, the optical fibers were embedded at the outmost layer and were all along the loading direction. Four types of materials, using each kind of laminated prepreg respectively, were manufactured. The embedded optical fibers for the 4 material types were 0, 10, 30 and 50 respectively. Three-point bending tests were carried out on the produced specimens to study the influence of embedded optical fiber on host composite. The experimental results indicated that the materials in group 2 were more sensitive to the embedded optical fibers.

Graphite polystyryl pyridine (PSP) structural composites

NASA Technical Reports Server (NTRS)

Malassine, B.

1981-01-01

PSP6022 M resin, PSP 6024 M resin and W 133 Thormel T 300 graphite fabric reinforced panels were fabricated and provided to NASA Ames Research Center. PSP6022 and PSP6024 characteristics, process specifications for the fabriation of prepregs and of laminates are detailed. Mechanical properties, thermomechanical properties and moisture resistance were evaluated. PSP6022 and PSP6024 appear as high performance thermostable systems, very easy to process, being soluble in MEK for prepregging and being cured at no more than 250C, and even 200C.

Double Vacuum Bag Process for Resin Matrix Composite Manufacturing

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung (Inventor); Jensen, Brian J. (Inventor)

2007-01-01

A double vacuum bag molding assembly with improved void management and laminate net shape control which provides a double vacuum enviromnent for use in fabricating composites from prepregs containing air and/or volatiles such as reactive resin matrix composites or composites from solvent containing prepregs with non-reactive resins matrices. By using two vacuum environments during the curing process, a vacuum can be drawn during a B-stage of a two-step cycle without placing the composite under significant relative pressure. During the final cure stage, a significant pressure can be applied by releasing the vacuum in one of the two environments. Inner and outer bags are useful for creating the two vacuum environments with a perforated tool intermediate the two. The composite is placed intermediate a tool plate and a caul plate in the first environment with the inner bag and tool plate defining the first environment. The second environment is characterized by the outer bag which is placed over the inner bag and the tool plate.

Airborne occupational allergic contact dermatitis from triglycidyl-p-aminophenol and tetraglycidyl-4,4'-methylene dianiline in preimpregnated epoxy products in the aircraft industry.

PubMed

Kanerva, L; Jolanki, R; Estlander, T; Henriks-Eckerman, M; Tuomi, M; Tarvainen, K

2000-01-01

Very little is known about allergic contact dermatitis (ACD) from preimpregnated epoxy products (prepregs). To describe a patient with occupational ACD from prepregs, and report new quantitative data on the content of prepregs. A laminator developed work-related vesicular hand dermatitis. He worked in an aircraft plant assembling aircraft parts, being exposed to preimpregnated carbon fiber and fiberglass sheets (prepregs), and epoxy adhesive tapes and foams. Triglycidyl-p-aminophenol (TGPAP; 1-0.25%, 2+; 0.05%, 1+) and tetraglycidyl-4,4'-methylene dianiline (TGMDA; 1%, 3+; 0.5-0.05%, 2+) provoked allergic patch test reactions, whereas o-diglycidyl phthalate was negative (1-0.05% pet) and standard epoxy provoked a weak (?+) reaction. Six prepreg products provoking allergic patch test reactions were analyzed for their TGPAP, TGMDA and diglycidyl ether of bisphenol A (DGEBA) content using gas and liquid chromatographic methods, showing up to 10% of TGPAP, 19% of TGMDA and 5% of DGEBA in the prepregs. An epoxy primer contained 61% of TGPAP. TGPAP and TGMDA caused occupational ACD. These chemicals need to be used when patch testing patients are exposed to prepregs, because patch testing with DGEBA may be negative. Copyright 2000 S. Karger AG, Basel.

A new NASA LaRC Multi-Purpose Prepregging Unit

NASA Technical Reports Server (NTRS)

Wilkinson, S. P.; Marchello, J. M.; Dixon, D.; Johnston, N. J.

1993-01-01

A multi-purpose prepregging machine has been designed and built for NASA Langley Research Center. The machine has numerous advantages over existing units due to its various modular components. Each of these can be used individually or simultaneously depending on the required prepregging method. A reverse roll coater provides the ability to prepare thin films from typical hot-melt thermoset formulations. Also, if necessary, the design allows direct fiber impregnation within the reverse roll coater gap. Included in the impregnation module is a solution dip tank allowing the fabrication of thermoplastic prepregs from solution. The proceeding modules within the unit consist of four nip stations, two hot-plates, a hot-sled option and a high temperature oven. This paper describes the advantages of such a modular construction and discusses the various processing combinations available to the prepregger. A variety of high performance prepreg material systems were produced on IM7 (Hercules) carbon fiber. These included LaRC RP46, a PMR-type resin processed from methanol and two polyamide acids, LaRC IA and LaRC ITPI, prpregged from N-methyl pyrrolidinone (NMP). Parameters involved in the production of these prepreg materials are presented as are the mechanical properties of the resulting good quality laminates. A brief introduction into the existing prepregging science is presented. Topics relating to solution prepregging are identified with a focus on the current research effort and its future development.

Composite sandwich structure and method for making same

NASA Technical Reports Server (NTRS)

Magurany, Charles J. (Inventor)

1995-01-01

A core for a sandwich structure which has multi-ply laminate ribs separated by voids is made as an integral unit in one single curing step. Tooling blocks corresponding to the voids are first wrapped by strips of prepreg layup equal to one half of each rib laminate so a continuous wall of prepreg material is formed around the tooling blocks. The wrapped tooling blocks are next pressed together laterally, like tiles, so adjoining walls from two tooling blocks are joined. The assembly is then cured by conventional methods, and afterwards the tooling blocks are removed so voids are formed. The ribs can be provided with integral tabs forming bonding areas for face sheets, and face sheets may be co-cured with the core ribs. The new core design is suitable for discrete ribcores used in space telescopes and reflector panels, where quasiisotropic properties and zero coefficient of thermal expansion are required.

A Fully Contained Resin Infusion Process for Fiber-Reinforced Polymer Composite Fabrication and Repair

DTIC Science & Technology

2013-01-01

Figures iv  Acknowledgments v  1.  Introduction 1  2.  Experimental 2  2.1  Composite Laminate Fabrication...2 Figure 2. Image of fiberglass composite being fabricated using VARTM processing. 2. Experimental 2.1 Composite Laminate Fabrication...style 5 × 5 plain 5 weave prepreg S-2 fiberglass fabric and a honeycomb core cured in an autoclave, much like the composite parts fielded in

Feasibility study on the development of tough, moisture-resistant laminating resins

NASA Technical Reports Server (NTRS)

Brand, R. A.; Harrison, E. S.

1979-01-01

The potential of cyanate resins as replacement for epoxy resins in composites with graphite fiber reinforcement was investigated in an effort to provide improved moisture resistance and toughness in laminating systems at a projected cost, handleability, and processing requirements equivalent to 400 K (260 F) curing epoxies. Monomer synthesis, formulation, blending, resin preparation, catalysis studies, prepreg preparation, laminate fabrication, and testing are discussed. A graphite fiber reinforced laminate was developed with 95 percent retention of the original 363 K (180 F) flexural strength and 70 percent retention of the 363 K (180 F) short beam shear strength after 500 hour exposure to 95 + 7 relative humidity at 324 K (120 F).

Experimental and Numerical Studies on Fiber Deformation and Formability in Thermoforming Process Using a Fast-Cure Carbon Prepreg: Effect of Stacking Sequence and Mold Geometry.

PubMed

Bae, Daeryeong; Kim, Shino; Lee, Wonoh; Yi, Jin Woo; Um, Moon Kwang; Seong, Dong Gi

2018-05-21

A fast-cure carbon fiber/epoxy prepreg was thermoformed against a replicated automotive roof panel mold (square-cup) to investigate the effect of the stacking sequence of prepreg layers with unidirectional and plane woven fabrics and mold geometry with different drawing angles and depths on the fiber deformation and formability of the prepreg. The optimum forming condition was determined via analysis of the material properties of epoxy resin. The non-linear mechanical properties of prepreg at the deformation modes of inter- and intra-ply shear, tensile and bending were measured to be used as input data for the commercial virtual forming simulation software. The prepreg with a stacking sequence containing the plain-woven carbon prepreg on the outer layer of the laminate was successfully thermoformed against a mold with a depth of 20 mm and a tilting angle of 110°. Experimental results for the shear deformations at each corner of the thermoformed square-cup product were compared with the simulation and a similarity in the overall tendency of the shear angle in the path at each corner was observed. The results are expected to contribute to the optimization of parameters on materials, mold design and processing in the thermoforming mass-production process for manufacturing high quality automotive parts with a square-cup geometry.

Experimental and Numerical Studies on Fiber Deformation and Formability in Thermoforming Process Using a Fast-Cure Carbon Prepreg: Effect of Stacking Sequence and Mold Geometry

PubMed Central

Bae, Daeryeong; Kim, Shino; Lee, Wonoh; Yi, Jin Woo; Um, Moon Kwang; Seong, Dong Gi

2018-01-01

A fast-cure carbon fiber/epoxy prepreg was thermoformed against a replicated automotive roof panel mold (square-cup) to investigate the effect of the stacking sequence of prepreg layers with unidirectional and plane woven fabrics and mold geometry with different drawing angles and depths on the fiber deformation and formability of the prepreg. The optimum forming condition was determined via analysis of the material properties of epoxy resin. The non-linear mechanical properties of prepreg at the deformation modes of inter- and intra-ply shear, tensile and bending were measured to be used as input data for the commercial virtual forming simulation software. The prepreg with a stacking sequence containing the plain-woven carbon prepreg on the outer layer of the laminate was successfully thermoformed against a mold with a depth of 20 mm and a tilting angle of 110°. Experimental results for the shear deformations at each corner of the thermoformed square-cup product were compared with the simulation and a similarity in the overall tendency of the shear angle in the path at each corner was observed. The results are expected to contribute to the optimization of parameters on materials, mold design and processing in the thermoforming mass-production process for manufacturing high quality automotive parts with a square-cup geometry. PMID:29883413

Structural Laminate Aluminum-Glass-Fiber Materials 1441-Sial

NASA Astrophysics Data System (ADS)

Shestov, V. V.; Antipov, V. V.; Senatorova, O. G.; Sidel'nikov, V. V.

2014-01-01

The structure, composition and set of properties of specimens and components, and some parameters of the process of production of a promising FML class of metallic polymers based on sheets of high-modulus ( E 79 GPa) alloy 1441 with reduced density ( d 2.6 g/cm3) and an optimized glued prepreg reinforced with fibers of high-strength high-modulus VMPglass are described. Results of fire and fatigue tests of a promising 1441-SIAL structural laminate are presented.

Effects of Carbon Nanomaterial Reinforcement on Composite Joints Under Cyclic and Impact Loading

DTIC Science & Technology

2012-03-01

prepreg . 2 Figure 1. Composite decks on DDG1000. (From [3]) Figure 2. USV built from nanotube-reinforced carbon fiber composites. (From [2...been proven that the infusion of CNTs enhances the strength and fracture toughness of CFRP laminates under static loading (mode I and mode II...Kostopoulos et al. [5] investigated the influence of the multi-walled carbon nanotubes (MWCNTs) on the impact and after-impact behavior of CFRP laminates

Intelligent processing for thick composites

NASA Astrophysics Data System (ADS)

Shin, Daniel Dong-Ok

2000-10-01

Manufacturing thick composite parts are associated with adverse curing conditions such as large in-plane temperature gradient and exotherms. The condition is further aggravated because the manufacturer's cycle and the existing cure control systems do not adequately counter such affects. In response, the forecast-based thermal control system is developed to have better cure control for thick composites. Accurate cure kinetic model is crucial for correctly identifying the amount of heat generated for composite process simulation. A new technique for identifying cure parameters for Hercules AS4/3502 prepreg is presented by normalizing the DSC data. The cure kinetics is based on an autocatalytic model for the proposed method, which uses dynamic and isothermal DSC data to determine its parameters. Existing models are also used to determine kinetic parameters but rendered inadequate because of the material's temperature dependent final degree of cure. The model predictions determined from the new technique showed good agreement to both isothermal and dynamic DSC data. The final degree of cure was also in good agreement with experimental data. A realistic cure simulation model including bleeder ply analysis and compaction is validated with Hercules AS4/3501-6 based laminates. The nonsymmetrical temperature distribution resulting from the presence of bleeder plies agreed well to the model prediction. Some of the discrepancies in the predicted compaction behavior were attributed to inaccurate viscosity and permeability models. The temperature prediction was quite good for the 3cm laminate. The validated process simulation model along with cure kinetics model for AS4/3502 prepreg were integrated into the thermal control system. The 3cm Hercules AS4/3501-6 and AS4/3502 laminate were fabricated. The resulting cure cycles satisfied all imposed requirements by minimizing exotherms and temperature gradient. Although the duration of the cure cycles increased, such phenomena was inevitable since longer time was required to maintain acceptable temperature gradient. The derived cure cycles were slightly different than what was anticipated by the offline simulation. Nevertheless, the system adapted to unanticipated events to satisfy the cure requirements.

Comparison of Autoclave and Out-of-Autoclave Composites

NASA Technical Reports Server (NTRS)

Sutter, James K.; Kenner, W. Scott; Pelham, Larry; Miller, Sandi G.; Polis, Danel L.; Nailadi, Chaitra; Zimmerman, Thomas J.; Lort, Richard D.; Hou, Tan-Hung; Quade, Derek J.;

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spellman, G.P.

A relatively new advanced composite matrix, polycyanate ester, was evaluated for cure shrinkage. The chemical cure shrinkage of composites is difficult to model but a number of clever experimental techniques are available to the investigator. In this work the method of curing a prepreg layup on top of a previously cured laminate of identical ply composition is utilized. The polymeric matrices used in advanced composites have been primarily epoxies and therefore a common system of this type, Fiberite 3501-6, was used as a base case material. Three polycyanate matrix systems were selected for the study. These are: Fiberite 954-2A, YLAmore » RS-3, and Bryte Technology BTCy-1. The first three of these systems were unidirectional prepreg with carbon fiber reinforcement. The Bryte Technology material was reinforced with E-glass fabric. The technique used to evaluate cure shrinkage results in distortion of the flatness of an otherwise symmetric laminate. The first laminate is cured in a conventional fashion. An identical layup is cured on this first laminate. During the second cure all constituents are exposed to the same thermal cycles. However, only the new portion of the laminate will experience volumetric changes associate with matrix cure. The additional strain of cure shrinkage results in an unsymmetric distribution of residual stresses and an associated warpage of the laminate. The baseline material, Fiberite 3501-6, exhibited cure shrinkage that was in accordance with expectations. Cure strains were {minus}4.5E-04. The YLA RS-3 material had cure strains somewhat lower at {minus}3.2E-04. The Fiberite 954-2A cure strain was {minus}1.5E-04 that is 70% lower than the baseline material. The glass fabric material with the Bryte BTCy-1 matrix did not result in meaningful results because the processing methods were not fully compatible with the material.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, K.M.; Manson, J.A.E.; Seferis, J.C.

Consolidation of thermoplastic prepregs was measured with an integrally-heated parallel platen apparatus attached to a servo-hydraulic mechanical testing machine. The apparatus was designed as a small-scale, well-instrumented press. The lamination or consolidation process was viewed as a superposition of three distinctly occurring events identified as void volume reduction, fiber spreading, and autohesion. Consolidation was measured in relation to the original prepreg thickness and was reported as compressive or consolidation strain as a function of temperature. The derivative of the consolidation strain, the consolidation strain rate, was found to be qualitatively descriptive of viscoelastic phenomena occurring in the prepreg stack duringmore » consolidation. The apparatus was sensitive enough to identify glass and melt transitions of the polymer matrix, and to provide a measure of the net consolidation for a given processing cycle. The strain and the strain rate data were compared to thermoanalytical prepreg data obtained by Differential Scanning Calorimetry, and Dynamic Mechanical Analysis. Three different thermoplastic matrix composite systems were examined with this apparatus: Poly (etheretherketone), Poly(etherimide), and Poly(ethylene terephthalate). 21 refs.« less

Manufacturing Methods and Technology (MANTECH) Program for a YAH-64 Composite Flexbeam Tail Rotor.

DTIC Science & Technology

1982-10-01

pitch link (feathering) motion to the blade. The laminated elastomeric pitch shear support aligns the pitch case with respect to the flexbeam. The pitch...15 for more details) In addition to these doublers, a longo bundle, consisting of S-2 unidirectional glass!5216 epoxy prepreg , extends from the inside...pitch st-ttings. ,-NUB BE R Th, elastomeric snubber is a laminated metal /elastomr bearing that is stiff with respi,,c to rdiat loading, but soft in

Ultrasonic NDE and mechanical testing of fiber placement composites

NASA Astrophysics Data System (ADS)

Liu, Zhanjie; Fei, Dong; Hsu, David K.; Dayal, Vinay; Hale, Richard D.

2002-05-01

A fiber placed composite, especially with fiber steering, has considerably more complex internal structure than a laminate laid up from unidirectional prepreg tapes. In this work, we performed ultrasonic imaging of ply interfaces of fiber placed composite laminates, with an eye toward developing a tool for evaluating their quality. Mechanical short-beam shear tests were also conducted on both nonsteered and steered specimens to examine their failure behavior and its relationship to the structural defects indicated by ultrasonic imaging.

Manufacturing processes for fabricating graphite/PMR 15 polyimide structural elements

NASA Technical Reports Server (NTRS)

Sheppard, C. H.; Hoggatt, J. T.; Symonds, W. A.

1979-01-01

Investigations were conducted to obtain commercially available graphite/PMR-15 polyimide prepreg, develop an autoclave manufacturing process, and demonstrate the process by manufacturing structural elements. Controls were established on polymer, prepreg, composite fabrication, and quality assurance, Successful material quality control and processes were demonstrated by fabricating major structural elements including flat laminates, hat sections, I beam sections, honeycomb sandwich structures, and molded graphite reinforced fittings. Successful fabrication of structural elements and simulated section of the space shuttle aft body flap shows that the graphite/PMR-15 polyimide system and the developed processes are ready for further evaluation in flight test hardware.

Combining LaRC-TPI powder with carbon fiber by electrostatic fluidized bed coating

NASA Technical Reports Server (NTRS)

Varughese, Babu; Muzzy, John; Baucom, Robert M.

1989-01-01

Thermoplastic polyimide prepreg tow is produced rapidly and efficiently by applying the LaRC-TPI matrix as an electrostatically charged and fluidized powder to electrically grounded and spread carbon fiber tow. The powder is melted after coating to insure adhesion to the fibers and to reduce tow friction. Excellent wetout in towpreg samples is obtained resulting in very flexible prepregs. Processing conditions of this towpreg produced with LaRC-TPI powders from Rogers Corp. and Mitsui Toatsu Chemicals are described. Mechanical properties of the towpreg and unidirectional laminates are presented in detail.

Study of Out-Time on the Processing and Properties of IM7/977-3 Composites

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Sutter, James K.; Scheiman, Daniel A.; Maryanski, Michael; Schlea, Michelle

2010-01-01

The capability to manufacture large structures leads to weight savings and reduced risk relative to joining smaller components. However, manufacture of increasingly large composite components is pushing the out-life limits of epoxy/ carbon fiber prepreg. IM7/977-3 is an autoclave processable prepreg material, commonly used in aerospace structures. The out-life limit is reported as 30 days by the manufacturer. The purpose of this work was to evaluate the material processability and composite properties of 977-3 resin and IM7/977-3 prepreg that had been aged at room temperature for up to 60 days. The neat resin was evaluated by differential scanning calorimetry, DSC, to characterize cure behavior of the aged material, as well as any change in activation energy. The rise in the modulus of the uncured prepreg was monitored throughout the 60 days by dynamic mechanical analysis, DMA. Composite panels made of the fresh and aged prepreg material were also characterized by DMA. The overall test results suggested that IM7/977-3 was a robust material that offered quality laminates throughout this aging process when processed by autoclave.

Out-Life Characteristics of IM7/977-3 Composites

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Sutter, James K.; Hou, Tan-Hung; Scheiman, Daniel A.; Martin, Richard E.; Maryanski, Michael; Schlea, Michelle; Gardner, John M.; Schiferl, Zack R.

2010-01-01

The capability to manufacture large structures leads to weight savings and reduced risk relative to joining smaller components. However, manufacture of increasingly large composite components is pushing the out-time limits of epoxy/ carbon fiber prepreg. IM7/977-3 is an autoclave processable prepreg material, commonly used in aerospace structures. The out-time limit is reported as 30 days by the manufacturer. The purpose of this work was to evaluate the material processability and composite properties of 977-3 resin and IM7/977-3 prepreg that had been aged at room temperature for up to 60 days. The effects of room temperature aging on the thermal and visco-elastic properties of the materials were investigated. Neat resin was evaluated by differential scanning calorimetry to characterize thermal properties and change in activation energy of cure. Neat resin was also evaluated by rheometry to characterize its processability in composite fabrication. IM7/977-3 prepreg was evaluated by dynamic mechanical analysis to characterize the curing behavior. Prepreg tack was also evaluated over 60 days. The overall test results suggested that IM7/977-3 was a robust material that offered quality laminates throughout this aging process when processed by autoclave.

Design and manufacture of a lightweight piezo-composite curved actuator

NASA Astrophysics Data System (ADS)

Yoon, K. Joon; Shin, Seokjun; Park, Hoon C.; Goo, Nam Seo

2002-02-01

In this paper we are concerned with the design, manufacture and performance test of a lightweight piezo-composite curved actuator (called LIPCA) using a top carbon fiber composite layer with near-zero coefficient of thermal expansion (CTE), a middle PZT ceramic wafer, and a bottom glass/epoxy layer with a high CTE. The main point of the design for LIPCA is to replace the heavy metal layers of THUNDERTM by lightweight fiber reinforced plastic layers without losing the capabilities for generating high force and large displacement. It is possible to save up to about 40% of the weight if we replace the metallic backing material by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use an epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a carbon prepreg were simply stacked and cured at an elevated temperature (177 °C) after following an autoclave bagging process. We found that the manufactured composite laminate device had a sufficient curvature after being detached from a flat mould. An analysis method using the classical lamination theory is presented to predict the curvature of LIPCA after curing at an elevated temperature. The predicted curvatures are in quite good agreement with the experimental values. In order to investigate the merits of LIPCA, performance tests of both LIPCA and THUNDERTM have been conducted under the same boundary conditions. From the experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDERTM.

Partial interlaminar separation system for composites

NASA Technical Reports Server (NTRS)

Elber, W. (Inventor)

1980-01-01

This inventor relates to an interlaminar separation system for composites wherein a thin layer of a perforated foil film is interposed between adjacent laminae of a composite formed from prepreg tapes to thereby permit laminate adherence through the perforations and produce a composite structure having improved physical property characteristics.

Microwave limb sounder, graphite epoxy support structure

NASA Technical Reports Server (NTRS)

Pynchon, G.

1980-01-01

The manufacturing and processing procedures which were used to fabricate a precision graphite/epoxy support structure for a spherical microwave reflecting surface are described. The structure was made fromm GY-70/930 ultra high modulus graphite prepreg, laminated to achieve an isotropic in plane thermal expansion of less than + or - 0.1 PPM/F. The structure was hand assembled to match the interface of the reflective surface, which was an array of 18 flexure supported, aluminum, spherically contoured tiles. Structural adhesives were used in the final assembly to bond the elements into their final configuration. A eutectic metal coating was applied to the composite surface to reduce dimensional instabilities arising from changes in the composite epoxy moisture content due to environmental effects. Basic materials properties data are reported and the results of a finite element structural analysis are referenced.

Powder Production From Waste Polyethylene Terephthalate (PET) Water Bottles

DTIC Science & Technology

2014-06-01

10 5. References 1. Van Brederode, R. A.; Steinkamp, R. A. Crosslinkable Polymer Powder and Laminate . U.S. Patent 42256560A, 1980, http...16. Parquette, B.; Giri, A.; Daniel, J.; O’Brien,D. J.; Brennan,S.; Cho, K.; Tzeng, J. Cryomilling of Thermoplastic Powder for Prepreg Applications

Allergic contact dermatitis from a nonbisphenol A epoxy in a graphite fiber reinforced epoxy laminate.

PubMed

Mathias, C G

1987-09-01

An employee of the Composites Division of an aircraft engine manufacturing firm developed dermatitis associated with the handling of a graphite fiber reinforced epoxy laminate (epoxy prepreg). Patch test investigation demonstrated that the responsible causal agent was the nonbisphenol A epoxy binder, 4-glycidyloxy-N, N-diglycidylaniline. A patch test with bisphenol A epoxy from a standard patch test screening series was negative. Subsequent interviews with employees of the Composites Division suggested that a relative lack of awareness of the cutaneous hazards of fiber reinforced epoxy laminates, compared with liquid epoxy resin systems, may be an important risk factor for allergic sensitization to these composite materials.

Embedding of MEMS pressure and temperature sensors in carbon fiber composites: a manufacturing approach

NASA Astrophysics Data System (ADS)

Javidinejad, Amir; Joshi, Shiv P.

2000-06-01

In this paper embedding of surface mount pressure and temperature sensors in the Carbon fiber composites are described. A commercially available surface mount pressure and temperature sensor are used for embedding in a composite lay- up of IM6/HST-7, IM6/3501 and AS4/E7T1-2 prepregs. The fabrication techniques developed here are the focus of this paper and provide for a successful embedding procedure of pressure sensors in fibrous composites. The techniques for positioning and insulating, the sensor and the lead wires, from the conductive carbon prepregs are described and illustrated. Procedural techniques are developed and discussed for isolating the sensor's flow-opening, from the exposure to the prepreg epoxy flow and exposure to the fibrous particles, during the autoclave curing of the composite laminate. The effects of the autoclave cycle (if any) on the operation of the embedded pressure sensor are discussed.

Modeling of Nonlinear Mechanical Response in CFRP Angle-Ply Laminates

NASA Astrophysics Data System (ADS)

Ogihara, Shinji

2014-03-01

It is known that the failure process in angle-ply laminate involves matrix cracking and delamination and that they exhibit nonlinear stress-strain relation. There may be a significant effect of the constituent blocked ply thickness on the mechanical behavior of angle-ply laminates. These days, thin prepregs whose thickness is, for example 50 micron, are developed and commercially available. Therefore, we can design wide variety of laminates with various constituent ply thicknesses. In this study, effects of constituent ply thickness on the nonlinear mechanical behavior and the damage behavior of CFRP angle-ply laminates are investigated experimentally. Based on the experimental results, the mechanical response in CFRP angle-ply laminates is modeled by using the finite strain viscoplasticity model. We evaluated the mechanical behavior and damage behavior in CFRP angle-ply laminates with different constituent ply thickness under tensile loading experimentally. It was found that as the constituent ply thickness decreases, the strength and failure strain increases. We also observed difference in damage behavior. The preliminary results of finite strain viscoplasticity model considering the damage effect for laminated composites are shown. A qualitative agreement is obtained.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mandell, John F.; Ashwill, Thomas D.; Wilson, Timothy J.

This report presents an analysis of trends in fatigue results from the Montana State University program on the fatigue of composite materials for wind turbine blades for the period 2005-2009. Test data can be found in the SNL/MSU/DOE Fatigue of Composite Materials Database which is updated annually. This is the fifth report in this series, which summarizes progress of the overall program since its inception in 1989. The primary thrust of this program has been research and testing of a broad range of structural laminate materials of interest to blade structures. The report is focused on current types of infusedmore » and prepreg blade materials, either processed in-house or by industry partners. Trends in static and fatigue performance are analyzed for a range of materials, geometries and loading conditions. Materials include: sixteen resins of three general types, five epoxy based paste adhesives, fifteen reinforcing fabrics including three fiber types, three prepregs, many laminate lay-ups and process variations. Significant differences in static and fatigue performance and delamination resistance are quantified for particular materials and process conditions. When blades do fail, the likely cause is fatigue in the structural detail areas or at major flaws. The program is focused strongly on these issues in addition to standard laminates. Structural detail tests allow evaluation of various blade materials options in the context of more realistic representations of blade structure than do the standard test methods. Types of structural details addressed in this report include ply drops used in thickness tapering, and adhesive joints, each tested over a range of fatigue loading conditions. Ply drop studies were in two areas: (1) a combined experimental and finite element study of basic ply drop delamination parameters for glass and carbon prepreg laminates, and (2) the development of a complex structured resin-infused coupon including ply drops, for comparison studies of various resins, fabrics and pry drop thicknesses. Adhesive joint tests using typical blade adhesives included both generic testing of materials parameters using a notched-lap-shear test geometry developed in this study, and also a series of simulated blade web joint geometries fabricated by an industry partner.« less

Application of small-diameter FBG sensors for detection of damages in composites

NASA Astrophysics Data System (ADS)

Okabe, Yoji; Mizutani, Tadahito; Yashiro, Shigeki; Takeda, Nobuo

2001-08-01

Small-diameter fiber Bragg grating (FBG) sensors have been developed by Hitachi Cable Ltd. and the authors. Since the outside diameter of polyimide coating is 52 micrometers , embedding of the sensors into carbon fiber reinforced plastic (CFRP) composites prepregs of 125 micrometers in thickness does not deteriorate the mechanical properties of the composite laminates. In this research, the small-diameter FBG sensor was applied for the detection of transverse cracks in CFRP composites. The FBG sensor was embedded in 0 degree(s) ply of a CFRP cross-ply laminate.

Experimental and Numerical Study on the Tensile Behaviour of UACS/Al Fibre Metal Laminate

NASA Astrophysics Data System (ADS)

Xue, Jia; Wang, Wen-Xue; Zhang, Jia-Zhen; Wu, Su-Jun; Li, Hang

2015-10-01

A new fibre metal laminate fabricated with aluminium sheets and unidirectionally arrayed chopped strand (UACS) plies is proposed. The UACS ply is made by cutting parallel slits into a unidirectional carbon fibre prepreg. The UACS/Al laminate may be viewed as aluminium laminate reinforced by highly aligned, discontinuous carbon fibres. The tensile behaviour of UACS/Al laminate, including thermal residual stress and failure progression, is investigated through experiments and numerical simulation. Finite element analysis was used to simulate the onset and propagation of intra-laminar fractures occurring within slits of the UACS plies and delamination along the interfaces. The finite element models feature intra-laminar cohesive elements inserted into the slits and inter-laminar cohesive elements inserted at the interfaces. Good agreement are obtained between experimental results and finite element analysis, and certain limitations of the finite element models are observed and discussed. The combined experimental and numerical studies provide a detailed understanding of the tensile behaviour of UACS/Al laminates.

Influence of the Hybrid Combination of Multiwalled Carbon Nanotubes and Graphene Oxide on Interlaminar Mechanical Properties of Carbon Fiber/Epoxy Laminates

NASA Astrophysics Data System (ADS)

Rodríguez-González, J. A.; Rubio-González, C.; Jiménez-Mora, M.; Ramos-Galicia, L.; Velasco-Santos, C.

2017-10-01

An effective strategy to improve the mode I and mode II interlaminar fracture toughness (G IC and G IIC ) of unidirectional carbon fiber/epoxy (CF/E) laminates using a hybrid combination of multiwalled carbon nanotubes (MWCNTs) and graphene oxide (GO) is reported. Double cantilever beam (DCB) and end notched flexure (ENF) tests were conducted to evaluate the G IC and G IIC of the CF/E laminates fabricated with sprayed MWCNTs, GO and MWCNTs/GO hybrid. Scanning electron microscopy was employed to observe the fracture surfaces of tested DCB and ENF specimens. Experimental results showed the positive effect on the G IC and G IIC by 17% and 14% improvements on CF/E laminates with 0.25 wt.% MWCNTs/GO hybrid content compared to the neat CF/E. Also, the interlaminar shear strength value was increased for MWCNTs/GO-CF/E laminates. A synergetic effect between MWCNTs and GO resulted in improved interlaminar mechanical properties of CF/E laminates made by prepregs.

Processing Robustness for A Phenylethynyl Terminated Polyimide Composite

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung

2004-01-01

The processability of a phenylethynyl terminated imide resin matrix (designated as PETI-5) composite is investigated. Unidirectional prepregs are made by coating an N-methylpyrrolidone solution of the amide acid oligomer (designated as PETAA-5/NMP) onto unsized IM7 fibers. Two batches of prepregs are used: one is made by NASA in-house, and the other is from an industrial source. The composite processing robustness is investigated with respect to the prepreg shelf life, the effect of B-staging conditions, and the optimal processing window. Prepreg rheology and open hole compression (OHC) strengths are found not to be affected by prolonged (i.e., up to 60 days) ambient storage. Rheological measurements indicate that the PETAA-5/NMP processability is only slightly affected over a wide range of B-stage temperatures from 250 deg C to 300 deg C. The OHC strength values are statistically indistinguishable among laminates consolidated using various B-staging conditions. An optimal processing window is established by means of the response surface methodology. IM7/PETAA-5/NMP prepreg is more sensitive to consolidation temperature than to pressure. A good consolidation is achievable at 371 deg C (700 deg F)/100 Psi, which yields an RT OHC strength of 62 Ksi. However, processability declines dramatically at temperatures below 350 deg C (662 deg F), as evidenced by the OHC strength values. The processability of the IM7/LARC(TM) PETI-5 prepreg was found to be robust.

Formulation and Characterization of Epoxy Resin Copolymer for Graphite Composites

NASA Technical Reports Server (NTRS)

Keck, F. L.

1983-01-01

Maximum char yield was obtained with a copolymer containing 25% mol fraction DGEBE and 75% mol fraction DGEBA (Epon 828). To achieve the high values (above 40%), a large quantity of catalyst (trimethoxyboroxine) was necessary. Although a graphite laminate 1/8" thick was successfully fabricated, the limited life of the catalyzed epoxy copolymer system precludes commercial application. Char yields of 45% can be achieved with phenolic cured epoxy systems as indicated by data generated under NAS2-10207 contract. A graphite laminate using this type of resin system was fabricated for comparison purposes. The resultant laminate was easier to process and because the graphite prepreg is more stable, the fabrication process could readily be adapted to commercial applications.

Building Block Approach' for Structural Analysis of Thermoplastic Composite Components for Automotive Applications

NASA Astrophysics Data System (ADS)

Carello, M.; Amirth, N.; Airale, A. G.; Monti, M.; Romeo, A.

2017-12-01

Advanced thermoplastic prepreg composite materials stand out with regard to their ability to allow complex designs with high specific strength and stiffness. This makes them an excellent choice for lightweight automotive components to reduce mass and increase fuel efficiency, while maintaining the functionality of traditional thermosetting prepreg (and mechanical characteristics) and with a production cycle time and recyclability suited to mass production manufacturing. Currently, the aerospace and automotive sectors struggle to carry out accurate Finite Elements (FE) component analyses and in some cases are unable to validate the obtained results. In this study, structural Finite Elements Analysis (FEA) has been done on a thermoplastic fiber reinforced component designed and manufactured through an integrated injection molding process, which consists in thermoforming the prepreg laminate and overmolding the other parts. This process is usually referred to as hybrid molding, and has the provision to reinforce the zones subjected to additional stresses with thermoformed themoplastic prepreg as required and overmolded with a shortfiber thermoplastic resin in single process. This paper aims to establish an accurate predictive model on a rational basis and an innovative methodology for the structural analysis of thermoplastic composite components by comparison with the experimental tests results.

Development of lightweight THUNDER with fiber composite layers

NASA Astrophysics Data System (ADS)

Yoon, Kwang J.; Shin, Sukjoon; Kim, Jusik; Park, Hoon C.; Kwak, Moon K.

2000-06-01

This paper is concerned with design, manufacturing and performance test of lightweight THUNDER using a top fiber composite layer with near-zero CTE, a PZT ceramic wafer and a bottom glass/epoxy layer with high CTE. The main point of this design is to replace the heavy metal layers of THUNDER by the lightweight fiber reinforced plastic layers without losing capabilities to generate high force and displacement. It is possible to save weight up to about 30 percent if we replace the metallic backing materials by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a graphite/epoxy prepreg were simply stacked and cured at an elevated temperature by following autoclave bagging process. It was found that the manufactured composite laminate device had a sufficient curvature after detaching form a flat mold. From experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDER.

Flexible thermoset towpregs by electrostatic powder fusion coating

NASA Technical Reports Server (NTRS)

Yang, Pei-Hua; Varughese, Babu; Muzzy, John D.

1991-01-01

Thermoset prepregs of expoxy and polyimide have been produced by electrostatic deposition of charged fluidized polymer powders on spread continuous fiber tows. The powders are melted onto the fibers by radiant heating to adhere the polymer to the fiber. This process produces towpreg uniformly and rapidly without imposing severe stresses on the fibers. The towpregs produced by this novel process were consolidated to make unidirectional laminates for mechanical testing. Low void content samples have been made and demonstrated by C-scan and scanning electron microscopy. The mechanical properties of unidirectional laminates are equivalent to composites fabricated by conventional techniques.

Effects of ply thickness on thermal cycle induced damage and thermal strain

NASA Astrophysics Data System (ADS)

Tompkins, Stephen S.

1994-07-01

An experimental study was conducted to determine the effects of ply thickness in composite laminates on thermally induced cracking and changes in the coefficient of thermal expansion, CTE. A graphite-epoxy composite material, P75/ERL 1962, in thin (1 mil) and thick (5 mils) prepregs was used to make cross-ply laminates, ((0/90)(sub n))s, with equal total thickness (n=2, n=10) and cross-ply laminates with the same total number of plies (n=2). Specimens of each laminate configuration were cycled up to 1500 times between -250 and 250 F. Thermally induced microdamage was assessed as a function of the number of cycles as was the change in CTE. The results showed that laminates fabricated with thin-plies microcracked at significantly different rates and reached significantly different equilibrium crack densities than the laminate fabricated with thick-ply and n=2. The CTE of thin-ply laminates was less affected by thermal cycling and damage than the CTE of thick-ply laminates. These differences are attributed primarily to differences in interply constraints. Observed effects of ply thickness on crack density was qualitatively predicted by a combined shear-lag stress/energy method.

Effects of ply thickness on thermal cycle induced damage and thermal strain

NASA Technical Reports Server (NTRS)

Tompkins, Stephen S.

1994-01-01

An experimental study was conducted to determine the effects of ply thickness in composite laminates on thermally induced cracking and changes in the coefficient of thermal expansion, CTE. A graphite-epoxy composite material, P75/ERL 1962, in thin (1 mil) and thick (5 mils) prepregs was used to make cross-ply laminates, ((0/90)(sub n))s, with equal total thickness (n=2, n=10) and cross-ply laminates with the same total number of plies (n=2). Specimens of each laminate configuration were cycled up to 1500 times between -250 and 250 F. Thermally induced microdamage was assessed as a function of the number of cycles as was the change in CTE. The results showed that laminates fabricated with thin-plies microcracked at significantly different rates and reached significantly different equilibrium crack densities than the laminate fabricated with thick-ply and n=2. The CTE of thin-ply laminates was less affected by thermal cycling and damage than the CTE of thick-ply laminates. These differences are attributed primarily to differences in interply constraints. Observed effects of ply thickness on crack density was qualitatively predicted by a combined shear-lag stress/energy method.

A Comparison Study: The New Extended Shelf Life Isopropyl Ester PMR Technology versus The Traditional Methyl Ester PMR Approach

NASA Technical Reports Server (NTRS)

Alston, William B.; Scheiman, Daniel A.; Sivko, Gloria S.

2005-01-01

Polymerization of Monomeric Reactants (PMR) monomer solutions and carbon cloth prepregs of PMR II-50 and VCAP-75 were prepared using both the traditional limited shelf life methanol based PMR approach and a novel extended shelf life isopropanol based PMR approach. The methyl ester and isopropyl ester based PMR monomer solutions and PMR prepregs were aged for up to four years at freezer and room temperatures. The aging products formed were monitored using high pressure liquid chromatography (HPLC). The composite processing flow characteristics and volatile contents of the aged prepregs were also correlated versus room temperature storage time. Composite processing cycles were developed and six ply cloth laminates were fabricated with prepregs after various extended room temperature storage times. The composites were then evaluated for glass transition temperature (Tg), thermal decomposition temperature (Td), initial flexural strength (FS) and modulus (FM), long term (1000 hours at 316 C) thermal oxidative stability (TOS), and retention of FS and FM after 1000 hours aging at 316 C. The results for each ester system were comparable. Freezer storage was found to prevent the formation of aging products for both ester systems. Room temperature storage of the novel isopropyl ester system increased PMR monomer solution and PMR prepreg shelf life by at least an order of magnitude while maintaining composite properties.

Evaluation of shear-compressive strength properties for laminated GFRP composites in electromagnet system

NASA Astrophysics Data System (ADS)

Song, Jun Hee; Kim, Hak Kun; Kim, Sam Yeon

2014-07-01

Laminated fiber-reinforced composites can be applied to an insulating structure of a nuclear fusion device. It is necessary to investigate the interlaminar fracture characteristics of the laminated composites for the assurance of design and structural integrity. The three methods used to prepare the glass fiber reinforced plastic composites tested in this study were vacuum pressure impregnation, high pressure laminate (HPL), and prepreg laminate. We discuss the design criteria for safe application of composites and the shear-compressive test methods for evaluating mechanical properties of the material. Shear-compressive tests could be performed successfully using series-type test jigs that were inclined 0°, 30°, 45°, 60°, and 75° to the normal axis. Shear strength depends strongly on the applied compressive stress. The design range of allowable shear stress was extended by use of the appropriate composite fabrication method. HPL had the largest design range, and the allowable interlaminar shear stress was 0.254 times the compressive stress.

The development of an alternative thermoplastic powder prepregging technique

NASA Technical Reports Server (NTRS)

Ogden, A. L.; Hyer, M. W.; Wilkes, G. L.; Loos, A. C.

1992-01-01

An alternative powder prepregging technique is discussed that is based on the deposition of powder onto carbon fibers that have been moistened using an ultrasonic humidifier. The dry fiber tow is initially spread to allow a greater amount of the fiber surface to be exposed to the powder, thus ensuring a significant amount of intimate contact between the fiber and the matrix. Moisture in the form of ultrafine water droplets is then deposited onto the spread fiber tow. The moisture promotes adhesion to the fiber until the powder can be tacked to the fibers by melting. Powdered resin is then sieved onto the fibers and then tacked onto the fibers by quick heating in a convective oven. This study focuses on the production of prepregs and laminates made with LaRC-TPI (thermoplastic polyimide) using this process. Although the process appears to be successful, early evaluation was hampered by poor interfacial adhesion. The adhesion problem, however, seems to be the result of a material system incompatibility, rather than being influenced by the process.

Modeling the kinematics of multi-axial composite laminates as a stacking of 2D TIF plies

NASA Astrophysics Data System (ADS)

Ibañez, Ruben; Abisset-Chavanne, Emmanuelle; Chinesta, Francisco; Huerta, Antonio

2016-10-01

Thermoplastic composites are widely considered in structural parts. In this paper attention is paid to sheet forming of continuous fiber laminates. In the case of unidirectional prepregs, the ply constitutive equation is modeled as a transversally isotropic fluid, that must satisfy both the fiber inextensibility as well as the fluid incompressibility. When the stacking sequence involves plies with different orientations the kinematics of each ply during the laminate deformation varies significantly through the composite thickness. In our former works we considered two different approaches when simulating the squeeze flow induced by the laminate compression, the first based on a penalty formulation and the second one based on the use of Lagrange multipliers. In the present work we propose an alternative approach that consists in modeling each ply involved in the laminate as a transversally isotropic fluid - TIF - that becomes 2D as soon as incompressibility constraint and plane stress assumption are taken into account. Thus, composites laminates can be analyzed as a stacking of 2D TIF models that could eventually interact by using adequate friction laws at the inter-ply interfaces.

Effects of Constituents and Lay-up Configuration on Drop-Weight Tests of Fiber-Metal Laminates

NASA Astrophysics Data System (ADS)

Liu, Yanxiong; Liaw, Benjamin

2010-02-01

Impact responses and damage of various fiber-metal laminates were studied using a drop-weight instrument with the post-impact damage characteristics being evaluated through ultrasonic and mechanical sectioning techniques. The first severe failure induced by the low-velocity drop-weight impact occurred as delamination between the aluminum and fiber-epoxy layers at the non-impact side. It was followed by a visible shear crack in the outer aluminum layer on the non-impact face. Through-thickness shear cracks in the aluminum sheets and severe damage in the fiber laminated layers (including delamination between adjacent fiber-epoxy laminae with different fiber orientations) developed under higher energy impacts. The impact properties of fiber-metal laminates varied with different constituent materials and fiber orientations. Since it was punched through easily, the aramid-fiber reinforced fiber-metal laminates (ARALL) offered poorer impact resistance than the glass-fiber reinforced fiber-metal laminates (GLARE). Tougher and more ductile aluminum alloys improved the impact resistance. GLARE made of cross-ply prepregs provided better impact resistance than GLARE with unidirectional plies.

Deformation Behavior during Processing in Carbon Fiber Reinforced Plastics

NASA Astrophysics Data System (ADS)

Ogihara, Shinji; Kobayashi, Satoshi

In this study, we manufacture the device for measuring the friction between the prepreg curing process and subjected to pull-out tests with it The prepreg used in this study is a unidirectional carbon/epoxy, produced by TORAY designation of T700SC/2592.When creating specimens 4-ply prepregs are prepared and laminated. The 2-ply prepregs in the middle are shifted 50mm. In order to measure the friction between the prepreg during the cure process, we simulate the environment in the autoclave in the device, and we experiment in pull-out test. Test environment simulating temperature and pressure. The speed of displacement should be calculated by coefficient of thermal expansions (CTE). By calculation, 0.05mm/min gives the order of magnitude of displacement speed. In this study, 3 pull-out speeds are used: 0.01, 0.05 and 0.1mm/min. The specimen was heated by a couple of heaters, and we controlled the heaters with a temperature controller along the curing conditions of the prepreg. We put pressure using 4 bolts. Two strain gages were put on the bolt. We can understand the load applied to the specimen from the strain of the bolt. Pressure was adjusted the tightness of the bolt according to curing conditions. By using such a device, the pull-out test performed by tensile testing machine while adding temperature and pressure. During the 5 hours, we perform experiments while recording the load and stroke. The shear stress determined from the load and the stroke, and evaluated.

Elevated Temperature, Notched Compression Performance of Out of Autoclave Processed Composites

NASA Technical Reports Server (NTRS)

Grimsley, Brian W.; Sutter, James K.; Dixon, Genevieve D.; Smeltzer, Satn S.

2013-01-01

Curved honeycomb sandwich panels composed of carbon fiber reinforced toughened-epoxy polymer facesheets are being evaluated for potential use as payload fairing components on the NASA heavy-lift space launch system (HL-SLS). These proposed composite sandwich panels provide the most efficient aerospace launch structures, and offer mass and thermal advantages when compared with existing metallic payload fairing structures. NASA and industry are investigating recently developed carbon fiber epoxy prepreg systems which can be fabricated using out-of autoclave (OOA) processes. Specifically, OOA processes using vacuum pressure in an oven and thereby significantly reducing the cost associated with manufacturing large (up to 10 m diameter) composite structures when compared with autoclave. One of these OOA composite material systems, CYCOM(R) 5320-1, was selected for manufacture of a 1/16th scale barrel portion of the payload fairing; such that, the system could be compared with the well-characterized prepreg system, CYCOM(R) 977-3, typically processed in an autoclave. Notched compression coupons for each material were obtained from the minimum-gauge flat laminate [60/-60/0]S witness panels produced in this manufacturing study. The coupons were also conditioned to an effective moisture equilibrium point and tested according to ASTM D6484M-09 at temperatures ranging from 25 C up to 177 C. The results of this elevated temperature mechanical characterization study demonstrate that, for thin coupons, the OHC strength of the OOA laminate was equivalent to the flight certified autoclave processed composite laminates; the limitations on the elevated temperature range are hot-wet conditions up to 163 C and are only within the margins of testing error. At 25 C, both the wet and dry OOA material coupons demonstrated greater OHC failure strengths than the autoclave processed material laminates. These results indicate a substantial improvement in OOA material development and processing since previous studies have consistently reported OOA material strengths on par or below those of autoclave processed composite laminates.

The coupled effect of fiber volume fraction and void fraction on hydraulic fluid absorption of quartz/BMI laminates

NASA Astrophysics Data System (ADS)

Hurdelbrink, Keith R.; Anderson, Jacob P.; Siddique, Zahed; Altan, M. Cengiz

2016-03-01

Bismaleimide (BMI) resin with quartz (AQ581) fiber reinforcement is a composite material frequently used in aerospace applications, such as engine cowlings and radomes. Various composite components used in aircrafts are exposed to different types of hydraulic fluids, which may lead to anomalous absorption behavior over the service life of the composite. Accurate predictive models for absorption of liquid penetrants are particularly important as the composite components are often exposed to long-term degradation due to absorbed moisture, hydraulic fluids, or similar liquid penetrants. Microstructural features such as fiber volume fraction and void fraction can have a significant effect on the absorption behavior of fiber-reinforced composites. In this paper, hydraulic fluid absorption characteristics of quartz/BMI laminates fabricated from prepregs preconditioned at different relative humidity and subsequently cured at different pressures are presented. The composite samples are immersed into hydraulic fluid at room temperature, and were not subjected to any prior degradation. To generate process-induced microvoids, prepregs were conditioned in an environmental chamber at 2% or 99% relative humidity at room temperature for a period of 24 hours prior to laminate fabrication. To alter the fiber volume fraction, the laminates were fabricated at cure pressures of 68.9 kPa (10 psi) or 482.6 kPa (70 psi) via a hot-press. The laminates are shown to have different levels of microvoids and fiber volume fractions, which were observed to affect the absorption dynamics considerably and exhibited clear non-Fickian behavior. A one-dimensional hindered diffusion model (HDM) was shown to be successful in predicting the hydraulic fluid absorption. Model prediction indicates that as the fabrication pressure increased from 68.9 kPa to 482.6 kPa, the maximum fluid content (M∞) decreased from 8.0% wt. to 1.0% wt. The degree of non-Fickian behavior, measured by hindrance coefficient (μ), was shown to increase with the increased void fraction.

Design, fabrication and test of graphite/polyimide composite joints and attachments for advanced aerospace vehicles

NASA Technical Reports Server (NTRS)

Skoumal, D. E.

1980-01-01

Bonded and bolted designs are presented for each of four major attachment types. Prepreg processing problems are discussed and quality control data are given for lots 2W4604, 2W4632 and 2W4643. Preliminary design allowables test results for tension tests and compression tests of laminates are included. The final small specimen test matrix is defined and the configuration of symmetric step-lap joint specimens are shown. Finite element modeling studies of a double lap joint were performed to evaluate the number of elements required through the adhesive thickness to assess effects of various joint parameters on stress distributions. Results of finite element analyses assessing the effect of an adhesive fillet on the stress distribution in a double lap joint are examined.

Hot forming of composite prepreg : Experimental study

NASA Astrophysics Data System (ADS)

Tardif, Xavier; Duthille, Bertrand; Bechtel, Stephane; le Pinru, Louis; Campagne, Benjamin; Destombes, Gautier; Deshors, Antoine; Marchand, Christophe; Azzouzi, Khalid El; Moro, Tanguy

2017-10-01

The hot forming of thermoset prepreg consists in bending an uncured composite part by applying a mechanical constrain on the hot laminate. Most of the time, the mold is inserted in a vacuum box and the mechanical constrain is applied on the composite laminate by a single membrane or a double-membrane. But the performance improvement products resulted in forming increasingly complex parts with advanced materials having a less formability. These new complex parts require a finer comprehension of the process and an optimization of the key parameters to get acceptable quality. In this work, an experimental study has been carried out to identify the process conditions that do not lead to unacceptable defaults: undulations of fibers. In the present study, downward-bending has been evaluated with an original light mechanical forming concept, for a given stacking sequence. The influence of the part's temperature and the part's bending speed are investigated. To carry this study out, a hot forming test bench has been designed and manufactured to have a precise supervision of the process conditions. It is able to bend parts of 1500 mm length x 600 mm width x 20 mm thick.

Fabrication Of Carbon-Boron Reinforced Dry Polymer Matrix Composite Tape

NASA Technical Reports Server (NTRS)

Belvin, Harry L.; Cano, Roberto J.; Treasure, Monte; Shahood, Thomas W.

1999-01-01

Future generation aerospace vehicles will require specialized hybrid material forms for component structure fabrication. For this reason, high temperature composite prepregs in both dry and wet forms are being developed at NASA Langley Research Center (LaRC). In an attempt to improve compressive properties of carbon fiber reinforced composites, a hybrid carbon-boron tape was developed and used to fabricate composite laminates which were subsequently cut into flexural and compression specimens and tested. The hybrid material, given the designation HYCARB, was fabricated by modifying a previously developed process for the manufacture of dry polymer matrix composite (PMC) tape at LaRC. In this work, boron fibers were processed with IM7/LaRC(TradeMark)IAX poly(amide acid) solution-coated prepreg to form a dry hybrid tape for Automated Tow Placement (ATP). Boron fibers were encapsulated between two (2) layers of reduced volatile, low fiber areal weight poly(amide acid) solution-coated prepreg. The hybrid prepreg was then fully imidized and consolidated into a dry tape suitable for ATP. The fabrication of a hybrid boron material form for tow placement aids in the reduction of the overall manufacturing cost of boron reinforced composites, while realizing the improved compression strengths. Composite specimens were press-molded from the hybrid material and exhibited excellent mechanical properties.

Numerical and Experimental Investigations on Mechanical Behavior of Composite Corrugated Core

NASA Astrophysics Data System (ADS)

Dayyani, Iman; Ziaei-Rad, Saeed; Salehi, Hamid

2012-06-01

Tensile and flexural characteristics of corrugated laminate panels were studied using numerical and analytical methods and compared with experimental data. Prepreg laminates of glass fiber plain woven cloth were hand-laid by use of a heat gun to ease the creation of the panel. The corrugated panels were then manufactured by using a trapezoidal machined aluminium mould. First, a series of simple tension tests were performed on standard samples to evaluate the material characteristics. Next, the corrugated panels were subjected to tensile and three-point bending tests. The force-displacement graphs were recorded. Numerical and analytical solutions were proposed to simulate the mechanical behavior of the panels. In order to model the energy dissipation due to delamination phenomenon observed in tensile tests in all members of corrugated core, plastic behavior was assigned to the whole geometry, not only to the corner regions. Contrary to the literature, it is shown that the three-stage mechanical behavior of composite corrugated core is not confined to aramid reinforced corrugated laminates and can be observed in other types such as fiber glass. The results reveal that the mechanical behavior of the core in tension is sensitive to the variation of core height. In addition, for the first time, the behavior of composite corrugated core was studied and verified in bending. Finally, the analytical and numerical results were validated by comparing them with experimental data. A good degree of correlation was observed which showed the suitability of the finite element model for predicting the mechanical behavior of corrugated laminate panels.

Amine terminated bisaspartimide polymer

NASA Technical Reports Server (NTRS)

Kumar, D. (Inventor); Fohlen, G. M. (Inventor); Parker, J. A. (Inventor)

1986-01-01

Novel amine terminated bisaspartimides are prepared by a Michael-type reaction of an aromatic bismalteimide and an aromatic diamine in an aprotic solvent. These bisaspartimides are thermally polymerized to yield tough, resinous polymers cross-lined through -NH- groups. Such polymers are useful in applications requiring materials with resistance to change at elevated temperatures, e.g., as lightweight laminates with graphite cloth, molding material prepregs, adhesives and insulating material.

Temperature distribution of thick thermoset composites

NASA Astrophysics Data System (ADS)

Guo, Zhan-Sheng; Du, Shanyi; Zhang, Boming

2004-05-01

The development of temperature distribution of thick polymeric matrix laminates during an autoclave vacuum bag process was measured and compared with numerically calculated results. The finite element formulation of the transient heat transfer problem was carried out for polymeric matrix composite materials from the heat transfer differential equations including internal heat generation produced by exothermic chemical reactions. Software based on the general finite element software package was developed for numerical simulation of the entire composite process. From the experimental and numerical results, it was found that the measured temperature profiles were in good agreement with the numerical ones, and conventional cure cycles recommended by prepreg manufacturers for thin laminates should be modified to prevent temperature overshoot.

In situ simultaneous strain and temperature measurement of adaptive composite materials using a fiber Bragg grating based sensor

NASA Astrophysics Data System (ADS)

Yoon, Hyuk-Jin; Costantini, Daniele M.; Michaud, Veronique; Limberger, Hans G.; Manson, Jan-Anders; Salathe, Rene P.; Kim, Chun-Gon; Hong, Chang-Sun

2005-05-01

An optical fiber sensor to simultaneously measure strain and temperature was designed and embedded into an adaptive composite laminate which exhibits a shape change upon thermal activation. The sensor is formed by two fiber Bragg gratings, which are written in optical fibers with different core dopants. The two gratings were spliced close to each other and a sensing element resulted with Bragg gratings of similar strain sensitivity but different response to temperature. This is due to the dependence of the fiber thermo-optic coefficient on core dopants and relative concentrations. The sensor was tested on an adaptive composite laminate made of unidirectional Kevlar-epoxy pre-preg plies. Several 150μm diameter pre-strained NiTiCu shape memory alloy wires were embedded in the composite laminate together with one fiber sensor. Simultaneous monitoring of strain and temperature during the curing process and activation in an oven was demonstrated.

Failure Behaviour of Aluminium/CFRP Laminates with Varying Fibre Orientation in Quasi-static Indentation Test

NASA Astrophysics Data System (ADS)

Romli, N. K.; Rejab, M. R. M.; Bachtiar, D.; Siregar, J.; Rani, M. F.; Salleh, Salwani Mohd; Merzuki, M. N. M.

2018-03-01

The response of the aluminium/carbon laminate was examined by an experimental work. The investigation on fibre metal laminate behaviour was done through an indentation test in a quasi-static loading. The hybrid laminate was fabricated by a compression moulding technique and used two types of carbon fibre orientations; plain weave and unidirectional. The plain weave orientation is dry fibre, and unidirectional orientation is prepreg type fibre. The plain weave carbon fibre and aluminium alloy 2024-0 was laminated by using thermoset epoxy while the unidirectional carbon fibre was pressed by using a hot press machine and cured under a specific temperature and pressure. A compression moulding technique was used for the FML fabrication. The aluminium sheet metal has been roughening by a metal sanding method which to improve the bonding between the fibre and metal layer. The main objective of this paper is to determine the failure response of the laminate under five variation of the crosshead speeds in the quasi-static loading. Based on the experimental data of the test, the result of 1 mm/min in the plain weave CFRP has lower loading than unidirectional fibre which the value of both was 4.11 kN and 4.69 kN, respectively.

Autoclave processing for composite material fabrication. 1: An analysis of resin flows and fiber compactions for thin laminate

NASA Technical Reports Server (NTRS)

Hou, T. H.

1985-01-01

High quality long fiber reinforced composites, such as those used in aerospace and industrial applications, are commonly processed in autoclaves. An adequate resin flow model for the entire system (laminate/bleeder/breather), which provides a description of the time-dependent laminate consolidation process, is useful in predicting the loss of resin, heat transfer characteristics, fiber volume fraction and part dimension, etc., under a specified set of processing conditions. This could be accomplished by properly analyzing the flow patterns and pressure profiles inside the laminate during processing. A newly formulated resin flow model for composite prepreg lamination process is reported. This model considers viscous resin flows in both directions perpendicular and parallel to the composite plane. In the horizontal direction, a squeezing flow between two nonporous parallel plates is analyzed, while in the vertical direction, a poiseuille type pressure flow through porous media is assumed. Proper force and mass balances have been made and solved for the whole system. The effects of fiber-fiber interactions during lamination are included as well. The unique features of this analysis are: (1) the pressure gradient inside the laminate is assumed to be generated from squeezing action between two adjacent approaching fiber layers, and (2) the behavior of fiber bundles is simulated by a Finitely Extendable Nonlinear Elastic (FENE) spring.

Development and fabrication of an autoclave molded PES/Quartz sandwich radome

NASA Astrophysics Data System (ADS)

Stanton, Leonard E.; Levin, Stephen D.

1993-04-01

A cohesively bonded, thermoplastic composite sandwich radome for a leading edge supersonic aircraft has been built using autoclave processing with PES/Quartz prepreg and a PES coated honeycomb core. Processes were developed for solvent removal, thermoplastic laminate consolidation, surface etching to improve adhesion, honeycomb coating and forming, and ultrasound testing of bond integrity. Environmental testing was also conducted to verify the structural integrity of the radome for its intended application.

Simulating squeeze flows in multiaxial laminates using an improved TIF model

NASA Astrophysics Data System (ADS)

Ibañez, R.; Abisset-Chavanne, Emmanuelle; Chinesta, Francisco

2017-10-01

Thermoplastic composites are widely considered in structural parts. In this paper attention is paid to squeeze flow of continuous fiber laminates. In the case of unidirectional prepregs, the ply constitutive equation is modeled as a transversally isotropic fluid, that must satisfy both the fiber inextensibility as well as the fluid incompressibility. When laminate is squeezed the flow kinematics exhibits a complex dependency along the laminate thickness requiring a detailed velocity description through the thickness. In a former work the solution making use of an in-plane-out-of-plane separated representation within the PGD - Poper Generalized Decomposition - framework was successfully accomplished when both kinematic constraints (inextensibility and in-compressibility) were introduced using a penalty formulation for circumventing the LBB constraints. However, such a formulation makes difficult the calculation on fiber tractions and compression forces, the last required in rheological characterizations. In this paper the former penalty formulation is substituted by a mixed formulation that makes use of two Lagrange multipliers, while addressing the LBB stability conditions within the separated representation framework, questions never until now addressed.

Curing of Thick Thermoset Composite Laminates: Multiphysics Modeling and Experiments

NASA Astrophysics Data System (ADS)

Anandan, S.; Dhaliwal, G. S.; Huo, Z.; Chandrashekhara, K.; Apetre, N.; Iyyer, N.

2017-11-01

Fiber reinforced polymer composites are used in high-performance aerospace applications as they are resistant to fatigue, corrosion free and possess high specific strength. The mechanical properties of these composite components depend on the degree of cure and residual stresses developed during the curing process. While these parameters are difficult to determine experimentally in large and complex parts, they can be simulated using numerical models in a cost-effective manner. These simulations can be used to develop cure cycles and change processing parameters to obtain high-quality parts. In the current work, a numerical model was built in Comsol MultiPhysics to simulate the cure behavior of a carbon/epoxy prepreg system (IM7/Cycom 5320-1). A thermal spike was observed in thick laminates when the recommended cure cycle was used. The cure cycle was modified to reduce the thermal spike and maintain the degree of cure at the laminate center. A parametric study was performed to evaluate the effect of air flow in the oven, post cure cycles and cure temperatures on the thermal spike and the resultant degree of cure in the laminate.

Fatigue crack growth in fiber-metal laminates

NASA Astrophysics Data System (ADS)

Ma, YuE; Xia, ZhongChun; Xiong, XiaoFeng

2014-01-01

Fiber-metal laminates (FMLs) consist of three layers of aluminum alloy 2024-T3 and two layers of glass/epoxy prepreg, and it (it means FMLs) is laminated by Al alloy and fiber alternatively. Fatigue crack growth rates in notched fiber-metal laminates under constant amplitude fatigue loading were studied experimentally and numerically and were compared with them in monolithic 2024-T3 Al alloy plates. It is shown that the fatigue life of FMLs is about 17 times longer than monolithic 2024-T3 Al alloy plate; and crack growth rates in FMLs panels remain constant mostly even when the crack is long, unlike in the monolithic 2024-T3 Al alloy plates. The formula to calculate bridge stress profiles of FMLs was derived based on the fracture theory. A program by Matlab was developed to calculate the distribution of bridge stress in FMLs, and then fatigue growth lives were obtained. Finite element models of FMLs were built and meshed finely to analyze the stress distributions. Both results were compared with the experimental results. They agree well with each other.

Compaction behavior of out-of-autoclave prepreg materials

NASA Astrophysics Data System (ADS)

Serrano, Léonard; Olivier, Philippe; Cinquin, Jacques

2017-10-01

The main challenges with composite parts manufacturing are related to the curing means, mainly autoclaves, the length of their cycles and their operating costs. In order to decrease this dependency, out of autoclave materials have been considered as a solution for high production rate parts such as spars, flaps, etc… However, most out-of-autoclave process do not possess the same maturity as their counterpart, especially concerning part quality1. Some pre-cure processes such as compaction and ply lay-up are usually less of a concern for autoclave manufacturing: the pressure applied during the cycle participates to reduce the potential defects (porosity caused by a poor quality lay-up, bad compaction, entrapped air or humidity…). For out-of-autoclave parts, those are crucial steps which may have many consequences on the final quality of the laminate2. In order to avoid this quality loss, those steps must be well understood.

Bismaleimide resins for flame resistant honeycomb sandwich panels

NASA Technical Reports Server (NTRS)

Stenzenberger, H. D.

1978-01-01

Bismaleimide resins are prime candidates for nonflammable aircraft interior panels. Three resin types with different structures and processing characteristics were formulated. Resin M 751 was used to fabricate 100 kg of glass fabric prepregs which were used for the preparation of face sheets for honeycomb sandwich panels. Prepreg characteristics and curing cycles for laminate fabrication are provided. In order to advance beyond the current solvent resin technology for fibre and fabric impregnation, a hot melt solvent-less resin system was prepared and characterized. Preliminary tests were performed to develop a wet bonding process for the fabrication of advanced sandwich honeycomb panels by use of polybismaleimide glass fabric face sheets and polybismaleimide Nomex honeycomb core. B-stage material was used for both the core and the face sheet, providing flatwise tensile properties equivalent to those obtained by the state-of-the-art 3-step process which includes an epoxy adhesive resin.

Multi-step cure kinetic model of ultra-thin glass fiber epoxy prepreg exhibiting both autocatalytic and diffusion-controlled regimes under isothermal and dynamic-heating conditions

NASA Astrophysics Data System (ADS)

Kim, Ye Chan; Min, Hyunsung; Hong, Sungyong; Wang, Mei; Sun, Hanna; Park, In-Kyung; Choi, Hyouk Ryeol; Koo, Ja Choon; Moon, Hyungpil; Kim, Kwang J.; Suhr, Jonghwan; Nam, Jae-Do

2017-08-01

As packaging technologies are demanded that reduce the assembly area of substrate, thin composite laminate substrates require the utmost high performance in such material properties as the coefficient of thermal expansion (CTE), and stiffness. Accordingly, thermosetting resin systems, which consist of multiple fillers, monomers and/or catalysts in thermoset-based glass fiber prepregs, are extremely complicated and closely associated with rheological properties, which depend on the temperature cycles for cure. For the process control of these complex systems, it is usually required to obtain a reliable kinetic model that could be used for the complex thermal cycles, which usually includes both the isothermal and dynamic-heating segments. In this study, an ultra-thin prepreg with highly loaded silica beads and glass fibers in the epoxy/amine resin system was investigated as a model system by isothermal/dynamic heating experiments. The maximum degree of cure was obtained as a function of temperature. The curing kinetics of the model prepreg system exhibited a multi-step reaction and a limited conversion as a function of isothermal curing temperatures, which are often observed in epoxy cure system because of the rate-determining diffusion of polymer chain growth. The modified kinetic equation accurately described the isothermal behavior and the beginning of the dynamic-heating behavior by integrating the obtained maximum degree of cure into the kinetic model development.

Effects of water during cure on the properties of a carbon/phenolic system

NASA Technical Reports Server (NTRS)

Penn, B. G.; Clemons, J. M.; Ledbetter, F. E., III; Daniels, J. G.; Thompson, L. M.

1984-01-01

The effects of prepreg water contamination on interlaminar shear strength, tranverse compressive strength, and longitudinal compressive strength were determined. Decreases in these properties due to water contamination were sugstantial: 28 percent for the interlaminar shear strength, 21 percent for the transverse compressive strength and 31 percent for the longitudinal compressive strength. Since voids were not detected by X-ray analysis, the most likely cause for these results is fiber-matrix debounding in the laminate.

Effect of Stitching on Debonding in Composite Structural Elements

NASA Technical Reports Server (NTRS)

Raju, I. S.; Glaessgen, E. H.

2001-01-01

Stitched multiaxial warp knit materials have been suggested as viable alternatives to laminated prepreg materials for large aircraft structures such as wing skins. Analyses have been developed to quantify the effectiveness of stitching for reducing strain energy release rates in skin-stiffener debond, lap joint and sandwich debond configurations. Strain energy release rates were computed using the virtual crack closure technique. In all configurations, the stitches were shown to significantly reduce the strain energy release rate.

Optimization of sensor introduction into laminated composite materials

NASA Astrophysics Data System (ADS)

Schaaf, Kristin; Nemat-Nasser, Sia

2008-03-01

This work seeks to extend the functionality of the composite material beyond that of simply load-bearing and to enable in situ sensing, without compromising the structural integrity of the host composite material. Essential to the application of smart composites is the issue of the mechanical coupling of the sensor to the host material. Here we present various methods of embedding sensors within the host composite material. In this study, quasi-static three-point bending (short beam) and fatigue three-point bending (short beam) tests are conducted in order to characterize the effects of introducing the sensors into the host composite material. The sensors that are examined include three types of polyvinylidene fluoride (PVDF) thin film sensors: silver ink with a protective coating of urethane, silver ink without a protective coating, and nickel-copper alloy without a protective coating. The methods of sensor integration include placement at the midplane between the layers of prepreg material as well as a sandwich configuration in which a PVDF thin film sensor is placed between the first and second and nineteenth and twentieth layers of prepreg. Each PVDF sensor is continuous and occupies the entire layer, lying in the plane normal to the thickness direction in laminated composites. The work described here is part of an ongoing effort to understand the structural effects of integrating microsensor networks into a host composite material.

Development of a heterogeneous laminating resin system

NASA Technical Reports Server (NTRS)

Biermann, T. F.; Hopper, L. C.

1985-01-01

The factors which effect the impact resistance of laminating resin systems and yet retain equivalent performance with the conventional 450 K curing epoxy matrix systems in other areas were studied. Formulation work was conducted on two systems, an all-epoxy and an epoxy/bismaleimide, to gain fundamental information on the effect formulation changes have upon neat resin and composite properties. The all-epoxy work involved formulations with various amounts and combinations of eight different epoxy resins, four different hardeners, fifteen different toughening agents, a filler, and a catalyst. The epoxy/bismaleimide effort improved formulations with various amounts and combinations of nine different resins, four different hardeners, eight different toughening agents, four different catalysts, and a filler. When a formulation appeared to offer the proper combination of properties required for a laminating resin Celion 3K-70P fabric was prepregged. Initial screening tests on composites primarily involved Gardner type impact and measurement of short beam shear strengths under dry and hot/wet conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paulauskas, F.L.

The objective of this work was to investigate the beneficial effect of the variable frequency microwave (VFM) technology to cure thermosetting prepreg laminates. Further, it was to investigate the interrelationship and effect on the curing process of frequency, band width, and curing time with different types of laminates. Previous studies of microwave-assisted curing of neat resins (epoxy) and unidirectional glass and carbon fiber laminates with a fixed frequency of 2.45 GHz, have shown that a substantial reduction in the curing time was obtained. Results of this earlier work indicate that the microwave-assisted curing of multidirectional glass fiber laminates also showmore » a substantial reduction of the required curing time. This may be explained by the penetration of microwave energy directly and throughout the laminate with enhancement of the kinetics of the chemical reaction. The fixed frequency microwave radiation of 2.45 GHz has been demonstrated to be a partially acceptable method to cure unidirectional carbon fiber laminates. Multidirectional carbon fiber/epoxy laminates demonstrate a lack of coupling during the curing process. A direct curing of these laminates was not possible by microwave radiation with the experimental approach used in agreement with previous work. In addition to this short coming, the unidirectional laminate samples cured with the fixed frequency are visually nonuniform. Localized areas of darker colors (burn, hot spots, overheating) are attributed to the formation of standing waves within the microwave cavity. For this reason, the laminates are subject to proper rotation while curing through fixed frequency. The present research indicates that variable frequency microwave technology is a sound and acceptable processing method to effectively cure uni-, bi- or multi-directional thermosetting glass fiber laminates. Also, this methodology will effectively cure unidirectional thermosetting carbon fiber laminates. For all these cases, this technology yielded a substantial reduction in the required cure time of these laminates. Multidirectional carbon fiber laminates demonstrated a lack of coupling of VFM energy during the curing process.« less

Design guidelines for high dimensional stability of CFRP optical bench

NASA Astrophysics Data System (ADS)

Desnoyers, Nichola; Boucher, Marc-André; Goyette, Philippe

2013-09-01

In carbon fiber reinforced plastic (CFRP) optomechanical structures, particularly when embodying reflective optics, angular stability is critical. Angular stability or warping stability is greatly affected by moisture absorption and thermal gradients. Unfortunately, it is impossible to achieve the perfect laminate and there will always be manufacturing errors in trying to reach a quasi-iso laminate. Some errors, such as those related to the angular position of each ply and the facesheet parallelism (for a bench) can be easily monitored in order to control the stability more adequately. This paper presents warping experiments and finite-element analyses (FEA) obtained from typical optomechanical sandwich structures. Experiments were done using a thermal vacuum chamber to cycle the structures from -40°C to 50°C. Moisture desorption tests were also performed for a number of specific configurations. The selected composite material for the study is the unidirectional prepreg from Tencate M55J/TC410. M55J is a high modulus fiber and TC410 is a new-generation cyanate ester designed for dimensionally stable optical benches. In the studied cases, the main contributors were found to be: the ply angular errors, laminate in-plane parallelism (between 0° ply direction of both facesheets), fiber volume fraction tolerance and joints. Final results show that some tested configurations demonstrated good warping stability. FEA and measurements are in good agreement despite the fact that some defects or fabrication errors remain unpredictable. Design guidelines to maximize the warping stability by taking into account the main dimensional stability contributors, the bench geometry and the optical mount interface are then proposed.

Incorporation of Tin on copper clad laminate to increase the interface adhesion for signal loss reduction of high-frequency PCB lamination

NASA Astrophysics Data System (ADS)

Wang, Chong; Wen, Na; Zhou, Guoyun; Wang, Shouxu; He, Wei; Su, Xinhong; Hu, Yongsuan

2017-11-01

A novel method of improving the adhesion between copper and prepreg in high frequency PCB was proposed and studied in this work. This process which aimed to decrease the IEP (isoelectric point) of the copper to obtain higher adhesion, was achieved by depositing a thin tin layer with lower IEP on copper. It was characterized by scanning electron microscopy (SEM), 3D microscope, peel strength test, X-Ray thickness test, grazing incidence X-ray diffraction (GXRD), X-ray photoelectron spectroscopy (XPS), Agilent vector network analyzer (VNA), which confirmed its excellent adhesion performance and outstanding electrical properties in high-frequency signal transmission compared with traditional brown oxide method. Moreover, the mechanism of achieving high adhesion for this method was also investigated.

Design, fabrication and test of graphite/polyimide composite joints and attachments for advanced aerospace vehicles

NASA Technical Reports Server (NTRS)

1980-01-01

Principal program activities dealt with the literature survey, design of joint concepts, assessment of GR/PI material quality, fabrication of test panels and specimens, and small specimen testing. Bonded and bolted designs are presented for each of the four major attachment types. Quality control data are presented for prepreg Lots 2W4651 and 3W2020. Preliminary design allowables test results for tension tests and compression tests of laminates are also presented.

Modeling the curing process of thermosetting resin matrix composites

NASA Technical Reports Server (NTRS)

Loos, A. C.

1986-01-01

A model is presented for simulating the curing process of a thermosetting resin matrix composite. The model relates the cure temperature, the cure pressure, and the properties of the prepreg to the thermal, chemical, and rheological processes occurring in the composite during cure. The results calculated with the computer code developed on the basis of the model were compared with the experimental data obtained from autoclave-curved composite laminates. Good agreement between the two sets of results was obtained.

Study of flexural rigidity of weavable powder-coated towpreg

NASA Technical Reports Server (NTRS)

Hirt, Douglas E.; Marchello, Joseph M.; Baucom, Robert M.

1990-01-01

An effort has been made to weave powder-impregnated tow into a two-dimensional preform, controlling process variables to obtain high flexural rigidity in the warp direction and greater flexibility in the fill direction. The resulting prepregs have been consolidated into laminates with LaRC-TPI matrices. Complementary SEM and DSC studies have been performed to deepen understanding of the relationship between tow flexibility and heat treatment. Attention is also given to the oven temperature and residence time variables' effects on power/fiber fusion.

Apparatus for consolidating a pre-impregnated, filament-reinforced polymeric prepreg material

NASA Technical Reports Server (NTRS)

Sandusky, Donald A. (Inventor)

1995-01-01

An apparatus and method were developed for providing a uniform, consolidated, unidirectional, continuous, fiber-reinforced polymeric material. The apparatus comprises a supply means, a forming means, a shaping means, and a take-up means. The forming means further comprises a pre-melting chamber and a stationary bar assembly. The shaping means is a loaded cooled nip-roller apparatus. Forming takes place by heating a polymeric prepreg material to a temperature where the polymer becomes viscous and applying pressure gradients at separate locations along the prepreg material. Upon exiting the forming means, the polymeric prepreg material is malleable, consolidated, and flattened. Shaping takes place by passing the malleable, consolidated, flattened prepreg material through a shaped, matched groove in a loaded, cooled nip-roller apparatus to provide the final solid product.

Feasibility on fiber orientation detection on unidirectional CFRP composite laminates using nondestructive evaluation techniques

NASA Astrophysics Data System (ADS)

Yang, In-Young; Kim, Ji-Hoon; Cha, Cheon-Seok; Lee, Kil-Sung; Hsu, David K.; Im, Kwang-Hee

2007-07-01

In particular, CFRP (carbon fiber reinforced plastics) composite materials have found wide applicability because of their inherent design flexibility and improved material properties. CFRP composites were manufactured from uni-direction prepreg sheet in this paper. It is important to assess fiber orientation, material properties and part defect in order to ensure product quality and structural integrity of CFRP because strength and stiffness of composites depend on fiber orientation. It is desirable to perform nondestructive evaluation which is very beneficial. An new method for nondestructively determining the fiber orientation in a composite laminate is presented. A one-sided pitch-catch setup was used in the detection and evaluation of flaws and material anomalies in the unidirectional CFRP composite laminates. Two Rayleigh wave transducers were joined head-to-head and used in the pitch-catch mode on the surface of the composites. The pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composite. Especially, ultrasonic waves were extensively characterized in the CFRP composite laminates both normal to fiber and along to fiber with using a one-sided direction of Rayleigh wave transducers. Also, one-sided ultrasonic measurement was made with using a Rayleigh wave transducers and a conventional scanner was used in an immersion tank for extracting fiber orientation information from the ultrasonic reflection in the unidirectional laminate. Therefore, it is thought that the proposed method is useful to evaluate integrity of CFRP laminates.

Liquid crystal polyester-carbon fiber composites

NASA Technical Reports Server (NTRS)

Chung, T. S.

1984-01-01

Liquid crystal polymers (LCP) have been developed as a thermoplastic matrix for high performance composites. A successful melt impregnation method has been developed which results in the production of continuous carbon fiber (CF) reinforced LCP prepreg tape. Subsequent layup and molding of prepreg into laminates has yielded composites of good quality. Tensile and flexural properties of LCP/CF composites are comparable to those of epoxy/CF composites. The LCP/CF composites have better impact resistance than the latter, although epoxy/CF composites possess superior compression and shear strength. The LCP/CF composites have good property retention until 200 F (67 % of room temperature value). Above 200 F, mechanical properties decrease significantly. Experimental results indicate that the poor compression and shear strength may be due to the poor interfacial adhesion between the matrix and carbon fiber as adequate toughness of the LCP matrix. Low mechanical property retention at high temperatures may be attributable to the low beta-transition temperature (around 80 C) of the LCP matrix material.

Mechanisms of CFR composites destruction studying with pulse acoustic microscopy

NASA Astrophysics Data System (ADS)

Petronyuk, Y. S.; Morokov, E. S.; Levin, V. M.; Ryzhova, T. B.; Chernov, A. V.

2016-05-01

Non-destructive inspection of carbon-fiber-reinforced (CFR) composites applied in aerospace industry attracts a wide attention. In the paper, high frequency focused ultrasound (50-100 MHz) has been applied to study the bulk microstructure of the CFR material and mechanisms of its destruction under the mechanical loading. It has been shown impulse acoustic microscopy provides detecting the areas of adhesion loss at millimeter and micron level. Behavior of the CFR laminate structure fabricated by prepreg or infusion technology has been investigated under the tensile and impact loading.

NERVA turbopump bearing retainer fabrication on nonmetallic retainer

NASA Technical Reports Server (NTRS)

Accinelli, J. B.

1972-01-01

The need for a low-wear, lightweight, high strength bearing retainer material with a radiation degradation threshold of 10 to the 9th power rads (C) prompted development of nonmetallic reinforced polymers of the following types: (1) polybenzimidazole, (2) polyimide, and (3) polyquinoxaline. Retainers were machined from tubular laminates (billets), including reinforcement by either glass or graphite fabric or filament. Fabrication of billets involves hot preimpregnation of the reinforcement fabric or filament with polymer followed by wrapping this prepreg over a heated mandrel to form a tube with the required thickness and length.

Improving Interlaminar Shear Strength

NASA Technical Reports Server (NTRS)

Jackson, Justin

2015-01-01

To achieve NASA's mission of space exploration, innovative manufacturing processes are being applied to the fabrication of complex propulsion elements.1 Use of fiber-reinforced, polymeric composite tanks are known to reduce weight while increasing performance of propulsion vehicles. Maximizing the performance of these materials is needed to reduce the hardware weight to result in increased performance in support of NASA's missions. NASA has partnered with the Mississippi State University (MSU) to utilize a unique scalable approach of locally improving the critical properties needed for composite structures. MSU is responsible for the primary development of the concept with material and engineering support provided by NASA. The all-composite tank shown in figure 1 is fabricated using a prepreg system of IM7 carbon fiber/CYCOM 5320-1 epoxy resin. This is a resin system developed for out-of-autoclave applications. This new technology is needed to support the fabrication of large, all composite structures and is currently being evaluated on a joint project with Boeing for the Space Launch System (SLS) program. In initial efforts to form an all composite pressure vessel using this prepreg system, a 60% decrease in properties was observed in scarf joint regions. Inspection of these areas identified interlaminar failure in the adjacent laminated structure as the main failure mechanism. This project seeks to improve the interlaminar shear strength (ILSS) within the prepreg layup by locally modifying the interply region shown in figure 2.2

Development of design data for graphite reinforced epoxy and polyimide composites

NASA Technical Reports Server (NTRS)

Scheck, W. G.

1974-01-01

Processing techniques and design data were characterized for a graphite/epoxy composite system that is useful from 75 K to 450 K, and a graphite/polyimide composite system that is useful from 75 K to 589 K. The Monsanto 710 polyimide resin was selected as the resin to be characterized and used with the graphite fiber reinforcement. Material was purchased using the prepreg specification for the design data generation for both the HT-S/710 and HM-S/710 graphite/polyimide composite system. Lamina and laminate properties were determined at 75 K, 297 K, and 589 K. The test results obtained on the skin-stringer components proved that graphite/polyimide composites can be reliably designed and analyzed much like graphite/epoxy composites. The design data generated in the program includes the standard static mechanical properties, biaxial strain data, creep, fatigue, aging, and thick laminate data.

Development and demonstration of manufacturing processes for fabricating graphite/Larc-160 polyimide structural elements, part 4, paragraph C

NASA Technical Reports Server (NTRS)

1981-01-01

Progress in the development of processes for production of Celion/LARC-160 graphite-polyimide materials, quality control methods, and the fabrication of Space Shuttle composite structure components is reported. The formulation and processing limits for three batches of resin are presented. Process improvements for simplification of the imidizing and autoclave cure cycles are described. Imidized and autoclave cured test panels were prepared. Celion/LARC-160 cure process verification and the fabrication of honeycomb sandwich panel elements and skin/stringer panels are described. C-scans of laminates imidized at 163 C to 218 C for periods from 30 to 180 minutes, and of process verification laminates made from different batches of prepreg are presented. Failure modes and load/strain characteristics of sandwich elements and C-scans of stringer to skin bond joints are also given.

Out of the Autoclave Fabrication of LaRC[TradeMark] PETI-9 Polyimide Laminates

NASA Technical Reports Server (NTRS)

Cano, Robert J.; Jensen, Brian J.

2013-01-01

The NASA Langley Research Center developed polyimide system, LaRC PETI-9, has successfully been processed into composites by high temperature vacuum assisted resin transfer molding (HT-VARTM). To extend the application of this high use temperature material to other out-of-autoclave (OOA) processing techniques, the fabrication of PETI- 9 laminates was evaluated using only a vacuum bag and oven cure. A LaRC PETI-9 polyimide solution in NMP was prepared and successfully utilized to fabricate unidirectional IM7 carbon fiber prepreg that was subsequently processed into composites with a vacuum bag and oven cure OOA process. Composite panels of good quality were successfully fabricated and mechanically tested. Processing characteristics, composite panel quality and mechanical properties are presented in this work. The resultant properties are compared to previously developed LaRC material systems processed by both autoclave and OOA techniques including the well characterized, autoclave processed LaRC PETI-5.

Effect of load eccentricity on the buckling of thin-walled laminated C-columns

NASA Astrophysics Data System (ADS)

Wysmulski, Pawel; Teter, Andrzej; Debski, Hubert

2018-01-01

The study investigates the behaviour of short, thin-walled laminated C-columns under eccentric compression. The tested columns are simple-supported. The effect of load inaccuracy on the critical and post-critical (local buckling) states is examined. A numerical analysis by the finite element method and experimental tests on a test stand are performed. The samples were produced from a carbon-epoxy prepreg by the autoclave technique. The experimental tests rest on the assumption that compressive loads are 1.5 higher than the theoretical critical force. Numerical modelling is performed using the commercial software package ABAQUS®. The critical load is determined by solving an eigen problem using the Subspace algorithm. The experimental critical loads are determined based on post-buckling paths. The numerical and experimental results show high agreement, thus demonstrating a significant effect of load inaccuracy on the critical load corresponding to the column's local buckling.

Non-destructive evaluation of porosity and its effect on mechanical properties of carbon fiber reinforced polymer composite materials

NASA Astrophysics Data System (ADS)

Bhat, M. R.; Binoy, M. P.; Surya, N. M.; Murthy, C. R. L.; Engelbart, R. W.

2012-05-01

In this work, an attempt is made to induce porosity of varied levels in carbon fiber reinforced epoxy based polymer composite laminates fabricated using prepregs by varying the fabrication parameters such as applied vacuum, autoclave pressure and curing temperature. Different NDE tools have been utilized to evaluate the porosity content and correlate with measurable parameters of different NDE techniques. Primarily, ultrasonic imaging and real time digital X-ray imaging have been tried to obtain a measurable parameter which can represent or reflect the amount of porosity contained in the composite laminate. Also, effect of varied porosity content on mechanical properties of the CFRP composite materials is investigated through a series of experimental investigations. The outcome of the experimental approach has yielded interesting and encouraging trend as a first step towards developing an NDE tool for quantification of effect of varied porosity in the polymer composite materials.

Development of a metal-based composite actuator

NASA Astrophysics Data System (ADS)

Asanuma, Hiroshi; Haga, Osamu; Ishii, Toshio; Kurihara, Haruki; Ohira, Junichiro; Hakoda, Genji

2000-06-01

This paper describes a basic concept and elemental developments to realize a metal based composite actuator to be used for smart structures. In this study, CFRP prepreg was laminated on aluminum plate to develop an actuator and this laminate could perform unidirectional actuation. SiC continuous fiber/Al composite thin plate could also be used for form a modified type of actuator instead of using CFRP. As sensors to be embedded in this actuator, the following ones wee developed. (1) A pre-notched optical fiber filament could be embedded in aluminum matrix without fracture by the interphase forming/bonding method with copper insert and could be fractured in it at the notch, which enabled forming of an optical interference type strain sensor. (2) Nickel wire could be uniformly oxidized and embedded in aluminum matrix without fracture, which could successfully work as a temperature sensor and a strain sensor.

Influence of Fibre Architecture on Impact Damage Tolerance in 3D Woven Composites

NASA Astrophysics Data System (ADS)

Potluri, P.; Hogg, P.; Arshad, M.; Jetavat, D.; Jamshidi, P.

2012-10-01

3D woven composites, due to the presence of through-thickness fibre-bridging, have the potential to improve damage tolerance and at the same time to reduce the manufacturing costs. However, ability to withstand damage depends on weave topology as well as geometry of individual tows. There is an extensive literature on damage tolerance of 2D prepreg laminates but limited work is reported on the damage tolerance of 3D weaves. In view of the recent interest in 3D woven composites from aerospace as well as non-aerospace sectors, this paper aims to provide an understanding of the impact damage resistance as well as damage tolerance of 3D woven composites. Four different 3D woven architectures, orthogonal, angle interlocked, layer-to-layer and modified layer-to-layer structures, have been produced under identical weaving conditions. Two additional structures, Unidirectional (UD) cross-ply and 2D plain weave, have been developed for comparison with 3D weaves. All the four 3D woven laminates have similar order of magnitude of damage area and damage width, but significantly lower than UD and 2D woven laminates. Damage Resistance, calculated as impact energy per unit damage area, has been shown to be significantly higher for 3D woven laminates. Rate of change of CAI strength with impact energy appears to be similar for all four 3D woven laminates as well as UD laminate; 2D woven laminate has higher rate of degradation with respect to impact energy. Undamaged compression strength has been shown to be a function of average tow waviness angle. Additionally, 3D weaves exhibit a critical damage size; below this size there is no appreciable reduction in compression strength. 3D woven laminates have also exhibited a degree of plasticity during compression whereas UD laminates fail instantly. The experimental work reported in this paper forms a foundation for systematic development of computational models for 3D woven architectures for damage tolerance.

Investigation of a carbon fiber/epoxy prepreg curing behavior for thick composite materials production: An industrial case-study

NASA Astrophysics Data System (ADS)

Giorgini, Loris; Mazzocchetti, Laura; Minak, Giangiacomo; Dolcini, Enrico

2012-07-01

A case-study is presented, in cooperation with RI-BA Composites srl, where the industrial production of a thick part for primary structural application is analysed. The final product is a bulk carbon fiber reinforced object characterized by great dimensions, with thickness ranging between 10mm and 35mm and obtained by Hand-Lay-Up of prepregs. The study shows that prepregs age along the time required for the process work up. Moreover, the isothermal curing investigation of the prepreg used in the production gives some useful hint for the design of a new thermal curing cycle, in order to avoid exotherm problems along the thickness of the object. The effect of the applied curing cycle on thermal properties of the object are reported.

Poly-m-aramid nanofiber mats: Production for application as structural modifiers in CFRP laminates

NASA Astrophysics Data System (ADS)

Mazzocchetti, Laura; D'Angelo, Emanuele; Benelli, Tiziana; Belcari, Juri; Brugo, Tommaso Maria; Zucchelli, Andrea; Giorgini, Loris

2016-05-01

Poly(m-phenylene isophtalamide) electrospun nanofibrous membranes were produced to be used as structural reinforcements for carbon fiber reinforced composites production. In order for the polymer to be electrospun, it needs however to be fully solubilized, so the addition of some salts is required to help disrupt the tight macromolecular packing based on intra- and inter-molecular hydrogen bonding. Such salts may also contribute to the electrospinnability of the overall solution, since the provide it with a higher conductivity, whatever the solvent might be. The salt haobwever stays in the final nanofibrous mat. The membranes containing the salt are also observed to be highly hygroscopic, with a water content up to 26%, in the presence of 20%wt LiCl in the nanofibrous mat. When those membranes were interleaved among prepregs to produce a laminates, the obtained composite displayed thermal properties comparable to those of a reference nanofiber-free composite, though the former showed also easier delamination. Hence the removal of the hygroscopic salt was performed, that lead to thinner membranes, whose water content matched that of the pristine polymer. The washing step induced a thinning of the layers and of the fibers diameters, though no fiber shrinking nor membrane macroscopic damages were observed. These preliminary encouraging results thus pave the way to a deeper study of the optimized condition for producing convenient poly(m-phenylene isophtalamide) electrospun nanofibrous membranes to be used for carbon fiber reinforced composites structural modification.

Titanium reinforced boron-polyimide composite

NASA Technical Reports Server (NTRS)

Clark, G. A.; Clayton, K. I.

1969-01-01

Processing techniques for boron polyimide prepreg were developed whereby composites could be molded under vacuum bag pressure only. A post-cure cycle was developed which resulted in no loss in room temperature mechanical properties of the composite at any time during up to 16 hours at 650 F. A design utilizing laminated titanium foil was developed to achieve a smooth transition of load from the titanium attachment points into the boron-reinforced body of the structure. The box beam test article was subjected to combined bending and torsional loads while exposed to 650 F. Loads were applied incrementally until failure occurred at 83% design limit load.

Thermochemical tests on resins: Char resistance of selected phenolic cured epoxides

NASA Technical Reports Server (NTRS)

Keck, F. L.

1982-01-01

Curing epoxy resins with novalac phenolic resins is a feasible approach for increasing intact char of the resin system. Char yields above 40% at 700 C were achieved with epoxy novalac (DEN 438)/novalac phenolic (BRWE 5833) resin systems with or without catalyst such as ethyl tri-phenyl phosphonium iodide. These char yields are comparable to commercially used epoxy resin systems like MY-720/DDS/BF3. Stable prepregs are easily made from a solvent solution of the epoxy/phenolic system and this provides a feasible process for fabrication of same into commercial laminates.

Enhanced microwave shielding and mechanical properties of high loading MWCNT-epoxy composites

NASA Astrophysics Data System (ADS)

Singh, B. P.; Prasanta; Choudhary, Veena; Saini, Parveen; Pande, Shailaja; Singh, V. N.; Mathur, R. B.

2013-04-01

Dispersion of high loading of carbon nanotubes (CNTs) in epoxy resin is a challenging task for the development of efficient and thin electromagnetic interference (EMI) shielding materials. Up to 20 wt% of multiwalled carbon nanotubes (MWCNTs) loading in the composite was achieved by forming CNT prepreg in the epoxy resin as a first step. These prepreg laminates were then compression molded to form composites which resulted in EMI shielding effectiveness of -19 dB for 0.35 mm thick film and -60 dB at for 1.75 mm thick composites in the X-band (8.2-12.4 GHz). One of the reasons for such high shielding is attributed to the high electrical conductivity of the order of 9 S cm-1 achieved in these composites which is at least an order of magnitude higher than previously reported results at this loading. In addition, an improvement of 40 % in the tensile strength over the neat resin value is observed. Thermal conductivity of the MWCNTs-epoxy composite reached 2.18 W/mK as compared to only 0.14 W/mK for cured epoxy.

Additive Manufacturing of Silicon Carbide-Based Ceramic Matrix Composites: Technical Challenges and Opportunities

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay; Halbig, Michael C.; Grady, Joseph E.

2016-01-01

Advanced SiC-based ceramic matrix composites offer significant contributions toward reducing fuel burn and emissions by enabling high overall pressure ratio (OPR) of gas turbine engines and reducing or eliminating cooling air in the hot-section components, such as shrouds, combustor liners, vanes, and blades. Additive manufacturing (AM), which allows high value, custom designed parts layer by layer, has been demonstrated for metals and polymer matrix composites. However, there has been limited activity on additive manufacturing of ceramic matrix composites (CMCs). In this presentation, laminated object manufacturing (LOM), binder jet process, and 3-D printing approaches for developing ceramic composite materials are presented. For the laminated object manufacturing (LOM), fiber prepreg laminates were cut into shape with a laser and stacked to form the desired part followed by high temperature heat treatments. For the binder jet, processing optimization was pursued through silicon carbide powder blending, infiltration with and without SiC nano powder loading, and integration of fibers into the powder bed. Scanning electron microscopy was conducted along with XRD, TGA, and mechanical testing. Various technical challenges and opportunities for additive manufacturing of ceramics and CMCs will be presented.

A Mixed-Mode (I-II) Fracture Criterion for AS4/8552 Carbon/Epoxy Composite Laminate

NASA Astrophysics Data System (ADS)

Karnati, Sidharth Reddy

A majority of aerospace structures are subjected to bending and stretching loads that introduce peel and shear stresses between the plies of a composite laminate. These two stress components cause a combination of mode I and II fracture modes in the matrix layer of the composite laminate. The most common failure mode in laminated composites is delamination that affects the structural integrity of composite structures. Damage tolerant designs of structures require two types of materials data: mixed-mode (I-II) delamination fracture toughness that predicts failure and delamination growth rate that predicts the life of the structural component. This research focuses determining mixed-mode (I-II) fracture toughness under a combination of mode I and mode II stress states and then a fracture criterion for AS4/8552 composite laminate, which is widely used in general aviation. The AS4/8552 prepreg was supplied by Hexcel Corporation and autoclave fabricated into a 20-ply unidirectional laminate with an artificial delamination by a Fluorinated Ethylene Propylene (FEP) film at the mid-plane. Standard split beam specimens were prepared and tested in double cantilever beam (DCB) and end notched flexure modes to determine mode I (GIC) and II (GIIC) fracture toughnesses, respectively. The DCB specimens were also tested in a modified mixed-mode bending apparatus at GIIm /GT ratios of 0.18, 0.37, 0.57 and 0.78, where GT is total and GIIm is the mode II component of energy release rates. The measured fracture toughness, GC, was found to follow the locus a power law equation. The equation was validated for the present and literature experimental data.

Vacuum-bag-only processing of composites

NASA Astrophysics Data System (ADS)

Thomas, Shad

Ultrasonic imaging in the C-scan mode in conjunction with the amplitude of the reflected signal was used to measure flow rates of an epoxy resin film penetrating through the thickness of single layers of woven carbon fabric. Assemblies, comprised of a single layer of fabric and film, were vacuum-bagged and ultrasonically scanned in a water tank during impregnation at 50°C, 60°C, 70°C, and 80°C. Measured flow rates were plotted versus inverse viscosity to determine the permeability in the thin film, non-saturated system. The results demonstrated that ultrasonic imaging in the C-scan mode is an effective method of measuring z-direction resin flow through a single layer of fabric. The permeability values determined in this work were consistent with permeability values reported in the literature. Capillary flow was not observed at the temperatures and times required for pressurized flow to occur. The flow rate at 65°C was predicted from the linear plot of flow rate versus inverse viscosity. The effects of fabric architecture on through-thickness flow rates during impregnation of an epoxy resin film were measured by ultrasonic imaging. Multilayered laminates comprised of woven carbon fabrics and epoxy films (prepregs) were fabricated by vacuum-bagging. Ultrasonic imaging was performed in a heated water tank (65°C) during impregnation. Impregnation rates showed a strong dependence on fabric architecture, despite similar areal densities. Impregnation rates are directly affected by inter-tow spacing and tow nesting, which depend on fabric architecture, and are indirectly affected by areal densities. A new method of predicting resin infusion rates in prepreg and resin film infusion processes was proposed. The Stokes equation was used to derive an equation to predict the impregnation rate of laminates as a function of fabric architecture. Flow rate data previously measured by ultrasound was analyzed with the new equation and the Kozeny-Carman equation. A fiber interaction parameter was determined as a function of fabric architecture. The derived equation is straight-forward to use, unlike the Kozeny-Carman equation. The results demonstrated that the newly derived equation can be used to predict the resin infusion rate of multilayer laminates.

Monitoring Pre-Stressed Composites Using Optical Fibre Sensors.

PubMed

Krishnamurthy, Sriram; Badcock, Rodney A; Machavaram, Venkata R; Fernando, Gerard F

2016-05-28

Residual stresses in fibre reinforced composites can give rise to a number of undesired effects such as loss of dimensional stability and premature fracture. Hence, there is significant merit in developing processing techniques to mitigate the development of residual stresses. However, tracking and quantifying the development of these fabrication-induced stresses in real-time using conventional non-destructive techniques is not straightforward. This article reports on the design and evaluation of a technique for manufacturing pre-stressed composite panels from unidirectional E-glass/epoxy prepregs. Here, the magnitude of the applied pre-stress was monitored using an integrated load-cell. The pre-stressing rig was based on a flat-bed design which enabled autoclave-based processing. A method was developed to end-tab the laminated prepregs prior to pre-stressing. The development of process-induced residual strain was monitored in-situ using embedded optical fibre sensors. Surface-mounted electrical resistance strain gauges were used to measure the strain when the composite was unloaded from the pre-stressing rig at room temperature. Four pre-stress levels were applied prior to processing the laminated preforms in an autoclave. The results showed that the application of a pre-stress of 108 MPa to a unidirectional [0]16 E-glass/913 epoxy preform, reduced the residual strain in the composite from -600 µε (conventional processing without pre-stress) to approximately zero. A good correlation was observed between the data obtained from the surface-mounted electrical resistance strain gauge and the embedded optical fibre sensors. In addition to "neutralising" the residual stresses, superior axial orientation of the reinforcement can be obtained from pre-stressed composites. A subsequent publication will highlight the consequences of pres-stressing on fibre alignment, the tensile, flexural, compressive and fatigue performance of unidirectional E-glass composites.

Monitoring Pre-Stressed Composites Using Optical Fibre Sensors

PubMed Central

Krishnamurthy, Sriram; Badcock, Rodney A.; Machavaram, Venkata R.; Fernando, Gerard F.

2016-01-01

Residual stresses in fibre reinforced composites can give rise to a number of undesired effects such as loss of dimensional stability and premature fracture. Hence, there is significant merit in developing processing techniques to mitigate the development of residual stresses. However, tracking and quantifying the development of these fabrication-induced stresses in real-time using conventional non-destructive techniques is not straightforward. This article reports on the design and evaluation of a technique for manufacturing pre-stressed composite panels from unidirectional E-glass/epoxy prepregs. Here, the magnitude of the applied pre-stress was monitored using an integrated load-cell. The pre-stressing rig was based on a flat-bed design which enabled autoclave-based processing. A method was developed to end-tab the laminated prepregs prior to pre-stressing. The development of process-induced residual strain was monitored in-situ using embedded optical fibre sensors. Surface-mounted electrical resistance strain gauges were used to measure the strain when the composite was unloaded from the pre-stressing rig at room temperature. Four pre-stress levels were applied prior to processing the laminated preforms in an autoclave. The results showed that the application of a pre-stress of 108 MPa to a unidirectional [0]16 E-glass/913 epoxy preform, reduced the residual strain in the composite from −600 µε (conventional processing without pre-stress) to approximately zero. A good correlation was observed between the data obtained from the surface-mounted electrical resistance strain gauge and the embedded optical fibre sensors. In addition to “neutralising” the residual stresses, superior axial orientation of the reinforcement can be obtained from pre-stressed composites. A subsequent publication will highlight the consequences of pres-stressing on fibre alignment, the tensile, flexural, compressive and fatigue performance of unidirectional E-glass composites. PMID:27240378

Prepreg effects on honeycomb composite manufacturing

NASA Astrophysics Data System (ADS)

Martin, Cary Joseph

Fiber reinforced composites offer many advantages over traditional materials and are widely utilized in aerospace applications. Advantages include a high stiffness to weight ratio and excellent fatigue resistance. However, the pace of new implementation is slow. The manufacturing processes used to transform composite intermediates into final products are poorly understood and are a source of much variability. This limits new implementation and increases the manufacturing costs of existing designs. One such problem is honeycomb core crush, in which a core-stiffened structure collapses during autoclave manufacture, making the structure unusable and increasing the overall manufacturing cost through increased scrap rates. Consequently, the major goal of this research was to investigate the scaling of core crush from prepreg process-structure-property relations to commercial composite manufacture. The material dependent nature of this defect was of particular interest. A methodology and apparatus were developed to measure the frictional resistance of prepreg materials under typical processing conditions. Through a characterization of commercial and experimental prepregs, it was found that core crush behavior was the result of differences in prepreg frictional resistance. This frictional resistance was related to prepreg morphology and matrix rheology and elasticity. Resin composition and prepreg manufacturing conditions were also found to affect manufacturing behavior. Mechanical and dimensional models were developed and demonstrated utility for predicting this crushing behavior. Collectively, this work explored and identified the process-structure-property relations as they relate to the manufacture of composite materials and suggested several avenues by which manufacturing-robust materials may be developed.

Outgassing of Out-of-Autoclave Composite Primary Structures for Small Satellites

NASA Astrophysics Data System (ADS)

Komus, Alastair

Out-of-autoclave vacuum-bagged-only (VBO) processing is capable of producing lower cost composite primary structures for small satellites than autoclave processing. However, the outgassing performance of VBO structures in a vacuum environment has not been examined. Panels were manufactured from CYCOM 5320-1 and TC275-1 carbon fiber/epoxy prepreg using VBO processing. The humidity level, pre-cure dwell time, and cure cycle parameters were varied during manufacturing. The degree of cure and glass transition temperature were shown to increase with increasing oven temperature. Processing humidity levels and the length of pre-cure dwell times had no discernable effect on the total mass loss (TML) and collected volatile condensable material (CVCM) that were outgassed under vacuum. Instead the TML was controlled by moisture saturation after manufacturing. Fourier transform infrared spectroscopy showed that epoxy oligomers were the primary CVCM. The study showed the VBO laminates had outgassing values that were comparable to the autoclave-cured laminates.

Mechanical properties of carbon fibre-reinforced polymer/magnesium alloy hybrid laminates

NASA Astrophysics Data System (ADS)

Zhou, Pengpeng; Wu, Xuan; Pan, Yingcai; Tao, Ye; Wu, Guoqing; Huang, Zheng

2018-04-01

In this study, we prepared fibre metal laminates (FMLs) consisting of high-modulus carbon fibre-reinforced polymer (CFRP) prepregs and thin AZ31 alloy sheets by using hot-pressing technology. Tensile and low-velocity impact tests were performed to evaluate the mechanical properties and fracture behaviour of the magnesium alloy-based FMLs (Mg-FMLs) and to investigate the differences in the fracture behaviour between the Mg-FMLs and traditional Mg-FMLs. Results show that the Mg-FMLs exhibit higher specific tensile strength and specific tensile modulus than traditional Mg-FMLs and that the tensile behaviour of the Mg-FMLs is mainly governed by the CFRP because of the combination of high interlaminar shear properties and thin magnesium alloy layers. The Mg-FMLs exhibit excellent bending stiffness. Hence, no significant difference between the residual displacement d r and indentation depth d i , and the permanent deformation is mainly limited to a small zone surrounding the impact location after the impact tests.

Structural analysis and testing of a carbon-composite wing using fiber Bragg gratings

NASA Astrophysics Data System (ADS)

Nicolas, Matthew James

The objective of this study was to determine the deflected wing shape and the out-of-plane loads of a large-scale carbon-composite wing of an ultralight aerial vehicle using Fiber Bragg Grating (FBG) technology. The composite wing was instrumented with an optical fiber on its top and bottom surfaces positioned over the main spar, resulting in approximately 780 strain sensors bonded to the wings. The strain data from the FBGs was compared to that obtained from four conventional strain gages, and was used to obtain the out-of-plane loads as well as the wing shape at various load levels using NASA-developed real-time load and displacement algorithms. The composite wing measured 5.5 meters and was fabricated from laminated carbon uniaxial and biaxial prepreg fabric with varying laminate ply patterns and wall thickness dimensions. A three-tier whiffletree system was used to load the wing in a manner consistent with an in-flight loading condition.

Optimal cure cycle design of a resin-fiber composite laminate

NASA Technical Reports Server (NTRS)

Hou, Jean W.; Hou, Tan H.; Sheen, Jeen S.

1987-01-01

Fibers reinforced composites are used in many applications. The composite parts and structures are often manufactured by curing the prepreg or unmolded material. The magnitudes and durations of the cure temperature and the cure pressure applied during the cure process have significant consequences on the performance of the finished product. The goal of this study is to exploit the potential of applying the optimization technique to the cure cycle design. The press molding process of a polyester is used as an example. Various optimization formulations for the cure cycle design are investigated. Recommendations are given for further research in computerizing the cure cycle design.

Effects of processing induced defects on laminate response - Interlaminar tensile strength

NASA Technical Reports Server (NTRS)

Gurdal, Zafer; Tomasino, Alfred P.; Biggers, S. B.

1991-01-01

Four different layup methods were used in the present study of the interlaminar tensile strength of AS4/3501-6 graphite-reinforced epoxy as a function of defects from manufacturing-induced porosity. The methods were: (1) baseline hand layup, (2) solvent wipe of prepreg for resin removal, (3) moisture-introduction between plies, and (4) a low-pressure cure cycle. Pore characterization was conducted according to ASTM D-2734. A significant reduction is noted in the out-of-plane tensile strength as a function of increasing void content; the porosity data were used in an empirical model to predict out-of-plane strength as a function of porosity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hopmann, Ch., E-mail: kerschbaum@ikv.rwth-aachen.de; Kerschbaum, M., E-mail: kerschbaum@ikv.rwth-aachen.de; Küsters, K., E-mail: kerschbaum@ikv.rwth-aachen.de

The evaluation of damages caused during processing, assembly or usage of fibre reinforced plastics is still a challenge. The use of inspection technology like ultrasonic scanning enables a detailed damage analysis but requires high investments and trained staff. Therefore, the visual inspection method is widely used. A drawback of this method is the difficult identification of barely visible damages, which can already be detrimental for the structural integrity. Therefore an approach is undertaken to integrate microencapsulated dyes into the laminates of fibre reinforced plastic parts to highlight damages on the surface. In case of a damage, the microcapsules rupture whichmore » leads to a release of the dye and a visible bruise on the part surface. To enable a wide application spectrum for this technology the microcapsules must be processable without rupturing with established manufacturing processes for fibre reinforced plastics. Therefore the incorporation of microcapsules in the filament winding, prepreg autoclave and resin transfer moulding (RTM) process is investigated. The results show that the use of a carrier medium is a feasible way to incorporate the microcapsules into the laminate for all investigated manufacturing processes. Impact testing of these laminates shows a bruise formation on the specimen surface which correlates with the impact energy level. This indicates a microcapsule survival during processing and shows the potential of this technology for damage detection and characterization.« less

An addressable conducting network for autonomic structural health management of composite structures

NASA Astrophysics Data System (ADS)

Takahashi, Kosuke; Park, Jong Se; Hahn, H. Thomas

2010-10-01

The electrical resistance change method (ERCM) has long been an area of interest as an in-service health monitoring system. To apply the ERCM to existing structures, a new concept, the addressable conducting network (ACN), is proposed for autonomic structural health management of graphite/polymer composites. The ACN consists of two sets of conducting lines normal to each other, where one set resides on the top surface of the laminate and the other on the bottom surface. Damage can be detected by monitoring the resistance change 'through the laminate thickness' between two lines. By using a thermally mendable polymer as the matrix, the same conducting lines can be used to supply the electric current needed for resistive heating, thereby allowing the detected damage to be healed. As shown experimentally, the electrical resistance change method using an ACN distinguishes between laminates made of properly and improperly cured prepreg as well as revealing damage generated during three-point bending tests. Finite element analysis was performed to examine the feasibility of the ACN and indicated that the damage can be easily located from the spatial distribution of resistance changes and that the damaged area can be locally heated by supplying a large amount of current to selected conducting lines.

DOE Office of Scientific and Technical Information (OSTI.GOV)

John J. Gangloff Jr; Shatil Sinha; Suresh G. Advani

The formation and transport of voids in composite materials remains a key research area in composite manufacturing science. Knowledge of how voids, resin, and fiber reinforcement propagate throughout a composite material continuum from green state to cured state during an automated tape layup process is key to minimizing defects induced by void-initiated stress concentrations under applied loads for a wide variety of composite applications. This paper focuses on modeling resin flow in a deforming fiber tow during an automated process of partially impregnated thermoset prepreg composite material tapes. In this work, a tow unit cell based model has been presentedmore » that determines the consolidation and impregnation of a thermoset prepreg tape under an input pressure profile. A parametric study has been performed to characterize the behavior of varying tow speed and compaction forces on the degree of consolidation. Results indicate that increased tow consolidation is achieved with slower tow speeds and higher compaction forces although the relationship is not linear. The overall modeling of this project is motivated to address optimization of the 'green state' composite properties and processing parameters to reduce or eliminate 'cured state' defects, such as porosity and de-lamination. This work is partially funded by the Department of Energy under Award number DE-EE0001367.« less

An improved compression molding technology for continuous fiber reinforced composite laminate. Part 1: AS-4/LaRC-TPI 1500 (HFG) Prepreg system

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung; Kidder, Paul W.; Reddy, Rakasi M.

1991-01-01

Poor processability of fiber reinforced high performance polyimide thermoplastic resin composites is a well recognized issue which, in many cases, prohibits the fabrication of composite parts with satisfactorily consolidated quality. Without modifying the resin matrix chemistry, improved compression modeling procedures were proposed and investigated with the AS-4/LaRC-TPI 1500 High Flow Grade (HFG) prepreg system. Composite panels with excellent C-scans can be consistently molded by this method under 700 F and a consolidation pressure as low as 100 psi. A mechanism for the consolidation of the composite under this improved molding technique is discussed. This mechanism reveals that a certain degree of matrix shear and tow filament slippage and nesting between plies occur during consolidation, which leads to a reduction of the consolidating pressure necessary to offset the otherwise intimate inter fiber-fiber contact and consequently achieves a better consolidation quality. Outstanding short beam shear strength and flexural strength were obtained from the molded panels. A prolonged consolidation step under low pressure, i.e., 100 psi at 700 F for 75 minutes, was found to significantly enhance the composite mechanical properties.

Characterization of Hybrid CNT Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Grimsley, Brian W.; Cano, Roberto J.; Kinney, Megan C.; Pressley, James; Sauti, Godfrey; Czabaj, Michael W.; Kim, Jae-Woo; Siochi, Emilie J.

2015-01-01

Carbon nanotubes (CNTs) have been studied extensively since their discovery and demonstrated at the nanoscale superior mechanical, electrical and thermal properties in comparison to micro and macro scale properties of conventional engineering materials. This combination of properties suggests their potential to enhance multi-functionality of composites in regions of primary structures on aerospace vehicles where lightweight materials with improved thermal and electrical conductivity are desirable. In this study, hybrid multifunctional polymer matrix composites were fabricated by interleaving layers of CNT sheets into Hexcel® IM7/8552 prepreg, a well-characterized toughened epoxy carbon fiber reinforced polymer (CFRP) composite. The resin content of these interleaved CNT sheets, as well as ply stacking location were varied to determine the effects on the electrical, thermal, and mechanical performance of the composites. The direct-current electrical conductivity of the hybrid CNT composites was characterized by in-line and Montgomery four-probe methods. For [0](sub 20) laminates containing a single layer of CNT sheet between each ply of IM7/8552, in-plane electrical conductivity of the hybrid laminate increased significantly, while in-plane thermal conductivity increased only slightly in comparison to the control IM7/8552 laminates. Photo-microscopy and short beam shear (SBS) strength tests were used to characterize the consolidation quality of the fabricated laminates. Hybrid panels fabricated without any pretreatment of the CNT sheets resulted in a SBS strength reduction of 70 percent. Aligning the tubes and pre-infusing the CNT sheets with resin significantly improved the SBS strength of the hybrid composite To determine the cause of this performance reduction, Mode I and Mode II fracture toughness of the CNT sheet to CFRP interface was characterized by double cantilever beam (DCB) and end notch flexure (ENF) testing, respectively. Results are compared to the control IM7/8552 laminate.

In-plane shearing of a UD prepreg modeled as transversely isotropic fluid: Comparison between continuous and discontinuous fiber tension approaches

NASA Astrophysics Data System (ADS)

Sorba, Grégoire; Binetruy, Christophe; Chinesta, Francisco

2016-10-01

In this paper a model of Transversely Isotropic Fluid (TIF), developed by Pipkin in [1], is presented and used for example to model in 2D the in-plane shearing of UD prepreg. This problem demonstrates the need to have a continuous fiber tension field over the elements, with the final objective of detecting the wrinkling of fibers during the forming process, at the price of a lower accuracy of the velocity field.

Design and manufacturing of the CFRP lightweight telescope structure

NASA Astrophysics Data System (ADS)

Stoeffler, Guenter; Kaindl, Rainer

2000-06-01

Design of earthbound telescopes is normally based on conventional steel constructions. Several years ago thermostable CFRP Telescope and reflector structures were developed and manufacturing for harsh terrestrial environments. The airborne SOFIA TA requires beyond thermostability an excessive stiffness to mass ratio for the structure fulfilling performance and not to exceed mass limitations by the aircraft Boeing 747 SP. Additional integration into A/C drives design of structure subassemblies. Thickness of CFRP Laminates, either filament wound or prepreg manufactured need special attention and techniques to gain high material quality according to aerospace requirements. Sequential shop assembly of the structure subassemblies minimizes risk for assembling TA. Design goals, optimization of layout and manufacturing techniques and results are presented.

Composite Laminate With Coefficient of Thermal Expansion Matching D263 Glass

NASA Technical Reports Server (NTRS)

Robinson, David; Rodini, Benjamin

2012-01-01

The International X-ray Observatory project seeks to make an X-ray telescope assembly with 14,000 flexible glass segments. The glass used is commercially available SCHOTT D263 glass. Thermal expansion causes the mirror to distort out of alignment. A housing material is needed that has a matching coefficient of thermal expansion (CTE) so that when temperatures change in the X-ray mirror assembly, the glass and housing pieces expand equally, thus reducing or eliminating distortion. Desirable characteristics of this material include a high stiffness/weight ratio, and low density. Some metal alloys show promise in matching the CTE of D263 glass, but their density is high compared to aluminum, and their stiffness/weight ratio is not favorable. A laminate made from carbon fiber reinforced plastic (CFRP) should provide more favorable characteristics, but there has not been any made with the CTE matching D263 Glass. It is common to create CFRP laminates of various CTEs by stacking layers of prepreg material at various angles. However, the CTE of D263 glass is 6.3 ppm/ C at 20 C, which is quite high, and actually unachievable solely with carbon fiber and resin. A composite laminate has been developed that has a coefficient of thermal expansion identical to that of SCHOTT D263 glass. The laminate is made of a combination of T300 carbon fiber, Eglass, and RS3C resin. The laminate has 50% uni-T300 plies and 50% uni-E-glass plies, with each fiber-layer type laid up in a quasi-isotropic laminate for a total of 16 plies. The fiber volume (percent of fiber compared to the resin) controls the CTE to a great extent. Tests have confirmed that a fiber volume around 48% gives a CTE of 6.3 ppm/ C. This is a fairly simple composite laminate, following well established industry procedures. The unique feature of this laminate is a somewhat unusual combination of carbon fiber with E-glass (fiberglass). The advantage is that the resulting CTE comes out to 6.3 ppm/ C at 20 C, which matches D263 glass. The trick with this laminate is to establish the proper fiber volume to get the desired CTE. Laminates were made with several different fiber volumes and coupons were tested to establish the relationship between fiber volume and CTE. Testing proved that fiber volume should be about 48%.

Influence of the Metal Volume Fraction on the maximum deflection and impact load of GLARE plates subjected to low velocity impact

NASA Astrophysics Data System (ADS)

Bikakis, GSE; Savaidis, A.; Zalimidis, P.; Tsitos, S.

2016-11-01

Fiber-metal laminates are hybrid composite materials, consisting of alternating metal layers bonded to fiber-reinforced prepreg layers. GLARE (GLAss REinforced) belongs to this new family of materials. GLARE is the most successful fiber-metal laminate up to now and is currently being used for the construction of primary aerospace structures, such as the fuselage of the Airbus A380 air plane. Impact properties are very important in aerospace structures, since impact damage is caused by various sources, such as maintenance damage from dropped tools, collision between service cars or cargo and the structure, bird strikes and hail. The principal objective of this article is to evaluate the influence of the Metal Volume Fraction (MVF) on the low velocity impact response of GLARE fiber-metal laminates. Previously published differential equations of motion are employed for this purpose. The low velocity impact behavior of various circular GLARE plates is predicted and characteristic values of impact variables, which represent the impact phenomenon, are evaluated versus the corresponding MVF of the examined GLARE material grades. The considered GLARE plates are subjected to low velocity impact under identical impact conditions. A strong effect of the MVF on the maximum impact load and a significant effect on the maximum plate deflection of GLARE plates has been found.

Influence of the Metal Volume Fraction on the permanent dent depth and energy absorption of GLARE plates subjected to low velocity impact

NASA Astrophysics Data System (ADS)

Bikakis, GSE; Savaidis, A.; Zalimidis, P.; Tsitos, S.

2016-11-01

Fiber-metal laminates are hybrid composite materials, consisting of alternating metal layers bonded to fiber-reinforced prepreg layers. GLARE (GLAss REinforced) belongs to this new family of materials. GLARE is the most successful fiber-metal laminate up to now and is currently being used for the construction of primary aerospace structures, such as the fuselage of the Airbus A380 air plane. Impact properties are very important in aerospace structures, since impact damage is caused by various sources, such as maintenance damage from dropped tools, collision between service cars or cargo and the structure, bird strikes and hail. The principal objective of this article is to evaluate the influence of the Metal Volume Fraction (MVF) on the low velocity impact response of GLARE fiber-metal laminates. Previously published differential equations of motion are employed for this purpose. The low velocity impact behavior of various circular GLARE plates is predicted and characteristic values of impact variables, which represent the impact phenomenon, are evaluated versus the corresponding MVF of the examined GLARE material grades. The considered GLARE plates are subjected to low velocity impact under identical impact conditions. A strong effect of the MVF on the maximum impact load and a significant effect on the maximum plate deflection of GLARE plates has been found.

Processing of microencapsulated dyes for the visual inspection of fibre reinforced plastics

NASA Astrophysics Data System (ADS)

Hopmann, Ch.; Kerschbaum, M.; Küsters, K.

2014-05-01

The evaluation of damages caused during processing, assembly or usage of fibre reinforced plastics is still a challenge. The use of inspection technology like ultrasonic scanning enables a detailed damage analysis but requires high investments and trained staff. Therefore, the visual inspection method is widely used. A drawback of this method is the difficult identification of barely visible damages, which can already be detrimental for the structural integrity. Therefore an approach is undertaken to integrate microencapsulated dyes into the laminates of fibre reinforced plastic parts to highlight damages on the surface. In case of a damage, the microcapsules rupture which leads to a release of the dye and a visible bruise on the part surface. To enable a wide application spectrum for this technology the microcapsules must be processable without rupturing with established manufacturing processes for fibre reinforced plastics. Therefore the incorporation of microcapsules in the filament winding, prepreg autoclave and resin transfer moulding (RTM) process is investigated. The results show that the use of a carrier medium is a feasible way to incorporate the microcapsules into the laminate for all investigated manufacturing processes. Impact testing of these laminates shows a bruise formation on the specimen surface which correlates with the impact energy level. This indicates a microcapsule survival during processing and shows the potential of this technology for damage detection and characterization.

Process simulations for manufacturing of thick composites

NASA Astrophysics Data System (ADS)

Kempner, Evan A.

The availability of manufacturing simulations for composites can significantly reduce the costs associated with process development. Simulations provide a tool for evaluating the effect of processing conditions on the quality of parts produced without requiring numerous experiments. This is especially significant in parts that have troublesome features such as large thickness. The development of simulations for thick walled composites has been approached by examining the mechanics of resin flow and fiber deformation during processing, applying these evaluations to develop simulations, and evaluating the simulation with experimental results. A unified analysis is developed to describe the three-dimensional resin flow and fiber preform deformation during processing regardless of the manufacturing process used. It is shown how the generic governing evaluations in the unified analysis can be applied to autoclave molding, compression molding, pultrusion, filament winding, and resin transfer molding. A comparison is provided with earlier models derived individually for these processes. The evaluations described for autoclave curing were used to produce a one-dimensional cure simulation for autoclave curing of thick composites. The simulation consists of an analysis for heat transfer and resin flow in the composite as well as bleeder plies used to absorb resin removed from the part. Experiments were performed in a hot press to approximate curing in an autoclave. Graphite/epoxy laminates of 3 cm and 5 cm thickness were cured while monitoring temperatures at several points inside the laminate and thickness. The simulation predicted temperatures fairly closely, but difficulties were encountered in correlation of thickness results. This simulation was also used to study the effects of prepreg aging on processing of thick composites. An investigation was also performed on filament winding with prepreg tow. Cylinders were wound of approximately 12 mm thickness with pressure gages at the mandrel-composite interface. Cylinders were hoop wound with tensions ranging from 13-34 N. An analytical model was developed to calculate change in stress due to relaxation during winding. Although compressive circumferential stresses occurred throughout each of the cylinders, the magnitude was fairly low.

Advanced tow placement of composite fuselage structure

NASA Technical Reports Server (NTRS)

Anderson, Robert L.; Grant, Carroll G.

1992-01-01

The Hercules NASA ACT program was established to demonstrate and validate the low cost potential of the automated tow placement process for fabrication of aircraft primary structures. The program is currently being conducted as a cooperative program in collaboration with the Boeing ATCAS Program. The Hercules advanced tow placement process has been in development since 1982 and was developed specifically for composite aircraft structures. The second generation machine, now in operation at Hercules, is a production-ready machine that uses a low cost prepreg tow material form to produce structures with laminate properties equivalent to prepreg tape layup. Current program activities are focused on demonstration of the automated tow placement process for fabrication of subsonic transport aircraft fuselage crown quadrants. We are working with Boeing Commercial Aircraft and Douglas Aircraft during this phase of the program. The Douglas demonstration panels has co-cured skin/stringers, and the Boeing demonstration panel is an intricately bonded part with co-cured skin/stringers and co-bonded frames. Other aircraft structures that were evaluated for the automated tow placement process include engine nacelle components, fuselage pressure bulkheads, and fuselage tail cones. Because of the cylindrical shape of these structures, multiple parts can be fabricated on one two placement tool, thus reducing the cost per pound of the finished part.

Analytical design model for a piezo-composite unimorph actuator and its verification using lightweight piezo-composite curved actuators

NASA Astrophysics Data System (ADS)

Yoon, K. J.; Park, K. H.; Lee, S. K.; Goo, N. S.; Park, H. C.

2004-06-01

This paper describes an analytical design model for a layered piezo-composite unimorph actuator and its numerical and experimental verification using a LIPCA (lightweight piezo-composite curved actuator) that is lighter than other conventional piezo-composite type actuators. The LIPCA is composed of top fiber composite layers with high modulus and low CTE (coefficient of thermal expansion), a middle PZT ceramic wafer, and base layers with low modulus and high CTE. The advantages of the LIPCA design are to replace the heavy metal layer of THUNDER by lightweight fiber-reinforced plastic layers without compromising the generation of high force and large displacement and to have design flexibility by selecting the fiber direction and the number of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use a resin prepreg system. A piezo-actuation model for a laminate with piezo-electric material layers and fiber composite layers is proposed to predict the curvature and residual stress of the LIPCA. To predict the actuation displacement of the LIPCA with curvature, a finite element analysis method using the proposed piezo-actuation model is introduced. The predicted deformations are in good agreement with the experimental ones.

Fabrication of Polyimide-Matrix/Carbon and Boron-Fiber Tape

NASA Technical Reports Server (NTRS)

Belvin, Harry L.; Cano, Roberto J.; Treasure, Monte; Shahood, Thomas W.

2007-01-01

The term HYCARB denotes a hybrid composite of polyimide matrices reinforced with carbon and boron fibers. HYCARB and an improved process for fabricating dry HYCARB tapes have been invented in a continuing effort to develop lightweight, strong composite materials for aerospace vehicles. Like other composite tapes in this line of development, HYCARB tapes are intended to be used to build up laminated structures having possibly complex shapes by means of automated tow placement (ATP) - a process in which a computer-controlled multiaxis machine lays down prepreg tape or tows. The special significance of the present process for making dry HYCARB for ATP is that it contributes to the reduction of the overall cost of manufacturing boron-reinforced composite-material structures while making it possible to realize increased compression strengths. The present process for making HYCARB tapes incorporates a "wet to dry" process developed previously at Langley Research Center. In the "wet to dry" process, a flattened bundle of carbon fiber tows, pulled along a continuous production line between pairs of rollers, is impregnated with a solution of a poly(amide acid) in N-methyl-2-pyrrolidinone (NMP), then most of the NMP is removed by evaporation in hot air. In the present case, the polyamide acid is, more specifically, that of LaRC. IAX (or equivalent) thermoplastic polyimide, and the fibers are, more specifically, Manganite IM7 (or equivalent) polyacrylonitrile- based carbon filaments that have a diameter of 5.2 m and are supplied in 12,000-filament tows. The present process stands in contrast to a prior process in which HYCARB tape was made by pressing boron fibers into the face of a wet carbon-fiber/ poly(amide acid) prepreg tape . that is, a prepreg tape from which the NMP solvent had not been removed. In the present process, one or more layer(s) of side-by-side boron fibers are pressed between dry prepreg tapes that have been prepared by the aforementioned gwet to dry h process. The multilayer tape is then heated to imidize the matrix material and remove most of the remaining solvent, and is pressed to consolidate the multiple layers into a dense tape. For tests, specimens of HYCARB tapes and laminated composite panels made from HYCARB tape were prepared as follows: HYCARB tapes were fabricated as described above. Each panel was made by laying down ten layers of tape, containing, variously, one, two, or three boron-fiber plies and the remainder carbon- fiber-only plies (see figure). Each panel was made by laying down ten layers of tape. Each panel was then cured by heating to a temperature of 225 C for 15 minutes, then pressing at 200 psi (A1.4 MPa) while heating to 371 C, holding at 371 C for 1 hour, then continuing to hold pressure during cooling. Control specimens that were otherwise identical except that they did not contain boron fibers also were prepared. In room-temperature flexural tests, the HYCARB specimens performed comparably to the control specimens; in room-temperature, open-hole compression tests, the HYCARB specimens performed slightly better, by amounts that increased with boron content.

Viscoelastic processing and characterization of high-performance polymeric composite systems

NASA Astrophysics Data System (ADS)

Buehler, Frederic Ulysse

2000-10-01

Fiber reinforced composites, a combination of reinforcing fiber and resin matrix, offer many advantages over traditional materials, and have therefore found wide application in the aerospace and sporting goods industry. Among the advantages that composite materials offer, the most often cited are weight saving, high modulus, high strength-to-weight ratio, corrosion resistance, and fatigue resistance. As much as their attributes are desirable, composites are difficult to process due to their heterogeneous, anisotropic, and viscoelastic nature. It is therefore not surprising that the interrelationship between structure, property, and process is not fully understood. Consequently, the major purpose of this research work was to investigate this interrelationship, and ways to scale it to utilization. First, four prepreg materials, which performed differently in the manufacturing of composite parts, but were supposedly identical, were characterized. The property variations that were found among these prepregs in terms of tack and frictional resistance assessed the need for improved understanding of the prepregging process. Therefore, the influence of the processing parameters on final prepreg quality were investigated, and led to the definition of more adequate process descriptors. Additionally, one of the characterization techniques used in this work, temperature modulated differential scanning calorimetry, was examined in depth with the development of a mathematical model. This model, which enabled the exploration of the relationship between user parameters, sample thermophysical properties, and final results, was then compared to literature data. Collectively, this work explored and identified the key connectors between process, structure, and property as they relate to the manufacturing, design, and performance of composite materials.

Prediction of thermal cycling induced cracking in polmer matrix composites

NASA Technical Reports Server (NTRS)

Mcmanus, Hugh L.

1994-01-01

The work done in the period August 1993 through February 1994 on the 'Prediction of Thermal Cycling Induced Cracking In Polymer Matrix Composites' program is summarized. Most of the work performed in this period, as well as the previous one, is described in detail in the attached Master's thesis, 'Analysis of Thermally Induced Damage in Composite Space Structures,' by Cecelia Hyun Seon Park. Work on a small thermal cycling and aging chamber was concluded in this period. The chamber was extensively tested and calibrated. Temperatures can be controlled very precisely, and are very uniform in the test chamber. Based on results obtained in the previous period of this program, further experimental progressive cracking studies were carried out. The laminates tested were selected to clarify the differences between the behaviors of thick and thin ply layers, and to explore other variables such as stacking sequence and scaling effects. Most specimens tested were made available from existing stock at Langley Research Center. One laminate type had to be constructed from available prepreg material at Langley Research Center. Specimens from this laminate were cut and prepared at MIT. Thermal conditioning was carried out at Langley Research Center, and at the newly constructed MIT facility. Specimens were examined by edge inspection and by crack configuration studies, in which specimens were sanded down in order to examine the distribution of cracks within the specimens. A method for predicting matrix cracking due to decreasing temperatures and/or thermal cycling in all plies of an arbitrary laminate was implemented as a computer code. The code also predicts changes in properties due to the cracking. Extensive correlations between test results and code predictions were carried out. The computer code was documented and is ready for distribution.

Double-Vacuum-Bag Process for Making Resin-Matrix Composites

NASA Technical Reports Server (NTRS)

Bradford, Larry J.

2007-01-01

A double-vacuum-bag process has been devised as a superior alternative to a single-vacuum-bag process used heretofore in making laminated fiber-reinforced resin-matrix composite-material structural components. This process is applicable to broad classes of high-performance matrix resins including polyimides and phenolics that emit volatile compounds (solvents and volatile by-products of resin-curing chemical reactions) during processing. The superiority of the double-vacuum-bag process lies in enhanced management of the volatile compounds. Proper management of volatiles is necessary for making composite-material components of high quality: if not removed and otherwise properly managed, volatiles can accumulate in interior pockets as resins cure, thereby forming undesired voids in the finished products. The curing cycle for manufacturing a composite laminate containing a reactive resin matrix usually consists of a two-step ramp-and-hold temperature profile and an associated single-step pressure profile as shown in Figure 1. The lower-temperature ramp-and-hold step is known in the art as the B stage. During the B stage, prepregs are heated and volatiles are generated. Because pressure is not applied at this stage, volatiles are free to escape. Pressure is applied during the higher-temperature ramp-and-hold step to consolidate the laminate and impart desired physical properties to the resin matrix. The residual volatile content and fluidity of the resin at the beginning of application of consolidation pressure are determined by the temperature and time parameters of the B stage. Once the consolidation pressure is applied, residual volatiles are locked in. In order to produce a void-free, high-quality laminate, it is necessary to design the curing cycle to obtain the required residual fluidity and the required temperature at the time of application of the consolidation pressure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahn, K.J.; Seferis, J.C.; Pelton, T.

A compression to tension apparatus and a methodology capable of measuring prepreg tack have been analyzed in detail in order to establish fundamental material and operating characteristics. Both intrinsic and extrinsic parameters influencing prepreg tack were identified and analyzed using commercially available carbon fiber/epoxy prepregs and mechanical testing equipment. Two different factors, (1) contact (or wetting) area of adjacent prepreg plies and (2) viscoelastic properties of the prepreg, were found to control prepreg tack. At low temperatures, contact area was the main deformation controlling step, while at high temperatures, the viscoelastic property of the prepreg was found to be dominant.more » Both interlaminar and intralaminar deformations were observed depending on the prepreg systems examined as well as the operating conditions of the test. In addition, hold time, hold pressure, loading rate, resin content, and out-time were also found to affect prepreg tack. Energy of separation, which may be viewed as a descriptor of prepreg tack, was observed to increase with increasing hold time, hold pressure, and loading rate. Energy of separation also showed a maximum value at a specific resin content for a specific prepreg system, while it decreased with increasing prepreg out-time due to prepreg surface characteristic change rather than bulk physical aging. Conclusively, it was observed that prepreg tack must be viewed as an extrinsic, bulk, but surface-sensitive, viscoelastic property which depends on material as well as operating conditions.« less

Multi-Scale Low-Entropy Method for Optimizing the Processing Parameters during Automated Fiber Placement

PubMed Central

Han, Zhenyu; Sun, Shouzheng; Fu, Hongya; Fu, Yunzhong

2017-01-01

Automated fiber placement (AFP) process includes a variety of energy forms and multi-scale effects. This contribution proposes a novel multi-scale low-entropy method aiming at optimizing processing parameters in an AFP process, where multi-scale effect, energy consumption, energy utilization efficiency and mechanical properties of micro-system could be taken into account synthetically. Taking a carbon fiber/epoxy prepreg as an example, mechanical properties of macro–meso–scale are obtained by Finite Element Method (FEM). A multi-scale energy transfer model is then established to input the macroscopic results into the microscopic system as its boundary condition, which can communicate with different scales. Furthermore, microscopic characteristics, mainly micro-scale adsorption energy, diffusion coefficient entropy–enthalpy values, are calculated under different processing parameters based on molecular dynamics method. Low-entropy region is then obtained in terms of the interrelation among entropy–enthalpy values, microscopic mechanical properties (interface adsorbability and matrix fluidity) and processing parameters to guarantee better fluidity, stronger adsorption, lower energy consumption and higher energy quality collaboratively. Finally, nine groups of experiments are carried out to verify the validity of the simulation results. The results show that the low-entropy optimization method can reduce void content effectively, and further improve the mechanical properties of laminates. PMID:28869520

Multi-Scale Low-Entropy Method for Optimizing the Processing Parameters during Automated Fiber Placement.

PubMed

Han, Zhenyu; Sun, Shouzheng; Fu, Hongya; Fu, Yunzhong

2017-09-03

Automated fiber placement (AFP) process includes a variety of energy forms and multi-scale effects. This contribution proposes a novel multi-scale low-entropy method aiming at optimizing processing parameters in an AFP process, where multi-scale effect, energy consumption, energy utilization efficiency and mechanical properties of micro-system could be taken into account synthetically. Taking a carbon fiber/epoxy prepreg as an example, mechanical properties of macro-meso-scale are obtained by Finite Element Method (FEM). A multi-scale energy transfer model is then established to input the macroscopic results into the microscopic system as its boundary condition, which can communicate with different scales. Furthermore, microscopic characteristics, mainly micro-scale adsorption energy, diffusion coefficient entropy-enthalpy values, are calculated under different processing parameters based on molecular dynamics method. Low-entropy region is then obtained in terms of the interrelation among entropy-enthalpy values, microscopic mechanical properties (interface adsorbability and matrix fluidity) and processing parameters to guarantee better fluidity, stronger adsorption, lower energy consumption and higher energy quality collaboratively. Finally, nine groups of experiments are carried out to verify the validity of the simulation results. The results show that the low-entropy optimization method can reduce void content effectively, and further improve the mechanical properties of laminates.

High-temperature resins

NASA Technical Reports Server (NTRS)

Serafini, T. T.

1982-01-01

The basic chemistry, cure processes, properties, and applications of high temperature resins known as polyimides are surveyed. Condensation aromatic polymides are prepared by reacting aromatic diamines with aromatic dianhydrides, aromatic tetracarboxylic acids, or with dialkyl esters of aromatic tetracarboxylic acids, depending on the intended end use. The first is for coatings or films while the latter two are more suitable for polyimide matrix resins. Prepreg solutions are made by dissolving reactants in an aprotic solvent, and advances in the addition of a diamine on the double bond and radical polymerization of the double bond are noted to have yielded a final cure product with void-free characteristics. Attention is given to properties of the Skybond, Pyralin, and NR-150B polyimide prepreg materials and characteristics of aging in the NP-150 polyimides. Finally, features of the NASA-developed PMR polyimides are reviewed.

Numerical Investigation of T-joints with 3D Four Directional Braided Composite Fillers Under Tensile Loading

NASA Astrophysics Data System (ADS)

Li, Xiao-kang; Liu, Zhen-guo; Hu, Long; Wang, Yi-bo; Lei, Bing; Huang, Xiang

2017-02-01

Numerical studied on T-joints with three-dimensional four directional (3D4D) braided composite fillers was presented in this article. Compared with conventional unidirectional prepreg fillers, the 3D braided composite fillers have excellent ability to prevent crack from penetrating trigone fillers, which constantly occurred in the conventional fillers. Meanwhile, the 3D braided composite fillers had higher fiber volume fraction and eliminated the fiber folding problem in unidirectional prepreg fillers. The braiding technology and mechanical performance of 3D4D braided fillers were studied. The numerical model of carbon fiber T-joints with 3D4D braided composite fillers was built by finite element analysis software. The damage formation, extension and failing process of T-joints with 3D4D braided fillers under tensile load were investigated. Further investigation was extended to the effect of 3D4D braided fillers with different braiding angles on mechanical behavior of the T-joints. The study results revealed that the filling area was the weakest part of the T-joints where the damage first appeared and the crack then rapidly spread to the glue film around the filling area and the interface between over-laminate and soleplate. The 3D4D braided fillers were undamaged and the braiding angle change induced a little effect on the bearing capacity of T-joints.

76 FR 21333 - Laminated Woven Sacks From the People's Republic of China: Final Results of Second Antidumping...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-15

... the People's Republic of China: Final Results of Second Antidumping Duty Administrative Review AGENCY... from the People's Republic of China (``PRC''). See Laminated Woven Sacks From the People's Republic of... to these reviews are addressed in the ``Laminated Woven Sacks from the People's Republic of China...

Experimental investigation of defect criticality in FRP laminate composites

NASA Astrophysics Data System (ADS)

Joyce, Peter James

1999-11-01

This work examines the defect criticality of fiber reinforced polymer Composites. The objective is to determine the sensitivity of the finished composite to various process-induced defects. This work focuses on two different classes of process-induced defects; (1) fiber waviness in high performance carbon-fiber reinforced unidirectional composites and (2) void volume in low cost glass-fabric reinforced composites. The role of fiber waviness in the compressive response of unidirectional composites has been studied by a number of other investigators. Because of difficulties associated with producing real composites with varying levels of fiber waviness, most experimental studies of fiber waviness have evaluated composites with artificially induced fiber waviness. Furthermore, most experimental studies have been concentrated on the effects of out-of-plane fiber waviness. The objective of this work is to evaluate the effects of in-plane fiber waviness naturally occurring in autoclave consolidated thermoplastic laminates. The first phase of this project involved the development of a simple technique for measuring the resulting fiber waviness levels. An experimental investigation of the compression strength reduction in composites with in-plane fiber waviness followed. The experimental program included carbon-fiber reinforced thermoplastic composites manufactured from prepreg tape by hand layup, and carbon-fiber and glass-fiber reinforced composites manufactured from an experimental powder towpreg by filament winding and autoclave consolidation. The compression specimens exhibited kink band failure in the prepreg composite and varying amounts of longitudinal splitting and kink banding in the towpreg composites. The compression test results demonstrated the same trend as predicted by microbudding theory but the overall quantitative correlation was poor. The second thrust of this research evaluated void effects in resin transfer molded composites. Much of the existing literature in this area has focused on composites with unidirectional fiber reinforcement. In this program, the influence of void volume on the mechanical behavior of RTM composites with plain weave reinforcement was investigated. The experimental program demonstrated that the effects of void volume are negligible in terms of the fiber dominated properties. Interlaminar shear strength tests on the other hand demonstrated a linear dependence on void volume in the range tested.

Multipurpose Prepregging Machine

NASA Technical Reports Server (NTRS)

Johnston, N. J.; Wilkinson, Steven; Marchello, J. M.; Dixon, D.

1995-01-01

Machine designed and built for variety of uses involving coating or impregnating ("prepregging") fibers, tows, yarns, or webs or tapes made of such fibrous materials with thermoplastic or thermosetting resins. Prepreg materials produced used to make matrix/fiber composite materials. Comprises modules operated individually, sequentially, or simultaneously, depending on nature of specific prepreg material and prepregging technique used. Machine incorporates number of safety features.

Manufacturing and testing of active composite panels with embedded piezoelectric sensors and actuators: wires out by molded-in holes

NASA Astrophysics Data System (ADS)

Ghasemi-Nejhad, Mehrdad N.; Pourjalali, Saeid

2003-08-01

This work presents manufacturing and testing of active composite panels (ACPs) with embedded piezoelectric sensors and actuators. The composite material employed here is a plain weave carbon epoxy prepreg fabric with about 0.33 mm ply thickness. The piezoelectric patches employed here are Continuum Control Corporation, CCC, (recently Continuum Photonics, Inc) active fiber composite patches with 0.33 mm thickness, i.e. close to the composite ply thickness. Composite cut-out layers are used to fill the space around the embedded piezoelectric patches to minimize the problems associated with ply drops in composites. The piezoelectric patches were embedded inside the composite laminate. High-temperature wires were soldered to the piezoelectric leads, insulated from the carbon substructure by high-temperature materials, and were taken out of the composite laminates employing a molded-in hole technique that reduces the stress concentration as opposed to a drilled hole, and thereby enhancing the performance of the composite structure. The laminated ACP"s were co-cured inside an autoclave employing the cure cycle recommended by the composite material supplier. The curie temperature of the embedded piezoelectric patches should be well above the curing temperature of the composite materials as was the case here. The manufactured ACP beams and plates were trimmed and then tested for their functionality. Vibration suppression as well as simultaneous vibration suppression and precision positioning tests, using PID control as well as Hybrid Adaptive Control techniques were successfully conducted on the manufactured ACP beams and their functionality were demonstrated. Recommendations on the use of this embedding technique for ACPs are provided.

Novel cost controlled materials and processing for primary structures

NASA Technical Reports Server (NTRS)

Dastin, S. J.

1993-01-01

Textile laminates, developed a number of years ago, have recently been shown to be applicable to primary aircraft structures for both small and large components. Such structures have the potential to reduce acquisition costs but require advanced automated processing to keep costs controlled while verifying product reliability and assuring structural integrity, durability and affordable life-cycle costs. Recently, resin systems and graphite-reinforced woven shapes have been developed that have the potential for improved RTM processes for aircraft structures. Ciba-Geigy, Brochier Division has registered an RTM prepreg reinforcement called 'Injectex' that has shown effectivity for aircraft components. Other novel approaches discussed are thermotropic resins producing components by injection molding and ceramic polymers for long-duration hot structures. The potential of such materials and processing will be reviewed along with initial information/data available to date.

Microstructure of the smart composite structures with embedded fiber optic sensing nerves

NASA Astrophysics Data System (ADS)

Liu, Jingyuan; Luo, Fei; Li, Changchun; Ma, Naibin

1997-11-01

The composite structures with embedded optical fiber sensors construct a smart composite structure system, which may have the characteristics of the in-service self-measurement, self- recognition and self-judgement action. In the present work, we studied the microstructures of carbon/epoxy composite laminates with embedded sensing optical fibers, and the integration of optical fiber with composites was also discussed. The preliminary experiment results show that because of the difference between the sensing optical fibers and the reinforcing fibers in their size, the microstructure of the composites with embedded optical fibers will produce partial local changes in the area of embedded optical fiber, these changes may affect the mechanical properties of composite structures. When the optical fibers are embedded parallel to the reinforcing fibers, due to the composite prepregs are formed under a press action during its curing process, the reinforcing fibers can be arranged equably around the optical fibers. But when the optical fibers are embedded perpendicularly to the reinforcement fibers, the resin rich pocket will appear in the composite laminates surrounding the embedded optical fiber. The gas holes will be easily produced in these zones which may produce a premature failure of the composite structure. The photoelastic experiments are also given in the paper.

Effect of surface treatment on the corrosion properties of magnesium-based fibre metal laminate

NASA Astrophysics Data System (ADS)

Zhang, X.; Zhang, Y.; Ma, Q. Y.; Dai, Y.; Hu, F. P.; Wei, G. B.; Xu, T. C.; Zeng, Q. W.; Wang, S. Z.; Xie, W. D.

2017-02-01

The surface roughness, weight of phosphating film and wettability of magnesium alloy substrates after abrasion and phosphating treatment were investigated in this work. The interfacial bonding and corrosion properties of a magnesium-based fibre metal laminate (MgFML) were analysed. The results showed that the wettability of the magnesium alloy was greatly influenced by the surface roughness, and the rough surface possessed a larger surface energy and better wettability. The surface energy and wettability of the magnesium alloy were significantly improved by the phosphating treatment. After phosphating for 5 min, a phosphating film with a double-layer structure was formed on the magnesium substrate, and the weight of the phosphating film and the surface energy reached their maximum values. The surface energies of the phosphated substrate after abrasion with #120 and #3000 grit abrasive papers were 84.31 mJ/m2 and 83.65 mJ/m2, respectively. The wettability of the phosphated magnesium was significantly better than the abraded magnesium. The phosphated AZ31B sheet had a better corrosion resistance than the abraded AZ31B sheet within short times. The corrosion resistance of the magnesium alloy was greatly increased by being composited with glass fibre/epoxy prepregs.

Maternal prepregnancy overweight and offspring fatness and blood pressure: role of physical activity.

PubMed

Eisenman, Joey C; Sarzynski, Mark A; Tucker, Jerod; Heelan, Kate A

2010-08-01

The purpose of this study was to examine if offspring physical activity may affect the relationship between maternal overweight and offspring fatness and blood pressure (BP). Subjects included 144 maternal-child pairs (n = 74 boys and 70 girls, mean age = 7.3 yrs). Maternal prepregnancy BMI was determined by self-report. Offspring characteristics included resting systolic and diastolic BP, body fatness by dual energy x-ray absorbtiometry, and moderate-to-vigorous physical activity (MVPA) using the Actigraph accelerometer. Children whose mothers were overweight or obese prepregnancy (Prepreg OW) were significantly larger and fatter than children from mothers with a normal prepregnancy BMI (Prepreg NORM). Prepreg OW children also had higher mean arterial pressure than Prepreg NORM children. BP values were not different across maternal Prepreg BMI/ MVPA groups. Percent fat was significantly different across Prepreg BMI/MVPA groups. Prepreg OW children that did not meet the daily recommended value of MVPA were the fattest. Prepreg OW children that attained (3)60 min of MVPA/ day had a mean percent body fat that was similar to Prepreg NORM children of either MVPA group.

Recycling of Reinforced Plastics

NASA Astrophysics Data System (ADS)

Adams, R. D.; Collins, Andrew; Cooper, Duncan; Wingfield-Digby, Mark; Watts-Farmer, Archibald; Laurence, Anna; Patel, Kayur; Stevens, Mark; Watkins, Rhodri

2014-02-01

This work has shown is that it is possible to recycle continuous and short fibre reinforced thermosetting resins while keeping almost the whole of the original material, both fibres and matrix, within the recyclate. By splitting, crushing hot or cold, and hot forming, it is possible to create a recyclable material, which we designate a Remat, which can then be used to remanufacture other shapes, examples of plates and tubes being demonstrated. Not only can remanufacturing be done, but it has been shown that over 50 % of the original mechanical properties, such as the E modulus, tensile strength, and interlaminar shear strength, can be retained. Four different forms of composite were investigated, a random mat Glass Fibre Reinforced Plastic (GFRP) bathroom component and boat hull, woven glass and carbon fibre cloth impregnated with an epoxy resin, and unidirectional carbon fibre pre-preg. One of the main factors found to affect composite recyclability was the type of resin matrix used in the composite. Thermoset resins tested were shown to have a temperature range around the Glass Transition Temperature (Tg) where they exhibit ductile behaviour, hence aiding reforming of the material. The high-grade carbon fibre prepreg was found to be less easy to recycle than the woven of random fibre laminates. One method of remanufacturing was by heating the Remat to above its glass transition temperature, bending it to shape, and then cooling it. However, unless precautions are taken, the geometric form may revert. This does not happen with the crushed material.

Materials for Heated Head Automated Thermoplastic Tape Placement

NASA Technical Reports Server (NTRS)

Jensen, Brian J.; Kinney, Megan C.; Cano, Roberto J.; Grimsley, Brian W.

2012-01-01

NASA Langley Research Center (LaRC) is currently pursuing multiple paths to develop out of autoclave (OOA) polymeric composite materials and processes. Polymeric composite materials development includes the synthesis of new and/or modified thermosetting and thermoplastic matrix resins designed for specific OOA processes. OOA processes currently under investigation include vacuum bag only (VBO) prepreg/composite fabrication, resin transfer molding (RTM), vacuum assisted resin transfer molding (VARTM) and heated head automated thermoplastic tape placement (HHATP). This paper will discuss the NASA Langley HHATP facility and capabilities and recent work on characterizing thermoplastic tape quality and requirements for quality part production. Samples of three distinct versions of APC-2 (AS4/PEEK) thermoplastic dry tape were obtained from two materials vendors, TENCATE, Inc. and CYTEC Engineered Materials** (standard grade and an experimental batch). Random specimens were taken from each of these samples and subjected to photo-microscopy and surface profilometry. The CYTEC standard grade of APC-2 tape had the most voids and splits and the highest surface roughness and/or waviness. Since the APC-2 tape is composed of a thermoplastic matrix, it offers the flexibility of reprocessing to improve quality, and thereby improve final quality of HHATP laminates. Discussions will also include potential research areas and future work that is required to advance the state of the art in the HHATP process for composite fabrication.

78 FR 19209 - Laminated Woven Sacks From the People's Republic of China: Final Results of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-29

... the People's Republic of China: Final Results of Antidumping Duty Administrative Review; 2011-2012...'') from the People's Republic of China (``PRC''). The period of review (``POR'') is August 1, 2011... the ``Final Results of Review'' section below. \\1\\ See Laminated Woven Sacks From the People's...

PMR-15 polyimide modifications for improved prepreg tack

NASA Technical Reports Server (NTRS)

Vannucci, R. D.

1982-01-01

The use of mixed solvents and of modified monomeric ester reactants was investigated as a means of improving the tack and drape retention characteristics of PMR-15 polyimide prepreg. Methanol, ethanol, 1-propanol and 1-butanol were used to prepare the esters, prepreg solutions, and T-300 graphite fabric and Celion 6000 unidirectional fiber prepregs. The tack retention characteristics of the T-300 fabric prepreg after exposure to simulated use conditions were determined using a simple lap shear test. Drape was qualitatively assessed by visually monitoring the deformability of the prepreg. Thermo-oxidative stability and mechanical properties retention of the Celion 6000 grahite fiber composites were determined as a function of exposure time in air at 600 F.

Influence of prepreg characteristics on stamp consolidation

NASA Astrophysics Data System (ADS)

Slange, T. K.; Warnet, L. L.; Grouve, W. J. B.; Akkerman, R.

2017-10-01

Stamp forming is a rapid manufacturing technology used to shape flat blanks of thermoplastic composite material into three-dimensional components. The development of automated lay-up technologies further extends the applicability of stamp forming by allowing rapid lay-up of tailored blanks and partial preconsolidation. This partial preconsolidation makes the influence of prepreg more critical compared to conventional preconsolidation methods which provide full preconsolidation. This paper aims to highlight consolidation challenges that can appear when stamp forming blanks manufactured by automated lay-up. Important prepreg characteristics were identified based on an experimental study where a comparison was made between various prepreg in their as-received, deconsolidated and stamp consolidated state. It was found that adding up small thickness variations across the width of a prepreg when stacking plies into a blank by automated lay-up can cause non-uniform consolidation. Additionally, deconsolidation of the prepreg does not seem to obstruct interlaminar bonding, while intralaminar voids initially present in a prepreg cannot be removed during stamp forming. An additional preconsolidation step after automated lay-up seems necessary to remove blank thickness variations and intralaminar voids for the current prepregs. Eliminating this process step and the successful combination of rapid automated lay-up and stamp forming requires prepregs which are void-free and have less thickness variation.

Modeling of fracture and durability of paste-bonded composite joints subjected to hygro-thermal-mechanical loading

NASA Astrophysics Data System (ADS)

Harris, David Lee

The objective of the research is to characterize the behavior of composite/composite joints with paste adhesive using both experimental testing and analytical modeling. In comparison with the conventional tape adhesive, joining composites using paste adhesive provides several advantages. The carbon fiber laminate material systems employed in this study included IM7 carbon fibers and 977-3 epoxy matrix assembled in prepreg tape, and AS4 carbon fibers and 977-3 epoxy matrix as a five-harness satin weave. The adhesive employed was EA 9394 epoxy. All laminates and test specimens were fabricated and inspected by Boeing using their standard propriety procedures. Three types of test specimens were used in the program. They were bonded double-lap shear (DLS), bonded double cantilever beam (DCB) and bonded interlaminar tension (ILT) specimens. A group of specimens were conditioned at elevated temperature and humidity in an environmental chamber at Boeing's facility and their moisture absorption recorded with time. Specimens were tested at room temperature dry and elevated temperatures. DCB and DLS specimens were tested in fatigue as well as static conditions. Two-dimensional finite element models of the three configurations were developed for determining stresses and strains using the ABAQUS finite element package code. Due to symmetry, only the one-half of the specimen needed to be considered thus reducing computational time. The effect of the test fixture is not taken into account instead equivalent distributed stresses are applied directly on the composite laminates. For each of the specimen, the distribution of Mises stress and the first strain invariant J1 are obtained to identify potential failure locations within a specimen.

Strain-energy release rate analysis of a laminate with a postbuckled delamination

NASA Technical Reports Server (NTRS)

Whitcomb, John D.; Shivakumar, K. N.

1987-01-01

The objectives are to present the derivation of the new virtual crack closure technique, evaluate the accuracy of the technique, and finally to present the results of a limited parametric study of laminates with a postbuckled delamination. Although the new virtual crack closure technique is general, only homogeneous, isotropic laminates were analyzed. This was to eliminate the variation of flexural stiffness with orientation, which occurs even for quasi-isotropic laminates. This made it easier to identify the effect of geometrical parameters on G. The new virtual crack closure technique is derived. Then the specimen configurations are described. Next, the stress analyses is discussed. Finally, the virtual crack closure technique is evaluated and then used to calculate the distribution of G along the delamination front of several laminates with a postbuckled delamination.

Pin bearing evaluation of LTM25 composite materials

NASA Technical Reports Server (NTRS)

Shah, C. H.; Postyn, A. S.

1996-01-01

This report summarizes pin bearing evaluations of LTM25 composite materials. Northrop Grumman Corporation conducted pin bearing testing and fabricate two panels from composite materials that cure at low temperatures. These materials are being incorporated into Unmanned Aerial Vehicles (UAVS) to reduce manufacturing costs since they allow the use of low-cost tooling and facilities. Two composite prepreg product forms were evaluated; MR50/LTM25 unidirectional tape, batch 2881vd and CFS003/LTM25 woven cloth, batch 2216. Northrop Grumman fabricated, machined, and tested specimens to determine the bearing strength in accordance with MIL-HDBK-17D, Volume 1, Section 7.2.4. Quasi-isotropic laminates from the two product forms were fabricated for these tests. In addition, 2 quasi-isotropic panels of dimensions 12 in. x 28 in. were fabricated (one each from the two product forms), inspected, and shipped to NASA Langley for further evaluation.

Investigation of the effects of NaOH dopant level on the physical and mechanical properties of carbon/phenolic composite material

NASA Technical Reports Server (NTRS)

Clinton, R. G., Jr.

1985-01-01

The near-catastrophic erosion of the STS-8A solid rocket booster nozzle was the instigating factor in the recent, and on-going, intensive investigation of carbon/phenolic composite materials. Much of this effort has been focused on the effect of sodium contamination on the carbon fibers. It is known that sodium acts as a catalyst in the oxidation of the fibers at elevated temperatures. A study was undertaken to determine what changes were caused by variation in sodium content. Investigations were conducted in three areas: (1) phenolic resin; (2) carbon/phenolic prepreg; and (3) cured laminates. Due to the exploratory nature of the studies, a variety of tests in addition to those normally run in production facilities were considered. The experimental methodologies and results of these experiments are discussed, and recommendations for improving techniques and extending the research program are presented.

Development of new and improved polymer matrix resin systems, phase 1

NASA Technical Reports Server (NTRS)

Hsu, M. S.

1983-01-01

Vinystilbazole (vinylstryrylpyridine) and vinylpolystyrulpyridine were prepared for the purpose of modifying bismaleimide composite resins. Cure studies of resins systems were investigated by differential scanning calorimetry. The vinylstyrylpyridine-modified bismaleimide composite resins were found to have lower cure and gel temperatures, and shorter cure times than the corresponding unmodified composite resins. The resin systems were reinforced with commercially avialable satin-weave carbon cloth. Prepregs were fabricated by solvent or hot melt techniques. Thermal stability, flammability, moisture absorption, and mechanical properties of the composites (such as flexural strength, modulus, tensile and short beam shear strength) were determined. Composite laminates showed substantial improvements in both processability and mechanical properties compared to he bismaleimide control systems. The vinylstyrylpyridine modified bismaleimide resins can be used as advanced matrix resins for graphite secondary structures where ease of processing, fireworthiness, and high temperature stability are required for aerospace applications.

Thermoplastic matrix composite processing model

NASA Technical Reports Server (NTRS)

Dara, P. H.; Loos, A. C.

1985-01-01

The effects the processing parameters pressure, temperature, and time have on the quality of continuous graphite fiber reinforced thermoplastic matrix composites were quantitatively accessed by defining the extent to which intimate contact and bond formation has occurred at successive ply interfaces. Two models are presented predicting the extents to which the ply interfaces have achieved intimate contact and cohesive strength. The models are based on experimental observation of compression molded laminates and neat resin conditions, respectively. Identified as the mechanism explaining the phenomenon by which the plies bond to themselves is the theory of autohesion (or self diffusion). Theoretical predictions from the Reptation Theory between autohesive strength and contact time are used to explain the effects of the processing parameters on the observed experimental strengths. The application of a time-temperature relationship for autohesive strength predictions is evaluated. A viscoelastic compression molding model of a tow was developed to explain the phenomenon by which the prepreg ply interfaces develop intimate contact.

Spring-back simulation of unidirectional carbon/epoxy L- shaped laminate composites manufactured through autoclave processing

NASA Astrophysics Data System (ADS)

Nasir, M. N. M.; Mezeix, L.; Aminanda, Y.; Seman, M. A.; Rivai, A.; Ali, K. M.

2016-02-01

This paper presents an original method in predicting the spring-back for composite aircraft structures using non-linear Finite Element Analysis (FEA) and is an extension of the previous accompanying study on flat geometry samples. Firstly, unidirectional prepreg lay-up samples are fabricated on moulds with different corner angles (30°, 45° and 90°) and the effect on spring-back deformation are observed. Then, the FEA model that was developed in the previous study on flat samples is utilized. The model maintains the physical mechanisms of spring-back such as ply stretching and tool-part interface properties with the additional mechanism in the corner effect and geometrical changes in the tool, part and the tool-part interface components. The comparative study between the experimental data and FEA results show that the FEA model predicts adequately the spring-back deformation within the range of corner angle tested.

Graphite nanoplatelet enabled embeddable fiber sensor for in situ curing monitoring and structural health monitoring of polymeric composites.

PubMed

Luo, Sida; Liu, Tao

2014-06-25

A graphite nanoplatelet (GNP) thin film enabled 1D fiber sensor (GNP-FibSen) was fabricated by a continuous roll-to-roll spray coating process, characterized by scanning electron microscopy and Raman spectroscopy and evaluated by coupled electrical-mechanical tensile testing. The neat GNP-FibSen sensor shows very high gauge sensitivity with a gauge factor of ∼17. By embedding the sensor in fiberglass prepreg laminate parts, the dual functionalities of the GNP-FibSen sensor were demonstrated. In the manufacturing process, the resistance change of the embedded sensor provides valuable local resin curing information. After the manufacturing process, the same sensor is able to map the strain/stress states and detect the failure of the host composite. The superior durability of the embedded GNP-FibSen sensor has been demonstrated through 10,000 cycles of coupled electromechanical tests.

Structural Acoustic Response of a Shape Memory Alloy Hybrid Composite Panel (Lessons Learned)

NASA Technical Reports Server (NTRS)

Turner, Travis L.

2002-01-01

This study presents results from an effort to fabricate a shape memory alloy hybrid composite (SMAHC) panel specimen and test the structure for dynamic response and noise transmission characteristics under the action of thermal and random acoustic loads. A method for fabricating a SMAHC laminate with bi-directional SMA reinforcement is described. Glass-epoxy unidirectional prepreg tape and Nitinol ribbon comprise the material system. Thermal activation of the Nitinol actuators was achieved through resistive heating. The experimental hardware required for mechanical support of the panel/actuators and for establishing convenient electrical connectivity to the actuators is presented. Other experimental apparatus necessary for controlling the panel temperature and acquiring structural acoustic data are also described. Deficiency in the thermal control system was discovered in the process of performing the elevated temperature tests. Discussion of the experimental results focuses on determining the causes for the deficiency and establishing means for rectifying the problem.

Characterization of polymer composites during autoclave manufacturing by Fourier transform Raman spectroscopy

NASA Astrophysics Data System (ADS)

Farquharson, Stuart; Smith, Wayne W.; Rigas, Elias J.; Granville, Dana

2001-02-01

12 The superior engineering properties of fiber reinforced polymer matrix composites, primarily the high strength-to- weight ratio, make them suitable to applications ranging from sporting goods to aircraft components (e.g. helicopter blades). Unfortunately, consistent fabrication of components with desired mechanical properties has proven difficult, and has led to high production costs. This is largely due to the inability to monitor and control polymer cure, loosely defined as the process of polymer chain extension and cross- linking. Even with stringent process control, slight variations in the pre-polymer formulations (e.g. prepreg) can influence reaction rates, reaction mechanisms, and ultimately, product properties. In an effort to optimize the performance of thermoset composite, we have integrated fiber optic probes between the plies of laminates and monitored cure by Raman spectroscopy, with the eventual goal of process control. Here we present real-time measurements of two high performance aerospace companies cured within an industrial autoclave.

Mechanical strength of an ITER coil insulation system under static and dynamic load after reactor irradiation

NASA Astrophysics Data System (ADS)

Bittner-Rohrhofer, K.; Humer, K.; Weber, H. W.; Hamada, K.; Sugimoto, M.; Okuno, K.

2002-12-01

The insulation system proposed by the Japanese Home Team for the ITER Toroidal Field coil (TF coil) is a T-glass-fiber/Kapton reinforced epoxy prepreg system. In order to assess the material performance under the actual operating conditions of the coils, the insulation system was irradiated in the TRIGA reactor (Vienna) to a fast neutron fluence of 2×10 22 m -2 ( E>0.1 MeV). After measurements of swelling, all mechanical tests were carried out at 77 K. Tensile and short-beam-shear (SBS) tests were performed under static loading conditions. In addition, tension-tension fatigue experiments up to about 10 6 cycles were made. The laminate swells in the through-thickness direction by 0.86% at the highest dose level. The fatigue tests as well as the static tests do not show significant influences of the irradiation on the mechanical behavior of this composite.

Failure of composite plates under static biaxial planar loading

NASA Technical Reports Server (NTRS)

Waas, Anthony M.; Khamseh, Amir R.

1992-01-01

The project involved detailed investigations into the failure mechanisms in composite plates as a function of hole size (holes centrally located in the plates) under static loading. There were two phases to the project, the first dealing with uniaxial loads along the fiber direction, and the second dealing with coplanar biaxial loading. Results for the uniaxial tests have been reported and published previously, thus this report will place emphasis on the second phase of the project, namely the biaxial tests. The composite plates used in the biaxial loading experiments, as well as the uniaxial, were composed of a single ply unidirectional graphite/epoxy prepreg sandwiched between two layers of transparent thermoplastic. This setup enabled us to examine the failure initiation and propagation modes nondestructively, during the test. Currently, similar tests and analysis of results are in progress for graphite/epoxy cruciform shaped flat laminates. The results obtained from these tests will be available at a later time.

Structural acoustic response of a shape memory alloy hybrid composite panel (lessons learned)

NASA Astrophysics Data System (ADS)

Turner, Travis L.

2002-07-01

This study presents results from an effort to fabricate a shape memory alloy hybrid composite (SMAHC) panel specimen and test the structure for dynamic response and noise transmission characteristics under the action of thermal and random acoustic loads. A method for fabricating a SMAHC laminate with bi-directional SMA reinforcement is described. Glass-epoxy unidirectional prepreg tape and Nitinol ribbon comprise the material system. Thermal activation of the Nitinol actuators was achieved through resistive heating. The experimental hardware required for mechanical support of the panel/actuators and for establishing convenient electrical connectivity to the actuators is presented. Other experimental apparatus necessary for controlling the panel temperature and acquiring structural acoustic data are also described. Deficiency in the thermal control system was discovered in the process of performing the elevated temperature tests. Discussion of the experimental results focuses on determining the causes for the deficiency and establishing means for rectifying the problem.

Investigation of compaction and permeability during the out-of-autoclave and vacuum-bag-only manufacturing of a laminate composite with aligned carbon nanofibers

NASA Astrophysics Data System (ADS)

Mann, Erin

Both industry and commercial entities are in the process of using more lightweight composites. Fillers, such as fibers, nanofibers and other nanoconstituents in polymer matrix composites have been proven to enhance the properties of composites and are still being studied in order to optimize the benefits. Further optimization can be studied during the manufacturing process. The air permeability during the out-of-autoclave-vacuum-bag-only (OOA-VBO) cure method is an important property to understand during the optimization of manufacturing processes. Changes in the manufacturing process can improve or decrease composite quality depending on the ability of the composite to evacuate gases such as air and moisture during curing. Therefore, in this study, the axial permeability of a prepreg stack was experimentally studied. Three types of samples were studied: control (no carbon nanofiber (CNF) modification), unaligned CNF modified and aligned CNF modified samples.

Manufacture of fiber-epoxy test specimens: Including associated jigs and instrumentation

NASA Technical Reports Server (NTRS)

Mathur, S. B.; Felbeck, D. K.

1980-01-01

Experimental work on the manufacture and strength of graphite-epoxy composites is considered. The correct data and thus a true assessment of the strength properties based on a proper and scientifically modeled test specimen with engineered design, construction, and manufacture has led to claims of a very broad spread in optimized values. Such behavior is in the main due to inadequate control during manufacture of test specimen, improper curing, and uneven scatter in the fiber orientation. The graphite fibers are strong but brittle. Even with various epoxy matrices and volume fraction, the fracture toughness is still relatively low. Graphite-epoxy prepreg tape was investigated as a sandwich construction with intermittent interlaminar bonding between the laminates in order to produce high strength, high fracture toughness composites. The quality and control of manufacture of the multilaminate test specimen blanks was emphasized. The dimensions, orientation and cure must be meticulous in order to produce the desired mix.

The behavior of delaminations in composite materials - experimental results

NASA Astrophysics Data System (ADS)

Chermoshentseva, A. S.; Pokrovskiy, A. M.; Bokhoeva, L. A.

2016-02-01

Delamination is one of the most common failure modes of composite materials. It may occur as a consequence of imperfections in the production process or the effects of external factors during the operational life of the composite laminates, such as the impact by foreign objects. This paper presents the results of mechanical tests and the optimum degrees of filling the composite materials (CM) with hydrophobic powder (Tarkosil T-20) depending on the latter mass concentration. The results present test samples of the CM with the underlying interlayer defects. The samples were fabricated of twenty-ply pre-preg (fiberglass or carbon fiber). The industrial grade glass is T-25 (VM) specification 6-11-380-76. The composite materials have nanosized additives in structure. The volume concentration of nanopowders is varying from 0.1% to 0.5%. This kind of research has been done for the first time.

Development of quality assurance methods for epoxy graphite prepreg

NASA Technical Reports Server (NTRS)

Chen, J. S.; Hunter, A. B.

1982-01-01

Quality assurance methods for graphite epoxy/prepregs were developed. Liquid chromatography, differential scanning calorimetry, and gel permeation chromatography were investigated. These methods were applied to a second prepreg system. The resin matrix formulation was correlated with mechanical properties. Dynamic mechanical analysis and fracture toughness methods were investigated. The chromatography and calorimetry techniques were all successfully developed as quality assurance methods for graphite epoxy prepregs. The liquid chromatography method was the most sensitive to changes in resin formulation. The were also successfully applied to the second prepreg system.

PMR polyimide prepreg with improved tack characteristics

NASA Technical Reports Server (NTRS)

Serafini, T. T.; Delvigs, P.

1976-01-01

Current PMR Polyimide prepreg technology utilizes methanol or ethanol solvents for preparation of the PMR prepreg solutions. The volatility of these solvents limits the tack and drape retention characteristics of unprotected prepreg exposed to ambient conditions. Studies conducted to achieve PMR 15 Polyimide prepreg with improved tack and drape characteristics were described. Improved tack and drape retention were obtained by incorporation of an additional monomer. The effects of various levels of the added monomer on the thermo-oxidative stability and mechanical properties of graphite fiber reinforced PMR 15 composites exposed and tested at 316 C (600 F) were discussed.

Additive Manufacturing of SiC Based Ceramics and Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Halbig, Michael Charles; Singh, Mrityunjay

2015-01-01

Silicon carbide (SiC) ceramics and SiC fiber reinforcedSiC ceramic matrix composites (SiCSiC CMCs) offer high payoff as replacements for metals in turbine engine applications due to their lighter weight, higher temperature capability, and lower cooling requirements. Additive manufacturing approaches can offer game changing technologies for the quick and low cost fabrication of parts with much greater design freedom and geometric complexity. Four approaches for developing these materials are presented. The first two utilize low cost 3D printers. The first uses pre-ceramic pastes developed as feed materials which are converted to SiC after firing. The second uses wood containing filament to print a carbonaceous preform which is infiltrated with a pre-ceramic polymer and converted to SiC. The other two approaches pursue the AM of CMCs. The first is binder jet SiC powder processing in collaboration with rp+m (Rapid Prototyping+Manufacturing). Processing optimization was pursued through SiC powder blending, infiltration with and without SiC nano powder loading, and integration of nanofibers into the powder bed. The second approach was laminated object manufacturing (LOM) in which fiber prepregs and laminates are cut to shape by a laser and stacked to form the desired part. Scanning electron microscopy was conducted on materials from all approaches with select approaches also characterized with XRD, TGA, and bend testing.

LSP Composite Susbtrate Manufacturing Processing Guide

NASA Technical Reports Server (NTRS)

Kovach, Daniel J.; Griess, Kenneth H.

2013-01-01

This document is intended to define Carbon Fiber Reinforced Plastic (CFRP) test panel configurations that can be employed for the purposes of evaluating the protection capabilities of Lightning Strike Protection (LSP) materials developed by the Aerospace Industry. The configurations are intended to provide consistent behavior in their response to simulated lightning strikes at pre-defined levels when tested by a capable vendor according to a test procedure written to enable consistent results (ref section 2.1.2). In response to an attachment of a simulated lightning strike on a CFRP panel, one can expect to see various levels of ablation and delamination, both through the thickness of the panel and with respect to the amount of panel surface area that exhibits damage. Panel configurations defined in this document include: An "unprotected" configuration 128694-1 (ref section 4.1), consisting of a cured CFRP laminate stackup of tape and fabric prepregs, coated with a typical aerospace primer and paint finishing scheme, attached to aluminum grounding bars intended to draw electrical current from the lightning attachment point to the panel edges and thus to ground. A "protected" configuration 128694-2 (ref section 4.1), wherein a layer of an LSP material form often used in the Aerospace Industry is included in the laminate stackup prior to cure. The CFRP materials, finishes and grounding arrangement for ths configuration are the same as for the "unprotected" configuration.

Cohesive Laws for Analyzing Through-Crack Propagation in Cross Ply Laminates

NASA Technical Reports Server (NTRS)

Bergan, Andrew C.; Davila, Carlos G.

2015-01-01

The laminate cohesive approach (LCA) is a methodology for the experimental characterization of cohesive through-the-thickness damage propagation in fiber-reinforced polymer matrix composites. LCA has several advantages over other existing approaches for cohesive law characterization, including: visual measurements of crack length are not required, structural effects are accounted for, and LCA can be applied when the specimen is too small to achieve steady-state fracture. In this work, the applicability of this method is investigated for two material systems: IM7/8552, a conventional prepreg, and AS4/VRM34, a non-crimp fabric cured using an out-of-autoclave process. The compact tension specimen configuration is used to propagate stable Mode I damage. Trilinear cohesive laws are characterized using the fracture toughness and the notch tip opening displacement. Test results are compared for the IM7/8552 specimens with notches machined by waterjet and by wire slurry saw. It is shown that the test results are nearly identical for both notch tip preparations methods, indicating that significant specimen preparation time and cost savings can be realized by using the waterjet to notch the specimen instead of the wire slurry saw. The accuracy of the cohesive laws characterized herein are assessed by reproducing the structural response of the test specimens using computational methods. The applicability of the characterization procedure for inferring lamina fracture toughness is also discussed.

Design and Analysis of Tow-Steered Composite Shells Using Fiber Placement

NASA Technical Reports Server (NTRS)

Wu, K. Chauncey

2008-01-01

In this study, a sub-scale advanced composite shell design is evaluated to determine its potential for use on a future aircraft fuselage. Two composite shells with the same nominal 8-ply [+/-45/+/-Theta](sub s) layup are evaluated, where Theta indicates a tow-steered ply. To build this shell, a fiber placement machine would be used to steer unidirectional prepreg tows as they are placed around the circumference of a 17-inch diameter right circular cylinder. The fiber orientation angle varies continuously from 10 degrees (with respect to the shell axis of revolution) at the crown, to 45 degrees on the side, and back to 10 degrees on the keel. All 24 tows are placed at each point on every fiber path in one structure designated as the shell with overlaps. The resulting pattern of tow overlaps causes the laminate thickness to vary between 8 and 16 plies. The second shell without tow overlaps uses the capability of the fiber placement machine to cut and add tows at any point along the fiber paths to fabricate a shell with a nearly uniform 8-ply laminate thickness. Issues encountered during the design and analysis of these shells are presented and discussed. Static stiffness and buckling loads of shells with tow-steered layups are compared with the performance of a baseline quasi-isotropic shell using both finite element analyses and classical strength of materials theory.

Cryomilling of Thermoplastic Powder for Prepreg Applications

DTIC Science & Technology

2013-09-01

Cryomilling of Thermoplastic Powder for Prepreg Applications by Brian Parquette, Anit Giri, Daniel J. O’Brien, Sarah Brennan, Kyu Cho, and...MD 21005-5066 ARL-TR-6591 September 2013 Cryomilling of Thermoplastic Powder for Prepreg Applications Brian Parquette and Sarah Brennan...COVERED (From - To) 1 March 2012–30 May 2013 4. TITLE AND SUBTITLE Cryomilling of Thermoplastic Powder for Prepreg Applications 5a. CONTRACT

Altering lamina assembly reveals lamina-dependent and -independent functions for A-type lamins.

PubMed

Zwerger, Monika; Roschitzki-Voser, Heidi; Zbinden, Reto; Denais, Celine; Herrmann, Harald; Lammerding, Jan; Grütter, Markus G; Medalia, Ohad

2015-10-01

Lamins are intermediate filament proteins that form a fibrous meshwork, called the nuclear lamina, between the inner nuclear membrane and peripheral heterochromatin of metazoan cells. The assembly and incorporation of lamin A/C into the lamina, as well as their various functions, are still not well understood. Here, we employed designed ankyrin repeat proteins (DARPins) as new experimental tools for lamin research. We screened for DARPins that specifically bound to lamin A/C, and interfered with lamin assembly in vitro and with incorporation of lamin A/C into the native lamina in living cells. The selected DARPins inhibited lamin assembly and delocalized A-type lamins to the nucleoplasm without modifying lamin expression levels or the amino acid sequence. Using these lamin binders, we demonstrate the importance of proper integration of lamin A/C into the lamina for nuclear mechanical properties and nuclear envelope integrity. Finally, our study provides evidence for cell-type-specific differences in lamin functions. © 2015. Published by The Company of Biologists Ltd.

Altering lamina assembly reveals lamina-dependent and -independent functions for A-type lamins

PubMed Central

Zwerger, Monika; Roschitzki-Voser, Heidi; Zbinden, Reto; Denais, Celine; Herrmann, Harald; Lammerding, Jan; Grütter, Markus G.; Medalia, Ohad

2015-01-01

ABSTRACT Lamins are intermediate filament proteins that form a fibrous meshwork, called the nuclear lamina, between the inner nuclear membrane and peripheral heterochromatin of metazoan cells. The assembly and incorporation of lamin A/C into the lamina, as well as their various functions, are still not well understood. Here, we employed designed ankyrin repeat proteins (DARPins) as new experimental tools for lamin research. We screened for DARPins that specifically bound to lamin A/C, and interfered with lamin assembly in vitro and with incorporation of lamin A/C into the native lamina in living cells. The selected DARPins inhibited lamin assembly and delocalized A-type lamins to the nucleoplasm without modifying lamin expression levels or the amino acid sequence. Using these lamin binders, we demonstrate the importance of proper integration of lamin A/C into the lamina for nuclear mechanical properties and nuclear envelope integrity. Finally, our study provides evidence for cell-type-specific differences in lamin functions. PMID:26275827

Biotransformation of an uncured composite material

NASA Technical Reports Server (NTRS)

Welsh, Clement J.; Glass, Michael J.; Cheslack, Brian; Pryor, Robert; Tran, Duan K.; Bowers-Irons, Gail

1994-01-01

The feasibility of biologically degrading prepreg wastes was studied. The work was conducted with the intention of obtaining baseline data that would facilitate the achievement of two long-range goals. These goals are: (1) the biological remediation of the hazardous components in the prepreg wastes, and (2) providing the potential for recycling the prepreg waste fibers. The experiments examined a prepreg that employs an bismaleimide resin system. Initial results demonstrated an obvious deterioration of the prepreg material when incubated with several bacterial strains. The most active cultures were identified as a mixture of 'Bacillus cereus' and 'Pseudomonas sp'. Gas chromatography analyses revealed seven primary compounds in the resin mixture. Biotransformation studies, using the complete prepreg material, demonstrated on obvious loss of all seven organic compounds. Gas chromatography-mass spectrometry analyses resulted in structure assignments for the two primary components of the resin. Both were analogs of Bisphenol A; one being bismaleimide, and the other being Bisphenol A containing a diglycidyl moiety. The 'diglycidyl analog' was purified using thin-layer chromatography and the biotransformation of this compound (at 27 ug/ml bacterial culture) was monitored. After a seven-day incubation, approximately 40% of the organic compound was biotransformed. These results demonstrate the biotransformation of the prepreg resin and indicate that biological remediation of the prepreg wastes is feasible.

PMR Polyimide prepreg with improved tack characteristics. [Polymerization of Monomer Reactants applications to fiber reinforced plastics

NASA Technical Reports Server (NTRS)

Serafini, T. T.; Delvigs, P.

1978-01-01

Current PMR Polyimide prepreg technology utilizes methanol or ethanol solvents for preparation of the PMR prepreg solutions. The volatility of these solvents limits the tack and drape retention characteristics of unprotected prepreg exposed to ambient conditions. Studies conducted to achieve PMR 15 Polyimide prepreg with improved tack and drape characteristics are described. Improved tack and drape retention were obtained by incorporation of an additional monomer. The effects of various levels of the added monomer on the thermo-oxidative stability and mechanical properties of graphite fiber reinforced PMR 15 composites exposed and tested at 316 C (600 F) are discussed.

Time Domain Reflectometry for Damage Detection of Laminated CFRP plate

DTIC Science & Technology

2011-08-18

Final Report PROJECT ID: AOARD-10-4112 Title: Time Domain Reflectometry for damage detection of laminated CFRP plate Researcher: Professor Akira...From July/2010 To July/2011 Abstract Recently, high toughness Carbon Fiber Reinforced Polymer (CFRP) laminates are used to primary structures. The...large laminated CFRP structures. In the previous study, Time Domain Reflectometry (TDR) method is adopted for the detection of the fiber breakages of

Efficient prepreg recycling at low temperatures

NASA Astrophysics Data System (ADS)

Pannkoke, Kord; Oethe, Marcus; Busse, Jürgen

When manufacturing fibre reinforced plastics engineers are still confronted with a lack of experience concerning efficient recycling methods for prepreg cutting waste. Normally, the prepregs are cured and subsequently milled to use them as a filler material for polymers. However, this method is expensive and it is difficult to find applications for the milled FRP. An alternative method to recycle CFRP prepregs will be presented in this paper. Cutting the uncured prepreg waste was done by means of a saw mill which was cooled down to low temperatures. Working temperatures of -30°C are sufficient to harden the uncured resin and to achieve cuttable prepregs. Furthermore, post-curing during the cutting process is avoided with this technique. The result is a `cotton'-like matted structure with random fibre orientation and fibre length distribution. Subsequent curing was done by means of a press and an autoclave, respectively. It will be shown by means of tension and bending tests that low-temperature cutting of uncured prepregs is a way to partly conserve the high valuation of FRP during recycling. Furthermore, it offers possibilities for various applications.

Dynamics-based Nondestructive Structural Monitoring Teclrniques

DTIC Science & Technology

2012-05-21

plate made from AS4/8552-2 carbon epoxy prepregs . The layup sequence: was [(0/45/90/-45)S]2 as illustrated in Figure 3.37. Each layer had the...at Penn State. Hexcel AS4/8552 unidirectional carbon/epoxy prepregs were used in the fabrication as raw materials. The prepregs were cut in pieces...with different fiber orientations and 132 stacked together following different stacking sequences. The stacked prepregs then went into a vacuum

Dynamics-based Nondestructive Structural Monitoring Techniques

DTIC Science & Technology

2012-06-21

made from AS4/8552-2 carbon epoxy prepregs . The layup sequence: was [(0/45/90/-45)S]2 as illustrated in Figure 3.37. Each layer had the thickness of...using facilities available at Penn State. Hexcel AS4/8552 unidirectional carbon/epoxy prepregs were used in the fabrication as raw materials. The... prepregs were cut in pieces with different fiber orientations and 132 stacked together following different stacking sequences. The stacked prepregs

Processing parameters for filament winding thick-section PEEK/carbon fiber composites

NASA Astrophysics Data System (ADS)

Colton, J.; Leach, D.

1992-12-01

The consolidation pressure and winding speed for thermoplastic filament winding were studied. Thermoplastic composite parts were manufactured from tape prepreg (APC-2); powder-coated, semi-consolidated towpreg; and commingled fiber towpreg. The material used was carbon fiber (AS-4) (60 vol pct) in a PEEK matrix. The parts made were open-ended cylinders of the three materials, 177.8-mm ID, 228.6 mm long, 17 plies thick with a 0 deg lay-up angle; and rings, 50 plies of APC-2 thick, 6.35 mm wide (one strip wide), 177.8-mm ID, and a lay-up of 0 deg. Their quality was determined by surface finish and void percentage. The tubes made from APC-2 appeared to have the best quality of the three prepregs. For the rings, the speed of lay-down had a significant effect on both the final width of the parts and on the percentage of voids. The pressure of the roller had a significant effect on the final widths at a 99 percent confidence level, but a significant effect on the percentage of voids at only a 95 percent confidence level.

Processing parameters for thermoplastic filament winding

NASA Astrophysics Data System (ADS)

Colton, J.; Leach, D.

The consolidation pressure and winding speed for thermoplastic filament winding were studied. Thermoplastic composite parts were manufactured from tape prepreg (APC-2); powder-coated, semiconsolidated towpreg; and commingled fiber towpeg. The material used was carbon fiber (AS-4) (60 vol pct) in a PEEK matrix. The parts made were open-ended cylinders of the three materials, 177.8 mmID, 228.6 mm long, 17 plies thick with a 0 deg lay-up angle; and rings, 50 plies of APC-2 thick, 6.35 mm wide (one strip wide), 177.8 mm ID, and a lay-up of 0 deg. Their quality was determined by surface finish and void percentage. The tubes made from APC-2 appeared to have the best quality of the three prepregs. For the rings, the speed of lay down had a significant effect on both the final width of the parts and on the percentage of voids. The pressure of the roller had a significant effect on the final widths at a 99 percent confidence level, but only a significant effect on the percentage of voids at a 95 percent confidence level.

Thermally Conductive Structural 2D Composite Materials

DTIC Science & Technology

2012-08-14

through-thickness thermal conductivity of up to 20 W/m.K. This novel structural prepreg material will be developed through engineering of an optimal fiber...with an EPON 862/Epikure W epoxy resin system to form unidirectional prepreg tapes. Each prepreg was then cut to 6 inch by 6 inch plies and...impregnated with an EPON 862/Epikure W epoxy resin system. The unidirectional prepreg tape was then cut into twelve 6 inch by 6 inch plies and

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Weizhao; Ren, Huaqing; Lu, Jie

This paper reports several characterization methods of the properties of the uncured woven prepreg during the preforming process. The uniaxial tension, bias-extension, and bending tests are conducted to measure the in-plane properties of the material. The friction tests utilized to reveal the prepreg-prepreg and prepreg-forming tool interactions. All these tests are performed within the temperature range of the real manufacturing process. The results serve as the inputs to the numerical simulation for the product prediction and preforming process parameter optimization.

Damage-Survivable and Damage-Tolerant Laminated Composites with Optimally Placed Piezoelectric Layers

DTIC Science & Technology

1992-11-13

AD-A269 879 Damage-Survivable j and Damage-Tolerant Laminated Composites .4.. with Optimally placed Piezoelectric Layers Final Report No. 1 S. P...Damage Surviable and Damage-Tolerant Laminated Composites With Optimally Placed Piezoelectric Layers 12. PERSONAL AUTHOR(S) S.P. Joshi, W.S. Chan ൕa...block number) The main objective of the research is to assure that the embedded sensors/actuators in a smart laminated composite structure are damage

Characterisation of Ductile Prepregs

NASA Astrophysics Data System (ADS)

Pinto, F.; White, A.; Meo, M.

2013-04-01

This study is focused on the analysis of micro-perforated prepregs created from standard, off the shelf prepregs modified by a particular laser process to enhance ductility of prepregs for better formability and drapability. Fibres are shortened through the use of laser cutting in a predetermined pattern intended to maintain alignment, and therefore mechanical properties, yet increase ductility at the working temperature. The increase in ductility allows the product to be more effectively optimised for specific forming techniques. Tensile tests were conducted on several specimens in order to understand the ductility enhancement offered by this process with different micro-perforation patterns over standard prepregs. Furthermore, the effects of forming temperature was also analysed to assess the applicability of this material to hot draping techniques and other heated processes.

Experimental Investigation of Widespread Delamination Damage to Composite Materials Caused by Radiant Heating

DTIC Science & Technology

2013-06-30

Rev. E) 2002. 7. RM-3002 Bismaleimide (BMI) Prepreg , Product Information, Renegade Materials Corporation, Revision Date: 16-May-2012 KOA 16... prepregs /polyimide- prepregs . Renegade Materials Corporation Website, Accessed June 20, 2013. 9. Shen, C. and G.S. Springer, “Moisture Absorption and

Resin-Powder Dispenser

NASA Technical Reports Server (NTRS)

Standfield, Clarence E.

1994-01-01

Resin-powder dispenser used at NASA's Langley Research Center for processing of composite-material prepregs. Dispenser evenly distributes powder (resin polymer and other matrix materials in powder form) onto wet uncured prepregs. Provides versatility in distribution of solid resin in prepreg operation. Used wherever there is requirement for even, continuous distribution of small amount of powder.

A Dry Powder Process for Preparing Uni-Tape Prepreg from Polymer Powder Coated Filamentary Towpregs

NASA Technical Reports Server (NTRS)

Wilkinson, Steven P. (Inventor); Johnston, Norman J. (Inventor); Marchello, Joseph M. (Inventor)

1995-01-01

A process for preparing uni-tape prepreg from polymer powder coated filamentary towpregs is provided. A plurality of polymer powder coated filamentary towpregs are provided. The towpregs are collimated so that each towpreg is parallel. The sandwich is heated to a temperature wherein the polymer flows and intimately contacts the filaments and pressure is repeatedly applied perpendicularly to the sandwich with a longitudinal oscillating action wherein the filaments move apart and the polymer wets the filaments forming a uni-tape prepreg. The uni-tape prepreg is subsequently cooled.

Processing and Damage Tolerance of Continuous Carbon Fiber Composites Containing Puncture Self-Healing Thermoplastic Matrix

NASA Technical Reports Server (NTRS)

Grimsley, Brian W.; Gordon, Keith L.; Czabaj, Michael W.; Cano, Roberto J.; Siochi, Emilie J.

2012-01-01

Research at NASA Langley Research Center (NASA LaRC) has identified several commercially available thermoplastic polymers that self-heal after ballistic impact and through-penetration. One of these resins, polybutadiene graft copolymer (PB(sub g)), was processed with unsized IM7 carbon fibers to fabricate reinforced composite material for further evaluation. Temperature dependent characteristics, such as the degradation point, glass transition (T(sub g)), and viscosity of the PBg polymer were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic parallel plate rheology. The PBg resin was processed into approximately equal to 22.0 cm wide unidirectional prepreg tape in the NASA LaRC Advanced Composites Processing Research Laboratory. Data from polymer thermal characterization guided the determination of a processing cycle used to fabricate quasi-isotropic 32-ply laminate panels in various dimensions up to 30.5cm x 30.5cm in a vacuum press. The consolidation quality of these panels was analyzed by optical microscopy and acid digestion. The process cycle was further optimized based on these results and quasi-isotropic, [45/0/-45/90]4S, 15.24cm x 15.24cm laminate panels were fabricated for mechanical property characterization. The compression strength after impact (CAI) of the IM7/pBG composites was measured both before and after an elevated temperature and pressure healing cycle. The results of the processing development effort of this composite material as well as the results of the mechanical property characterization are presented in this paper.

Fracture toughness of fibrous composite materials

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1984-01-01

Laminates with various proportions of 0 deg, 45 deg, and 90 deg plies were fabricated from T300/5208 and T300/BP-907 graphite/epoxy prepreg tape material. The fracture toughness of each laminate orientation or lay-up was determined by testing center-cracked specimens, and it was also predicted with the general fracture-toughness parameter. The predictions were good except when crack-tip splitting was large, at which time the toughness and strengths tended to be underpredicted. By using predictions, a parametric study was also made of factors that influence fracture toughness. Fiber and matrix properties as well as lay-up were investigated. Without crack-tip splitting, fracture toughness increases in proportion to fiber strength and fiber volume fraction, increases linearly with E(22)/E(11), is largest when the modulus for non-0 deg fibers is greater than that of 0 deg fibers, and is smallest for 0(m)/90(p)(s) lay-ups. (The E(11) and E(22) are Young's moduli of the lamina parallel to and normal to the direction of the fibers, respectively). For a given proportion of 0 deg plies, the most notch-sensitive lay-ups are 0(m)/90(p)(s) and the least sensitive are 0(m)/45(n)(s) and alpha(s). Notch sensitivity increases with the proportion of 0 deg plies and decreases with alpha. Strong, tough matrix materials, which inhibit crack-tip splitting, generally lead to minimum fracture toughness.

Fiber reinforced PMR polyimide composites

NASA Technical Reports Server (NTRS)

Cavano, P. J.; Winters, W. E.

1978-01-01

Commercially obtained PMR-15 polyimide prepregs with S-glass and graphite fiber reinforcements were evaluated along with in-house prepared glass and graphite cloth PMR 2 materials. A novel autoclave approach was conceived and used to demonstrate that both the PMR systems respond to 1.4 MPa (200 psi) autoclave pressures to produce void free composites equivalent to die molded laminates. Isothermal gravimetric analysis and subsequent mechanical property tests indicated that the PMR 2 system was significantly superior in thermo-oxidative stability, and that S-glass reinforcements may contribute to the accelerated degradation of composites at 316 C (600 F) when compared to graphite fiber reinforced composites. Fully reversed bending fatigue experiments were conducted with a type of fixture unused for organic matrix composites. These studies indicated that the graphite fiber composites were clearly superior in fatigue resistance to the glass fiber reinforced material and that PMR matrix composite systems yield performance of the same order as composite materials employing other families of matrices.

Enhancement of the in-plane shear properties of carbon fiber composites containing carbon nanotube mats

NASA Astrophysics Data System (ADS)

Kim, Hansang

2015-01-01

The in-plane shear property of carbon fiber laminates is one of the most important structural features of aerospace and marine structures. Fiber-matrix debonding caused by in-plane shear loading is the major failure mode of carbon fiber composites because of the stress concentration at the interfaces. In this study, carbon nanotube mats (CNT mat) were incorporated in two different types of carbon fiber composites. For the case of woven fabric composites, mechanical interlocking between the CNTs and the carbon fibers increased resistance to shear failure. However, not much improvement was observed for the prepreg composites as a result of incorporation of the CNT mats. The reinforcement mechanism of the CNT mat layer was investigated by a fractographic study using scanning electron microscopy. In addition, the CNT mat was functionalized by three different methods and the effectiveness of the functionalization methods was determined and the most appropriate functionalization method for the CNT mat was air oxidation.

Development of a Fully Automated Guided Wave System for In-Process Cure Monitoring of CFRP Composite Laminates

NASA Technical Reports Server (NTRS)

Hudson, Tyler B.; Hou, Tan-Hung; Grimsley, Brian W.; Yaun, Fuh-Gwo

2016-01-01

A guided wave-based in-process cure monitoring technique for carbon fiber reinforced polymer (CFRP) composites was investigated at NASA Langley Research Center. A key cure transition point (vitrification) was identified and the degree of cure was monitored using metrics such as amplitude and time of arrival (TOA) of guided waves. Using an automated system preliminarily developed in this work, high-temperature piezoelectric transducers were utilized to interrogate a twenty-four ply unidirectional composite panel fabricated from Hexcel (Registered Trademark) IM7/8552 prepreg during cure. It was shown that the amplitude of the guided wave increased sharply around vitrification and the TOA curve possessed an inverse relationship with degree of cure. The work is a first step in demonstrating the feasibility of transitioning the technique to perform in-process cure monitoring in an autoclave, defect detection during cure, and ultimately a closed-loop process control to maximize composite part quality and consistency.

Development of flax/carbon fibre hybrid composites for enhanced properties.

PubMed

Dhakal, H N; Zhang, Z Y; Guthrie, R; Macmullen, J; Bennett, N

2013-07-01

Uni-directional (UD) and cross-ply (CP) cellulosic flax fibre epoxy composites were produced by hybridising UD carbon fibre prepreg onto flax system. A compression moulding technique was used to produce both flax and carbon/flax hybridised laminates. The effect of carbon fibre hybridisation on the water absorption behaviour, thermal and mechanical properties of both UD and CP flax specimens were investigated by means of water absorption, tensile, thermogravemetric analysis and flexural testing. The results showed that water absorption behaviour of hybrid samples are markedly improved compared to those without hybridisation. Similarly, the thermal stability, tensile and flexural properties of the hybrid composites are significantly improved in comparison with UD and CP flax composites without hybridisation. The experimental results suggest that cellulosic flax fibre reinforcement contributed to improve the toughness properties by promoting crack propagation whereas the carbon fibre contributed in improving thermal stability, water absorption behaviour and the overall strength and the stiffness of the hybrid composites. Copyright © 2013 Elsevier Ltd. All rights reserved.

Analytical Modelling of Transverse Matrix Cracking of [plus or minus Theta/90(sub n)](sub s) Composite Laminates Under Multiaxial Loading

NASA Technical Reports Server (NTRS)

Mayugo, J A.; Camanho, P. P.; Maimi, P.; Davila, C. G.

2010-01-01

An analytical model based on the analysis of a cracked unit cell of a composite laminate subjected to multiaxial loads is proposed to predict the onset and accumulation of transverse matrix cracks in the 90(sub n) plies of uniformly stressed [plus or minus Theta/90(sub n)](sub s) laminates. The model predicts the effect of matrix cracks on the stiffness of the laminate, as well as the ultimate failure of the laminate, and it accounts for the effect of the ply thickness on the ply strength. Several examples describing the predictions of laminate response, from damage onset up to final failure under both uniaxial and multiaxial loads, are presented.

Nonlinear Spring Finite Elements for Predicting Mode I-Dominated Delamination Growth in Laminated Structure with Through-Thickness reinforcement

NASA Technical Reports Server (NTRS)

Ratcliffe, James G.; Krueger, Ronald

2006-01-01

One particular concern of polymer matrix composite laminates is the relatively low resistance to delamination cracking, in particular when the dominant type of failure is mode I opening. One method proposed for alleviating this problem involves the insertion pultruded carbon pins through the laminate thickness. The pins, known as z-pins, are inserted into the prepreg laminate using an ultrasonic hammer prior to the curing process, resulting in a field of pins embedded normal to the laminate plane as illustrated in Figure. 1. Pin diameters range between 0.28-mm to 0.5-mm and standard areal densities range from 0.5% to 4%. The z-pins are provided by the manufacturer, Aztex(Registered TradeMark) , in a low-density foam preform, which acts to stabilize orientation of the pins during the insertion process [1-3]. Typical pin materials include boron and carbon fibers embedded in a polymer matrix. A number of methods have been developed for predicting delamination growth in laminates reinforced with z-pins. During a study on the effect of z-pin reinforcement on mode I delamination resistance, finite element analyses of z-pin reinforced double cantilever beam (DCB) specimens were performed by Cartie and Partridge [4]. The z-pin bridging stresses were modeled by applying equivalent forces at the pin locations. Single z-pin pull-out tests were performed to characterize the traction law of the pins under mode I loading conditions. Analytical solutions for delamination growth in z-pin reinforced DCB specimens were independently derived by Robinson and Das [5] and Ratcliffe and O'Brien [6]. In the former case, pin bridging stresses were modeled using a distributed load and in the latter example the bridging stresses were discretely modeled by way of grounded springs. Additionally, Robinson and Das developed a data reduction strategy for calculating mode I fracture toughness, G(sub Ic), from a z-pin reinforced DCB specimen test [5]. In both cases a traction law similar to that adopted by Cartie and Partridge was used to represent z-pin failure under mode I loading conditions. In the current work spring elements available in most commercial finite element codes were used to model z-pins. The traction law used in previous analyses [4-6] was employed to represent z-pin damage. This method is intended for and is limited to simulating z-pins in composite laminate structure containing mode I-dominated delamination cracking. The current technique differs from previous analyses in that spring finite elements (available in commercial codes) are employed for simulating zpins, reducing the complexity of the analysis construction process. Furthermore, the analysis method can be applied to general structure that experiences mode I-dominated delamination cracking, in contrast to existing analytical solutions that are only applicable to coupon DCB specimens.

Characterization of Polyimide Matrix Resins and Prepregs

NASA Technical Reports Server (NTRS)

Maximovich, M. G.; Galeos, R. M.

1985-01-01

Graphite/polyimide composite materials are attractive candidates for a wide range of aerospace applications. They have many of the virtues of graphite/epoxies, i.e., high specific strengths and stiffness, and also outstanding thermal/oxidative stability. Yet they are not widely used in the aerospace industry due to problems of procesability. By their nature, modern addition polyimide (PI) resins and prepregs are more complex than epoxies; the key to processing lies in characterizing and understanding the materials. Chemical and rheological characterizations are carried out on several addition polyimide resins and graphite reinforced prepregs, including those based on PMR-15, LARC 160 (AP 22), LARC 160 (Curithane 103) and V378A. The use of a high range torque transducer with a Rheometrics mechanical spectrometer allows rheological data to be generated on prepreg materials as well as neat resins. The use of prepreg samples instead of neat resins eliminates the need for preimidization of the samples and the data correlates well with processing behavior found in the shop. Rheological characterization of the resins and prepregs finds significant differences not readily detected by conventional chemical characterization techniques.

Evaluation of a Progressive Failure Analysis Methodology for Laminated Composite Structures

NASA Technical Reports Server (NTRS)

Sleight, David W.; Knight, Norman F., Jr.; Wang, John T.

1997-01-01

A progressive failure analysis methodology has been developed for predicting the nonlinear response and failure of laminated composite structures. The progressive failure analysis uses C plate and shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms. The progressive failure analysis model is implemented into a general purpose finite element code and can predict the damage and response of laminated composite structures from initial loading to final failure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lula, J.W.

Copper foil adhesion to polyimide/glass prepreg was evaluated. Typical peel strength obtained between prepreg and the smooth side of the copper foil was 1 to 3 lb./in. width. Peel strength between prepreg and the rough side of the copper foil ranged between 6 and 7 lb./in. width. An alternate test for evaluating the integrity of multilayer printed wiring boards is described.

Fatigue Micromechanism Characterization in Carbon Fibre Reinforced Polymers Using Synchrotron Radiation Computed Tomography

DTIC Science & Technology

2014-12-18

Resources/DataSheets/ Prepreg -Data- Sheets/M21_global.pdf. [20] Hexcel HexPly 8552. http://www.hexcel.com/Resources/DataSheets/ Prepreg -Data- Sheets...8552_eu.pdf [21] 3501-6 Epoxy Matrix, Hexcel. http://www.hexcel.com/Resources/DataSheets/ Prepreg -Data- Sheets/3501-6_eu.pdf [22] B.A. Dowd, G.H

Healable Composites

DTIC Science & Technology

2012-03-28

composites: determine mechanical and crack healing properties (4, 5) Composite (3) Prepreg (2) Polymer (1) Furan (1) Maleimide Healable Composites...5. Characterize the composites: determine mechanical and crack healing properties (4, 5) Composite (3) Prepreg (1) Furan (1) Maleimide (2...Furan (1) Maleimide (4, 5) Composite (3) Prepreg Healable Composites AFOSR FA9550-08-1-0314 Christian Nielsen Challenges • At room temperature

Thermal modeling of carbon-epoxy laminates in fire environments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGurn, Matthew T.; DesJardin, Paul Edward; Dodd, Amanda B.

2010-10-01

A thermal model is developed for the response of carbon-epoxy composite laminates in fire environments. The model is based on a porous media description that includes the effects of gas transport within the laminate along with swelling. Model comparisons are conducted against the data from Quintere et al. Simulations are conducted for both coupon level and intermediate scale one-sided heating tests. Comparisons of the heat release rate (HRR) as well as the final products (mass fractions, volume percentages, porosity, etc.) are conducted. Overall, the agreement between available the data and model is excellent considering the simplified approximations to account formore » flame heat flux. A sensitivity study using a newly developed swelling model shows the importance of accounting for laminate expansion for the prediction of burnout. Excellent agreement is observed between the model and data of the final product composition that includes porosity, mass fractions and volume expansion ratio.« less

Studies on Hot-Melt Prepregging on PRM-II-50 Polyimide Resin with Graphite Fibers

NASA Technical Reports Server (NTRS)

Shin, E. Eugene; Sutter, James K.; Juhas, John; Veverka, Adrienne; Klans, Ojars; Inghram, Linda; Scheiman, Dan; Papadopoulos, Demetrios; Zoha, John; Bubnick, Jim

2004-01-01

A second generation PMR (in situ Polymerization of Monomer Reactants) polyimide resin PMR-II-50, has been considered for high temperature and high stiffness space propulsion composites applications for its improved high temperature performance. As part of composite processing optimization, two commercial prepregging methods: solution vs. hot-melt processes were investigated with M40J fabrics from Toray. In a previous study a systematic chemical, physical, thermal and mechanical characterization of these composites indicated the poor resin-fiber interfacial wetting, especially for the hot-melt process, resulted in poor composite quality. In order to improve the interfacial wetting, optimization of the resin viscosity and process variables were attempted in a commercial hot-melt prepregging line. In addition to presenting the results from the prepreg quality optimization trials, the combined effects of the prepregging method and two different composite cure methods, i.e. hot press vs. autoclave on composite quality and properties are discussed.

Studies on Hot-Melt Prepregging of PMR-II-50 Polyimide Resin with Graphite Fibers

NASA Technical Reports Server (NTRS)

Shin, E. Eugene; Sutter, James K.; Juhas, John; Veverka, Adrienne; Klans, Ojars; Inghram, Linda; Scheiman, Dan; Papadopoulos, Demetrios; Zoha, John; Bubnick, Jim

2003-01-01

A Second generation PMR (in situ Polymerization of Monomer Reactants) polyimide resin, PMR-II-50, has been considered for high temperature and high stiffness space propulsion composites applications for its improved high temperature performance. As part of composite processing optimization, two commercial prepregging methods: solution vs. hot-melt processes were investigated with M40J fabrics from Toray. In a previous study a systematic chemical, physical, thermal and mechanical characterization of these composites indicated that poor resin-fiber interfacial wetting, especially for the hot-melt process, resulted in poor composite quality. In order to improve the interfacial wetting, optimization of the resin viscosity and process variables were attempted in a commercial hot-melt prepregging line. In addition to presenting the results from the prepreg quality optimization trials, the combined effects of the prepregging method and two different composite cure methods, i.e., hot press vs. autoclave on composite quality and properties are discussed.

Effects of solvent on solution prepregging of the resin system LaRC{trademark}-IAX-2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cano, R.J.; Massey, C.P.; St. Clair, T.L.

1996-12-31

This work assesses the feasibility of using an alternative solvent for the production of composites from polyimide resin systems via solution prepregging. Previous work on solution prepregging of polyimide systems at NASA Langley Research Center has concentrated on the use of the solvent N-methylpyrrolidinone. An alternative solvent with a similar boiling point, -{gamma}-Butyrolactone, was used to prepare the poly(amide acid) version of LaRC{trademark}-IAX-2. These solutions were subsequently used to prepare prepreg and graphite-reinforced composites. Mechanical properties are presented for the resin system LaRC{trademark}-IAX-2 (4% and 5% offset in stoichiometry and endcapped with phthalic anhydride) impregnated onto Hercules IM7 carbon fiber.more » Results from this work were compared to data obtained on the same resin system which had been solution prepregged with the solvent N-methylpyrrolidinone.« less

Modeling of prepregs during automated draping sequences

NASA Astrophysics Data System (ADS)

Krogh, Christian; Glud, Jens A.; Jakobsen, Johnny

2017-10-01

The behavior of wowen prepreg fabric during automated draping sequences is investigated. A drape tool under development with an arrangement of grippers facilitates the placement of a woven prepreg fabric in a mold. It is essential that the draped configuration is free from wrinkles and other defects. The present study aims at setting up a virtual draping framework capable of modeling the draping process from the initial flat fabric to the final double curved shape and aims at assisting the development of an automated drape tool. The virtual draping framework consists of a kinematic mapping algorithm used to generate target points on the mold which are used as input to a draping sequence planner. The draping sequence planner prescribes the displacement history for each gripper in the drape tool and these displacements are then applied to each gripper in a transient model of the draping sequence. The model is based on a transient finite element analysis with the material's constitutive behavior currently being approximated as linear elastic orthotropic. In-plane tensile and bias-extension tests as well as bending tests are conducted and used as input for the model. The virtual draping framework shows a good potential for obtaining a better understanding of the drape process and guide the development of the drape tool. However, results obtained from using the framework on a simple test case indicate that the generation of draping sequences is non-trivial.

Processable Aromatic Polyimide Thermoplastic Blends

NASA Technical Reports Server (NTRS)

Baucom, Robert M; Johnston, Norman J.; St. Clair, Terry L.; Nelson, James B.; Gleason, John R.; Proctor, K. Mason

1988-01-01

Method developed for preparing readily-processable thermoplastic polyimides by blending linear, high-molecular-weight, polyimic acid solutions in ether solvents with ultrafine, semicrystalline, thermoplastic polyimide powders. Slurries formed used to make prepregs. Consolidation of prepregs into finsihed composites characterized by excellent melt flow during processing. Applied to film, fiber, fabric, metal, polymer, or composite surfaces. Used to make various stable slurries from which prepregs prepared.

Dry powder process for preparing uni-tape prepreg from polymer powder coated filamentary towpregs

NASA Technical Reports Server (NTRS)

Wilkinson, Steven P. (Inventor); Johnston, Norman J. (Inventor); Marchello, Joseph M. (Inventor)

1997-01-01

A process for preparing uni-tape prepreg from polymer powder coated filamentary towpregs is provided. A plurality of polymer powder coated filamentary towpregs are provided. The towpregs are collimated so that each towpreg is parallel. A material is applied to each side of the towpreg to form a sandwich. The sandwich is heated to a temperature wherein the polymer flows and intimately contacts the filaments and pressure is repeatedly applied perpendicularly to the sandwich with a longitudinal oscillating action wherein the filaments move apart and the polymer wets the filaments forming a uni-tape prepreg. The uni-tape prepreg is subsequently cooled.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Happe, J.A.; Morgan, R.J.; Walkup, C.M.

The chemical composition of commercial BF/sub 3/:amine complexes are variable and contain BF/sub 4//sup -/ and BF/sub 3/(OH)/sup -/ salts together with other unidentified highly reactive species. The BF/sub 3/:amine complexes, which are susceptible to hydrolysis, also partially convert to the BF/sub 4//sup -/ salt (i.e. BF/sub 4//sup -/NH/sub 3//sup +/C/sub 2/H/sub 5/) upon heating. This salt formation is accelerated in dimethyl sulfoxide solution and in the presence of the epoxides that are present in commercial prepregs. Commercial C fiber-epoxy prepregs are shown to contain either BF/sub 3/:NH/sub 2/C/sub 2/H/sub 5/ or BF/sub 3/:NHC/sub 5/H/sub 10/ species together with theirmore » BF/sub 4//sup -/ salts and a variety of boron-fluorine or carbon-fluorine prepreg species. Considerable variation in the relative quantities of BF/sub 3/:amine to its BF/sub 4//sup -/ salt was observed from prepreg lot to lot, which will cause variable viscosity-time-temperature prepreg cure profiles. It is concluded that the chemically stable and mobile BF/sub 4//sup -/ salt is the pre-dominant catalytic species, acting as a cationic catalyst for the prepreg cure reactions. During the early stages of cure the BF/sub 3/:amine catalyst converts to the BF/sub 4//sup -/ salt in the presence of epoxides, whereas the BF/sub 3/-prepreg species are susceptible to catalytic deactivation and immobilization.« less

Photovoltaic module and module arrays

DOEpatents

Botkin, Jonathan; Graves, Simon; Lenox, Carl J. S.; Culligan, Matthew; Danning, Matt

2013-08-27

A photovoltaic (PV) module including a PV device and a frame, The PV device has a PV laminate defining a perimeter and a major plane. The frame is assembled to and encases the laminate perimeter, and includes leading, trailing, and side frame members, and an arm that forms a support face opposite the laminate. The support face is adapted for placement against a horizontal installation surface, to support and orient the laminate in a non-parallel or tilted arrangement. Upon final assembly, the laminate and the frame combine to define a unitary structure. The frame can orient the laminate at an angle in the range of 3.degree.-7.degree. from horizontal, and can be entirely formed of a polymeric material. Optionally, the arm incorporates integral feature(s) that facilitate interconnection with corresponding features of a second, identically formed PV module.

Photovoltaic module and module arrays

DOEpatents

Botkin, Jonathan [El Cerrito, CA; Graves, Simon [Berkeley, CA; Lenox, Carl J. S. [Oakland, CA; Culligan, Matthew [Berkeley, CA; Danning, Matt [Oakland, CA

2012-07-17

A photovoltaic (PV) module including a PV device and a frame. The PV device has a PV laminate defining a perimeter and a major plane. The frame is assembled to and encases the laminate perimeter, and includes leading, trailing, and side frame members, and an arm that forms a support face opposite the laminate. The support face is adapted for placement against a horizontal installation surface, to support and orient the laminate in a non-parallel or tilted arrangement. Upon final assembly, the laminate and the frame combine to define a unitary structure. The frame can orient the laminate at an angle in the range of 3.degree.-7.degree. from horizontal, and can be entirely formed of a polymeric material. Optionally, the arm incorporates integral feature(s) that facilitate interconnection with corresponding features of a second, identically formed PV module.

Inkjet Assisted Creation of Self-Healing Layers Between Composite Plies

DTIC Science & Technology

2013-07-29

technology into a prepreg manufacturing process. The approach consisted of depositing novel thermoplastic low-viscosity microdroplets with chemically and...mechanically comparable properties to epoxy matrix in aerospace grade composites onto fiber-reinforced epoxy prepregs before curing using an ink-jet... prepreg Cycom977-2. Double cantilever beam (DCB) and short beam shear (SBS) tests were used to evaluate the self-healing efficiency. It was shown

Multifunctional Composites through Inkjet-printed Architectures

DTIC Science & Technology

2015-03-27

were printed onto prepreg before curing, and remained arrested between composite plies without direct contact with the neighboring micro-droplets after...micro-droplets were printed onto prepreg before curing, and remained arrested between composite plies without direct contact with the neighbouring...unidirectional carbon fibre prepreg (Cycom 977-2, Cytec Industries Inc., USA) was chosen as substrate in this work. Poly(methyl methacrylate) (PMMA) (Mn = 15 kDa

Monitoring Prepregs As They Cure

NASA Technical Reports Server (NTRS)

Young, P. R.; Gleason, J. R.; Chang, A. C.

1986-01-01

Quality IR spectra obtained in dynamic heating environment. New technique obtains quality infrared spectra on graphite-fiber-reinforced, polymeric-matrix-resin prepregs as they cure. Technique resulted from modification of diffuse reflectance/Fourier transform infrared (DR/FTIR) technique previously used to analyze environmentally exposed cured graphite composites. Technique contribute to better understanding of prepreg chemistry/temperature relationships and development of more efficient processing cycles for advanced materials.

Standard Operating Procedure - Manufacture of Carbon Fibre Reinforced Plastic Waveguides and Slotted Waveguide Antennas, Version 1.0

DTIC Science & Technology

2011-06-01

aerospace grade carbon fibre reinforced plastic (CFRP) prepreg . RELEASE LIMITATION Approved for public release UNCLASSIFIED Report...arrays manufactured from aerospace grade carbon fibre reinforced plastic (CFRP) prepreg . 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION...CFRP) prepreg tape and fabric. This report details Version 1.0 of a Standard Operating Procedure for this manufacture. UNCLASSIFIED

78 FR 69369 - Laminated Woven Sacks From the People's Republic of China: Final Results of the Expedited Sunset...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-19

... fabric; laminated by any method either to an exterior ply of plastic film such as biaxially-oriented... (Decision Memorandum). Analysis of Comments Received All issues raised in this sunset review are addressed...

Innovative Approach for High Strength, High Thermal Conductive Composite Materials: Data Base

DTIC Science & Technology

2013-11-01

pitch fiber types, from which we were able to down select K6356U pitch fiber with balanced TC and strength properties. A prepreg processing line was...Creating a robust prepreg processing line to infuse unidirectional pitch fiber tape that can be used with other fibers…Pan-based carbon or glass...pitch fiber composites • Compression molding process outperforms autoclaving in mechanical and thermal properties using the same prepreg material and

Computational simulation of composite structures with and without damage. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Wilt, Thomas F.

1994-01-01

A methodology is described which uses finite element analysis of various laminates to computationally simulate the effects of delamination damage initiation and growth on the structural behavior of laminated composite structures. The delamination area is expanded according to a set pattern. As the delamination area increases, how the structural response of the laminate changes with respect to buckling and strain energy release rate are investigated. Rules are presented for laminates of different configurations, materials and thickness. These results demonstrate that computational simulation methods can provide alternate methods to investigate the complex delamination damage mechanisms found in composite structures.

Development and Implementaton of Advanced Materials for Aircraft Engine Applications Development and Implementation of Nanostructure Laminates Final Report CRADA No. TC-0497-93-B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barbee, T. W.; Yee, W.

The objective of this project was to develop engineered nanostructure laminate materials for applications in gas turbine engines. Although the focus of this effort was on developing improved · thermal barrier coatings, the data and experience gained through such project tasks as basic theoretical work and modeling of composition/structure property relationships can be applied. to the development of microscructure laminates for other·applications.

Shear behavior of thermoformed woven-textile thermoplastic prepregs: An analysis combining bias-extension test and X-ray microtomography

NASA Astrophysics Data System (ADS)

Gassoumi, M.; Rolland du Roscoat, S.; Casari, P.; Dumont, P. J. J.; Orgéas, L.; Jacquemin, F.

2017-10-01

Thermoforming allows the manufacture of structural parts for the automotive and aeronautical domains using long fiber thermoplastic prepregs with short cycle times. During this operation, several sheets of molten prepregs are stacked and subjected to large macroscale strains, mainly via in-plane shear, out-of-plane consolidation or dilatation, and bending of the fibrous reinforcement. These deformation modes and the related meso and microstructure evolutions are still poorly understood. However, they can drastically alter the end-use macroscale properties of fabricated parts. To better understand these phenomena, bias extension tests were performed using specimens made of several stacked layers of glass woven fabrics and polyamide matrix. The macroscale shear behavior of these prepregs was investigated at various temperatures. A multiscale analysis of deformed samples was performed using X-ray microtomography images of the deformed specimens acquired at two different spatial resolutions. The low-resolution images were used to analyze the deformation mechanisms and the structural characteristics of prepregs at the macroscale and bundle scales. It was possible to analyze the 3D shapes of deformed samples and, in particular, the spatial variations of their thickness so as to quantify the out-of-plane dilatancy or consolidation phenomena induced by the in-plane shear of prepregs. At a lower scale, the analysis of the high-resolution images showed that these mechanisms were accompanied by the growth of pores and the deformation of fiber bundles. The orientation of the fiber bundles and its through-thickness evolution were measured along the weft and warp directions in the deformed samples, allowing the relevance of geometrical models currently used to analyze bias extension tests to be discussed. Results can be used to enhance the current rheological models for the prediction of thermoforming of thermoplastic prepregs.

Fabrication of a First Article Lightweight Composite Technology Demonstrator - Exospine

DTIC Science & Technology

2014-01-01

core, (b) 0/90, and (c) ± 45 ply cuts of ACG-MTM 45-1/CF0526 prepreg fabric...onboard diagnostics. 2. Experimental 2.1 Materials Plain woven carbon fiber/epoxy prepreg and a low-density foam core were provided to ARL for the...fabrication of the exospine technology demonstrator by UD-CCM. The prepreg was ACG - MTM∗ 45-1/CF0526 and has a cured ply thickness of 0.201 mm. It is

Effect of the conditions of prepreg preparation on the strength of structural plastics

NASA Astrophysics Data System (ADS)

Zaborskaya, L. V.; Yurkevich, O. R.

1995-05-01

A study is made of the effect of the temperature and duration of heat treatment of polymer composite prepregs on their strength. It is established that heat treatment under conditions ensuring close to maximal adhesive interaction between the components of the prepreg and subsequent shaping makes it possible to more than double the strength of the plastic (Table 1), A new approach is proposed to optimizing the conditions of formation of structural plastics.

Experimental evaluation and design of unfilled and concrete-filled FRP composite piles : Task 5 : laminate durability testing : final report.

DOT National Transportation Integrated Search

2015-05-01

The overall goal of this project is the experimental evaluation and design of unfilled and concrete-filled FRP composite piles for load-bearing in bridges. This report covers Task 5, Laminate Durability Testing. : Mechanical properties of the FRP mat...

Thermal Properties of Hybrid Carbon Nanotube/Carbon Fiber Polymer

NASA Technical Reports Server (NTRS)

Kang, Jin Ho; Cano, Roberto J.; Luong, Hoa; Ratcliffe, James G.; Grimsley, Brian W.; Siochi, Emilie J.

2016-01-01

Carbon fiber reinforced polymer (CFRP) composites possess many advantages for aircraft structures over conventional aluminum alloys: light weight, higher strength- and stiffness-to-weight ratio, and low life-cycle maintenance costs. However, the relatively low thermal and electrical conductivities of CFRP composites are deficient in providing structural safety under certain operational conditions such as lightning strikes. One possible solution to these issues is to interleave carbon nanotube (CNT) sheets between conventional carbon fiber (CF) composite layers. However, the thermal and electrical properties of the orthotropic hybrid CNT/CF composites have not been fully understood. In this study, hybrid CNT/CF polymer composites were fabricated by interleaving layers of CNT sheets with Hexcel (Registered Trademark) IM7/8852 prepreg. The CNT sheets were infused with a 5% solution of a compatible epoxy resin prior to composite fabrication. Orthotropic thermal and electrical conductivities of the hybrid polymer composites were evaluated. The interleaved CNT sheets improved the in-plane thermal conductivity of the hybrid composite laminates by about 400% and the electrical conductivity by about 3 orders of magnitude.

Torque Limit for Bolted Joint For Composites. Part B; Experimentation

NASA Technical Reports Server (NTRS)

Kostreva, Kristian M.

2003-01-01

Today, aerospace quality composite parts are generally made from either a unidirectional tape or a fabric prepreg form depending on the application. The matrix material, typically epoxy because of it dimensional stability, is pre-impregnated onto the fibers to ensure uniform distribution. Both of these composite forms are finding themselves used in applications where a joint is required. Two widely used joint methods are the classic mechanically fastened joint, and the contemporary bonded joint; however, the mechanically fastened joint is most commonly used by design engineers. A major portion of the research up-to-date about bolted composite joints has dealt with the inplane static load capacity. This work has helped to spawn standards dealing with filled-hole static joint strength. Other research has clearly shown that the clamp-up load in the mechanical fastener significantly affects the joint strength in a beneficial manner by reducing the bearing strength dependence of the composite laminate. One author reported a maximum increase in joint strength of 28%. This finding has helped to improve the reliability and efficiency of the joint in a composite structure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

MANDELL, JOHN F.; SAMBORSKY, DANIEL D.; CAIRNS, DOUGLAS

This report presents the major findings of the Montana State University Composite Materials Fatigue Program from 1997 to 2001, and is intended to be used in conjunction with the DOE/MSU Composite Materials Fatigue Database. Additions of greatest interest to the database in this time period include environmental and time under load effects for various resin systems; large tow carbon fiber laminates and glass/carbon hybrids; new reinforcement architectures varying from large strands to prepreg with well-dispersed fibers; spectrum loading and cumulative damage laws; giga-cycle testing of strands; tough resins for improved structural integrity; static and fatigue data for interply delamination; andmore » design knockdown factors due to flaws and structural details as well as time under load and environmental conditions. The origins of a transition to increased tensile fatigue sensitivity with increasing fiber content are explored in detail for typical stranded reinforcing fabrics. The second focus of the report is on structural details which are prone to delamination failure, including ply terminations, skin-stiffener intersections, and sandwich panel terminations. Finite element based methodologies for predicting delamination initiation and growth in structural details are developed and validated, and simplified design recommendations are presented.« less

Development of active and sensitive material systems based on composites

NASA Astrophysics Data System (ADS)

Asanuma, Hiroshi

2002-07-01

This paper describes new concepts proposed by the author to realize active and sensitive structural material systems. Two examples of multifunctional composites were fabricated and evaluated in this study as follows: (1) An active laminate of aluminum plate (works as muscle), epoxy film (as insulator), unidirectional CFRP prepreg (as bone and blood vessel) and copper foil electrode (to apply voltage on CFRP) was made with an embedded optical fiber multiply fractured in the CFRP layer (works as nerve), of which curvature change could be effectively monitored with the fractured optical fiber. (2) A stainless steel fiber/aluminum active composite with embedded Ti oxide/Ti composite fiber was fabricated. The Ti oxide/Ti fiber could work as a sensor for temperature by removing a part of the oxide before embedment to make a metallic contact between the embedded titanium fiber and aluminum matrix to be able to generate thermal electromotive force, and also could work as a sensor for strain and as a heater for actuation. In the both cases, the outputs from their embedded sensors can be used to control their actuations.

Compression Testing of Textile Composite Materials

NASA Technical Reports Server (NTRS)

Masters, John E.

1996-01-01

The applicability of existing test methods, which were developed primarily for laminates made of unidirectional prepreg tape, to textile composites is an area of concern. The issue is whether the values measured for the 2-D and 3-D braided, woven, stitched, and knit materials are accurate representations of the true material response. This report provides a review of efforts to establish a compression test method for textile reinforced composite materials. Experimental data have been gathered from several sources and evaluated to assess the effectiveness of a variety of test methods. The effectiveness of the individual test methods to measure the material's modulus and strength is determined. Data are presented for 2-D triaxial braided, 3-D woven, and stitched graphite/epoxy material. However, the determination of a recommended test method and specimen dimensions is based, primarily, on experimental results obtained by the Boeing Defense and Space Group for 2-D triaxially braided materials. They evaluated seven test methods: NASA Short Block, Modified IITRI, Boeing Open Hole Compression, Zabora Compression, Boeing Compression after Impact, NASA ST-4, and a Sandwich Column Test.

Properties of autoclaved Gr/PI composites made from improved tack PMR-15 prepreg

NASA Technical Reports Server (NTRS)

Vannucci, R. D.

1985-01-01

Autoclave processing studies were conducted, using improved tack PMR-15 prepreg, to determine the effect of tack enhancing PMR resin modifications on composite processability and mechanical properties. Improved tack graphite fiber reinforced PMR-15 prepregs were prepared and exposed to ambient conditions for various times and then autoclave molded into composites. Composite specimens were prepared and tested for flexural and interlaminar shear strengths at room temperature and 316 C. The retention of flexural and interlaminar shear strength as a function of exposure in air at 316 C was also determined. The results show that the modified PMR resin solutions provide prepreg with improved tack and drape retention characteristics without adversely affecting processability or mechanical properties of autoclave molded graphite fiber reinforced PMR-15 composites.

Peridynamics for failure and residual strength prediction of fiber-reinforced composites

NASA Astrophysics Data System (ADS)

Colavito, Kyle

Peridynamics is a reformulation of classical continuum mechanics that utilizes integral equations in place of partial differential equations to remove the difficulty in handling discontinuities, such as cracks or interfaces, within a body. Damage is included within the constitutive model; initiation and propagation can occur without resorting to special crack growth criteria necessary in other commonly utilized approaches. Predicting damage and residual strengths of composite materials involves capturing complex, distinct and progressive failure modes. The peridynamic laminate theory correctly predicts the load redistribution in general laminate layups in the presence of complex failure modes through the use of multiple interaction types. This study presents two approaches to obtain the critical peridynamic failure parameters necessary to capture the residual strength of a composite structure. The validity of both approaches is first demonstrated by considering the residual strength of isotropic materials. The peridynamic theory is used to predict the crack growth and final failure load in both a diagonally loaded square plate with a center crack, as well as a four-point shear specimen subjected to asymmetric loading. This study also establishes the validity of each approach by considering composite laminate specimens in which each failure mode is isolated. Finally, the failure loads and final failure modes are predicted in a laminate with various hole diameters subjected to tensile and compressive loads.

Testing procedures for carbon fiber reinforced plastic components

NASA Technical Reports Server (NTRS)

Gosse, H. J.; Kaitatzidi, M.; Roth, S.

1977-01-01

Tests for studying the basic material are considered and quality control investigations involving preimpregnated materials (prepreg) are discussed. Attention is given to the prepreg area weight, the fiber area weight of prepregs, the resin content, volatile components, the effective thickness, resin flow, the resistance to bending strain, tensile strength, and shear strength. A description of tests conducted during the manufacturing process is also presented, taking into account X-ray methods, approaches of neutron radiography, ultrasonic procedures, resonance methods and impedance studies.

Long-term strength and damage accumulation in laminates

NASA Astrophysics Data System (ADS)

Dzenis, Yuris A.; Joshi, Shiv P.

1993-04-01

A modified version of the probabilistic model developed by authors for damage evolution analysis of laminates subjected to random loading is utilized to predict long-term strength of laminates. The model assumes that each ply in a laminate consists of a large number of mesovolumes. Probabilistic variation functions for mesovolumes stiffnesses as well as strengths are used in the analysis. Stochastic strains are calculated using the lamination theory and random function theory. Deterioration of ply stiffnesses is calculated on the basis of the probabilities of mesovolumes failures using the theory of excursions of random process beyond the limits. Long-term strength and damage accumulation in a Kevlar/epoxy laminate under tension and complex in-plane loading are investigated. Effects of the mean level and stochastic deviation of loading on damage evolution and time-to-failure of laminate are discussed. Long-term cumulative damage at the time of the final failure at low loading levels is more than at high loading levels. The effect of the deviation in loading is more pronounced at lower mean loading levels.

Failure analysis of single-bolted joint for lightweight composite laminates and metal plate

NASA Astrophysics Data System (ADS)

Li, Linjie; Qu, Junli; Liu, Xiangdong

2018-01-01

A three-dimensional progressive damage model was developed in ANSYS to predict the damage accumulation of single bolted joint in composite laminates under in-plane tensile loading. First, we describe the formulation and algorithm of this model. Second, we calculate the failure loads of the joint in fibre reinforced epoxy laminated composite plates and compare it with the experiment results, which validates that our model can appropriately simulate the ultimate tensile strength of the joints and the whole process of failure of structure. Finally, this model is applied to study the failure process of the light-weight composite material (USN125). The study also has a great potential to provide a strong basis for bolted joints design in composite Laminates as well as a simple tool for comparing different laminate geometries and bolt arrangements.

Experimental verification of a progressive damage model for composite laminates based on continuum damage mechanics. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Coats, Timothy William

1994-01-01

Progressive failure is a crucial concern when using laminated composites in structural design. Therefore the ability to model damage and predict the life of laminated composites is vital. The purpose of this research was to experimentally verify the application of the continuum damage model, a progressive failure theory utilizing continuum damage mechanics, to a toughened material system. Damage due to tension-tension fatigue was documented for the IM7/5260 composite laminates. Crack density and delamination surface area were used to calculate matrix cracking and delamination internal state variables, respectively, to predict stiffness loss. A damage dependent finite element code qualitatively predicted trends in transverse matrix cracking, axial splits and local stress-strain distributions for notched quasi-isotropic laminates. The predictions were similar to the experimental data and it was concluded that the continuum damage model provided a good prediction of stiffness loss while qualitatively predicting damage growth in notched laminates.

Prepreg cure monitoring using diffuse reflectance-FTIR. [Fourier Transform Infrared Technique

NASA Technical Reports Server (NTRS)

Young, P. R.; Chang, A. C.

1984-01-01

An in situ diffuse reflectance-Fourier transform infrared technique was developed to determine infrared spectra of graphite fiber prepregs as they were being cured. A bismaleimide, an epoxy, and addition polyimide matrix resin prepregs were studied. An experimental polyimide adhesive was also examined. Samples were positioned on a small heater at the focal point of diffuse reflectance optics and programmed at 15 F/min while FTIR spectra were being scanned, averaged, and stored. An analysis of the resulting spectra provided basic insights into changes in matrix resin molecular structure which accompanied reactions such as imidization and crosslinking. An endo-exothermal isomerization involving reactive end-caps was confirmed for the addition polyimide prepregs. The results of this study contribute to a fundamental understanding of the processing of composites and adhesives. Such understanding will promote the development of more efficient cure cycles.

Near Infrared Spectroscopy for On-line Monitoring of Alkali- Free Cloth/Phenolic Resin Prepreg During Manufacture

PubMed Central

Jiang, Bo; Huang, Yu Dong

2007-01-01

A NIR method was developed for the on-line monitoring of alkali-free cloth/phenolic resin prepreg during its manufacturing process. First, the sizing content of the alkali-free cloth was analyzed, and then the resin, soluble resin and volatiles content of the prepreg was analyzed simultaneously using the FT-NIR spectrometer. Partial least square (PLS) regression was used to develop the calibration models, which for the sizing content was preprocessed by 1stDER +MSC, for the volatile content by 1stDER +VN, for the soluble resin content by 1stDER +MSC and for the resin content by the VN spectral data preprocessing method. RMSEP of the prediction model for the sizing content was 0.732 %, for the resin content it was 0.605, for the soluble resin content it was 0.101 and for volatiles content it was 0.127. The results of the paired t-test revealed that there was no significant difference between the NIR method and the standard method. The NIR spectroscopy method could be used to predict the resin, soluble resin and the volatiles content of the prepreg simultaneously, as well as sizing content of alkali-free cloth. The processing parameters of the prepreg during manufacture could be adjusted quickly with the help of the NIR analysis results. The results indicated that the NIR spectroscopy method was sufficiently accurate and effective for the on-line monitoring of alkali-free cloth/phenolic resin prepreg.

Performance of resin transfer molded multiaxial warp knit composites

NASA Technical Reports Server (NTRS)

Dexter, H. Benson; Hasko, Gregory H.

1993-01-01

Composite materials that are subjected to complex loads have traditionally been fabricated with multidirectionally oriented prepreg tape materials. Some of the problems associated with this type of construction include low delamination resistance, poor out-of-plane strength, and labor intensive fabrication processes. Textile reinforced composites with through-the-thickness reinforcement have the potential to solve some of these problems. Recently, a relatively new class of noncrimp fabrics designated as multiaxial warp knits have been developed to minimize some of the high cost and damage tolerance concerns. Multiple stacks of warp knit fabrics can be knitted or stitched together to reduce layup labor cost. The through-the-thickness reinforcement can provide significant improvements in damage tolerance and out-of-plane strength. Multilayer knitted/stitched preforms, in conjunction with resin transfer molding (RTM), offer potential for significant cost savings in fabrication of primary aircraft structures. The objectives of this investigation were to conduct RTM processing studies and to characterize the mechanical behavior of composites reinforced with three multiaxial warp knit fabrics. The three fabrics investigated were produced by Hexcel and Milliken in the United States, and Saerbeck in Germany. Two resin systems, British Petroleum E9O5L and 3M PR 500, were characterized for RTM processing. The performance of Hexcel and Milliken quasi-isotropic knitted fabrics are compared to conventional prepreg tape laminates. The performance of the Saerbeck fabric is compared to uniweave wing skin layups being investigated by Douglas Aircraft Company in the NASA Advanced Composites Technology (ACT) program. Tests conducted include tension, open hole tension, compression, open hole compression, and compression after impact. The effects of fabric defects, such as misaligned fibers and gaps between tows, on material performance are also discussed. Estimated material and labor cost savings are projected for the Saerbeck fabric as compared to uniweave fabric currently being used by Douglas in the NASA ACT wing development program.

Noncontact analysis of the fiber weight per unit area in prepreg by near-infrared spectroscopy.

PubMed

Jiang, B; Huang, Y D

2008-05-26

The fiber weight per unit area in prepreg is an important factor to ensure the quality of the composite products. Near-infrared spectroscopy (NIRS) technology together with a noncontact reflectance sources has been applied for quality analysis of the fiber weight per unit area. The range of the unit area fiber weight was 13.39-14.14mgcm(-2). The regression method was employed by partial least squares (PLS) and principal components regression (PCR). The calibration model was developed by 55 samples to determine the fiber weight per unit area in prepreg. The determination coefficient (R(2)), root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) were 0.82, 0.092, 0.099, respectively. The predicted values of the fiber weight per unit area in prepreg measured by NIRS technology were comparable to the values obtained by the reference method. For this technology, the noncontact reflectance sources focused directly on the sample with neither previous treatment nor manipulation. The results of the paired t-test revealed that there was no significant difference between the NIR method and the reference method. Besides, the prepreg could be analyzed one time within 20s without sample destruction.

Progressive Failure Analysis Methodology for Laminated Composite Structures

NASA Technical Reports Server (NTRS)

Sleight, David W.

1999-01-01

A progressive failure analysis method has been developed for predicting the failure of laminated composite structures under geometrically nonlinear deformations. The progressive failure analysis uses C(exp 1) shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms and several options are available to degrade the material properties after failures. The progressive failure analysis method is implemented in the COMET finite element analysis code and can predict the damage and response of laminated composite structures from initial loading to final failure. The different failure criteria and material degradation methods are compared and assessed by performing analyses of several laminated composite structures. Results from the progressive failure method indicate good correlation with the existing test data except in structural applications where interlaminar stresses are important which may cause failure mechanisms such as debonding or delaminations.

Recovery behaviour of shape memory polyurethane based laminates after thermoforming

NASA Astrophysics Data System (ADS)

Wu, Shuiliang; Xu, Wensen; Prasath Balamurugan, G.; Thompson, Michael R.; Nielsen, Kent E.; Brandys, Frank A.

2017-11-01

Shape memory polymers (SMPs) can be used to produce a new class of decorative films capable of improved formability and shape recovery in polymer laminates, which are increasingly being used for automotive, aerospace, construction and commercial applications. As a relatively new field there is little knowledge on the shape recovery behaviour of laminates with a SMP film and few methods of quantify that behaviour. The influences of different variables that affect the recovery behaviour of thermoplastic shape memory polyurethanes based laminates including ambient temperature (45 °C and 65 °C), material modulus, and adhesive strength were investigated after thermoforming, through both experimental and modelling methods. The empirical model assisted in identifying the contributions of the adhesive to transfer stresses, which dampened the recovery of the laminate with lower shear strength adhesives. Increasing ambient temperature and the film modulus increased both the final angle recovery ratios and recovery rates.

LARC powder prepreg system

NASA Technical Reports Server (NTRS)

Baucom, Robert M.; Marchello, Joseph M.

1990-01-01

Thermoplastic prepregs of LARC-TPI have been produced in a fluidized bed unit on spread continuous fiber tows. The powders are melted on the fibers by radiant heating to adhere the polymer to the fiber. This process produces tow prepreg uniformly without imposing severe stress on the fibers or requiring long high temperature residence times for the polymer. Unit design theory and operating correlations have been developed to provide the basis for scale up to commercial operation. Special features of the operation are the pneumatic tow spreader, fluidized bed and resin feed systems.

Sub-ply level scaling approach investigated for graphite-epoxy composite beam columns

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Kellas, Sotiris

1994-01-01

Scale model graphite-epoxy composite specimens were fabricated using the 'sub-ply level' approach and tested as beam-columns under an eccentric axial load to determine the effect of specimen size on flexural response and failure. In the current research project, although the fiber diameters are not scaled, the thickness of the pre-preg material itself has been scaled by adjusting the number of fibers through the thickness of a single ply. Three different grades of graphite-epoxy composite material (AS4/3502) were obtained from Hercules, Inc., in which the number of fibers through the thickness of a single ply was reduced (Grade 190 with 12 to 16 fibers, Grade 95 with 6 to 8 fibers, and Grade 48 with 3 to 4 fibers). Thus, using the sub-ply level approach, a baseline eight ply quasi-isotropic laminate could be fabricated using either the Grade 48 or Grade 95 material and the corresponding full-scale laminate would be constructed from Grade 95 or standard Grade 190 material, respectively. Note that in the sub-ply level approach, the number of ply interfaces is constant for the baseline and full-scale laminates. This is not true for the ply level and sublaminate level scaled specimens. The three grades of graphite-epoxy composite material were used to fabricate scale model beam-column specimens with in-plane dimensions of 0.5*n x 5.75*n, where n=1,2,4 corresponsing to 1/4, 1/2, and full-scale factors. Angle ply, cross ply, and quasi-isotropic laminate stacking sequences were chosen for the investigation and the test matrices for each laminate type are given. Specimens in each laminate family with the same in-plane dimensions but different thicknesses were tested to isolate the influence of the thickness dimension on the flexural response and failure. Also, specific lay-ups were chosen with blocked plies and dispersed plies for each laminate type. Specimens were subjected to an eccentric axial load until failure. The load offset was introduced through a set of hinges which were attached to the platens of a standard load test machine. Three sets of geometrically scaled hinges were used to ensure that scaled loading conditions were applied. This loading condition was chosen because it promotes large flexural deformations and specimens fail at the center of the beam, away from the grip supports. Five channels of data including applied vertical load, end shortening displacement, strain from gages applied back-to-back at the midspan of the beam, and rotation of the hinge from a bubble inclinometer were recorded for each specimen. The beam-column test configuration was used previously to study size effects in ply level scaled composite specimens of the same material system, sizes, and stacking sequences. Thus, a direct comparison between the two scaling approaches is possible. Ply level scaled beam-columns with angle ply, cross ply, and quasi-isotropic lay-ups exhibited no size dependencies in the flexural response, but significant size effects in strength. The reduction in strength with increasing specimen size was not predicted successfully by analysis techniques. It is anticipated that results from this investigation will lead to a better understanding of the strength scale effect in composite structures.

Characteristics of energy harvesting using BaTiO3/Cu laminates with changes in temperature

NASA Astrophysics Data System (ADS)

Mori, K.; Takeuchi, H.; Narita, F.

2018-03-01

The energy harvesting characteristics of piezoelectric/copper (BaTiO3/Cu) laminates rising from sharp temperature changes were investigated both numerically and experimentally. First, a phase field simulation was performed to determine the temperature-dependent piezoelectric coefficient and permittivity values. Then, the output voltages of the BaTiO3/Cu laminates were calculated for variations from room temperature to either a cryogenic temperature (77 K) or a higher temperature (333 K) using a 3D finite element simulation with the properties calculated from the phase field simulation. Finally, the output voltages of the piezoelectric BaTiO3/Cu laminates were measured for the same temperature changes and were compared to the simulation results.

A-Type Lamins Maintain the Positional Stability of DNA Damage Repair Foci in Mammalian Nuclei

PubMed Central

Mahen, Robert; Hattori, Hiroyoshi; Lee, Miyoung; Sharma, Pooja; Jeyasekharan, Anand D.; Venkitaraman, Ashok R.

2013-01-01

A-type lamins encoded by LMNA form a structural fibrillar meshwork within the mammalian nucleus. How this nuclear organization may influence the execution of biological processes involving DNA transactions remains unclear. Here, we characterize changes in the dynamics and biochemical interactions of lamin A/C after DNA damage. We find that DNA breakage reduces the mobility of nucleoplasmic GFP-lamin A throughout the nucleus as measured by dynamic fluorescence imaging and spectroscopy in living cells, suggestive of incorporation into stable macromolecular complexes, but does not induce the focal accumulation of GFP-lamin A at damage sites. Using a proximity ligation assay and biochemical analyses, we show that lamin A engages chromatin via histone H2AX and its phosphorylated form (γH2AX) induced by DNA damage, and that these interactions are enhanced after DNA damage. Finally, we use three-dimensional time-lapse imaging to show that LMNA inactivation significantly reduces the positional stability of DNA repair foci in living cells. This defect is partially rescued by the stable expression of GFP-lamin A. Thus collectively, our findings suggest that the dynamic structural meshwork formed by A-type lamins anchors sites of DNA repair in mammalian nuclei, providing fresh insight into the control of DNA transactions by nuclear structural organization. PMID:23658700

Evaluation of Graphite Fiber/Polyimide PMCs from Hot Melt vs Solution Prepreg

NASA Technical Reports Server (NTRS)

Shin, E. Eugene; Sutter, James K.; Eakin, Howard; Inghram, Linda; McCorkle, Linda; Scheiman, Dan; Papadopoulos, Demetrios; Thesken, John; Fink, Jeffrey E.

2002-01-01

Carbon fiber reinforced high temperature polymer matrix composites (PMC) have been extensively investigated as potential weight reduction replacements of various metallic components in next generation high performance propulsion rocket engines. The initial phase involves development of comprehensive composite material-process-structure-design-property-in-service performance correlations and database, especially for a high stiffness facesheet of various sandwich structures. Overview of the program plan, technical approaches and current multi-team efforts will be presented. During composite fabrication, it was found that the two large volume commercial prepregging methods (hot-melt vs. solution) resulted in considerably different composite cure behavior. Details of the process-induced physical and chemical modifications in the prepregs, their effects on composite processing, and systematic cure cycle optimization studies will be discussed. The combined effects of prepregging method and cure cycle modification on composite properties and isothermal aging performance were also evaluated.

Effect of Lamina Thickness of Prepreg on the Surface Accuracy of Carbon Fiber Composite Space Mirrors

NASA Astrophysics Data System (ADS)

Yang, Zhiyong; Tang, Zhanwen; Xie, Yongjie; Shi, Hanqiao; Zhang, Boming; Guo, Hongjun

2018-02-01

Composite space mirror can completely replicate the high-precision surface of mould by replication process, but the actual surface accuracy of the replication composite mirror always decreases. Lamina thickness of prepreg affects the layers and layup sequence of composite space mirror, and which would affect surface accuracy of space mirror. In our research, two groups of contrasting cases through finite element analyses (FEA) and comparative experiments were studied; the effect of different lamina thicknesses of prepreg and corresponding lay-up sequences was focused as well. We describe a special analysis model, validated process and result analysis. The simulated and measured surface figures both get the same conclusion. Reducing lamina thickness of prepreg used in replicating composite space mirror is propitious to optimal design of layup sequence for fabricating composite mirror, and could improve its surface accuracy.

Evaluation of Graphite Fiber/Polyimide PMCs from Hot Melt versus Solution Prepreg

NASA Technical Reports Server (NTRS)

Shin, Eugene E.; Sutter, James K.; Eakin, Howard; Inghram, Linda; McCorkle, Linda; Scheiman, Dan; Papadopoulos, Demetrios; Thesken, John; Fink, Jeffrey E.; Gray, Hugh R. (Technical Monitor)

2002-01-01

Carbon fiber reinforced high temperature polymer matrix composites (PMC) have been extensively investigated as potential weight reduction replacements of various metallic components in next generation high performance propulsion rocket engines. The initial phase involves development of comprehensive composite material-process-structure-design-property in-service performance correlations and database, especially for a high stiffness facesheet of various sandwich structures. Overview of the program plan, technical approaches and current multi-team efforts will be presented. During composite fabrication, it was found that the two large volume commercial prepregging methods (hot-melt vs. solution) resulted in considerably different composite cure behavior. Details of the process-induced physical and chemical modifications in the prepregs, their effects on composite processing, and systematic cure cycle optimization studies will be discussed. The combined effects of prepregging method and cure cycle modification on composite properties and isothermal aging performance were also evaluated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Weizhao; Zhang, Zixuan; Lu, Jie

Carbon fiber composites have received growing attention because of their high performance. One economic method to manufacturing the composite parts is the sequence of forming followed by the compression molding process. In this sequence, the preforming procedure forms the prepreg, which is the composite with the uncured resin, to the product geometry while the molding process cures the resin. Slip between different prepreg layers is observed in the preforming step and this paper reports a method to characterize the properties of the interaction between different prepreg layers, which is critical to predictive modeling and design optimization. An experimental setup wasmore » established to evaluate the interactions at various industrial production conditions. The experimental results were analyzed for an in-depth understanding about how the temperature, the relative sliding speed, and the fiber orientation affect the tangential interaction between two prepreg layers. The interaction factors measured from these experiments will be implemented in the computational preforming program.« less

Comparison of the thermomechanical characteristics of porcher carbon fabric-based composites for orthopaedic applications

NASA Astrophysics Data System (ADS)

Molchanov, E. S.; Yudin, V. E.; Kydralieva, K. A.; Elokhovskii, V. Yu.

2012-07-01

Prepregs of fiber-reinforced plastics based on a PORCHER-43200 carbon twill-weave fabric and two types of binders — thermoreactive and thermoplastic — were fabricated using electrostatic spraying, followed by rolling the prepregs in temperature-controlled calenders. A solid epoxy olygomer with dicyandiamine as a hardener and Fortron® polyphenylene sulfide were used as the thermoreactive and thermoplastic binders. The thermomechanical properties of carbon-fiber-reinforced plastics processed from these prepregs, as well as commercial Sigranex® PREPREGCE8201-200-45 S prepregs as model ones, and composites manufactured from them were investigated for comparison. The latter ones are being used for the design of orthopaedic products. It is shown that the composites based on polyphenylene sulfide are characterized by higher values of flexural strength, flexural and shear moduli, and interlaminar fracture toughness ( G IC), the latter being the most important parameter.

78 FR 12716 - Laminated Woven Sacks From the People's Republic of China: Negative Final Determination of...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-25

... colors printed in register at two different print stations. However, the artwork, by use of a screen...-circumvention inquiry is laminated woven sacks produced with two ink colors printed in register and a screening... have adapted the screening process to create graphics that appear to have three or more distinct colors...

Effect of shallow angles on compressive strength of biaxial and triaxial laminates.

PubMed

Jia, Hongli; Yang, Hyun-Ik

2016-01-01

Biaxial (BX) and triaxial (TX) composite laminates with ±45° angled plies have been widely used in wind turbine blades. As the scale of blades increases, BX and TX laminates with shallow-angled plies (i.e. off-axis ply angle <45°) might be utilized for reducing mass and/or improving performance. The compressive properties of shallow-angled BX and TX laminates are critical considering their locations in a wind turbine blade, and therefore in this study, the uniaxial static compression tests were conducted using BX and TX laminates with angled-plies of ±45°, ±35°, and ±25°, for the purpose of evaluation. On the other hand, Mori-Tanaka mean field homogenization method was employed to predict elastic constants of plies in BX and TX laminates involved in tests; linear regression analyses of experimentally measured ply strengths collected from various sources were then performed to estimate strengths of plies in BX and TX laminates; finally, Tsai-Wu, Hashin, and Puck failure criteria were chosen to predict compressive strengths of BX and TX laminates. Comparison between theoretical predictions and test results were carried out to illustrate the effectiveness of each criterion. The compressive strength of BX laminate decreases as ply angle increases, and the trend was successfully predicted by all three failure criteria. For TX laminates, ±35° angled plies rather than ±45° angled plies led to the lowest laminate compressive strength. Hashin and Puck criteria gave good predictions at certain ply angles for TX laminates, but Tsai-Wu criterion was able to capture the unexpected strength variation of TX laminates with ply angle. It was concluded that the transverse tensile stress in 0° plies of TX laminates, which attains its maximum when the off-axis ply angle is 35°, is the dominant factor in failure determination if using Tsai-Wu criterion. This explains the unexpected strength variation of TX laminates with ply angle, and also indicates that proper selection of ply angle is the key to fully utilizing the advantages of shallow-angled laminates.

Free Vibration of Fiber Composite Thin Shells in a Hot Environment

NASA Technical Reports Server (NTRS)

Gotsis, Pascal K.; Guptill, James D.

1995-01-01

Results are presented of parametric studies to assess the effects of various parameters on the free vibration behavior (natural frequencies) of (plus or minus theta)2, angle-ply fiber composite thin shells in a hot environment. These results were obtained by using a three-dimensional finite element structural analysis computer code. The fiber composite shell is assumed to be cylindrical and made from T-300 graphite fibers embedded in an intermediate-modulus high-strength matrix (IMHS). The residual stresses induced into the laminated structure during curing are taken into account. The following parameters are investigated: the length and the thickness of the shell, the fiber orientations, the fiber volume fraction, the temperature profile through the thickness of the laminate and the different ply thicknesses. Results obtained indicate that: the fiber orientations and the length of the laminated shell had significant effect on the natural frequencies. The fiber volume fraction, the laminate thickness and the temperature profile through the shell thickness had a weak effect on the natural frequencies. Finally, the laminates with different ply thicknesses had insignificant influence on the behavior of the vibrated laminated shell.

Bending analysis of a general cross-ply laminate using 3D elasticity solution and layerwise theory

NASA Astrophysics Data System (ADS)

Yazdani Sarvestani, H.; Naghashpour, A.; Heidari-Rarani, M.

2015-12-01

In this study, the analytical solution of interlaminar stresses near the free edges of a general (symmetric and unsymmetric layups) cross-ply composite laminate subjected to pure bending loading is presented based on Reddy's layerwise theory (LWT) for the first time. First, the reduced form of displacement field is obtained for a general cross-ply composite laminate subjected to a bending moment by elasticity theory. Then, first-order shear deformation theory of plates and LWT is utilized to determine the global and local deformation parameters appearing in the displacement fields, respectively. One of the main advantages of the developed solution based on the LWT is exact prediction of interlaminar stresses at the boundary layer regions. To show the accuracy of this solution, three-dimensional elasticity bending problem of a laminated composite is solved for special set of boundary conditions as well. Finally, LWT results are presented for edge-effect problems of several symmetric and unsymmetric cross-ply laminates under the bending moment. The obtained results indicate high stress gradients of interlaminar stresses near the edges of laminates.

Development of lightweight graphite/polyimide sandwich panels. Phase 2: Thin gage material manufacture

NASA Technical Reports Server (NTRS)

Merlette, J. B.

1972-01-01

Thin gage materials selected and the rationale for their basic requirements are discussed. The resin used in all prepreg manufacture is Monsanto RS-6234 polyimide. The selected fiber for core manufacture is Hercules HT-S, and the selected fiber for face sheets is Hercules HM-S. The technique for making thin gage prepreg was to wind spread carbon fiber tows into a resin film on a large drum. This technique was found to be superior to others investigated. A total of 22 pounds of 1 to 2 mil/ply prepreg was fabricated for use on the program.

Liquid chromatographic characterization of PMR-15 resin and prepreg

NASA Technical Reports Server (NTRS)

Reed, K. E.

1980-01-01

A liquid chromatographic method has been developed capable of providing a chemical fingerprint of PMR-15 resin solutions and prepreg. The amounts of two of the monomers can be quantified so their experimentally determined molar ratio can be compared to the formulated one. Only the monomers were detected in fresh resin solution, whereas several additional components, resulting from an association or reaction between the norbornenyl endcap and the amine, were detected in a resin solution aged for three days. Two commercial prepregs exhibited fingerprints similar to that of laboratory material, but three others contained additional components corresponding to higher esters and nadimides.

Effect of viscosity of a thermoplastic prepreg and matrix upon winding of rings

NASA Astrophysics Data System (ADS)

Stavrov, V. P.; Markov, A. V.; Zhernovskii, A. V.; Friedrich, K. F.

2000-05-01

The problem of compression of a unidirectional layer and shear of a polymer interlayer during winding of rings is considered. The equations determining the dependence of the layer thickness and stresses on the parameters entering into the power flow law for a prepreg and polymer matrix and on the basic parameters of the winding process—the initial tension of the prepreg, its placement rate, and the radius of a mandrel—are derived. The ring thickness measurements obtained at various temperatures and initial tension forces of plies confirm the adequacy of the model offered. It is found that the viscous properties of the prepreg and matrix upon winding affect the relative change in the layer thickness to a greater extent than the stresses in these layers. With increase in temperature and tension force upon winding, the effect of viscous deformations of the prepreg and matrix increases. A decrease in viscosity and an increase in the tension force of the tape lead to a higher strength of the ring in tension and interlaminar shear; however, the growing percolation of the polymer melt leads to a greater inhomogeneity of the structure of the composite in the ring and to a lower reinforcing effect of the factors mentioned.

Live load distribution on longitudinal glued-laminated timber deck bridges : final report : conclusions and recommendations

Treesearch

Fouad Fanous; Jeremy May; Terry Wipf; Michael Ritter

2010-01-01

Over the past few years the United States Department of Agriculture (USDA), Forest Products Laboratory (FPL), and the Federal Highway Administration (FHWA) have supported several research programs. This paper is a result of a study sponsored by FPL, with the objective of determining how truckloads are distributed to the deck panels of a longitudinal glued-laminated...

A comparison of simple shear characterization methods for composite laminates

NASA Technical Reports Server (NTRS)

Yeow, Y. T.; Brinson, H. F.

1978-01-01

Various methods for the shear stress/strain characterization of composite laminates are examined and their advantages and limitations are briefly discussed. Experimental results and the necessary accompanying analysis are then presented and compared for three simple shear characterization procedures. These are the off-axis tensile test method, the (+/- 45 deg)s tensile test method and the (0/90 deg)s symmetric rail shear test method. It is shown that the first technique indicates the shear properties of the graphite/epoxy laminates investigated are fundamentally brittle in nature while the latter two methods tend to indicate that these laminates are fundamentally ductile in nature. Finally, predictions of incrementally determined tensile stress/strain curves utilizing the various different shear behaviour methods as input information are presented and discussed.

A comparison of simple shear characterization methods for composite laminates

NASA Technical Reports Server (NTRS)

Yeow, Y. T.; Brinson, H. F.

1977-01-01

Various methods for the shear stress-strain characterization of composite laminates are examined, and their advantages and limitations are briefly discussed. Experimental results and the necessary accompanying analysis are then presented and compared for three simple shear characterization procedures. These are the off-axis tensile test method, the + or - 45 degs tensile test method and the 0 deg/90 degs symmetric rail shear test method. It is shown that the first technique indicates that the shear properties of the G/E laminates investigated are fundamentally brittle in nature while the latter two methods tend to indicate that the G/E laminates are fundamentally ductile in nature. Finally, predictions of incrementally determined tensile stress-strain curves utilizing the various different shear behavior methods as input information are presented and discussed.

76 FR 14906 - Laminated Woven Sacks From the People's Republic of China: Final Results of First Antidumping...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-18

... has added several case numbers to the Case Reference file within the Automated Commercial Environment... Vietnam: Preliminary Results, Preliminary Partial Rescission and Final Partial Rescission of the Second... the Socialist Republic of Vietnam: Final Results and Final Partial Rescission of Antidumping Duty...

UTILIZATION OF SCRAP PREPREG WASTES AS A REINFORCEMENT IN A WHOLLY RECYCLED PLASTIC - PHASE II

EPA Science Inventory

Foster-Miller is proposing to combine Municipal Solid Waste (MSW) commingled plastics with a high performance reinforcement (scrap prepreg) to form a durable and cost competitive wood substitute with superior moisture, rodent and insect resistance. This proposed technology ...

Mechanics of Multifunctional Materials and Microsystems

DTIC Science & Technology

2013-03-07

unlimited 46  Successfully processed the 1st self-healing prepreg in continuous production mode SEM image of E-glass fiber tow (200 count) with 3.3...healing composite with well dispersed microcapsules were fabricated from prepreg . E-glass fiber/epoxy resin Matrix: EPON862/EPIKURE3274

Polymer infiltration studies

NASA Technical Reports Server (NTRS)

Marchello, Joseph M.

1993-01-01

During the past three months, significant progress has been made on the preparation of carbon fiber composites using advanced polymer resins. The results are set forth in recent reports and publications, and will be presented at forthcoming national and international meetings. Current and ongoing research activities reported herein include: textile composites from powder-coated towpreg; role of surface coating in braiding; prepregger hot sled operation; ribbonizing powder-impregenated towpreg; textile composites from powder-coated towpreg; role of bulk factor powder curtain prepreg process advanced tow placement (ATP) open-section part warpage control. During the coming months research will be directed toward further development of the new powder curtain prepregging method and on ways to customize dry powder towpreg for textile and robotic applications in aircraft part fabrication. Studies of multi-tow powder prepregging and ribbon preparation will be conducted in conjunction with continued development of prepregging technology and the various aspects of composite part fabrication using customized towpreg. Also, during the period ahead work will continue on the analysis of the performance of the new solution prepregger.

[A development of FRP frame for crown and bridge resin. (2) Rigidity and adaptability of FRP frame].

PubMed

Kimura, H; Teraoka, F

1990-05-01

Retainer and pontic of FRP frame for crown and bridge resin were constructed with two different prepregs, used glass cloth and roving as reinforcement. Rigidity and adaptability of the FRP frame and bonding strength of jointing of retainer and pontic were investigated. The glass content was about 50 wt% for both kinds of prepregs. Bonding strength and modulus of FRP plate reinforced with glass roving were about 1.5 times larger than that of the FRP plate reinforced with glass cloth. Bonding strength of FRP specimen constructed by curing the prepreg put on the FRP plate was about 3 kgf/mm2. However, the bonding strength of specimen constructed by curing simultaneously the two prepregs was about 12 kgf/mm2. Though discrepancy of the FRP frame to stone cast of abutment tooth was proportional to the length of pontic, that of the FRP frame with a 50 mm pontic was less than 0.05 mm.

Nanoporous Al sandwich foils using size effect of Al layer thickness during Cu/Al/Cu laminate rolling

NASA Astrophysics Data System (ADS)

Yu, Hailiang; Lu, Cheng; Tieu, A. Kiet; Li, Huijun; Godbole, Ajit; Kong, Charlie

2018-06-01

The roll bonding technique is one of the most widely used methods to produce metal laminate sheets. Such sheets offer interesting research opportunities for both scientists and engineers. In this paper, we report on an experimental investigation of the 'thickness effect' during laminate rolling for the first time. Using a four-high multifunction rolling mill, Cu/Al/Cu laminate sheets were fabricated with a range of thicknesses (16, 40, 70 and 130 μm) of the Al layer. The thickness of the Cu sheets was a constant 300 μm. After rolling, TEM images show good bonding quality between the Cu and Al layers. However, there are many nanoscale pores in the Al layer. The fraction of nanoscale pores in the Al layer increases with a reduction in the Al layer thickness. The finite element method was used to simulate the Cu/Al/Cu rolling process. The simulation results reveal the effect of the Al layer thickness on the deformation characteristics of the Cu/Al/Cu laminate. Finally, we propose that the size effect of the Al layer thickness during Cu/Al/Cu laminate rolling may offer a method to fabricate 'nanoporous' Al sandwich laminate foils. Such foils can be used in electromagnetic shielding of electrical devices and noisy shielding of building.

Effect of stacking angles on mechanical properties and damage propagation of plain woven carbon fiber laminates

NASA Astrophysics Data System (ADS)

Zhuang, Weimin; Ao, Wenhong

2018-03-01

Damage propagation induced failure is a predominant damage mechanism. This study is aimed at assessing the damage state and damage propagation induced failure with different stacking angles, of woven carbon fiber/epoxy laminates subjected to quasi-static tensile and bending load. Different stages of damage processing and damage behavior under the bending load are investigated by Scanning Electron Microscopy (SEM). The woven carbon fiber/epoxy laminates which are stacked at six different angles (0°, 15°, 30°, 45°, 60°, 75°) with eight plies have been analyzed: [0]8, [15]8, [30]8, [45]8, [60]8, [75]8. Three-point bending test and quasi-static tensile test are used in validating the woven carbon fiber/epoxy laminates’ mechanical properties. Furthermore, the damage propagation and failure modes observed under flexural loading is correlated with flexural force and load-displacement behaviour respectively for the laminates. The experimental results have indicated that [45]8 laminate exhibits the best flexural performance in terms of energy absorption duo to its pseudo-ductile behaviour but the tensile strength and flexural strength drastically decreased compared to [0]8 laminate. Finally, SEM micrographs of specimens and fracture surfaces are used to reveal the different types of damage of the laminates with different stacking angles.

Multi-scale modelling of non-uniform consolidation of uncured toughened unidirectional prepregs

NASA Astrophysics Data System (ADS)

Sorba, G.; Binetruy, C.; Syerko, E.; Leygue, A.; Comas-Cardona, S.; Belnoue, J. P.-H.; Nixon-Pearson, O. J.; Ivanov, D. S.; Hallett, S. R.; Advani, S. G.

2018-05-01

Consolidation is a crucial step in manufacturing of composite parts with prepregs because its role is to eliminate inter- and intra-ply gaps and porosity. Some thermoset prepreg systems are toughened with thermoplastic particles. Depending on their size, thermoplastic particles can be either located in between plies or distributed within the inter-fibre regions. When subjected to transverse compaction, resin will bleed out of low-viscosity unidirectional prepregs along the fibre direction, whereas one would expect transverse squeeze flow to dominate for higher viscosity prepregs. Recent experimental work showed that the consolidation of uncured toughened prepregs involves complex flow and deformation mechanisms where both bleeding and squeeze flow patterns are observed [1]. Micrographs of compacted and cured samples confirm these features as shown in Fig.1. A phenomenological model was proposed [2] where bleeding flow and squeeze flow are combined. A criterion for the transition from shear flow to resin bleeding was also proposed. However, the micrographs also reveal a resin rich layer between plies which may be contributing to the complex flow mechanisms during the consolidation process. In an effort to provide additional insight into these complex mechanisms, this work focuses on the 3D numerical modelling of the compaction of uncured toughened prepregs in the cross-ply configuration described in [1]. A transversely isotropic fluid model is used to describe the flow behaviour of the plies coupled with interplay resin flow of an isotropic fluid. The multi-scale flow model used is based on [3, 4]. A numerical parametric study is carried out where the resin viscosity, permeability and inter-ply thickness are varied to identify the role of important variables. The squeezing flow and the bleeding flow are compared for a range of process parameters to investigate the coupling and competition between the two flow mechanisms. Figure 4 shows the predicted displacement of the sample edge with the multi-scale compaction model after one time step [3]. The ply distortion and resin flow observed in Fig.1 is qualitatively retrieved by the computational model.

Standardization of carbon-phenolic composite test methodology

NASA Technical Reports Server (NTRS)

Hall, W. B.

1986-01-01

The objective of this study was to evaluate the residual volatiles, filler content, and resin flow test procedures for carbon-phenolic prepreg materials. The residual volatile test procedure was rewritten with tighter procedure control which was then evaluated by round robin testing by four laboratories on the same rolls of prepreg. Results indicated that the residual volatiles test was too operator and equipment dependent to be reliable, and it was recommended that the test be discontinued. The resin flow test procedures were rewritten with tighter procedure control, and it is now considered to be an acceptable test. It was recommended that the filler content determination be made prior to prepregging.

Development of a Spectra Fabric PASGT-Type Personnel Helmet

DTIC Science & Technology

2015-06-01

ABSTRACT This report documents an effort that took place from October 1987 to September 1989 by AlliedSignal Inc. to develop a resin prepreg ...PASGT) helmet, but with at least 1/3 weight reduction utilizing Spectra® woven fabric prepreg . During the performance period, Allied evaluated

Process Makes Thermoplastic Prepreg Ribbon

NASA Technical Reports Server (NTRS)

Wilson, Maywood L.; Johnson, Gary S.

1995-01-01

Manufacturing process produces ribbon of composite material (prepreg) consisting of continuous lengthwise fibers impregnated with thermoplastic resin. Ribbon can later be cut into sheets of required sizes and shapes, stacked, then heated under pressure to form composite-material structural components. Process accommodates variety of thermoplastic resins and variety of fibers.

Fracture Toughness of Carbon Fiber Composites Containing Various Fiber Sizings and a Puncture Self-Healing Thermoplastic Matrix

NASA Technical Reports Server (NTRS)

Cano, Roberto J.; Grimsley, Brian W.; Ratcliffe, James G.; Gordon, Keith L.; Smith, Joseph G.; Siochi, Emilie J.

2015-01-01

Ongoing efforts at NASA Langley Research Center (LaRC) have resulted in the identification of several commercially available thermoplastic resin systems which self-heal after ballistic impact and through penetration. One of these resins, polybutylene graft copolymer (PBg), was selected as a matrix for processing with unsized carbon fibers to fabricate reinforced composites for further evaluation. During process development, data from thermo-physical analyses was utilized to determine a processing cycle to fabricate laminate panels, which were analyzed by photo microscopy and acid digestion. The process cycle was further optimized based on these results to fabricate panels for mechanical property characterization. The results of the processing development effort of this composite material, as well as the results of the mechanical property characterization, indicated that bonding between the fiber and PBg was not adequate. Therefore, three sizings were investigated in this work to assess their potential to improve fiber/matrix bonding compared to previously tested unsized IM7 fiber. Unidirectional prepreg was made at NASA LaRC from three sized carbon fibers and utilized to fabricate test coupons that were tested in double cantilever beam configurations to determine GIc fracture toughness.

Polyimide Composites from 'Salt-Like' Solution Precursors

NASA Technical Reports Server (NTRS)

Cano, Roberto J.; Hou, Tan H.; Weiser, Erik S.; SaintClair, Terry L.

2001-01-01

Four NASA Langley-developed polyimide matrix resins, LaRC(TM)-IA, LaRC(TM)-IAX, LaRC(TM)-8515 and LaRC(TM)-PETI-5, were produced via a 'saltlike' process developed by Unitika Ltd. The salt-like solutions (65% solids in NMP) were prepregged onto Hexcel IM7 carbon fiber using the NASA LaRC multipurpose tape machine. Process parameters were determined and composite panels fabricated. The temperature dependent volatile depletion rates, the thermal crystallization behavior and the resin rheology were characterized. Composite molding cycles were developed which consistently yielded well consolidated, void-free laminated parts. Composite mechanical properties such as the short beam shear strength; the longitudinal and transverse flexural strength and flexural modulus; the longitudinal compression strength and modulus; and the open hole compression strength and compression after impact strength were measured at room temperature and elevated temperatures. The processing characteristics and the composite mechanical properties of the four intermediate modulus carbon fiber/polyimide matrix composites were compared to existing data on the same polyimide resin systems and IM7 carbon fiber manufactured via poly(amide acid) solutions (30-35% solids in NMP). This work studies the effects of varying the synthetic route on the processing and mechanical properties of the polyimide composites.

Manufacturing and shear response characterization of carbon nanofiber modified CFRP using the out-of-autoclave-vacuum-bag-only cure process.

PubMed

McDonald, Erin E; Wallace, Landon F; Hickman, Gregory J S; Hsiao, Kuang-Ting

2014-01-01

The interlaminar shear response is studied for carbon nanofiber (CNF) modified out-of-autoclave-vacuum-bag-only (OOA-VBO) carbon fiber reinforced plastic (CFRP). Commercial OOA-VBO prepregs were coated with a CNF modified epoxy solution and a control epoxy solution without CNF to make CNF modified samples and control samples, respectively. Tensile testing was used to study the in-plane shear performance of [± 45°]4s composite laminates. Significant difference in failure modes between the control and CNF modified CFRPs was identified. The control samples experienced half-plane interlaminar delamination, whereas the CNF modified samples experienced a localized failure in the intralaminar region. Digital image correlation (DIC) surface strain results of the control sample showed no further surface strain increase along the delaminated section when the sample was further elongated prior to sample failure. On the other hand, the DIC results of the CNF modified sample showed that the surface strain increased relatively and uniformly across the CFRP as the sample was further elongated until sample failure. The failure mode evidence along with microscope pictures indicated that the CNF modification acted as a beneficial reinforcement inhibiting interlaminar delamination.

Manufacturing and Shear Response Characterization of Carbon Nanofiber Modified CFRP Using the Out-of-Autoclave-Vacuum-Bag-Only Cure Process

PubMed Central

McDonald, Erin E.; Wallace, Landon F.; Hickman, Gregory J. S.; Hsiao, Kuang-Ting

2014-01-01

The interlaminar shear response is studied for carbon nanofiber (CNF) modified out-of-autoclave-vacuum-bag-only (OOA-VBO) carbon fiber reinforced plastic (CFRP). Commercial OOA-VBO prepregs were coated with a CNF modified epoxy solution and a control epoxy solution without CNF to make CNF modified samples and control samples, respectively. Tensile testingwas used to study the in-plane shear performance of [±45°]4s composite laminates. Significant difference in failure modes between the control and CNF modified CFRPs was identified. The control samples experienced half-plane interlaminar delamination, whereas the CNF modified samples experienced a localized failure in the intralaminar region. Digital image correlation (DIC) surface strain results of the control sample showed no further surface strain increase along the delaminated section when the sample was further elongated prior to sample failure. On the other hand, the DIC results of the CNF modified sample showed that the surface strain increased relatively and uniformly across the CFRP as the sample was further elongated until sample failure. The failure mode evidence along with microscope pictures indicated that the CNF modification acted as a beneficial reinforcement inhibiting interlaminar delamination. PMID:24688435

Flytrap-inspired robot using structurally integrated actuation based on bistability and a developable surface.

PubMed

Kim, Seung-Won; Koh, Je-Sung; Lee, Jong-Gu; Ryu, Junghyun; Cho, Maenghyo; Cho, Kyu-Jin

2014-09-01

The Venus flytrap uses bistability, the structural characteristic of its leaf, to actuate the leaf's rapid closing motion for catching its prey. This paper presents a flytrap-inspired robot and novel actuation mechanism that exploits the structural characteristics of this structure and a developable surface. We focus on the concept of exploiting structural characteristics for actuation. Using shape memory alloy (SMA), the robot actuates artificial leaves made from asymmetrically laminated carbon fiber reinforced prepregs. We exploit two distinct structural characteristics of the leaves. First, the bistability acts as an implicit actuator enabling rapid morphing motion. Second, the developable surface has a kinematic constraint that constrains the curvature of the artificial leaf. Due to this constraint, the curved artificial leaf can be unbent by bending the straight edge orthogonal to the curve. The bending propagates from one edge to the entire surface and eventually generates an overall shape change. The curvature change of the artificial leaf is 18 m(-1) within 100 ms when closing. Experiments show that these actuation mechanisms facilitate the generation of a rapid and large morphing motion of the flytrap robot by one-way actuation of the SMA actuators at a local position.

Mechanistic Effects of Porosity on Structural Composite Materials

NASA Astrophysics Data System (ADS)

Siver, Andrew

As fiber reinforced composites continue to gain popularity as primary structures in aerospace, automotive, and powersports industries, quality control becomes an extremely important aspect of materials and mechanical engineering. The ability to recognize and control manufacturing induced defects can greatly reduce the likelihood of unexpected catastrophic failure. Porosity is the result of trapped volatiles or air bubbles during the layup process and can significantly compromise the strength of fiber reinforced composites. A comprehensive study was performed on an AS4C-UF3352 TCR carbon fiber-epoxy prepreg system to determine the effect of porosity on flexural, shear, low-velocity impact, and damage residual strength properties. Autoclave cure pressure was controlled to induce varying levels of porosity to construct six laminates with porosity concentrations between 0-40%. Porosity concentrations were measured using several destructive and nondestructive techniques including resin burnoff, sectioning and optical analysis, and X-ray computed tomography (CT) scanning. Ultrasonic transmission, thermography, and CT scanning provided nondestructive imaging to evaluate impact damage. A bilinear relationship accurately characterizes the change in mechanical properties with increasing porosity. Strength properties are relatively unaffected when porosity concentrations are below approximately 2.25% and decrease linearly by up to 40% in high porosity specimens.

Damage Tolerance of Pre-Stressed Composite Panels Under Impact Loads

NASA Astrophysics Data System (ADS)

Johnson, Alastair F.; Toso-Pentecôte, Nathalie; Schueler, Dominik

2014-02-01

An experimental test campaign studied the structural integrity of carbon fibre/epoxy panels preloaded in tension or compression then subjected to gas gun impact tests causing significant damage. The test programme used representative composite aircraft fuselage panels composed of aerospace carbon fibre toughened epoxy prepreg laminates. Preload levels in tension were representative of design limit loads for fuselage panels of this size, and maximum compression preloads were in the post-buckle region. Two main impact scenarios were considered: notch damage from a 12 mm steel cube projectile, at velocities in the range 93-136 m/s; blunt impact damage from 25 mm diameter glass balls, at velocities 64-86 m/s. The combined influence of preload and impact damage on panel residual strengths was measured and results analysed in the context of damage tolerance requirements for composite aircraft panels. The tests showed structural integrity well above design limit loads for composite panels preloaded in tension and compression with visible notch impact damage from hard body impact tests. However, blunt impact tests on buckled compression loaded panels caused large delamination damage regions which lowered plate bending stiffness and reduced significantly compression strengths in buckling.

Study of interface influence on bending performance of CFRP with embedded optical fibers

NASA Astrophysics Data System (ADS)

Liu, Rong-mei; Liang, Da-kai

2008-11-01

Studies showed that the bending strength of composite would be affected by embedded optical fibers. Interface strength between the embedded optical fiber and the matrix was studied in this paper. Based on the single fiber pull out tests, the interfacial shear strength between the coating and the clad is the weakest. The shear strength of the optical fiber used in this study is near to 0.8MPa. In order to study the interfacial effect on bending property of generic smart structure, a quasi-isotropic composite laminates were produced from Toray T300C/ epoxy prepreg. Optical fibers were embedded within different orientation plies of the plates, with the optical fibers embedded in the same direction. Accordingly, five different types of plates were produced. Impact tests were carried out on the 5 different plate types. It is shown that when the fiber was embedded at the upper layer, the bending strength drops mostly. The bending normal stress on material arrives at the maximum. So does the normal stress applied on the optical fiber at the surface. Therefore, destructions could originate at the interface between the coating and the clad foremost. The ultimate strength of the smart structure will be affected furthest.

Layerwise Finite Elements for Smart Piezoceramic Composite Plates in Thermal Environments

NASA Technical Reports Server (NTRS)

Saravanos, Dimitris A.; Lee, Ho-Jun

1996-01-01

Analytical formulations are presented which account for the coupled mechanical, electrical, and thermal response of piezoelectric composite laminates and plate structures. A layerwise theory is formulated with the inherent capability to explicitly model the active and sensory response of piezoelectric composite plates having arbitrary laminate configurations in thermal environments. Finite element equations are derived and implemented for a bilinear 4-noded plate element. Application cases demonstrate the capability to manage thermally induced bending and twisting deformations in symmetric and antisymmetric composite plates with piezoelectric actuators, and show the corresponding electrical response of distributed piezoelectric sensors. Finally, the resultant stresses in the thermal piezoelectric composite laminates are investigated.

Synthesis and characterization of laminated Si/SiC composites.

PubMed

Naga, Salma M; Kenawy, Sayed H; Awaad, Mohamed; Abd El-Wahab, Hamada S; Greil, Peter; Abadir, Magdi F

2013-01-01

Laminated Si/SiC ceramics were synthesized from porous preforms of biogenous carbon impregnated with Si slurry at a temperature of 1500 °C for 2 h. Due to the capillarity infiltration with Si, both intrinsic micro- and macrostructure in the carbon preform were retained within the final ceramics. The SEM micrographs indicate that the final material exhibits a distinguished laminar structure with successive Si/SiC layers. The produced composites show weight gain of ≈5% after heat treatment in air at 1300 °C for 50 h. The produced bodies could be used as high temperature gas filters as indicated from the permeability results.

Polyimide Prepregs With Improved Tack

NASA Technical Reports Server (NTRS)

Vanucci, R.

1987-01-01

Drape and tack improved without loss of strength. Composites made with PMR-15 (or equivalent) polyimides have gained acceptance as viable engineering materials for high-use-temperature applications. Acceptance due to both thermo-oxidative stability of PMR-15 (or equivalent) and ease which PMR-15 (or equivalent) prepreg materials processed into composite structures.

Laminated Thin Shell Structures Subjected to Free Vibration in a Hygrothermal Environment

NASA Technical Reports Server (NTRS)

Gotsis, Pascal K.; Guptill, James D.

1994-01-01

Parametric studies were performed to assess the effects of various parameters on the free-vibration behavior (natural frequencies) of (+/- theta)(sub 2) angle-ply, fiber composite, thin shell structures in a hygrothermal environment. Knowledge of the natural frequencies of structures is important in considering their response to various kinds of excitation, especially when structures and force systems are complex and when excitations are not periodic. The three dimensional, finite element structural analysis computer code CSTEM was used in the Cray YMP computer environment. The fiber composite shell was assumed to be cylindrical and made from T300 graphite fibers embedded in an intermediate-modulus, high-strength matrix. The following parameters were investigated: the length and the laminate thickness of the shell, the fiber orientation, the fiber volume fraction, the temperature profile through the thickness of the laminate, and laminates with different ply thicknesses. The results indicate that the fiber orientation and the length of the laminated shell had significant effects on the natural frequencies. The fiber volume fraction, the laminate thickness, and the temperature profile through the shell thickness had weak effects on the natural frequencies. Finally, the laminates with different ply thicknesses had an insignificant influence on the behavior of the vibrated laminated shell. Also, a single through-the-thickness, eight-node, three dimensional composite finite element analysis appears to be sufficient for investigating the free-vibration behavior of thin, composite, angle-ply shell structures.

Aspects of the Fracture Toughness of Carbon Nanotube Modified Epoxy Polymer Composites

NASA Astrophysics Data System (ADS)

Mirjalili, Vahid

Epoxy resins used in fibre reinforced composites exhibit a brittle fracture behaviour, because they show no sign of damage prior to a catastrophic failure. Rubbery materials and micro-particles have been added to epoxy resins to improve their fracture toughness, which reduces strength and elastic properties. In this research, carbon nanotubes (CNTs) are investigated as a potential toughening agent for epoxy resins and carbon fibre reinforced composites, which can also enhance strength and elastic properties. More specifically, the toughening mechanisms of CNTs are investigated theoretically and experimentally. The effect of aligned and randomly oriented carbon nanotubes (CNTs) on the fracture toughness of polymers was modelled using Elastic Plastic Fracture Mechanics. Toughening from CNT pull-out and rupture were considered, depending on the CNTs critical length. The model was used to identify the effect of CNTs geometrical and mechanical properties on the fracture toughness of CNT-modified epoxies. The modelling results showed that a uniform dispersion and alignment of a high volume fraction of CNTs normal to the crack growth plane would lead to the maximum fracture toughness enhancement. To achieve a uniform dispersion, the effect of processing on the dispersion of single walled and multi walled CNTs in epoxy resins was investigated. An instrumented optical microscope with a hot stage was used to quantify the evolution of the CNT dispersion during cure. The results showed that the reduction of the resin viscosity at temperatures greater than 100 °C caused an irreversible re-agglomeration of the CNTs in the matrix. The dispersion quality was then directly correlated to the fracture toughness of the modified resin. It was shown that the fine tuning of the ratio of epoxy resin, curing agent and CNT content was paramount to the improvement of the base resin fracture toughness. For the epoxy resin (MY0510 from Hexcel), an improvement of 38% was achieved with 0.3 wt.% of Single Walled CNT (SWNT). Finally, the CNT-modified epoxy resin was used to manufacture carbon fibre laminates by resin film infusion and prepreg technologies. The Mode I and Mode II delamination properties of the CNT-modified composite increased by 140% and 127%, respectively. In contrast, this improvement was not observed for the base CNT-modified polymers, used to manufacture the composite laminates. A qualitative analysis of the fractured surface using a Scanning Electron Microscope revealed a good dispersion in the composites samples, confirming the importance of processing to harness the full potential of carbon nanotubes for toughening polymer composites.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mensah, P.F.; Stubblefield, M.A.; Pang, S.S.

Thermal characterization of a prepreg fabric used as the bonding material to join composite pipes has been modeled and solved using finite difference modeling (FDM) numerical analysis technique for one dimensional heat transfer through the material. Temperature distributions within the composite pipe joint are predicted. The prepreg material has temperature dependent thermal properties. Thus the resulting boundary value equations are non linear and analytical solutions cannot be obtained. This characterization is pertinent in determining the temperature profile in the prepreg layer during the manufacturing process for optimization purposes. In addition, in order to assess the effects of induced thermal stressmore » in the joint, the temperature profile is needed. The methodology employed in this analysis compares favorably with data from experimentation.« less

Integrated analysis and design of thick composite structures for optimal passive damping characteristics

NASA Technical Reports Server (NTRS)

Saravanos, D. A.

1993-01-01

The development of novel composite mechanics for the analysis of damping in composite laminates and structures and the more significant results of this effort are summarized. Laminate mechanics based on piecewise continuous in-plane displacement fields are described that can represent both intralaminar stresses and interlaminar shear stresses and the associated effects on the stiffness and damping characteristics of a composite laminate. Among other features, the mechanics can accurately model the static and damped dynamic response of either thin or thick composite laminates, as well as, specialty laminates with embedded compliant damping layers. The discrete laminate damping theory is further incorporated into structural analysis methods. In this context, an exact semi-analytical method for the simulation of the damped dynamic response of composite plates was developed. A finite element based method and a specialty four-node plate element were also developed for the analysis of composite structures of variable shape and boundary conditions. Numerous evaluations and applications demonstrate the quality and superiority of the mechanics in predicting the damped dynamic characteristics of composite structures. Finally, additional development was focused on the development of optimal tailoring methods for the design of thick composite structures based on the developed analytical capability. Applications on composite plates illustrated the influence of composite mechanics in the optimal design of composites and the potential for significant deviations in the resultant designs when more simplified (classical) laminate theories are used.

Integration of Carbon Fiber Composite Materials into Air-Cooled Reciprocating Piston Engines for UA V Applications

DTIC Science & Technology

2012-05-04

Wrapping Pre-impregnated CFRP unidirectional and +/-45° woven carbon fiber fabric prepreg was used for the loop. Pre-impregnated material was a...viable application for the connecting rod because there are no complex geometries for the CFRP to negotiate. Prepreg aids in maintaining proper fiber

Out-of-Autoclave Cure Composites

NASA Technical Reports Server (NTRS)

Hayes, Brian S.

2015-01-01

As the size of aerospace composite parts exceeds that of even the largest autoclaves, the development of new out-of-autoclave processes and materials is necessary to ensure quality and performance. Many out-of-autoclave prepreg systems can produce high-quality composites initially; however, due to long layup times, the resin advancement commonly causes high void content and variations in fiber volume. Applied Poleramic, Inc. (API), developed an aerospace-grade benzoxazine matrix composite prepreg material that offers more than a year out-time at ambient conditions and provides exceptionally low void content when out-of-autoclave cured. When compared with aerospace epoxy prepreg systems, API's innovation offers significant improvements in terms of out-time at ambient temperature and the corresponding tack retention. The carbon fiber composites developed with the optimized matrix technology have significantly better mechanical performance in terms of hot-wet retention and compression when compared with aerospace epoxy matrices. These composites also offer an excellent overall balance of properties. This matrix system imparts very low cure shrinkage, low coefficient of thermal expansion, and low density when compared with most aerospace epoxy prepreg materials.

Flanking genes of an essential gene give information about the evolution of metazoa.

PubMed

Zimek, Alexander; Weber, Klaus

2011-04-01

We collected as much information as possible on new lamin genes and their flanking genes. The number of lamin genes varies from 1 to 4 depending more or less on the phylogenetic position of the species. Strong genome drift is recognised by fewer and unusually placed introns and a change in flanking genes. This applies to the nematode Caenorhabditis elegans, the insect Drosophila melanogaster, the urochordate Ciona intestinalis, the annelid Capitella teleta and the planaria Schmidtea mediterranea. In contrast stable genomes show astonishing conservation of the flanking genes. These are identical in the sea anemone Nematostella vectensis and the cephalochordate Branchiostoma floridae lamin B1 gene. Even in the lamin B1 genes from Xenopus tropicalis and man one of the flanking genes is conserved. Finally our analysis forms the basis for a molecular analysis of metazoan phylogeny. Copyright © 2010 Elsevier GmbH. All rights reserved.

Development of optimized PPP insulated pipe-cable systems in the commercial voltage range. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allam, E.M.; McKean, A.L.

1992-05-01

The primary objectives of this project included the development of an alternate domestic source of Paper-Polypropylene-Paper (PPP) laminate and the development of optimized designs for PPP-insulated pipe-type cable systems in the commercial voltage range. The development of a domestic source of PPP laminate was successfully completed. This laminate was utilized throughout the program for fabrication of full-size prototype cables submitted for laboratory qualification tests. Selected cables at rated voltages of 138, 230 and 345kV have been designed, fabricated and subjected to the series of qualification tests leading to full laboratory qualification. An optimized design of 2000 kcmil, 345kV cable insulatedmore » with 600 mils of domestic PPP laminate was fabricated and successfully passed all laboratory qualification tests. This cable design was subsequently installed at Waltz Mill to undergo the series of field tests leading to full commercial qualification.« less

Master plot analysis of microcracking in graphite/epoxy and graphite/PEEK laminates

NASA Technical Reports Server (NTRS)

Nairn, John A.; Hu, Shoufeng; Bark, Jong Song

1993-01-01

We used a variational stress analysis and an energy release rate failure criterion to construct a master plot analysis of matrix microcracking. In the master plot, the results for all laminates of a single material are predicted to fall on a single line whose slope gives the microcracking toughness of the material. Experimental results from 18 different layups of AS4/3501-6 laminates show that the master plot analysis can explain all observations. In particular, it can explain the differences between microcracking of central 90 deg plies and of free-surface 90 deg plies. Experimental results from two different AS4/PEEK laminates tested at different temperatures can be explained by a modified master plot that accounts for changes in the residual thermal stresses. Finally, we constructed similar master plot analyses for previous literature microcracking models. All microcracking theories that ignore the thickness dependence of the stresses gave poor results.

[Absorbable shanching satin rb-bFGF prepreg sheet and expansion hemostatic sponge together to cure epistaxis with blood disease].

PubMed

Liu, Hua; Gao, Zhanmei; Song, Yang; Lu, Mancun

2014-01-01

This study investigated the effects and Numerical Rating Pain Scale (NRS) of using absorbable shanching satin rb-bFGF prepreg sheet and expansion hemostatic sponge together nasal packing in the control of epistaxis with blood disease, and compared it with traditional vaseline gauze. Ninety-six blood disease patient with epistaxis were enrolled between January 2009 and February 2011, they were divided into two groups at random, and differently treated with absorbable shanching satin rb-bFGF prepreg sheet and the vaseline gauze nasal packing for haemostasis. Then haemostasis efficacy,the hemorrhage rate after nasal packing removed and host response, such as nasal pain and headache, which evaluated pain degrees against NRS, were all observed. There was no significant difference between the two groups of the haemostatic effect. But the hemorrhage rate of treatment group was obviously lower than that of the control group after paching,in addition, host responses, such as nasal pain and headache, remarkably better than the control group, the difference had statistical significance. It is indicate that absorbable shanching satin rb-bFGF prepreg sheet presents reliable hemostasis effect, good biocompatibility and compliance; the pain and headache caused by packing are superior to vaseline gauze. Moreover, this method avoids the direct touch of vaseline gauze with nasal mucosal wound, and reduce hemorrhage after packing. Absorbable shanching satin rb-bFGF prepreg sheet and expansion hemostatic sponge together is better to select the nasal packing material for blood disease patient with epistaxis.

Evaluation of Workpiece Temperature during Drilling of GLARE Fiber Metal Laminates Using Infrared Techniques: Effect of Cutting Parameters, Fiber Orientation and Spray Mist Application.

PubMed

Giasin, Khaled; Ayvar-Soberanis, Sabino

2016-07-28

The rise in cutting temperatures during the machining process can influence the final quality of the machined part. The impact of cutting temperatures is more critical when machining composite-metal stacks and fiber metal laminates due to the stacking nature of those hybrids which subjects the composite to heat from direct contact with metallic part of the stack and the evacuated hot chips. In this paper, the workpiece surface temperature of two grades of fiber metal laminates commercially know as GLARE is investigated. An experimental study was carried out using thermocouples and infrared thermography to determine the emissivity of the upper, lower and side surfaces of GLARE laminates. In addition, infrared thermography was used to determine the maximum temperature of the bottom surface of machined holes during drilling GLARE under dry and minimum quantity lubrication (MQL) cooling conditions under different cutting parameters. The results showed that during the machining process, the workpiece surface temperature increased with the increase in feed rate and fiber orientation influenced the developed temperature in the laminate.

Evaluation of Workpiece Temperature during Drilling of GLARE Fiber Metal Laminates Using Infrared Techniques: Effect of Cutting Parameters, Fiber Orientation and Spray Mist Application

PubMed Central

Giasin, Khaled; Ayvar-Soberanis, Sabino

2016-01-01

The rise in cutting temperatures during the machining process can influence the final quality of the machined part. The impact of cutting temperatures is more critical when machining composite-metal stacks and fiber metal laminates due to the stacking nature of those hybrids which subjects the composite to heat from direct contact with metallic part of the stack and the evacuated hot chips. In this paper, the workpiece surface temperature of two grades of fiber metal laminates commercially know as GLARE is investigated. An experimental study was carried out using thermocouples and infrared thermography to determine the emissivity of the upper, lower and side surfaces of GLARE laminates. In addition, infrared thermography was used to determine the maximum temperature of the bottom surface of machined holes during drilling GLARE under dry and minimum quantity lubrication (MQL) cooling conditions under different cutting parameters. The results showed that during the machining process, the workpiece surface temperature increased with the increase in feed rate and fiber orientation influenced the developed temperature in the laminate. PMID:28773757

Etude expérimentale de la lamination des stromatolithes à Rivularia haematites en climat tempéré: édification des lamines micritiques

NASA Astrophysics Data System (ADS)

Caudwell, Christiane; Lang, Jacques; Pascal, André

1997-06-01

The lamination of Rivularia haematites stromatolites (D.C.) Agardh was studied experimentally for 7 years. Micritic laminae are found to form in three stages: biological formation of dark laminae during the wet season, microsparitic calcification of these laminae in the form of clearly individualized polycrystalline aggregates and, finally, micritization of the latter by bacterial action. These three stages develop over 2 to 3 years. The occurrence of transverse, longitudinal and circular microfibrils in the outer sheath is thought to explain the nucleation and the three-dimensional structure of the microsparitic crystals of the dark laminae and of the polycrystalline aggregates.

Viscoelastic behavior and lifetime (durability) predictions. [for laminated fiber reinforced plastics

NASA Technical Reports Server (NTRS)

Brinson, R. F.

1985-01-01

A method for lifetime or durability predictions for laminated fiber reinforced plastics is given. The procedure is similar to but not the same as the well known time-temperature-superposition principle for polymers. The method is better described as an analytical adaptation of time-stress-super-position methods. The analytical constitutive modeling is based upon a nonlinear viscoelastic constitutive model developed by Schapery. Time dependent failure models are discussed and are related to the constitutive models. Finally, results of an incremental lamination analysis using the constitutive and failure model are compared to experimental results. Favorable results between theory and predictions are presented using data from creep tests of about two months duration.

Synthesis and characterization of laminated Si/SiC composites

PubMed Central

Naga, Salma M.; Kenawy, Sayed H.; Awaad, Mohamed; Abd El-Wahab, Hamada S.; Greil, Peter; Abadir, Magdi F.

2012-01-01

Laminated Si/SiC ceramics were synthesized from porous preforms of biogenous carbon impregnated with Si slurry at a temperature of 1500 °C for 2 h. Due to the capillarity infiltration with Si, both intrinsic micro- and macrostructure in the carbon preform were retained within the final ceramics. The SEM micrographs indicate that the final material exhibits a distinguished laminar structure with successive Si/SiC layers. The produced composites show weight gain of ≈5% after heat treatment in air at 1300 °C for 50 h. The produced bodies could be used as high temperature gas filters as indicated from the permeability results. PMID:25685404

On Healable Polymers and Fiber-Reinforced Composites

NASA Astrophysics Data System (ADS)

Nielsen, Christian Eric

Polymeric materials capable of healing damage would be valuable in structural applications where access for repair is limited. Approaches to creating such materials are reviewed, with the present work focusing on polymers with thermally reversible covalent cross-links. These special cross-links are Diels-Alder (DA) adducts, which can be separated and re-formed, enabling healing of mechanical damage at the molecular level. Several DA-based polymers, including 2MEP4FS, are mechanically and thermally characterized. The polymerization reaction of 2MEP4FS is modeled and the number of established DA adducts is associated with the glass transition temperature of the polymer. The models are applied to concentric cylinder rotational measurements of 2MEP4FS prepolymer at room and elevated temperatures to describe the viscosity as a function of time, temperature, and conversion. Mechanical damage including cracks and scratches are imparted in cured polymer samples and subsequently healed. Damage due to high temperature thermal degradation is observed to not be reversible. The ability to repair damage without flowing polymer chains makes DA-based healable polymers particularly well-suited for crack healing. The double cleavage drilled compression (DCDC) fracture test is investigated as a useful method of creating and incrementally growing cracks in a sample. The effect of sample geometry on the fracture behavior is experimentally and computationally studied. Computational and empirical models are developed to estimate critical stress intensity factors from DCDC results. Glass and carbon fiber-reinforced composites are fabricated with 2MEP4FS as the matrix material. A prepreg process is developed that uses temperature to control the polymerization rate of the monomers and produce homogeneous prepolymer for integration with a layer of unidirectional fiber. Multiple prepreg layers are laminated to form multi-layered cross-ply healable composites, which are characterized in bending using dynamic mechanical analysis (DMA). Simple, theory-based analyses indicate that numerous cracks are present before testing due to thermal expansion mismatches, and during testing, these cracks must be healing. Extending healable composites to include healable fiber-matrix interfaces is discussed as future work and interfacial healing characterization approaches are considered.

Modelling and simulation of the consolidation behavior during thermoplastic prepreg composites forming process

NASA Astrophysics Data System (ADS)

Xiong, H.; Hamila, N.; Boisse, P.

2017-10-01

Pre-impregnated thermoplastic composites have recently attached increasing interest in the automotive industry for their excellent mechanical properties and their rapid cycle manufacturing process, modelling and numerical simulations of forming processes for composites parts with complex geometry is necessary to predict and optimize manufacturing practices, especially for the consolidation effects. A viscoelastic relaxation model is proposed to characterize the consolidation behavior of thermoplastic prepregs based on compaction tests with a range of temperatures. The intimate contact model is employed to predict the evolution of the consolidation which permits the microstructure prediction of void presented through the prepreg. Within a hyperelastic framework, several simulation tests are launched by combining a new developed solid shell finite element and the consolidation models.

Probabilistic analysis of the behavior of polymer matrix composite materials reinforced by different types of fibers

NASA Astrophysics Data System (ADS)

Harb, N.; Bezzazi, B.; Mehraz, S.; Hamitouche, K.; Dilmi, H.

2017-11-01

The requests of lightening of the structures and gains in performance lead to search for new materials and the associated processes for aeronautical and space applications. Long-fiber composites have been used for many years for these applications; they make it possible to reduce the mass of the structures because of their excellent compromise of mass/rigidity / resistance. The materials in general contain defects which are essentially due to their nature and their mode of elaboration. To this purpuse, we carried out a probabilistic analysis of the mechanical behavior in three-point bending of composite materials with a thermosetting matrix in order to highlight the influence of the number of folds of the fibers and the nature of the fibers on the dispersion of the defects in the stratified structures fiberglass, carbon fiber laminates and hybrid (carbon / glass) laminates. From the results obtained, the dispersion of the defects is lower in the laminates of greater number of plies of the fibers and the hybrid laminates; the more the number of folds increases the more the mechanical characteristics increase; the hybrid laminates exhibit better mechanical properties compared to laminates of the same type of fiber. Finally, a morphological analysis of fracture structures and facies was investigated by scanning electron microscope (SEM) observations.

Quality control developments for graphite/PMR15 polyimide composites materials

NASA Technical Reports Server (NTRS)

Sheppard, C. H.; Hoggatt, J. T.

1979-01-01

The problem of lot-to-lot and within-lot variability of graphite/PMR-15 prepreg was investigated. The PMR-15 chemical characterization data were evaluated along with the processing conditions controlling the manufacture of PMR-15 resin and monomers. Manufacturing procedures were selected to yield a consistently reproducible graphite prepreg that could be processed into acceptable structural elements.

A New Silarylene-Siloxane Monomeric Resin for Structural Composites: Cure-Chemistry Insight and Thermal Properties of the Cured Matrix

DTIC Science & Technology

2013-03-01

remain nonvolatile during the entire fiber-infusion process and curing operation. The resin must offer several days of storage life before the prepreg ...shipboard handling and in-flight cyclic loading. The raw materials for the new resin and the process for making and curing the prepreg must be affordable

Development of Optimized Piezoelectric Bending Actuators for Use in an Insect Sized Flapping Wing Micro Air Vehicle

DTIC Science & Technology

2013-03-01

of microelectromechanical systems (MEMS) [37], and the epoxy in uncured pre-impregnated ( prepreg ) carbon fiber has also been used in bending [42] and...to assemble due to challenges in working with the carbon fiber. When the epoxy in the prepreg carbon fiber is used as a bonding agent, there is no

A study of damage zones or characteristic lengths as related to the fracture behavior of graphite/epoxy laminates

NASA Technical Reports Server (NTRS)

Yeow, Y. T.; Brinson, H. F.

1977-01-01

Uniaxial tensile tests conducted on a variety of graphite/epoxy laminates, containing narrow rectangular slits, square or circular holes with various aspect ratios are discussed. The techniques used to study stable crack or damage zone growth--namely, birefringence coatings, COD gages, and microscopic observations are discussed. Initial and final fracture modes are discussed as well as the effect of notch size and shape, and laminate type on the fracture process. Characteristic lengths are calculated and compared to each other using the point, average and inherent flaw theories. Fracture toughnesses are calculated by the same theories and compared to a boundary integral equation technique. Finite width K-calibration factors are also discussed.

77 FR 69790 - Certain Hot-Rolled Carbon Steel Flat Products From the People's Republic of China: Final Results...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-21

... fully stabilized; high strength low alloy; and the substrate for motor lamination steel may also enter... Steel Flat Products From the People's Republic of China: Final Results and Final No Shipments... antidumping duty order on certain hot- rolled carbon steel flat products (``hot-rolled steel'') from the...

Polymer Infiltration Studies

NASA Technical Reports Server (NTRS)

Marchello, Joseph M.

1993-01-01

Significant progress has been made on the preparation of carbon fiber composites using advanced polymer resins during the past three months. Current and ongoing research activities reported herein include: (1) Prepregger Hot Sled Operation; (2) Ribbonizing Powder-Impregnated Towpreg; (3) Textile Composites from Powder-Coated Towpreg: Role of Bulk Factor; and (4) Powder Curtain Prepreg Process. During the coming months research will be directed toward further development of the new powder curtain prepregging method and on ways to customize dry powder towpreg for textile and robotic applications in aircraft part fabrication. Studies of multi-tow powder prepregging and ribbon preparation will be conducted in conjunction with continued development of prepegging technology and the various aspects of composite part fabrication using customized towpreg. Also, work will continue on the analysis of the new solution prepegger.

Efficiency loss of thin film Cu(InxGa1-x)Se(S) solar panels by lamination process

NASA Astrophysics Data System (ADS)

Xu, Li

2017-04-01

Efficiency loss of thin film Cu(InxGa1-x)Se(S) (CIGS) solar panels by lamination process has been compromising the final output power in commercial products of solar modules, but few reports have been published on such issue, as the majority of the investigation is focused on the efficiency at the circuit level, i.e., before lamination process. In this paper, we studied the effect of lamination process to the efficiency loss of thin film CIGS solar panels. It was observed that the fill factor degradation dominated the efficiency loss with the small change of Voc and Jsc. Experiments showed that neither the temperature nor the pressure, nor the two combined in the lamination process is the root cause of the efficiency loss; instead, the ethylene vinyl acetate (EVA) layer as the encapsulation material which directly contacts the solar cell devices was the major factor responsible for the efficiency loss. It was found that the gel content of the cured EVA film after lamination was highly correlated to the efficiency loss. The higher the gel content, the higher the efficiency loss. The mismatch of coefficient of thermal expansion between the EVA film and the CIGS thin film resulted in compressive stress in the device layer after lamination process. The compressive stress is speculated to affect the lattice defects, but need to be confirmed with the measurement of capacitance voltage (CV) and drive level capacitance profiling (DLCP). Three-day sun soak was then carried out and it was observed that the fill factor recovered significantly and so did the efficiency. Experiments also showed that there was no impact of chemical erosion on the front electrode of transparent conductive oxide (TCO) films by chemicals released from the EVA films during lamination.

Studies of the Surface Treatment and Sizing of Carbon Fiber Surfaces on the Mechanical Properties of Composites Containing Carbon Fibers

NASA Technical Reports Server (NTRS)

Sherwood, Peter M. A.; Lease, Kevin B.; Locke, James E.; Tomblin, John S.; Wang, Youqi

1996-01-01

Carbon fiber reinforced composites are materials where carbon fibers are used to reinforce a matrix to produce a light and strong material with important applications in the aerospace industry. There are many aspects of the preparation of these materials that would benefit from a study which combines the research of groups involved in the production, testing and analysis of these materials, and studies of the basic surface chemistry involved. This final reports presents the results of a project that has developed a collaboration between groups in all three of the major research universities in the State of Kansas, and promises to lead to a collaborative program that covers the major aspects of composite development and application. Sherwood has provided initial fiber surface treatment and sizing together with fiber and composite surface analysis; Lease, Tomblin and Wang have worked together toward the goal of preparing pre-preg and fabrication of laminated panels; Locke has developed computational models to evaluate the effect of surface treatment (and chemistry) on mechanical properties; Lease, Tomblin and Wang have worked together to perform all necessary mechanical testing. The research has been focused on materials that would benefit the High Speed Civil Transport (HSCT) program. The group has visited Dr. Howard Maars and his colleagues at NASA Langley, and has focused their studies on the NASA requirements discussed in this meeting. An important development, requested by NASA scientists, has been the acquisition and study of K3B as a matrix material for the composites. The project has led to the successful acquisition and surface analysis of K3B, together with the successful deposition of this material onto surface oxidized carbon fibers. Mechanical testing, modelling and the construction of composite preparation equipment has been achieved during the grant period.

Detection of CFRP Composite Manufacturing Defects Using a Guided Wave Approach

NASA Technical Reports Server (NTRS)

Hudson, Tyler B.; Hou, Tan-Hung; Grimsley, Brian W.; Yuan, Fuh-Gwo

2015-01-01

NASA Langley Research Center is investigating a guided-wave based defect detection technique for as-fabricated carbon fiber reinforced polymer (CFRP) composites. This technique will be extended to perform in-process cure monitoring, defect detection and size determination, and ultimately a closed-loop process control to maximize composite part quality and consistency. The overall objective of this work is to determine the capability and limitations of the proposed defect detection technique, as well as the number and types of sensors needed to identify the size, type, and location of the predominant types of manufacturing defects associated with laminate layup and cure. This includes, porosity, gaps, overlaps, through-the-thickness fiber waviness, and in-plane fiber waviness. The present study focuses on detection of the porosity formed from variations in the matrix curing process, and on local overlaps intentionally introduced during layup of the prepreg. By terminating the cycle prematurely, three 24-ply unidirectional composite panels were manufactured such that each subsequent panel had a higher final degree of cure, and lower level of porosity. It was demonstrated that the group velocity, normal to the fiber direction, of a guided wave mode increased by 5.52 percent from the first panel to the second panel and 1.26 percent from the second panel to the third panel. Therefore, group velocity was utilized as a metric for degree of cure and porosity measurements. A fully non-contact guided wave hybrid system composed of an air-coupled transducer and a laser Doppler vibrometer (LDV) was used for the detection and size determination of an overlap By transforming the plate response from the time-space domain to the frequency-wavenumber domain, the total wavefield was then separated into the incident and backscatter waves. The overlap region was accurately imaged by using a zero-lag cross-correlation (ZLCC) imaging condition, implying the incident and backscattered waves are in phase over the overlap boundaries.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Janke, C.J.

Electron beam (EB) curing is a technology that promises, in certain applications, to deliver lower cost and higher performance polymer matrix composite (PMC) structures compared to conventional thermal curing processes. PMCs enhance performance by making products lighter, stronger, more durable, and less energy demanding. They are essential in weight- and performance-dominated applications. Affordable PMCs can enhance US economic prosperity and national security. US industry expects rapid implementation of electron beam cured composites in aircraft and aerospace applications as satisfactory properties are demonstrated, and implementation in lower performance applications will likely follow thereafter. In fact, at this time and partly becausemore » of discoveries made in this project, field demonstrations are underway that may result in the first fielded applications of electron beam cured composites. Serious obstacles preventing the widespread use of electron beam cured PMCs in many applications are their relatively poor interfacial properties and resin toughness. The composite shear strength and resin toughness of electron beam cured carbon fiber reinforced epoxy composites were about 25% and 50% lower, respectively, than those of thermally cured composites of similar formulations. The essential purpose of this project was to improve the mechanical properties of electron beam cured, carbon fiber reinforced epoxy composites, with a specific focus on composite shear properties for high performance aerospace applications. Many partners, sponsors, and subcontractors participated in this project. There were four government sponsors from three federal agencies, with the US Department of Energy (DOE) being the principal sponsor. The project was executed by Oak Ridge National Laboratory (ORNL), NASA and Department of Defense (DOD) participants, eleven private CRADA partners, and two subcontractors. A list of key project contacts is provided in Appendix A. In order to properly manage the large project team and properly address the various technical tasks, the CRADA team was organized into integrated project teams (IPT's) with each team focused on specific research areas. Early in the project, the end user partners developed ''exit criteria'', recorded in Appendix B, against which the project's success was to be judged. The project team made several important discoveries. A number of fiber coatings or treatments were developed that improved fiber-matrix adhesion by 40% or more, according to microdebond testing. The effects of dose-time and temperature-time profiles during the cure were investigated, and it was determined that fiber-matrix adhesion is relatively insensitive to the irradiation procedure, but can be elevated appreciably by thermal postcuring. Electron beam curable resin properties were improved substantially, with 80% increase in electron beam 798 resin toughness, and {approx}25% and 50% improvement, respectively, in ultimate tensile strength and ultimate tensile strain vs. earlier generation electron beam curable resins. Additionally, a new resin electron beam 800E was developed with generally good properties, and a very notable 120% improvement in transverse composite tensile strength vs. earlier generation electron beam cured carbon fiber reinforced epoxies. Chemical kinetics studies showed that reaction pathways can be affected by the irradiation parameters, although no consequential effects on material properties have been noted to date. Preliminary thermal kinetics models were developed to predict degree of cure vs. irradiation and thermal parameters. These models are continually being refined and validated. Despite the aforementioned impressive accomplishments, the project team did not fully realize the project objectives. The best methods for improving adhesion were combined with the improved electron beam 3K resin to make prepreg and uni-directional test laminates from which composite properties could be determined. Nevertheless, only minor improvements in the composite shear strength, and moderate improvements in the transverse tensile strength, were achieved. The project team was not satisfied with the laminate quality achieved, and low quality (specifically, high void fraction) laminates will compromise the composite properties. There were several problems with the prepregging and fabrication, many of them related to the use of new fiber treatments.« less

Finite element analysis of drilling in carbon fiber reinforced polymer composites

NASA Astrophysics Data System (ADS)

Phadnis, V. A.; Roy, A.; Silberschmidt, V. V.

2012-08-01

Carbon fiber reinforced polymer composite (CFRP) laminates are attractive for many applications in the aerospace industry especially as aircraft structural components due to their superior properties. Usually drilling is an important final machining process for components made of composite laminates. In drilling of CFRP, it is an imperative task to determine the maximum critical thrust forces that trigger inter-laminar and intra-laminar damage modes owing to highly anisotropic fibrous media; and negotiate integrity of composite structures. In this paper, a 3D finite element (FE) model of drilling in CFRP composite laminate is developed, which accurately takes into account the dynamic characteristics involved in the process along with the accurate geometrical considerations. A user defined material model is developed to account for accurate though thickness response of composite laminates. The average critical thrust forces and torques obtained using FE analysis, for a set of machining parameters are found to be in good agreement with the experimental results from literature.

Fatigue Damage-Strength Relationships in Composite Laminates. Volume 1

DTIC Science & Technology

1983-09-01

NUMBER 2. A ES ION N • /NT’S CATALOG NUMBER AFWAL-TR-83-3084, Vol I .A_"_.._ 4. TITLE (ad Subtitle) S. TYPE OF REPORT & PERIOD COVERED 1 June 1981...Fatigue Damage-Strength Relationships in Final: 31 May 1983 Composite Laminates 6. PERFORMING OAG. REPORT NUMBER 7. AUTHOR(e) 6. CONTRACT OR GRANT...I1. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE September 1983 AFWAL/FIBEC 13. NUMBER OF PAGES Wright Patterson AFB, OH 45433 55 14. MONITORING

Sensor assembly

DOEpatents

Bennett, Thomas E.; Nelson, Drew V.

2004-04-13

A ribbon-like sensor assembly is described wherein a length of an optical fiber embedded within a similar lengths of a prepreg tow. The fiber is ""sandwiched"" by two layers of the prepreg tow which are merged to form a single consolidated ribbon. The consolidated ribbon achieving a generally uniform distribution of composite filaments near the embedded fiber such that excess resin does not ""pool"" around the periphery of the embedded fiber.

3D modelling of squeeze flow of unidirectional and fabric composite inserts

NASA Astrophysics Data System (ADS)

Ghnatios, Chady; Abisset-Chavanne, Emmanuelle; Chinesta, Francisco; Keunings, Roland

2016-10-01

The enhanced design flexibility provided to the thermo-forming of thermoplastic materials arises from the use of both continuous and discontinuous thermoplastic prepregs. Discontinuous prepregs are patches used to locally strengthen the part. In this paper, we propose a new modelling approach for suspensions involving composite patches that uses theoretical concepts related to discontinuous fibres suspensions, transversally isotropic fluids and extended dumbbell models.

An overview of development and status of fiber-reinforced composites as dental and medical biomaterials

PubMed Central

Vallittu, Pekka K.

2018-01-01

Abstract Fibr-reinforced composites (FRC) have been used successfully for decades in many fields of science and engineering applications. Benefits of FRCs relate to physical properties of FRCs and versatile production methods, which can be utilized. Conventional hand lamination of prefabricated FRC prepregs is utilized still most commonly in fabrication of dental FRC devices but CAD-CAM systems are to be come for use in certain production steps of dental constructions and medical FRC implants. Although metals, ceramics and particulate filler resin composites have successfully been used as dental and medical biomaterials for decades, devices made out of these materials do not meet all clinical requirements. Only little attention has been paid to FRCs as dental materials and majority of the research in dental field has been focusing on particulate filler resin composites and in medical biomaterial research to biodegradable polymers. This is paradoxical because FRCs can potentially resolve many of the problems related to traditional isotropic dental and medical materials. This overview reviews the rationale and status of using biostable glass FRC in applications from restorative and prosthetic dentistry to cranial surgery. The overview highlights also the critical material based factors and clinical requirement for the succesfull use of FRCs in dental reconstructions. PMID:29707613

Multifunctional Hybrid Carbon Nanotube/Carbon Fiber Polymer Composites

NASA Technical Reports Server (NTRS)

Kang, Jin Ho; Cano, Roberto J.; Ratcliffe, James G.; Luong, Hoa; Grimsley, Brian W.; Siochi, Emilie J.

2016-01-01

For aircraft primary structures, carbon fiber reinforced polymer (CFRP) composites possess many advantages over conventional aluminum alloys due to their light weight, higher strengthand stiffness-to-weight ratio, and low life-cycle maintenance costs. However, the relatively low electrical and thermal conductivities of CFRP composites fail to provide structural safety in certain operational conditions such as lightning strikes. Despite several attempts to solve these issues with the addition of carbon nanotubes (CNT) into polymer matrices, and/or by interleaving CNT sheets between conventional carbon fiber (CF) composite layers, there are still interfacial problems that exist between CNTs (or CF) and the resin. In this study, hybrid CNT/CF polymer composites were fabricated by interleaving layers of CNT sheets with Hexcel® IM7/8852 prepreg. Resin concentrations from 1 wt% to 50 wt% were used to infuse the CNT sheets prior to composite fabrication. The interlaminar properties of the resulting hybrid composites were characterized by mode I and II fracture toughness testing (double cantilever beam and end-notched flexure test). Fractographical analysis was performed to study the effect of resin concentration. In addition, multi-directional physical properties like thermal conductivity of the orthotropic hybrid polymer composite were evaluated. Interleaving CNT sheets significantly improved the in-plane (axial and perpendicular direction of CF alignment) thermal conductivity of the hybrid composite laminates by 50 - 400%.

On impact damage detection and quantification for CFRP laminates using structural response data only

NASA Astrophysics Data System (ADS)

Sultan, M. T. H.; Worden, K.; Pierce, S. G.; Hickey, D.; Staszewski, W. J.; Dulieu-Barton, J. M.; Hodzic, A.

2011-11-01

The overall purpose of the research is to detect and attempt to quantify impact damage in structures made from composite materials. A study that uses simplified coupon specimens made from a Carbon Fibre-Reinforced Polymer (CFRP) prepreg with 11, 12 and 13 plies is presented. PZT sensors were placed at three separate locations in each test specimen to record the responses from impact events. To perform damaging impact tests, an instrumented drop-test machine was used and the impact energy was set to cover a range of 0.37-41.72 J. The response signals captured from each sensor were recorded by a data acquisition system for subsequent evaluation. The impacted specimens were examined with an X-ray technique to determine the extent of the damaged areas and it was found that the apparent damaged area grew monotonically with impact energy. A number of simple univariate and multivariate features were extracted from the sensor signals recorded during impact by computing their spectra and calculating frequency centroids. The concept of discordancy from the statistical discipline of outlier analysis is employed in order to separate the responses from non-damaging and damaging impacts. The results show that the potential damage indices introduced here provide a means of identifying damaging impacts from the response data alone.

An overview of development and status of fiber-reinforced composites as dental and medical biomaterials.

PubMed

Vallittu, Pekka K

2018-01-01

Fibr-reinforced composites (FRC) have been used successfully for decades in many fields of science and engineering applications. Benefits of FRCs relate to physical properties of FRCs and versatile production methods, which can be utilized. Conventional hand lamination of prefabricated FRC prepregs is utilized still most commonly in fabrication of dental FRC devices but CAD-CAM systems are to be come for use in certain production steps of dental constructions and medical FRC implants. Although metals, ceramics and particulate filler resin composites have successfully been used as dental and medical biomaterials for decades, devices made out of these materials do not meet all clinical requirements. Only little attention has been paid to FRCs as dental materials and majority of the research in dental field has been focusing on particulate filler resin composites and in medical biomaterial research to biodegradable polymers. This is paradoxical because FRCs can potentially resolve many of the problems related to traditional isotropic dental and medical materials. This overview reviews the rationale and status of using biostable glass FRC in applications from restorative and prosthetic dentistry to cranial surgery. The overview highlights also the critical material based factors and clinical requirement for the succesfull use of FRCs in dental reconstructions.

Fiber optic sensor for continuous health monitoring in CFRP composite materials

NASA Astrophysics Data System (ADS)

Rippert, Laurent; Papy, Jean-Michel; Wevers, Martine; Van Huffel, Sabine

2002-07-01

An intensity modulated sensor, based on the microbending concept, has been incorporated in laminates produced from a C/epoxy prepreg. Pencil lead break tests (Hsu-Neilsen sources) and tensile tests have been performed on this material. In this research study, fibre optic sensors will be proven to offer an alternative for the robust piezoelectric transducers used for Acoustic Emission (AE) monitoring. The main emphasis has been put on the use of advanced signal processing techniques based on time-frequency analysis. The signal Short Time Fourier Transform (STFT) has been computed and several robust noise reduction algorithms, such as Wiener adaptive filtering, improved spectral subtraction filtering, and Singular Value Decomposition (SVD) -based filtering, have been applied. An energy and frequency -based detection criterion is put forward to detect transient signals that can be correlated with Modal Acoustic Emission (MAE) results and thus damage in the composite material. There is a strong indication that time-frequency analysis and the Hankel Total Least Squares (HTLS) method can also be used for damage characterization. This study shows that the signal from a quite simple microbend optical sensor contains information on the elastic energy released whenever damage is being introduced in the host material by mechanical loading. Robust algorithms can be used to retrieve and analyze this information.

Design and Manufacturing of Tow-Steered Composite Shells Using Fiber Placement

NASA Technical Reports Server (NTRS)

Wu, K. Chauncey; Tatting, Brian F.; Smith, Brett H.; Stevens, Randy S.; Occhipiniti, Gina P.; Swift, Jonathan B.; Achary, David C.; Thornburgh, Robert P.

2009-01-01

Advanced composite shells that may offer the potential to improve the structural performance of future aircraft fuselage structures were developed under this joint NASA-industry collaborative effort. Two cylindrical shells with tailored, tow-steered layups and continuously varying fiber angle orientations were designed and built at the National Center for Advanced Manufacturing - Louisiana Partnership. The shells were fabricated from unidirectional IM7/8552 graphite-epoxy pre-preg slit tape material fiber-placed on a constant-diameter mandrel. Each shell had the same nominal 8-ply [plus or minus 45/plus or minus Theta]s layup, where the nominal fiber angle in the tow-steered plies varied continuously from 10 degrees along the crown to 45 degrees on each side, then back to 10 degrees on the keel. One shell was fabricated with all 24 tows placed during each pass of the fiber placement machine, resulting in many tow overlaps on the shell surface. The fiber placement machine's individual tow cut/restart capability was also used to manufacture a second shell with tow drops and a more uniform laminate thickness. This paper presents an overview of the detailed design and manufacturing processes for these shells, and discusses issues encountered during their fabrication and post-cure evaluation. Future plans for structural testing and analyses of the shells are also discussed.

Experience-based training of students on concretes reinforced by recycled carbon fibers

NASA Astrophysics Data System (ADS)

Cosgun, Cumhur; Patlolla, Vamsidhar R.; Alzahrani, Naif; Zeineddine, Hatim F.; Asmatulu, Eylem

2017-04-01

Fiber reinforcement increases many properties of the concretes, such as toughness, strength, abrasion, and resistance to corrosion. Use of recycled carbon fibers from industrial waste offers many advantages because it will reduce the waste, contribute the economy, protect natural resources and improve the property of structural units. The City of Wichita, KS is known to be "Air Capital of the World" where many aircraft companies have been producing aircraft, parts and components. Due to the superior properties of composites (e.g., light weight, low density, high impact resistance), they have been highly used by aircraft industry. Prepreg is the most preferred combination of the fiber and resin due to the easy application, but it has a limited shelf life (e.g., three months to one year at most) and scrap has no use after all in the same industry. Every year tons of un-used prepreg or after use scrap are being collected in Wichita, KS. Recycling prepreg from the post-consumer waste offers great advantages of waste reduction and resource conservation in the city. Reusing the carbon fibers obtained from outdated prepreg composites for concrete reinforcement will offer double advantages for our environment and concrete structures. In this study, recycled carbon fibers of the outdated prepreg composites were collected, and then incorporated with concretes at different ratios prior to the molding and mechanical testing. An undergraduate student was involved in the project and observed all the process during the laboratory studies, as well as data collection, analysis and presentation. We believe that experience based learning will enhance the students' skills and interest into the scientific and engineering studies.

Prediction of wrinklings and porosities of thermoplastic composits after thermostamping

NASA Astrophysics Data System (ADS)

Hamila, Nahiene; Guzman-Maldonado, Eduardo; Xiong, Hu; Wang, Peng; Boisse, Philippe; Bikard, Jerome

2018-05-01

During thermoforming process, the consolidation deformation mode of thermoplastic prepregs is one of the key deformation modes especially in the consolidation step, where the two resin flow phenomena: resin percolation and transverse squeeze flow, play an important role. This occurs a viscosity behavior for consolidation mode. Based on a visco-hyper-elastic model for the characterization of thermoplastic prepregs proposed by Guzman, which involves different independent modes of deformation: elongation mode, bending mode with thermo-dependent, and viscoelastic in-plan shearing mode with thermo-dependent, a viscoelastic model completed with consolidation behavior will be presented in this paper. A completed three-dimensional mechanical behavior with compaction effect for thermoplastic pre-impregnated composites is constituted, and the associated parameters are identified by compaction test. Moreover, a seven-node prismatic solid-shell finite element approach is used for the forming simulation. To subdue transverse shear locking, an intermediate material frame related to the element sides is introduced in order to fix nodal transverse shear strain components. Indeed, the enhanced assumed strain method and a reduced integration scheme are combined offering a linear varying strain field along the thickness direction to circumvent thickness locking, and an hourglass stabilization procedure is employed in order to correct the element's rank deficiency for pinching. An additional node is added at the center providing a quadratic interpolation of the displacement in the thickness direction. The predominance of this element is the ability of three dimensional analysis, especially for the transverse stress existence through the thickness of material, which is essential for the consolidation modelling. Finally, an intimate contact model is employed to predict the evolution of the consolidation which permits the microstructure prediction of void presented through the prepreg. Several tests including a thermoforming test are launched to evaluate the consolidation model and the accuracy of the proposed element.

Simulation Study of Stress and Deformation Behaviour of Debonded Laminated Structure

NASA Astrophysics Data System (ADS)

Hirwani, C. K.; Mittal, H.; Panda, S. K.; Mahapatra, S. S.; Mandal, S. K.; De, A. K.

2017-02-01

The bending strength and deformation characteristics of the debonded laminated plate under the uniformly distributed loading (UDL) have been investigated in this research article. For the simulation study, an internally damaged laminated plate structure model has been developed in ANSYS based on the first-order shear deformable kinematic theory via ANSYS parametric design language (APDL) code. The internal debonding within the laminated structure is incorporated using two sub-laminate approach. Further, the convergence (different mesh densities), as well as the validity (comparing the responses with published results) of the present simulation model, have been performed by solving the deflection responses under the influence of transversely loaded layered structure. Also, to show the coherence of the simulation analysis the results are compared with the experimental bending results of the homemade Glass/Epoxy composite with artificial delamination. For the experimental analysis, Glass/Epoxy laminated composite seeded with delamination at the central mid-plane of the laminate is fabricated using an open mould hand lay-up composites fabrication technique. For the computational purpose, the necessary material properties of fabricated composite plate evaluated experimentally via uniaxial tensile test (Universal Testing Machine INSTRON-1195). Further, the bending (three-point bend test) test is conducted with the help of Universal Testing Machine INSTRON-5967. Finally, the effect different geometrical and material parameters (thickness ratio, modular ratio, constraint conditions) and magnitude of the loading on the static deflection and stress behaviour of the delaminated composite plate are investigated thoroughly by solving different kinds of numerical illustrations and discussed in detail.

Decreased Bone Formation and Osteopenia in Lamin A/C-Deficient Mice

PubMed Central

Vidal, Christopher; McCorquodale, Thomas; Herrmann, Markus; Fatkin, Diane; Duque, Gustavo

2011-01-01

Age-related bone loss is associated with changes in bone cellularity with characteristically low levels of osteoblastogenesis. The mechanisms that explain these changes remain unclear. Although recent in vitro evidence has suggested a new role for proteins of the nuclear envelope in osteoblastogenesis, the role of these proteins in bone cells differentiation and bone metabolism in vivo remains unknown. In this study, we used the lamin A/C null (Lmna −/−) mice to identify the role of lamin A/C in bone turnover and bone structure in vivo. At three weeks of age, histological and micro computed tomography measurements of femurs in Lmna −/− mice revealed a significant decrease in bone mass and microarchitecture in Lmna −/− mice as compared with their wild type littermates. Furthermore, quantification of cell numbers after normalization with bone surface revealed a significant reduction in osteoblast and osteocyte numbers in Lmna −/− mice compared with their WT littermates. In addition, Lmna −/− mice have significantly lower osteoclast number, which show aberrant changes in their shape and size. Finally, mechanistic analysis demonstrated that absence of lamin A/C is associated with increase expression of MAN-1 a protein of the nuclear envelope closely regulated by lamin A/C, which also colocalizes with Runx2 thus affecting its capacity as osteogenic transcription factor. In summary, these data clearly indicate that the presence of lamin A/C is necessary for normal bone turnover in vivo and that absence of lamin A/C induces low bone turnover osteopenia resembling the cellular changes of age-related bone loss. PMID:21547077

Consolidation modelling for thermoplastic composites forming simulation

NASA Astrophysics Data System (ADS)

Xiong, H.; Rusanov, A.; Hamila, N.; Boisse, P.

2016-10-01

Pre-impregnated thermoplastic composites are widely used in the aerospace industry for their excellent mechanical properties, Thermoforming thermoplastic prepregs is a fast manufacturing process, the automotive industry has shown increasing interest in this manufacturing processes, in which the reconsolidation is an essential stage. The model of intimate contact is investigated as the consolidation model, compression experiments have been launched to identify the material parameters, several numerical tests show the influents of the temperature and pressure applied during processing. Finally, a new solid-shell prismatic element has been presented for the simulation of consolidation step in the thermoplastic composites forming process.

Method for producing components with internal architectures, such as micro-channel reactors, via diffusion bonding sheets

DOEpatents

Alman, David E [Corvallis, OR; Wilson, Rick D [Corvallis, OR; Davis, Daniel L [Albany, OR

2011-03-08

This invention relates to a method for producing components with internal architectures, and more particularly, this invention relates to a method for producing structures with microchannels via the use of diffusion bonding of stacked laminates. Specifically, the method involves weakly bonding a stack of laminates forming internal voids and channels with a first generally low uniaxial pressure and first temperature such that bonding at least between the asperites of opposing laminates occurs and pores are isolated in interfacial contact areas, followed by a second generally higher isostatic pressure and second temperature for final bonding. The method thereby allows fabrication of micro-channel devices such as heat exchangers, recuperators, heat-pumps, chemical separators, chemical reactors, fuel processing units, and combustors without limitation on the fin aspect ratio.

Portable Device Slices Thermoplastic Prepregs

NASA Technical Reports Server (NTRS)

Taylor, Beverly A.; Boston, Morton W.; Wilson, Maywood L.

1993-01-01

Prepreg slitter designed to slit various widths rapidly by use of slicing bar holding several blades, each capable of slicing strip of preset width in single pass. Produces material evenly sliced and does not contain jagged edges. Used for various applications in such batch processes involving composite materials as press molding and autoclaving, and in such continuous processes as pultrusion. Useful to all manufacturers of thermoplastic composites, and in slicing B-staged thermoset composites.

Manufacture and mechanical characterisation of high voltage insulation for superconducting busbars - (Part 1) Materials selection and development

NASA Astrophysics Data System (ADS)

Clayton, N.; Crouchen, M.; Devred, A.; Evans, D.; Gung, C.-Y.; Lathwell, I.

2017-04-01

It is planned that the high voltage electrical insulation on the ITER feeder busbars will consist of interleaved layers of epoxy resin pre-impregnated glass tapes ('pre-preg') and polyimide. In addition to its electrical insulation function, the busbar insulation must have adequate mechanical properties to sustain the loads imposed on it during ITER magnet operation. This paper reports an investigation into suitable materials to manufacture the high voltage insulation for the ITER superconducting busbars and pipework. An R&D programme was undertaken in order to identify suitable pre-preg and polyimide materials from a range of suppliers. Pre-preg materials were obtained from 3 suppliers and used with Kapton HN, to make mouldings using the desired insulation architecture. Two main processing routes for pre-pregs have been investigated, namely vacuum bag processing (out of autoclave processing) and processing using a material with a high coefficient of thermal expansion (silicone rubber), to apply the compaction pressure on the insulation. Insulation should have adequate mechanical properties to cope with the stresses induced by the operating environment and a low void content necessary in a high voltage application. The quality of the mouldings was assessed by mechanical testing at 77 K and by the measurement of the void content.

Processing and Properties of Fiber Reinforced Polymeric Matrix Composites. Part 2; Processing Robustness of IM7/PETI Polyimide Composites

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung

1996-01-01

The processability of a phenylethynyl terminated imide (PETI) resin matrix composite was investigated. Unidirectional prepregs were made by coating an N-methylpyrrolidone solution of the amide acid oligomer onto unsized IM7. Two batches of prepregs were used: one was made by NASA in-house, and the other was from an industrial source. The composite processing robustness was investigated with respect to the effect of B-staging conditions, the prepreg shelf life, and the optimal processing window. Rheological measurements indicated that PETI's processability was only slightly affected over a wide range of B-staging temperatures (from 250 C to 300 C). The open hole compression (OHC) strength values were statistically indistinguishable among specimens consolidated using various B-staging conditions. Prepreg rheology and OHC strengths were also found not to be affected by prolonged (i.e., up to 60 days) ambient storage. An optimal processing window was established using response surface methodology. It was found that IM7/PETI composite is more sensitive to the consolidation temperature than to the consolidation pressure. A good consolidation was achievable at 371 C/100 Psi, which yielded an OHC strength of 62 Ksi at room temperature. However, processability declined dramatically at temperatures below 350 C.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giorgio, E.; Robyr, D.; Spielmann, M.

Chromosomal rearrangements with duplication of the lamin B1 (LMNB1) gene underlie autosomal dominant adult-onset demyelinating leukodystrophy (ADLD), a rare neurological disorder in which overexpression of LMNB1 causes progressive central nervous system demyelination. However, we previously reported an ADLD family (ADLD-1-TO) without evidence of duplication or other mutation in LMNB1 despite linkage to the LMNB1 locus and lamin B1 overexpression. By custom array-CGH, we further investigated this family and report here that patients carry a large (~660 kb) heterozygous deletion that begins 66 kb upstream of the LMNB1 promoter. Lamin B1 overexpression was confirmed in further ADLD-1-TO tissues and in amore » postmortem brain sample, where lamin B1 was increased in the frontal lobe. Through parallel studies, we investigated both loss of genetic material and chromosomal rearrangement as possible causes of LMNB1 overexpression, and found that ADLD-1-TO plausibly results from an enhancer adoption mechanism. The deletion eliminates a genome topological domain boundary, allowing normally forbidden interactions between at least three forebrain-directed enhancers and the LMNB1 promoter, in line with the observed mainly cerebral localization of lamin B1 overexpression and myelin degeneration. Finally, this second route to LMNB1 overexpression and ADLD is a new example of the relevance of regulatory landscape modifications in determining Mendelian phenotypes.« less

Deleterious localized stress fields: the effects of boundaries and stiffness tailoring in anisotropic laminated plates

PubMed Central

Weaver, P. M.

2016-01-01

The safe design of primary load-bearing structures requires accurate prediction of stresses, especially in the vicinity of geometric discontinuities where deleterious three-dimensional stress fields can be induced. Even for thin-walled structures significant through-thickness stresses arise at edges and boundaries, and this is especially precarious for laminates of advanced fibre-reinforced composites because through-thickness stresses are the predominant drivers in delamination failure. Here, we use a higher-order equivalent single-layer model derived from the Hellinger–Reissner mixed variational principle to examine boundary layer effects in laminated plates comprising constant-stiffness and variable-stiffness laminae and deforming statically in cylindrical bending. The results show that zigzag deformations, which arise due to layerwise differences in the transverse shear moduli, drive boundary layers towards clamped edges and are therefore critically important in quantifying localized stress gradients. The relative significance of the boundary layer scales with the degree of layerwise anisotropy and the thickness to characteristic length ratio. Finally, we demonstrate that the phenomenon of alternating positive and negative transverse shearing deformation through the thickness of composite laminates, previously only observed at clamped boundaries, can also occur at other locations as a result of smoothly varying the material properties over the in-plane dimensions of the laminate. PMID:27843401

Hybrid Fiber Layup and Fiber-Reinforced Polymeric Composites Produced Therefrom

NASA Technical Reports Server (NTRS)

Barnell, Thomas J. (Inventor); Garrigan, Sean P. (Inventor); Rauscher, Michael D. (Inventor); Dietsch, Benjamin A. (Inventor); Cupp, Gary N. (Inventor)

2018-01-01

Embodiments of a hybrid fiber layup used to form a fiber-reinforced polymeric composite, and a fiber-reinforced polymeric composite produced therefrom are disclosed. The hybrid fiber layup comprises one or more dry fiber strips and one or more prepreg fiber strips arranged side by side within each layer, wherein the prepreg fiber strips comprise fiber material impregnated with polymer resin and the dry fiber strips comprise fiber material without impregnated polymer resin.

Inhibition and Cathalysis as a Method to Improve the Mechanical Properties of a Fiberglass-Reinforced Plastic

NASA Astrophysics Data System (ADS)

Protsenko, A. E.; Telesh, V. V.

2015-11-01

The possibility of increasing the static flexural strength of polymer composite materials and reducing their anisotropy by vacuum autoclave curing, during which gelation across the whole thickness of prepregs is carried out in a narrow time range, is shown. This is achieved by introducing a preset concentration of catalysts into the less heated layers or inhibitors in the more heated ones of the prepreg.

Polymer infiltration studies

NASA Technical Reports Server (NTRS)

Marchello, Joseph M.

1992-01-01

Significant progress has been made during the past three months on the preparation of carbon fiber composites using advanced polymer resins. The results are set forth in recent reports and publications, and will be presented at forthcoming national and international meetings. Current and ongoing research activities reported herein include: powdered tow ribbonizing; unitape from powdered tow; customized towpreg for textiles and ATP; and textile composite research. During the period ahead research will be directed toward further development of the new powder curtain prepregging method and on ways to customize dry powder towpreg for textile and robotic applications in aircraft part fabrication. Studies of multi-tow powder prepregging and ribbon preparation will be initiated in conjunction with continued development of prepregging technology and the various aspects of composite part fabrication using customized towpreg. Also, a major effort during the coming months will be participating in the analysis of the performance of the new solution prepregger.

A large genomic deletion leads to enhancer adoption by the lamin B1 gene: a second path to autosomal dominant adult-onset demyelinating leukodystrophy (ADLD)

DOE PAGES

Giorgio, E.; Robyr, D.; Spielmann, M.; ...

2015-02-20

Chromosomal rearrangements with duplication of the lamin B1 (LMNB1) gene underlie autosomal dominant adult-onset demyelinating leukodystrophy (ADLD), a rare neurological disorder in which overexpression of LMNB1 causes progressive central nervous system demyelination. However, we previously reported an ADLD family (ADLD-1-TO) without evidence of duplication or other mutation in LMNB1 despite linkage to the LMNB1 locus and lamin B1 overexpression. By custom array-CGH, we further investigated this family and report here that patients carry a large (~660 kb) heterozygous deletion that begins 66 kb upstream of the LMNB1 promoter. Lamin B1 overexpression was confirmed in further ADLD-1-TO tissues and in amore » postmortem brain sample, where lamin B1 was increased in the frontal lobe. Through parallel studies, we investigated both loss of genetic material and chromosomal rearrangement as possible causes of LMNB1 overexpression, and found that ADLD-1-TO plausibly results from an enhancer adoption mechanism. The deletion eliminates a genome topological domain boundary, allowing normally forbidden interactions between at least three forebrain-directed enhancers and the LMNB1 promoter, in line with the observed mainly cerebral localization of lamin B1 overexpression and myelin degeneration. Finally, this second route to LMNB1 overexpression and ADLD is a new example of the relevance of regulatory landscape modifications in determining Mendelian phenotypes.« less

Modeling of Failure Mechanisms in Composites With Z-Pins-Damage Validation of Z-Pin Reinforced Co-Cured Composite Laminates

DTIC Science & Technology

2011-04-01

there it is a computer implementation of the method just introduced. It uses Scilab ® programming language, and the Young modulus is calculated as final...laminate without Z-pins, its thickness, lamina stacking sequence and lamina’s engineering elastic constants, the second Scilab ® code can be used to find...EL thickness, the second Scilab ® code is employed once again; this time, though, a new Young’s modulus estimate would be produced. On the other hand

77 FR 35425 - Crystalline Silicon Photovoltaic Cells and Modules From China; Scheduling of the Final Phase of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-13

... Silicon Photovoltaic Cells and Modules From China; Scheduling of the Final Phase of Countervailing Duty... silicon photovoltaic cells and modules, provided for in subheadings 8501.31.80, 8501.61.00, 8507.20.80... photovoltaic cells, and modules, laminates, and panels, consisting of crystalline silicon photovoltaic cells...

Numerical simulating and experimental study on the woven carbon fiber-reinforced composite laminates under low-velocity impact

NASA Astrophysics Data System (ADS)

Liu, Hanyang; Tang, Zhanwen; Pan, Lingying; Zhao, Weidong; Sun, Baogang; Jiang, Wenge

2016-05-01

Impact damage has been identified as a critical form of the defects that constantly threatened the reliability of composite structures, such as those used in the aerospace structures and systems. Low energy impacts can introduce barely visible damage and cause the degradation of structural stiffness, furthermore, the flaws caused by low-velocity impact are so dangerous that they can give rise to the further extended delaminations. In order to improve the reliability and load carrying capacity of composite laminates under low-velocity impact, in this paper, the numerical simulatings and experimental studies on the woven fiber-reinforced composite laminates under low-velocity impact with impact energy 16.7J were discussed. The low velocity impact experiment was carried out through drop-weight system as the reason of inertia effect. A numerical progressive damage model was provided, in which the damages of fiber, matrix and interlamina were considered by VUMT subroutine in ABAQUS, to determine the damage modes. The Hashin failure criteria were improved to cover the failure modes of fiber failure in the directions of warp/weft and delaminations. The results of Finite Element Analysis (FEA) were compared with the experimental results of nondestructive examination including the results of ultrasonic C-scan, cross-section stereomicroscope and contact force - time history curves. It is found that the response of laminates under low-velocity impact could be divided into stages with different damage. Before the max-deformation of the laminates occurring, the matrix cracking, fiber breakage and delaminations were simulated during the impactor dropping. During the releasing and rebounding period, matrix cracking and delaminations areas kept increasing in the laminates because of the stress releasing of laminates. Finally, the simulating results showed the good agreements with the results of experiment.

Creep and creep rupture of laminated graphite/epoxy composites. Ph.D. Thesis. Final Report, 1 Oct. 1979 - 30 Sep. 1980

NASA Technical Reports Server (NTRS)

Dillard, D. A.; Morris, D. H.; Brinson, H. F.

1981-01-01

An incremental numerical procedure based on lamination theory is developed to predict creep and creep rupture of general laminates. Existing unidirectional creep compliance and delayed failure data is used to develop analytical models for lamina response. The compliance model is based on a procedure proposed by Findley which incorporates the power law for creep into a nonlinear constitutive relationship. The matrix octahedral shear stress is assumed to control the stress interaction effect. A modified superposition principle is used to account for the varying stress level effect on the creep strain. The lamina failure model is based on a modification of the Tsai-Hill theory which includes the time dependent creep rupture strength. A linear cumulative damage law is used to monitor the remaining lifetime in each ply.

Uncertainty-enabled design of electromagnetic reflectors with integrated shape control

NASA Astrophysics Data System (ADS)

Haque, Samiul; Kindrat, Laszlo P.; Zhang, Li; Mikheev, Vikenty; Kim, Daewa; Liu, Sijing; Chung, Jooyeon; Kuian, Mykhailo; Massad, Jordan E.; Smith, Ralph C.

2018-03-01

We implemented a computationally efficient model for a corner-supported, thin, rectangular, orthotropic polyvinylidene fluoride (PVDF) laminate membrane, actuated by a two-dimensional array of segmented electrodes. The laminate can be used as shape-controlled electromagnetic reflector and the model estimates the reflector's shape given an array of control voltages. In this paper, we describe a model to determine the shape of the laminate for a given distribution of control voltages. Then, we investigate the surface shape error and its sensitivity to the model parameters. Subsequently, we analyze the simulated deflection of the actuated bimorph using a Zernike polynomial decomposition. Finally, we provide a probabilistic description of reflector performance using statistical methods to quantify uncertainty. We make design recommendations for nominal parameter values and their tolerances based on optimization under uncertainty using multiple methods.

Ultrasonic stress wave characterization of composite materials

NASA Technical Reports Server (NTRS)

Duke, J. C., Jr.; Henneke, E. G., II; Stinchcomb, W. W.

1986-01-01

The work reported covers three simultaneous projects. The first project was concerned with: (1) establishing the sensitivity of the acousto-ultrasonic method for evaluating subtle forms of damage development in cyclically loaded composite materials, (2) establishing the ability of the acousto-ultrasonic method for detecting initial material imperfections that lead to localized damage growth and final specimen failure, and (3) characteristics of the NBS/Proctor sensor/receiver for acousto-ultrasonic evaluation of laminated composite materials. The second project was concerned with examining the nature of the wave propagation that occurs during acoustic-ultrasonic evaluation of composite laminates and demonstrating the role of Lamb or plate wave modes and their utilization for characterizing composite laminates. The third project was concerned with the replacement of contact-type receiving piezotransducers with noncontacting laser-optical sensors for acousto-ultrasonic signal acquisition.

Damping mathematical modelling and dynamic responses for FRP laminated composite plates with polymer matrix

NASA Astrophysics Data System (ADS)

Liu, Qimao

2018-02-01

This paper proposes an assumption that the fibre is elastic material and polymer matrix is viscoelastic material so that the energy dissipation depends only on the polymer matrix in dynamic response process. The damping force vectors in frequency and time domains, of FRP (Fibre-Reinforced Polymer matrix) laminated composite plates, are derived based on this assumption. The governing equations of FRP laminated composite plates are formulated in both frequency and time domains. The direct inversion method and direct time integration method for nonviscously damped systems are employed to solve the governing equations and achieve the dynamic responses in frequency and time domains, respectively. The computational procedure is given in detail. Finally, dynamic responses (frequency responses with nonzero and zero initial conditions, free vibration, forced vibrations with nonzero and zero initial conditions) of a FRP laminated composite plate are computed using the proposed methodology. The proposed methodology in this paper is easy to be inserted into the commercial finite element analysis software. The proposed assumption, based on the theory of material mechanics, needs to be further proved by experiment technique in the future.

Connections: Superplasticity, Damascus Steels, Laminated Steels, and Carbon Dating

NASA Astrophysics Data System (ADS)

Wadsworth, Jeffrey

2016-12-01

In this paper, a description is given of the connections that evolved from the initial development of a family of superplastic plain carbon steels that came to be known as Ultra-High Carbon Steels (UHCS). It was observed that their very high carbon contents were similar, if not identical, to those of Damascus steels. There followed a series of attempts to rediscover how the famous patterns found on Damascus steels blades were formed. At the same time, in order to improve the toughness at room temperature of the newly-developed UHCS, laminated composites were made of alternating layers of UHCS and mild steel (and subsequently other steels and other metals). This led to a study of ancient laminated composites, the motives for their manufacture, and the plausibility of some of the claims relating to the number of layers in the final blades. One apparently ancient laminated composite, recovered in 1837 from the great pyramid of Giza which was constructed in about 2750 B.C., stimulated a carbon dating study of ancient steels. The modern interest in "Bladesmithing" has connections back to many of these ancient weapons.

Dynamics of Lamin-A Processing Following Precursor Accumulation

PubMed Central

Liu, Qian; Kim, Dae In; Syme, Janet; LuValle, Phyllis; Burke, Brian; Roux, Kyle J.

2010-01-01

Lamin A (LaA) is a component of the nuclear lamina, an intermediate filament meshwork that underlies the inner nuclear membrane (INM) of the nuclear envelope (NE). Newly synthesized prelamin A (PreA) undergoes extensive processing involving C-terminal farnesylation followed by proteolysis yielding non-farnesylated mature lamin A. Different inhibitors of these processing events are currently used therapeutically. Hutchinson-Gilford Progeria Syndrome (HGPS) is most commonly caused by mutations leading to an accumulation of a farnesylated LaA isoform, prompting a clinical trial using farnesyltransferase inhibitors (FTI) to reduce this modification. At therapeutic levels, HIV protease inhibitors (PI) can unexpectedly inhibit the final processing step in PreA maturation. We have examined the dynamics of LaA processing and associated cellular effects during PI or FTI treatment and following inhibitor washout. While PI reversibility was rapid, with respect to both LaA maturation and associated cellular phenotype, recovery from FTI treatment was more gradual. FTI reversibility is influenced by both cell type and rate of proliferation. These results suggest a less static lamin network than has previously been observed. PMID:20526372

The Effect of Nylon and Polyester Peel Ply Surface Preparation on the Bond Quality of Composite Laminates

NASA Astrophysics Data System (ADS)

Moench, Molly K.

The preparation of the surfaces to be bonded is critical to the success of composite bonds. Peel ply surface preparation is attractive from a manufacturing and quality assurance standpoint, but is a well known example of the extremely system-specific nature of composite bonds. This study examined the role of the surface energy, morphology, and chemistry left by peel ply removal in resulting bond quality. It also evaluated the use of contact angle surface energy measurement techniques for predicting the resulting bond quality of a prepared surface. The surfaces created by preparing three aerospace fiber-reinforced composite prepregs were compared when prepared with a nylon vs a polyester peel ply. The prepared surfaces were characterized with contact angle measurements with multiple fluids, scanning electron microscopy (SEM), and x-ray electron spectroscopy. The laminates were bonded with aerospace grade film adhesives. Bond quality was assessed via double cantilever beam testing followed by optical and scanning electron microscopy of the fracture surfaces.The division was clear between strong bonds (GIC of 600- 1000J/m2 and failure in cohesion) and weak bonds (GIC of 80-400J/m2 and failure in adhesion). All prepared laminates showed the imprint of the peel ply texture and evidence of peel ply remnants after fabric removal, either through SEM or XPS. Within an adhesive system, large amounts of SEM-visible peel ply material transfer correlated with poor bond quality and cleaner surfaces with higher bond quality. The both sides of failed weak bonds showed evidence of peel ply remnants under XPS, showing that at least some failure is occurring through the remnants. The choice of adhesive was found to be significant. AF 555 adhesive was more tolerant of peel ply contamination than MB 1515-3. Although the bond quality results varied substantially between tested combinations, the total surface energies of all prepared surfaces were very similar. Single fluid contact angle measurements/water break tests were therefore not predictive of bond quality, and are recommended against. The multiple fluids used allowed the construction of wettability envelopes, a more detailed look at the surface energy profile. The envelopes of nylon and polyester prepared systems were noticeably different, but while potentially useful for detecting changes or errors in surface preparation of known systems, they were not valid for predicting bond quality in new systems. Ultimately, it was determined that wetting is a necessary but not sufficient condition for bonding.

Comparison of load-bearing capacity of direct resin-bonded fiber-reinforced composite FPDs with four framework designs.

PubMed

Xie, Qiufei; Lassila, Lippo V J; Vallittu, Pekka K

2007-07-01

This in vitro study was aimed to compare the fracture resistance of directly fabricated inlay-retained fiber-reinforced composite (FRC) fixed partial dentures (FPDs) with four types of framework designs. Forty-eight directly fabricated inlay retained FPDs were made of FRC and particulate resin composite (everStick/Tetric flow and Ceram). Extracted human mandibular first premolars and first molars were as abutments. The following framework designs were tested: in the Group A (control group), the framework was made of two prepregs of unidirectional glass FRC; the Group B, two prepregs in pontic portion were covered with one layer of multidirectional fiber veil FRC; the Group C, the FRC prepregs were covered in pontic portion with four short unidirectional FRC pieces along the main prepregs; in Group D, one short unidirectional FRC prepregs were placed on the main prepregs in 90 degrees angle to the main framework. After thermal cycling, FPDs of each group (n=12) were randomly divided into two subgroups (n=6). Fracture test was performed at the universal testing machine (1mm/min) where FPDs were loaded from the occlusal direction to the occlusal fossa or to the buccal cusp. Failure patterns were observed with stereomicroscope. Median and 25%/75% percentile values were calculated and nonparametric analysis was performed. Compared with three other framework designs, the FPDs in Group D showed the highest resistance when loading to the occlusal fossa, with maximum load of 2,353.8N (25%/75%: 2,155.5/2,500.0) (p=0.000, 0.000, and 0.005 for compared with Group A, B, and C). The same group showed also higher resistance when loaded to the buccal cusp (1,416.3N (1,409.2/1,480.8)) if compared to the FPDs of the Group A and Group C (p=0.044, 0.010). In general the FPDs showed higher resistant to loading at the occlusal fossa (p<0.05). This in vitro study showed that inlay-retained FRC FPD constructed with direct technique provided high fracture resistance. The framework design that provided support for the veneering composite of the pontic contributed to the highest load-bearing capacity even when loaded to the buccal cusp.

Teaching learning algorithm based optimization of kerf deviations in pulsed Nd:YAG laser cutting of Kevlar-29 composite laminates

NASA Astrophysics Data System (ADS)

Gautam, Girish Dutt; Pandey, Arun Kumar

2018-03-01

Kevlar is the most popular aramid fiber and most commonly used in different technologically advanced industries for various applications. But the precise cutting of Kevlar composite laminates is a difficult task. The conventional cutting methods face various defects such as delamination, burr formation, fiber pullout with poor surface quality and their mechanical performance is greatly affected by these defects. The laser beam machining may be an alternative of the conventional cutting processes due to its non-contact nature, requirement of low specific energy with higher production rate. But this process also faces some problems that may be minimized by operating the machine at optimum parameters levels. This research paper examines the effective utilization of the Nd:YAG laser cutting system on difficult-to-cut Kevlar-29 composite laminates. The objective of the proposed work is to find the optimum process parameters settings for getting the minimum kerf deviations at both sides. The experiments have been conducted on Kevlar-29 composite laminates having thickness 1.25 mm by using Box-Benkhen design with two center points. The experimental data have been used for the optimization by using the proposed methodology. For the optimization, Teaching learning Algorithm based approach has been employed to obtain the minimum kerf deviation at bottom and top sides. A self coded Matlab program has been developed by using the proposed methodology and this program has been used for the optimization. Finally, the confirmation tests have been performed to compare the experimental and optimum results obtained by the proposed methodology. The comparison results show that the machining performance in the laser beam cutting process has been remarkably improved through proposed approach. Finally, the influence of different laser cutting parameters such as lamp current, pulse frequency, pulse width, compressed air pressure and cutting speed on top kerf deviation and bottom kerf deviation during the Nd:YAG laser cutting of Kevlar-29 laminates have been discussed.

System Applies Polymer Powder To Filament Tow

NASA Technical Reports Server (NTRS)

Baucom, Robert M.; Snoha, John J.; Marchello, Joseph M.

1993-01-01

Polymer powder applied uniformly and in continuous manner. Powder-coating system applies dry polymer powder to continuous fiber tow. Unique filament-spreading technique, combined with precise control of tension on fibers in system, ensures uniform application of polymer powder to web of spread filaments. Fiber tows impregnated with dry polymer powders ("towpregs") produced for preform-weaving and composite-material-molding applications. System and process valuable to prepreg industry, for production of flexible filament-windable tows and high-temperature polymer prepregs.

Processing effects in production of composite prepreg by hot melt impregnation

NASA Astrophysics Data System (ADS)

Chmielewski, C.; Jayaraman, K.; Petty, C. A.

1993-06-01

The hot melt impregnation process for producing composite prepreg has been studied. The role of the exit die is highlighted by operating without impregnation bars. Experimental results show that when a fiber tow is pulled through a resin bath and then through a wedge shaped die, the total resin mass fraction and the extent of resin impregnation in the tow increase with the processing viscosity. The penetration of resin into a fiber bundle is greater when the resin viscosity is higher. This trend is unchanged over a range of tow speeds up to the breaking point. A theoretical model is developed to describe the effect of processing conditions and die geometry on the degree of impregnation. Calculations with this model indicate that for a given die geometry, the degree of impregnation increases from 58 percent to 90 percent as the ratio of the clearance between the tow and the die wall, to the total die gap is decreased from 0.15 to 0.05. Physical arguments related to the effective viscosity of the prepreg show that the clearance ratio is independent of the tow speed, but decreases as the ratio of the effective shear viscosity of the prepreg to the resin viscosity increases. This provides a connection between the experimental results obtained with varying resin viscosity and the computational results obtained with varying clearance values at the die inlet.

Method for Coating a Tow with an Electrospun Nanofiber

NASA Technical Reports Server (NTRS)

Kohlman, Lee W. (Inventor); Roberts, Gary D. (Inventor)

2015-01-01

Method and apparatus for enhancing the durability as well as the strength and stiffness of prepreg fiber tows of the sort used in composite materials are disclosed. The method involves adhering electrospun fibers onto the surface of such composite materials as filament-wound composite objects and the surface of prepreg fiber tows of the sort that are subsequently used in the production of composite materials of the filament-wound, woven, and braided sorts. The apparatus performs the methods described herein.

Polymer Infiltration Studies

NASA Technical Reports Server (NTRS)

Marchello, Joseph M.

1991-01-01

Progress was made on the preparation of carbon fiber composites using advanced polymer resins. Processes reported include powder towpreg process, weaving towpreg made from dry powder prepreg, composite from powder coated towpreg, and toughening of polyimide resin (PMR) composites by semi-interpenetrating networks. Several important areas of polymer infiltration into fiber bundles will be researched. Preparation to towpreg for textile preform weaving and braiding and for automated tow placement is a major goal, as are the continued development of prepregging technology and the various aspects of composite part fabrication.

Determination of thermal contact conductance in vacuum-bagged thermoplastic prepreg stacks using infrared thermography

NASA Astrophysics Data System (ADS)

Baumard, Théo; De Almeida, Olivier; Menary, Gary; Le Maoult, Yannick; Schmidt, Fabrice; Bikard, Jérôme

2016-10-01

The infrared heating of a vacuum-bagged, thermoplastic prepreg stack of glass/PA66 was studied to investigate the influence of vacuum level on thermal contact resistance between plies. A higher vacuum level was shown experimentally to decrease the transverse heat transfer efficiency, indicating that considering only the effect of heat conduction at the plies interfaces is not sufficient to predict the temperature distribution. An inverse analysis was used to retrieve the contact resistance coefficients as a function of vacuum pressure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baucom, R.M.; Marchello, J.M.

Thermoplastic prepregs of LARC-TPI have been produced in a fluidized bed unit on spread continuous fiber tows. The powders are melted on the fibers by radiant heating to adhere the polymer to the fiber. This process produces tow prepreg uniformly without imposing severe stress on the fibers or requiring long high temperature residence times for the polymer. Unit design theory and operating correlations have been developed to provide the basis for scale up to commercial operation. Special features of the operation are the pneumatic tow spreader, fluidized bed and resin feed systems.

Rheological characterization of addition polyimide matrix resins and prepregs

NASA Technical Reports Server (NTRS)

Maximovich, M. G.; Galeos, R. M.

1984-01-01

Although graphite-reinforced polyimide matrix composites offer outstanding specific strength and stiffness, together with high thermal oxidative stability, processing problems connected with their rheological behavior remain to be addressed. The present rheological studies on neat polyimide resin systems encountered outgassing during cure. A staging technique has been developed which can successfully handle polyimide samples, and novel methods were applied to generate rheological curves for graphite-reinforced prepregs. The commercial graphite/polyimide systems studied were PRM 15, LARC 160, and V378A.

Equivalent circuit and optimum design of a multilayer laminated piezoelectric transformer.

PubMed

Dong, Shuxiang; Carazo, Alfredo Vazquez; Park, Seung Ho

2011-12-01

A multilayer laminated piezoelectric Pb(Zr(1-x)Ti(x))O(3) (PZT) ceramic transformer, operating in a half- wavelength longitudinal resonant mode (λ/2 mode), has been analyzed. This piezoelectric transformer is composed of one thickness-polarized section (T-section) for exciting the longitudinal mechanical vibrations, two longitudinally polarized sections (L-section) for generating high-voltage output, and two insulating layers laminated between the T-section and L-section layers to provide insulation between the input and output sections. Based on the piezoelectric constitutive and motion equations, an electro-elasto-electric (EEE) equivalent circuit has been developed, and correspondingly, an effective EEE coupling coefficient was proposed for optimum design of this multilayer transformer. Commercial finite element analysis software is used to determine the validity of the developed equivalent circuit. Finally, a prototype sample was manufactured and experimental data was collected to verify the model's validity.

Design of multiple-ply laminated composite tapered beams

NASA Technical Reports Server (NTRS)

Rodriguez, P.

1993-01-01

A study of a special case of symmetric laminated composite cantilever beams is presented. The approach models beams that are tapered both in depth and width and investigates the effect of the ply layup angle and the ply taper on bending and interlaminar shearing stresses. For the determination of stresses and deflections, the beam stiffness matrices are expressed as linear functions of the beam length. Using classical lamination theory (CLT) the stiffness matrices are determined and assembled at strategic locations along the length of the beam. They are then inverted and necessary stiffness parameters are obtained numerically and extracted for determination of design information at each location chosen. Several ply layup configurations are investigated, and design considerations are presented based on the findings. Finally, recommendations for the design of these beams are presented, and a means for anticipating the location of highest stresses is offered.

Design of multiple-ply laminated composite tapered beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez, P.

1993-06-01

A study of a special case of symmetric laminated composite cantilever beams is presented. The approach models beams that are tapered both in depth and width and investigates the effect of the ply layup angle and the ply taper on bending and interlaminar shearing stresses. For the determination of stresses and deflections, the beam stiffness matrices are expressed as linear functions of the beam length. Using classical lamination theory (CLT) the stiffness matrices are determined and assembled at strategic locations along the length of the beam. They are then inverted and necessary stiffness parameters are obtained numerically and extracted formore » determination of design information at each location chosen. Several ply layup configurations are investigated, and design considerations are preSDsented based on the findings. Finally, recommendations for the design of these beams are presented, and a means for anticipating the location of highest stresses is offered.« less

Beams from boltwood: a feasibility study

Treesearch

Peter Koch

1964-01-01

Previous papers in this series of four have explored technical aspects of converting southern pine boltwood into long laminated beams of uniform high strength. This final discussion examines production and economic aspects of the proposed system.

Effect of low-velocity or ballistic impact damage on the strength of thin composite and aluminum shear panels

NASA Technical Reports Server (NTRS)

Farley, G. L.

1985-01-01

Impact tests were conducted on shear panels fabricated from 6061-T6 aluminum and from woven fabric prepreg of Du Pont Kevlara fiber/epoxy resin and graphite fiber/epoxy resin. The shear panels consisted of three different composite laminates and one aluminum material configuration. Three panel aspect ratios were evaluated for each material configuration. Composite panels were impacted with a 1.27-cm (0.05-in) diameter aluminum sphere at low velocities of 46 m/sec (150 ft/sec) and 67 m/sec (220 ft/sec). Ballistic impact conditions consisted of a tumbled 0.50-caliber projectile impacting loaded composite and aluminum shear panels. The results of these tests indicate that ballistic threshold load (the lowest load which will result in immediate failure upon penetration by the projectile) varied between 0.44 and 0.61 of the average failure load of undamaged panels. The residual strengths of the panels after ballistic impact varied between 0.55 and 0.75 of the average failure strength of the undamaged panels. The low velocity impacts at 67 m/sec (220 ft/sec) caused a 15 to 20 percent reduction in strength, whereas the impacts at 46 m/sec (150 ft/sec) resulted in negligible strength loss. Good agreement was obtained between the experimental failure strengths and the predicted strength with the point stress failure criterion.

Dry Process for Making Polyimide/ Carbon-and-Boron-Fiber Tape

NASA Technical Reports Server (NTRS)

Belvin, Harry L.; Cano, Roberto J.; Johnston, Norman J.; Marchello, Joseph M.

2003-01-01

A dry process has been invented as an improved means of manufacturing composite prepreg tapes that consist of high-temperature thermoplastic polyimide resin matrices reinforced with carbon and boron fibers. Such tapes are used (especially in the aircraft industry) to fabricate strong, lightweight composite-material structural components. The inclusion of boron fibers results in compression strengths greater than can be achieved by use of carbon fibers alone. The present dry process is intended to enable the manufacture of prepreg tapes (1) that contain little or no solvent; (2) that have the desired dimensions, fiber areal weight, and resin content; and (3) in which all of the fibers are adequately wetted by resin and the boron fibers are fully encapsulated and evenly dispersed. Prepreg tapes must have these properties to be useable in the manufacture of high-quality composites by automated tape placement. The elimination of solvent and the use of automated tape placement would reduce the overall costs of manufacturing.

Continuous fiber thermoplastic prepreg

NASA Technical Reports Server (NTRS)

Wilson, Maywood L. (Inventor); Johnson, Gary S. (Inventor)

1993-01-01

A pultrusion machine employing a corrugated impregnator vessel to immerse multiple, continuous strand, fiber tow in an impregnating material, and an adjustable metered exit orifice for the impregnator vessel to control the quantity of impregnating material retained by the impregnated fibers, is provided. An adjustable height insert retains transverse rod elements within each depression of the corrugated vessel to maintain the individual fiber tows spread and in contact with the vessel bottom. A series of elongated heating dies, transversely disposed on the pultrusion machine and having flat heating surfaces with radiused edges, ensure adequate temperature exposed dwell time and exert adequate pressure on the impregnated fiber tows, to provide the desired thickness and fiber/resin ratio in the prepreg formed. The prepreg passing through the pulling mechanism is wound on a suitable take-up spool for subsequent use. A formula is derived for determining the cross sectional area opening of the metering device. A modification in the heating die system employs a heated nip roller in lieu of one of the pressure applying flat dies.

Fatigue of cord-rubber composites for tires

NASA Astrophysics Data System (ADS)

Song, Jaehoon

Fatigue behaviors of cord-rubber composite materials forming the belt region of radial pneumatic tires have been characterized to assess their dependence on stress, strain and temperature history as well as materials composition and construction . Using actual tires, it was found that interply shear strain is one of the crucial parameters for damage assessment from the result that higher levels of interply shear strain of actual tires reduce the fatigue lifetime. Estimated at various levels of load amplitude were the fatigue life, the extent and rate of resultant strain increase ("dynamic creep"), cyclic strains at failure, and specimen temperature. The interply shear strain of 2-ply 'tire belt' composite laminate under circumferential tension was affected by twisting of specimen due to tension-bending coupling. However, a critical level of interply shear strain, which governs the gross failure of composite laminate due to the delamination, appeared to be independent of different lay-up of 2-ply vs. symmetric 4-ply configuration. Reflecting their matrix-dominated failure modes such as cord-matrix debonding and delamination, composite laminates with different cord reinforcements showed the same S-N relationship as long as they were constructed with the same rubber matrix, the same cord angle, similar cord volume, and the same ply lay-up. Because of much lower values of single cycle strength (in terms of gross fracture load per unit width), the composite laminates with larger cord angle and the 2-ply laminates exhibited exponentially shorter fatigue lifetime, at a given stress amplitude, than the composite laminates with smaller cord angle and 4-ply symmetric laminates, respectively. The increase of interply rubber thickness lengthens their fatigue lifetime at an intermediate level of stress amplitude. However, the increase in the fatigue lifetime of the composite laminate becomes less noticeable at very low stress amplitude. Even with small compressive cyclic stresses, the fatigue life of belt composites is predominantly influenced by the magnitude of maximum stress. Maximum cyclic strain of composite laminates at failure, which measures the total strain accumulation for gross failure, was independent of stress amplitude and close to the level of static failure strain. For all composite laminates under study, a linear correlation could be established between the temperature rise rate and dynamic creep rate which was, in turn, inversely proportional to the fatigue lifetime. Using the acoustic emission (AE) initiation stress value, better prediction of fatigue life was available for the fiber-reinforced composites having fatigue limit. The accumulation rate of AE activities during cyclic loading was linearly proportional to the maximum applied load and to the inverse of the fatigue life of cord-rubber composite laminates. Finally, a modified fatigue modulus model based on combination of power-law and logarithmic relation was proposed to predict the fatigue lifetime profile of cord-rubber composite laminates.

Research on Damage Models for Continuous Fiber Composites

DTIC Science & Technology

1988-07-01

r ~.F (~ Mechanics and Materials Center TEXAS A&M UNIVERSITY College Station, Texas RESEARCH ON DAMAGE MODELS FOR CONTINUOUS FIBER COMPOSITES Final...Washington, DC 20332 11. TITLE (Include Security Clas=fication) Research on Damage Models for Continuous Fiber Composites - Final Technical Report 1...GROUP SUB-GROU ::=, COMPOsites ) continuum mechanics , ~ idamage, internal state variables V experimental mechanics, laminated composites o 19. ABSTRACT

Hydraulics of subaqueous ash flows as deduced from their deposits

NASA Astrophysics Data System (ADS)

Doronzo, Domenico M.; Dellino, Pierfrancesco

2012-09-01

Subaqueous ash flows are gravity currents consisting of a mixture of sea water and ash particles. Also called volcaniclastic turbidity currents (VTCs), they can be generated because of remobilization of pyroclastic fall deposits, which are emplaced into the sea around a volcanic island, as well as far away, during an explosive eruption. The VTC upper part is the turbulent transport system for the flow, whereas the viscous basal one is the depositional system. Typical sequences of VTC deposits are characterized by cross-laminations, planar and convolute laminations, and massive beds, which reflect the stratified nature of the flow. Here, the analysis of some VTC hydraulic parameters is presented in order to depict flow behavior and sedimentation during deposition. A reverse engineering approach is proposed, which consists of calculating hydraulic parameters by starting from deposit features. The calculated values show that a VTC is homogeneously-turbulent for most of the thickness, but is viscous at its base. First, cross-laminations are directly acquired over the rough pre-existing seafloor, then planar or convolute laminations aggrade over the newly formed substrate. Finally, fine-grained suspended particles gently settle and cap the flow deposit.

Engineered Polymer Composites Through Electrospun Nanofiber Coating of Fiber Tows

NASA Technical Reports Server (NTRS)

Kohlman, Lee W.

2013-01-01

Toughening and other property enhancements of composite materials are typically implemented by-modifying the bulk properties of the constituents, either the fiber or matrix materials. This often leads to difficulties in processing and higher material costs. Many composites consist of tows or yarns (thousands of individual fibers) that are either filament wound or processed into a fabric by weaving or braiding. The matrix material can be added to the tow or fabric before final processing, resulting in a prepreg material, or infused into the fiber material during final processing by a variety of methods. By using a direct electrospun deposition method to apply thermoplastic nanofiber to the surface of the tows, the tow-tow interface in the resulting composite can be modified while using otherwise conventional materials and handling processes. Other materials of interest could also be incorporated into the electrospun precursor.

Fatigue Analysis of Notched Laminates: A Time-Efficient Macro-Mechanical Approach

NASA Technical Reports Server (NTRS)

Naghipour, P.; Pineda, E. J.; Bednarcyk, B. A.; Arnold, S. M.; Waas, A. M.

2016-01-01

A coupled transversely isotropic deformation and damage fatigue model is implemented within the finite element method and was utilized along with a static progressive damage model to predict the fatigue life, stiffness degradation as a function of number of cycles, and post-fatigue tension and compression response of notched, multidirectional laminates. Initially, the material parameters for the fatigue model were obtained utilizing micromechanics simulations and the provided [0], [90] and [plus or minus 45] experimental composite laminate S-N (stress-cycle) data. Within the fatigue damage model, the transverse and shear properties of the plies were degraded with an isotropic scalar damage variable. The damage in the longitudinal (fiber) ply direction was suppressed, and only the strength of the fiber was degraded as a function of fatigue cycles. A maximum strain criterion was used to capture the failure in each element, and once this criterion was satisfied, the longitudinal stiffness of the element was decreased by a factor of 10 (sup 4). The resulting, degraded properties were then used to calculate the new stress state. This procedure was repeated until final failure of the composite laminate was achieved or a specified number of cycles reached. For post-fatigue tension and compression behavior, four internal state variables were used to control the damage and failure. The predictive capability of the above-mentioned approach was assessed by performing blind predictions of the notched multidirectional IM7/977-3 composite laminates response under fatigue and post-fatigue tensile and compressive loading, followed by a recalibration phase. Although three different multidirectional laminates were analyzed in the course of this study, only detailed results (i.e., stiffness degradation and post-fatigue stress-train curves as well as damage evolution states for a single laminate ([30/60/90/minus 30/minus 60] (sub 2s)) are discussed in detail here.

Influence of Material Distribution on Impact Resistance of Hybrid Composites

NASA Technical Reports Server (NTRS)

Abatan, Ayu; Hu, Hurang

1998-01-01

Impact events occur in a wide variety of circumstances. A typical example is a bullet impacting a target made of composite material. These impact events produce time-varying loads on a structure that can result in damage. As a first step to understanding the damage resistance issue in composite laminates, an accurate prediction of the transient response during an impact event is necessary. The analysis of dynamic loadings on laminated composite plates has undergone considerable development recently. Rayleigh-Ritz energy method was used to determine the impact response of laminated plates. The impact response of composite plates using shear deformation plate theory was analyzed. In recent work a closed-form solution was obtained for a rectangular plate with four edges simply supported subjected to a center impact load using classical plate theory. The problem was further investigated and the analysis results compared of both classical plate theory and shear deformation theory, and found that classical plate theory predicts very accurate results for the range of small deformations considered. In this study, the influence of cross sectional material distribution on the comparative impact responses of hybrid metal laminates subjected to low and medium velocity impacts is investigated. A simple linear model to evaluate the magnitude of the impact load is proposed first, and it establishes a relation between the impact velocity and the impact force. Then a closed-form solution for impact problem is presented. The results were compared with the finite element analysis results. For an 11 layer-hybrid laminate, the impact response as a function of material distribution in cross-section is presented. With equal areal weight, the effect of the number of laminate layers on the impact resistance is also investigated. Finally, the significance of the presented results is discussed.

Development of antioxidant packaging material by applying corn-zein to LLDPE film in combination with phenolic compounds.

PubMed

Park, Hye-Yeon; Kim, Sung-Jin; Kim, Ki Myong; You, Young-Sun; Kim, So Yeon; Han, Jaejoon

2012-10-01

Functional active packaging materials were successfully developed by incorporating antioxidant agents into corn-zein-laminated linear low-density polyethylene (LLDPE) film. The minimum effective concentrations of the active compounds (for example, thymol, carvacrol, eugenol) were determined and these compounds were then laminated into LLDPE films to develop corn-zein-laminated films with antioxidant agents. The release rate of antioxidant agents in gas and liquid media were determined along with the mechanical and water barrier properties of the films containing these compounds. Tensile strength and percentage elongation at break were reduced in the corn-zein-laminated LLDPE films when compared to typical LLDPE film. Furthermore, the ability of the corn-zein-laminated films to repel moisture decreased by approximately 12.2%, but was improved by incorporating hydrophobic antioxidant compounds in the corn-zein layer. Examination of release kinetics in the gas and liquid phases verified that antioxidants were effectively released from the films and inhibited oxidation during testing. Finally, the films were used for fresh ground beef packaging, and effectively inhibited lipid oxidation and had a positive effect on the color stability of beef patties during storage. These results indicate that the developed antioxidant films are a novel active packaging material that can be effectively implemented by the food industry to improve the quality and safety of foods. Zein protein, a by-product of corn processing industry, was laminated into plastic films in combination with natural phenolic compounds to develop antioxidant packaging films. The films demonstrated their efficient release patterns of antioxidant compounds, which are suitable for packaging applications and food protection. © 2012 Institute of Food Technologists®

Electrostatic dry powder prepregging of carbon fiber

NASA Technical Reports Server (NTRS)

Throne, James L.; Sohn, Min-Seok

1990-01-01

Ultrafine, 5-10 micron polymer-matrix resin powders are directly applied to carbon fiber tows by passing then in an air or nitrogen stream through an electrostatic potential; the particles thus charged will strongly adhere to grounded carbon fibers, and can be subsequently fused to the fiber in a continuously-fed radiant oven. This electrostatic technique derived significant end-use mechanical property advantages from the obviation of solvents, binders, and other adulterants. Additional matrix resins used to produce prepregs to date have been PMR-15, Torlon 40000, and LaRC TPI.

Technical assessment for quality control of resins

NASA Technical Reports Server (NTRS)

Gosnell, R. B.

1977-01-01

Survey visits to companies involved in the manufacture and use of graphite-epoxy prepregs were conducted to assess the factors which may contribute to variability in the mechanical properties of graphite-epoxy composites. In particular, the purpose was to assess the contributions of the epoxy resins to variability. Companies represented three segments of the composites industry - aircraft manufacturers, prepreg manufacturers, and epoxy resin manufacturers. Several important sources of performance variability were identified from among the complete spectrum of potential sources which ranged from raw materials to composite test data interpretation.

Development of RTM and powder prepreg resins for subsonic aircraft primary structures

NASA Technical Reports Server (NTRS)

Woo, Edmund P.; Groleau, Michael R.; Bertram, James L.; Puckett, Paul M.; Maynard, Shawn J.

1993-01-01

Dow developed a thermoset resin which could be used to produce composites via the RTM process. The composites formed are useful at 200 F service temperatures after moisture saturation, and are tough systems that are suitable for subsonic aircraft primary structure. At NASA's request, Dow also developed a modified version of the RTM resin system which was suitable for use in producing powder prepreg. In the course of developing the RTM and powder versions of these resins, over 50 different new materials were produced and evaluated.

Fabrication and characterization of tapered graphite/epoxy box beams

NASA Astrophysics Data System (ADS)

Yen, S.-C.; Gopal, P.; Dharani, L. R.

1993-04-01

Graphite/epoxy (T300/934) prepreg is used to fabricate tapered box beams with a taper angle of 2 deg between the top and bottom walls. The prepreg is cured on a segmented steel core using a hot-press. A screw arrangement is used to apply curing pressure in the horizontal direction, while the platens of the hot-press apply pressure in the vertical direction. The inplane bending stiffness of the beam is determined by 3-point bend test and is found to be in agreement with theory.

HPLC for quality control of polyimides

NASA Technical Reports Server (NTRS)

Young, P. R.; Sykes, G. F.

1979-01-01

High Pressure Liquid Chromatography (HPLC) as a quality control tool for polyimide resins and prepregs are presented. A data base to help establish accept/reject criteria for these materials was developed. This work is intended to supplement, not replace, standard quality control tests normally conducted on incoming resins and prepregs. To help achieve these objectives, the HPLC separation of LARC-160 polyimide precursor resin was characterized. Room temperature resin aging effects were studied. Graphite reinforced composites made from fresh and aged resin were fabricated and tested to determine if changes observed by HPLC were significant.

Thermoviscoelastic characterization and prediction of Kevlar/epoxy composite laminates

NASA Technical Reports Server (NTRS)

Gramoll, K. C.; Dillard, D. A.; Brinson, H. F.

1990-01-01

The thermoviscoelastic characterization of Kevlar 49/Fiberite 7714A epoxy composite lamina and the development of a numerical procedure to predict the viscoelastic response of any general laminate constructed from the same material were studied. The four orthotropic material properties, S sub 11, S sub 12, S sub 22, and S sub 66, were characterized by 20 minute static creep tests on unidirectional (0) sub 8, (10) sub 8, and (90) sub 16 lamina specimens. The Time-Temperature Superposition-Principle (TTSP) was used successfully to accelerate the characterization process. A nonlinear constitutive model was developed to describe the stress dependent viscoelastic response for each of the material properties. A numerical procedure to predict long term laminate properties from lamina properties (obtained experimentally) was developed. Numerical instabilities and time constraints associated with viscoelastic numerical techniques were discussed and solved. The numerical procedure was incorporated into a user friendly microcomputer program called Viscoelastic Composite Analysis Program (VCAP), which is available for IBM PC type computers. The program was designed for ease of use. The final phase involved testing actual laminates constructed from the characterized material, Kevlar/epoxy, at various temperatures and load level for 4 to 5 weeks. These results were compared with the VCAP program predictions to verify the testing procedure and to check the numerical procedure used in the program. The actual tests and predictions agreed for all test cases which included 1, 2, 3, and 4 fiber direction laminates.

Characterization of impact damage in composite laminates using guided wavefield imaging and local wavenumber domain analysis.

PubMed

Rogge, Matthew D; Leckey, Cara A C

2013-09-01

Delaminations in composite laminates resulting from impact events may be accompanied by minimal indication of damage at the surface. As such, inspections are required to ensure defects are within allowable limits. Conventional ultrasonic scanning techniques have been shown to effectively characterize the size and depth of delaminations but require physical contact with the structure and considerable setup time. Alternatively, a non-contact scanning laser vibrometer may be used to measure guided wave propagation in the laminate structure generated by permanently bonded transducers. A local Fourier domain analysis method is presented for processing guided wavefield data to estimate spatially dependent wavenumber values, which can be used to determine delamination depth. The technique is applied to simulated wavefields and results are analyzed to determine limitations of the technique with regards to determining defect size and depth. Based on simulation results, guidelines for application of the technique are developed. Finally, experimental wavefield data is obtained in quasi-isotropic carbon fiber reinforced polymer (CFRP) laminates with impact damage. The recorded wavefields are analyzed and wavenumber is measured to an accuracy of up to 8.5% in the region of shallow delaminations. These results show the promise of local wavenumber domain analysis to characterize the depth of delamination damage in composite laminates. The technique can find application in automated vehicle health assurance systems with potential for high detection rates and greatly reduced operator effort and setup time. Published by Elsevier B.V.

Process development for automated solar cell and module production. Task 4: Automated array assembly

NASA Technical Reports Server (NTRS)

Hagerty, J. J.

1981-01-01

The Unimate robot was programmed for the final 35 cell pattern to be used in the fabrication of the deliverable modules. Mechanical construction of the Automated Lamination Station and Final Assembly Station were completed on schedule. All final wiring and interconnect cables were also completed and the first operational testing began. The final controlling program was written. A local fabricator was contracted to produce the glass reinforced concrete panels to be used for testing and deliverables. A video tape showing all three stations in operation was produced.

Composite Design and Manufacturing Development for Human Spacecrafts

NASA Technical Reports Server (NTRS)

Litteken, Douglas; Lowry, David

2013-01-01

The Structural Engineering Division at the NASA Johnson Space Center (JSC) has begun work on lightweight, multi-functional pressurized composite structures. The first candidate vehicle for technology development is the Multi-Mission Space Exploration Vehicle (MMSEV) cabin, known as the Gen 2B cabin, which has been built at JSC by the Robotics Division. Of the habitable MMSEV vehicle prototypes designed to date, this is the first one specifically analyzed and tested to hold internal pressure and the only one made out of composite materials. This design uses a laminate base with zoned reinforcement and external stringers, intended to demonstrate certain capabilities, and to prepare for the next cabin design, which will be a composite sandwich panel construction with multi-functional capabilities. As part of this advanced development process, a number of new technologies were used to assist in the design and manufacturing process. One of the methods, new to JSC, was to build the Gen 2B cabin with Out of Autoclave technology to permit the creation of larger parts with fewer joints. An 8-ply pre-preg layup was constructed to form the cabin body. Prior to lay-up, a design optimization software called FiberSIM was used to create each ply pattern. This software is integrated with Pro/Engineer to allow for customized draping of each fabric ply over the complex tool surface. Slits and darts are made in the software model to create an optimal design that maintains proper fiber placement and orientation. The flat pattern of each ply is then exported and sent to an automated cutting table where the patterns are cut out of graphite material. Additionally, to assist in lay-up, a laser projection system (LPT) is used to project outlines of each ply directly onto the tool face for accurate fiber placement and ply build-up. Finally, as part of the OoA process, a large oven was procured to post-cure each part. After manufacturing complete, the cabin underwent modal and pressure testing (currently in progress at date of writing) and will go on to be outfitted and used for further ops usage.

Thermally sprayed prepregs for thixoforging of UD fiber reinforced light metal MMCs

NASA Astrophysics Data System (ADS)

Silber, Martin; Wenzelburger, Martin; Gadow, Rainer

2007-04-01

Low density and good mechanical properties are the basic requirements for lightweight structures in automotive and aerospace applications. With their high specific strength and strain to failure values, aluminum alloys could be used for such applications. Only the insufficient stiffness and thermal and fatigue strength prevented their usage in high-end applications. One possibility to solve this problem is to reinforce the light metal with unidirectional fibers. The UD fiber allows tailoring of the reinforcement to meet the direction of the component's load. In this study, the production of thermally sprayed prepregs for the manufacturing of continuous fiber reinforced MMC by thixoforging is analysed. The main aim is to optimize the winding procedure, which determines the fiber strand position and tension during the coating process. A method to wind and to coat the continuous fibers with an easy-to-use handling technique for the whole manufacturing process is presented. The prepregs were manufactured by producing arc wire sprayed AlSi6 coatings on fibers bundles. First results of bending experiments showed appropriate mechanical properties.

Moisture and temperature influence on mechanical behavior of PPS/buckypapers carbon fiber laminates

NASA Astrophysics Data System (ADS)

Rojas, J. A.; Santos, L. F. P.; Costa, M. L.; Ribeiro, B.; Botelho, E. C.

2017-07-01

In this work, multiwall carbon nanotubes (MWCNT) were dispersed in water with the assistance of water based surfactant and then sonicated in order to obtain a very well dispersed solution. The suspension was filtrate under vaccum conditions, generating a thin film called buckypapers (BP). Poly (phenylene sulphide) (PPS) reinforced carbon fiber (CF) and PPS reinforced CF/BP composites were manufactured through hot compression molding technique. Subsequently the samples were exposed to extreme humidity (90% of moisture) combined with high temperature (80 °C). The mechanical properties of the laminates were evaluated by dynamic mechanical analysis, compression shear test, interlaminar shear strength and impulse excitation of vibration. Volume fraction of pores were 10.93% for PPS/CF and 16.18% for PPS/BP/CF, indicating that the hot compression molding parameters employed in this investigation (1.4 MPa, 5 min and 330 °C) affected both the consolidation quality of the composites and the mechanical properties of the final laminates.

Characterization of the Acoustic Radiation Properties of Laminated and Sandwich Composite Panels in Thermal Environment

NASA Astrophysics Data System (ADS)

Sharma, Nitin; Ranjan Mahapatra, Trupti; Panda, Subrata Kumar; Sahu, Pruthwiraj

2018-03-01

In this article, the acoustic radiation characteristics of laminated and sandwich composite spherical panels subjected to harmonic point excitation under thermal environment are investigated. The finite element (FE) simulation model of the vibrating panel structure is developed in ANSYS using ANSYS parametric design language (APDL) code. Initially, the critical buckling temperatures of the considered structures are obtained and the temperature loads are assorted accordingly. Then, the modal analysis of the thermally stressed panels is performed and the thermo-elastic free vibration responses so obtained are validated with the benchmark solutions. Subsequently, an indirect boundary element (BE) method is utilized to conduct a coupled FE-BE analysis to compute the sound radiation properties of panel structure. The agreement of the present sound power responses with the existing results available in the published literature establishes the validity of the proposed scheme. Finally, the current standardised scheme is extended to solve several numerical examples to bring out the influence of various parameters on the thermo-acoustic characteristics of laminated composite panels.

Modelling the development of defects during composite reinforcements and prepreg forming

PubMed Central

Hamila, N.; Madeo, A.

2016-01-01

Defects in composite materials are created during manufacture to a large extent. To avoid them as much as possible, it is important that process simulations model the onset and the development of these defects. It is then possible to determine the manufacturing conditions that lead to the absence or to the controlled presence of such defects. Three types of defects that may appear during textile composite reinforcement or prepreg forming are analysed and modelled in this paper. Wrinkling is one of the most common flaws that occur during textile composite reinforcement forming processes. The influence of the different rigidities of the textile reinforcement is studied. The concept of ‘locking angle’ is questioned. A second type of unusual behaviour of fibrous composite reinforcements that can be seen as a flaw during their forming process is the onset of peculiar ‘transition zones’ that are directly related to the bending stiffness of the fibres. The ‘transition zones’ are due to the bending stiffness of fibres. The standard continuum mechanics of Cauchy is not sufficient to model these defects. A second gradient approach is presented that allows one to account for such unusual behaviours and to master their onset and development during forming process simulations. Finally, the large slippages that may occur during a preform forming are discussed and simulated with meso finite-element models used for macroscopic forming. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’. PMID:27242300

Modelling the development of defects during composite reinforcements and prepreg forming.

PubMed

Boisse, P; Hamila, N; Madeo, A

2016-07-13

Defects in composite materials are created during manufacture to a large extent. To avoid them as much as possible, it is important that process simulations model the onset and the development of these defects. It is then possible to determine the manufacturing conditions that lead to the absence or to the controlled presence of such defects. Three types of defects that may appear during textile composite reinforcement or prepreg forming are analysed and modelled in this paper. Wrinkling is one of the most common flaws that occur during textile composite reinforcement forming processes. The influence of the different rigidities of the textile reinforcement is studied. The concept of 'locking angle' is questioned. A second type of unusual behaviour of fibrous composite reinforcements that can be seen as a flaw during their forming process is the onset of peculiar 'transition zones' that are directly related to the bending stiffness of the fibres. The 'transition zones' are due to the bending stiffness of fibres. The standard continuum mechanics of Cauchy is not sufficient to model these defects. A second gradient approach is presented that allows one to account for such unusual behaviours and to master their onset and development during forming process simulations. Finally, the large slippages that may occur during a preform forming are discussed and simulated with meso finite-element models used for macroscopic forming. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'. © 2016 The Author(s).

Finite element modeling of reinforced concrete structures strengthened with FRP laminates : final report.

DOT National Transportation Integrated Search

2001-05-01

Linear and non-linear finite element method models were developed for a reinforced concrete bridge that had been strengthened with fiber reinforced polymer composites. ANSYS and SAP2000 modeling software were used; however, most of the development ef...

Process Development for Automated Solar Cell and Module Production. Task 4: Automated Array Assembly

NASA Technical Reports Server (NTRS)

Hagerty, J. J.

1981-01-01

The Automated Lamination Station is mechanically complete and is currently undergoing final wiring. The high current driver and isolator boards have been completed and installed, and the main interface board is under construction. The automated vacuum chamber has had a minor redesign to increase stiffness and improve the cover open/close mechanism. Design of the Final Assembly Station has been completed and construction is underway.

A development of visible light cured FRP plate denture.

PubMed

Kimura, H; Teraoka, F

1990-12-01

A FRP denture base, which was made from visible light curing prepreg, was developed. The visible light cured FRP denture base had advantages with respect to an adequate strength, bonding strength of acrylic base resin, esthetic properties and ease to manipulation. The matrix resin of Bis-GMA/UDMA/3 G at 48/48/4 was determined from the results of the bending test and manipulation processing. The sateen weave's glasscloth was used for the reinforcement of the prepreg. The adaptability of the FRP plate denture was better than that of the resin base denture constructed with microwave heating.

Composite prepreg application device

NASA Technical Reports Server (NTRS)

Sandusky, Donald A. (Inventor); Marchello, Joseph M. (Inventor)

1995-01-01

A heated shoe and cooled pressure roller assembly for composite prepreg application is provided. The shoe assembly includes a heated forward contact surface having a curved pressure surface. The following cooled roller provides a continuous pressure to the thermoplastic while reducing the temperature to approximately 5 C below glass transition temperature. Electric heating coils inside the forward portion of the shoe heat a thermoplastic workpiece to approximately 100 C above the glass transition. Immediately following the heated contact surface, a cooled roller cools the work. The end sharpened shape of the heated shoe trailing edge tends to prevent slag buildup and maintain a uniform, relaxed stress fabrication.

Advanced Material Intelligent Processing Center: Next Generation Scalable Lean Manufacturing

DTIC Science & Technology

2012-09-04

spacing) and initial resin distribution. This research is currently focused on characterizing Gurit® Single Sprint © ST94 Out-of-Autoclave prepreg for...consolidation). 200 400 600 Time (s) 1000 Figure 24. Images of ST 94 prepreg corresponding to the graph of the quantified area of resin observed...s) 1000 2kPa; 55C 4kPa; 55C 6kPa; 55C 15kPa.55C 30kPa. 55C 41kPa;55C 400 600 Time (s) 800 1000 Figure 25. (a) Effect of temperature and

78 FR 64472 - Laminated Woven Sacks From the People's Republic of China: Final Results of Expedited First...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-29

....218(e)(1)(ii)(C)(2). \\2\\ See Petitioners' July 30, 2013, submission. Analysis of Comments Received All... either to an exterior ply of plastic film such as biaxially-oriented polypropylene (``BOPP'') or to an...

Nanotechnologies for Composite Structures- From Nanocomposites to Multifunctional Nano-Enabled Fibre Reinforced Composites for Spacecrafts

NASA Astrophysics Data System (ADS)

Kostopoulos, Vassilis; Vavouliotis, Antonios; Baltopoulos, Athanasios; Sotiririadis, George; Masouras, Athanasios; Pambaguian, Laurent

2014-06-01

The past decade, extensive efforts have been invested in understanding the nano-scale and revealing the capabilities offered by nanotechnology products to structural materials. Nevertheless, a major issue faced lately more seriously due to the interest of industry is on how to incorporate these nano-species into the final composite structure through existing manufacturing processes and infrastructure. In this work, we present the experience obtained from the latest nanotechnology research activities supported by ESA. The paper focuses on prepreg composite manufacturing technology and addresses:- Approaches for nano-enabling of composites- Up-scaling strategies towards final structures- Latest results on performance of nano-enabledfiber reinforced compositesSeveral approaches for the utilization of nanotechnology products in structural composite structures have been proposed and are reviewed, in short along with respective achieved results. A variety of nano-fillers has been proposed and employed, individually or in combination in hybrid forms, to approach the desired performance. A major part of the work deals with the up-scaling routes of these technologies to reach final products and industrial scales and processes while meeting end-user performance.

Development of a finite element based delamination analysis for laminates subject to extension, bending, and torsion

NASA Technical Reports Server (NTRS)

Hooper, Steven J.

1989-01-01

Delamination is a common failure mode of laminated composite materials. This type of failure frequently occurs at the free edges of laminates where singular interlaminar stresses are developed due to the difference in Poisson's ratios between adjacent plies. Typically the delaminations develop between 90 degree plies and adjacent angle plies. Edge delamination has been studied by several investigators using a variety of techniques. Recently, Chan and Ochoa applied the quasi-three-dimensional finite element model to the analysis of a laminate subject to bending, extension, and torsion. This problem is of particular significance relative to the structural integrity of composite helicopter rotors. The task undertaken was to incorporate Chan and Ochoa's formulation into a Raju Q3DG program. The resulting program is capable of modeling extension, bending, and torsional mechanical loadings as well as thermal and hygroscopic loadings. The addition of the torsional and bending loading capability will provide the capability to perform a delamination analysis of a general unsymmetric laminate containing four cracks, each of a different length. The solutions obtained using this program are evaluated by comparing them with solutions from a full three-dimensional finite element solution. This comparison facilitates the assessment of three dimensional affects such as the warping constraint imposed by the load frame grips. It wlso facilitates the evaluation of the external load representation employed in the Q3D formulation. Finally, strain energy release rates computed from the three-dimensional results are compared with those predicted using the quasi-three-dimensional formulation.

Process development for automated solar cell and module production. Task 4: Automated array assembly

NASA Technical Reports Server (NTRS)

Hagerty, J. J.

1981-01-01

Progress in the development of automated solar cell and module production is reported. The unimate robot is programmed for the final 35 cell pattern to be used in the fabrication of the deliverable modules. The mechanical construction of the automated lamination station and final assembly station phases are completed and the first operational testing is underway. The final controlling program is written and optimized. The glass reinforced concrete (GRC) panels to be used for testing and deliverables are in production. Test routines are grouped together and defined to produce the final control program.

Modelling and simulating the forming of new dry automated lay-up reinforcements for primary structures

NASA Astrophysics Data System (ADS)

Bouquerel, Laure; Moulin, Nicolas; Drapier, Sylvain; Boisse, Philippe; Beraud, Jean-Marc

2017-10-01

While weight has been so far the main driver for the development of prepreg based-composites solutions for aeronautics, a new weight-cost trade-off tends to drive choices for next-generation aircrafts. As a response, Hexcel has designed a new dry reinforcement type for aircraft primary structures, which combines the benefits of automation, out-of-autoclave process cost-effectiveness, and mechanical performances competitive to prepreg solutions: HiTape® is a unidirectional (UD) dry carbon reinforcement with thermoplastic veil on each side designed for aircraft primary structures [1-3]. One privileged process route for HiTape® in high volume automated processes consists in forming initially flat dry reinforcement stacks, before resin infusion [4] or injection. Simulation of the forming step aims at predicting the geometry and mechanical properties of the formed stack (so-called preform) for process optimisation. Extensive work has been carried out on prepreg and dry woven fabrics forming behaviour and simulation, but the interest for dry non-woven reinforcements has emerged more recently. Some work has been achieved on non crimp fabrics but studies on the forming behaviour of UDs are seldom and deal with UD prepregs only. Tension and bending in the fibre direction, along with inter-ply friction have been identified as the main mechanisms controlling the HiTape® response during forming. Bending has been characterised using a modified Peirce's flexometer [5] and inter-ply friction study is under development. Anisotropic hyperelastic constitutive models have been selected to represent the assumed decoupled deformation mechanisms. Model parameters are then identified from associated experimental results. For forming simulation, a continuous approach at the macroscopic scale has been selected first, and simulation is carried out in the Zset framework [6] using proper shell finite elements.

Resin transfer molding of textile preforms for aircraft structural applications

NASA Technical Reports Server (NTRS)

Hasko, Gregory H.; Dexter, H. Benson; Weideman, Mark H.

1992-01-01

The NASA LaRC is conducting and supporting research to develop cost-effective fabrication methods that are applicable to primary composite aircraft structures. One of the most promising fabrication methods that has evolved is resin transfer molding (RTM) of dry textile material forms. RTM has been used for many years for secondary structures, but has received increased emphasis because it is an excellent method for applying resin to damage-tolerant textile preforms at low cost. Textile preforms based on processes such as weaving, braiding, knitting, stitching, and combinations of these have been shown to offer significant improvements in damage tolerance compared to laminated tape composites. The use of low-cost resins combined with textile preforms could provide a major breakthrough in achieving cost-effective composite aircraft structures. RTM uses resin in its lowest cost form, and storage and spoilage costs are minimal. Near net shape textile preforms are expected to be cost-effective because automated machines can be used to produce the preforms, post-cure operations such as machining and fastening are minimized, and material scrap rate may be reduced in comparison with traditional prepreg molding. The purpose of this paper is to discuss experimental and analytical techniques that are under development at NASA Langley to aid the engineer in developing RTM processes for airframe structural elements. Included are experimental techniques to characterize preform and resin behavior and analytical methods that were developed to predict resin flow and cure kinetics.

Imide Oligomers Containing Pendent and Terminal Phenylethynyl Groups-2

NASA Technical Reports Server (NTRS)

Connell, J. W.; Smith, J. G., Jr.; Hergenrother, P. M.

1998-01-01

As part of a program to develop high-performance/high-temperature structural resins for aeronautical applications, imide oligomers containing pendent and terminal phenylethynyl groups were prepared, characterized and the cured resins evaluated as composite matrices. The oligomers were prepared at a calculated number-average molecular weight of 5000 g/mol and contained 15-20 mol% pendent phenylethynyl groups. In previous work, an oligomer containing pendent and terminal phenylethynyl groups exhibited a high glass transition temperature (approximately 313 C), and laminates therefrom exhibited high compressive properties, but processability, fracture toughness, microcrack resistance and damage tolerance were less than desired. In an attempt to improve these deficiencies, modifications in the oligomeric backbone involving the incorporation of 1,3-bis(3-aminophenoxy)benzene were investigated as a means of improving processability and toughness without detracting from the high glass transition temperature and high compressive properties. The amide acid oligomeric solutions were prepared in N-methyl-2-pyrrolidinone and were subsequently processed into imide powder, thin films, adhesive tape and carbon fiber prepreg. Neat resin plaques were fabricated from imide powder by compression moulding. The maximum processing pressure was 1.4 MPa and the cure temperature ranged from 350 to 371 C for 1 h for the mouldings, adhesives, films and composites. The properties of the 1,3-bis(3-aniinophenoxy)benzene modified cured imide oligomers containing pendent and terminal phenylethynyl groups are compared with those of previously prepared oligomers containing pendent and terminal phenylethynyl groups of similar composition and molecular weight.

Process for application of powder particles to filamentary materials

NASA Technical Reports Server (NTRS)

Baucom, Robert M. (Inventor); Snoha, John J. (Inventor); Marchello, Joseph M. (Inventor)

1991-01-01

This invention is a process for the uniform application of polymer powder particles to a filamentary material in a continuous manner to form a uniform composite prepreg material. A tow of the filamentary material is fed under carefully controlled tension into a spreading unit, where it is spread pneumatically into an even band. The spread filamentary tow is then coated with polymer particles from a fluidized bed, after which the coated filamentary tow is fused before take-up on a package for subsequent utilization. This process produces a composite prepreg uniformly without imposing severe stress on the filamentary material, and without requiring long, high temperature residence times for the polymer.

Filament winding - Waking the sleeping giant

NASA Technical Reports Server (NTRS)

Freeman, W. T., Jr.; Stein, B. A.

1985-01-01

The use of filament winding (FW) in the production of aerospace composite structures is examined. The FW process applies spools of fiber and prepreg tow or prepreg tape to a male mandrel; the process is more efficient and cost effective than metallic construction. The fibers used in FW and the curing process are explained. The reduced storage and fabrication costs that result from FW are discussed. The use of FW to produce a filament-wound case for a solid rocket motor and the substructure and skin of an aircraft fuselage are described. Areas which require further development in order to expand the use of FW are listed and discussed.

Characterization of PMR polyimide resin and prepreg

NASA Technical Reports Server (NTRS)

Lindenmeyer, P. H.; Sheppard, C. H.

1984-01-01

Procedures for the chemical characterization of PMR-15 resin solutions and graphite-reinforced prepregs were developed, and a chemical data base was established. In addition, a basic understanding of PMR-15 resin chemistry was gained; this was translated into effective processing procedures for the production of high quality graphite composites. During the program the PMR monomers and selected model compounds representative of postulated PMR-15 solution chemistry were acquired and characterized. Based on these data, a baseline PMR-15 resin was formulated and evaluated for processing characteristics and composite properties. Commercially available PMR-15 resins were then obtained and chemically characterized. Composite panels were fabricated and evaluated.

Composite prepreg application device

NASA Technical Reports Server (NTRS)

Sandusky, Donald A. (Inventor); Marchello, Joseph M. (Inventor)

1996-01-01

A heated shoe and cooled pressure roller assembly for composite prepreg application is provided. The shoe assembly includes a heated forward contact surface having a curved pressure surface. The following cooled roller provides a continuous pressure to the thermoplastic while reducing the temperature to approximately 5.degree. C. below glass transition temperature. Electric heating coils inside the forward portion of the shoe heat a thermoplastic workpiece to approximately 100.degree. C. above the glass transition. Immediately following the heated contact surface, a cooled roller cools the work. The end sharpened shape of the heated shoe trailing edge tends to prevent slag buildup and maintain a uniform, relaxed stress fabrication.

Viscous and thermal modelling of thermoplastic composites forming process

NASA Astrophysics Data System (ADS)

Guzman, Eduardo; Liang, Biao; Hamila, Nahiene; Boisse, Philippe

2016-10-01

Thermoforming thermoplastic prepregs is a fast manufacturing process. It is suitable for automotive composite parts manufacturing. The simulation of thermoplastic prepreg forming is achieved by alternate thermal and mechanical analyses. The thermal properties are obtained from a mesoscopic analysis and a homogenization procedure. The forming simulation is based on a viscous-hyperelastic approach. The thermal simulations define the coefficients of the mechanical model that depend on the temperature. The forming simulations modify the boundary conditions and the internal geometry of the thermal analyses. The comparison of the simulation with an experimental thermoforming of a part representative of automotive applications shows the efficiency of the approach.

Vacuum Powder Injector

NASA Technical Reports Server (NTRS)

Working, Dennis C.

1991-01-01

Method developed to provide uniform impregnation of bundles of carbon-fiber tow with low-solubility, high-melt-flow polymer powder materials to produce composite prepregs. Vacuum powder injector expands bundle of fiber tow, applies polymer to it, then compresses bundle to hold powder. System provides for control of amount of polymer on bundle. Crystallinity of polymer maintained by controlled melt on takeup system. All powder entrapped, and most collected for reuse. Process provides inexpensive and efficient method for making composite materials. Allows for coating of any bundle of fine fibers with powders. Shows high potential for making prepregs of improved materials and for preparation of high-temperature, high-modulus, reinforced thermoplastics.

Fiber study involving a polyimide matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cano, R.J.; Rommel, M.; Hinkley, J.A.

1996-12-31

Mechanical properties are presented for eight different intermediate modulus carbon fiber/ polyimide matrix composites. Two unsized carbon fibers (Thornel T650-42 and Hercules IM9) and two sized carbon fibers (high temperature sized Thornel T650-42 HTS and epoxy sized Toray T1000) were prepregged on the NASA LaRC Multipurpose Tape Machine using the NASA LaRC developed polyimide resin matrix, LaRC{trademark}-PETI-5, and the DuPont developed Avitnid{reg_sign} R1-16. Composite panels fabricated from these prepregs were evaluated to determine their mechanical properties. The data show the effects of using sized fibers on the processing and mechanical properties of polyimide composites.

Properties of Two Carbon Composite Materials Using LTM25 Epoxy Resin

NASA Technical Reports Server (NTRS)

Cruz, Juan R.; Shah, C. H.; Postyn, A. S.

1996-01-01

In this report, the properties of two carbon-epoxy prepreg materials are presented. The epoxy resin used in these two materials can yield lower manufacturing costs due to its low initial cure temperature, and the capability of being cured using vacuum pressure only. The two materials selected for this study are MR50/LTM25, and CFS003/LTM25 with Amoco T300 fiber; both prepregs are manufactured by The Advanced Composites Group. MR50/LTM25 is a unidirectional prepreg tape using Mitsubishi MR50 carbon fiber impregnated with LTM25 epoxy resin. CRS003/LTM25 is a 2 by 2 twill fabric using Amoco T300 fiber and impregnated with LTM25 epoxy resin. Among the properties presented in this report are strength, stiffness, bolt bearing, and damage tolerance. Many of these properties were obtained at three environmental conditions: cold temperature/dry (CTD), room temperature/dry (RTD), and elevated temperature/wet (ETW). A few properties were obtained at room temperature/wet (RTW), and elevated temperature/dry (ETD). The cold and elevated temperatures used for testing were -125 F and 180 F, respectively. In addition, several properties related to processing are presented.

Narrative Necklaces ... and beyond

ERIC Educational Resources Information Center

West, Debi

2012-01-01

The author personally started making narrative collaged necklaces about 10 years ago, after being inspired by an artist friend. She would take mini images from magazines and collage them together onto laminate tile samples from a hardware store. She then adds colorful brads and stickers, and then paint and oil pastel over them, finally sealing…

Numerical Analysis of Stress Concentration in Isotropic and Laminated Plates with Inclined Elliptical Holes

NASA Astrophysics Data System (ADS)

Khechai, Abdelhak; Tati, Abdelouahab; Belarbi, Mohamed Ouejdi; Guettala, Abdelhamid

2018-03-01

The design of high-performance composite structures frequently includes discontinuities to reduce the weight and fastener holes for joining. Understanding the behavior of perforated laminates is necessary for structural design. In the current work, stress concentrations taking place in laminated and isotropic plates subjected to tensile load are investigated. The stress concentrations are obtained using a recent quadrilateral finite element of four nodes with 32 DOFs. The present finite element (PE) is a combination of two finite elements. The first finite element is a linear isoparametric membrane element and the second is a high precision Hermitian element. One of the essential objectives of the current investigation is to confirm the capability and efficiency of the PE for stress determination in perforated laminates. Different geometric parameters, such as the cutout form, sizes and cutout orientations, which have a considerable effect on the stress values, are studied. Using the present finite element formulation, the obtained results are found to be in good agreement with the analytical findings, which validates the capability and the efficiency of the proposed formulation. Finally, to understand the material parameters effect such as the orientation of fibers and degree of orthotropy ratio on the stress values, many figures are presented using different ellipse major to minor axis ratio. The stress concentration values are considerably affected by increasing the orientation angle of the fibers and degree of orthotropy.

A novel adaptive sun tracker for spacecraft solar panel based on hybrid unsymmetric composite laminates

NASA Astrophysics Data System (ADS)

Wu, Zhangming; Li, Hao

2017-11-01

This paper proposes a novel adaptive sun tracker which is constructed by hybrid unsymmetric composite laminates. The adaptive sun tracker could be applied on spacecraft solar panels to increase their energy efficiency through decreasing the inclined angle between the sunlight and the solar panel normal. The sun tracker possesses a large rotation freedom and its rotation angle depends on the laminate temperature, which is affected by the light condition in the orbit. Both analytical model and finite element model (FEM) are developed for the sun tracker to predict its rotation angle in different light conditions. In this work, the light condition of the geosynchronous orbit on winter solstice is considered in the numerical prediction of the temperatures of the hybrid laminates. The final inclined angle between the sunlight and the solar panel normal during a solar day is computed using the finite element model. Parametric study of the adaptive sun tracker is conducted to improve its capacity and effectiveness of sun tracking. The improved adaptive sun tracker is lightweight and has a state-of-the-art design. In addition, the adaptive sun tracker does not consume any power of the solar panel, since it has no electrical driving devices. The proposed adaptive sun tracker provides a potential alternative to replace the traditional sophisticated electrical driving mechanisms for spacecraft solar panels.

Equivalent orthotropic elastic moduli identification method for laminated electrical steel sheets

NASA Astrophysics Data System (ADS)

Saito, Akira; Nishikawa, Yasunari; Yamasaki, Shintaro; Fujita, Kikuo; Kawamoto, Atsushi; Kuroishi, Masakatsu; Nakai, Hideo

2016-05-01

In this paper, a combined numerical-experimental methodology for the identification of elastic moduli of orthotropic media is presented. Special attention is given to the laminated electrical steel sheets, which are modeled as orthotropic media with nine independent engineering elastic moduli. The elastic moduli are determined specifically for use with finite element vibration analyses. We propose a three-step methodology based on a conventional nonlinear least squares fit between measured and computed natural frequencies. The methodology consists of: (1) successive augmentations of the objective function by increasing the number of modes, (2) initial condition updates, and (3) appropriate selection of the natural frequencies based on their sensitivities on the elastic moduli. Using the results of numerical experiments, it is shown that the proposed method achieves more accurate converged solution than a conventional approach. Finally, the proposed method is applied to measured natural frequencies and mode shapes of the laminated electrical steel sheets. It is shown that the method can successfully identify the orthotropic elastic moduli that can reproduce the measured natural frequencies and frequency response functions by using finite element analyses with a reasonable accuracy.

Experimental Study and Numerical Modelling of Low Velocity Impact on Laminated Composite Reinforced with Thin Film Made of Carbon Nanotubes

NASA Astrophysics Data System (ADS)

El Moumen, A.; Tarfaoui, M.; Hassoon, O.; Lafdi, K.; Benyahia, H.; Nachtane, M.

2018-04-01

In this work, polymer laminated composites based on Epon 862 Epoxy resin, T300 6 k carbon fibers and carbon nanotubes (CNTs) were tested with the aim to elucidate the effect of CNTs on impact properties including impact force and capacity to absorb impact energy. The polymer matrix was reinforced by a random distribution of CNTs with fraction ranging from 0.5 to 4.wt%. Composite panels were manufactured by using the infusion process. Taylor impact test was used to obtain the impact response of specimens. Projectile manufactured from a high strength and hardened steel with a diameter of 20 mm and 1.5 kg of mass was launched by a compressed gas gun within the velocity of 3 m/s. Impact force histories and absorbed energy of specimens were recorded. A numerical model was employed to simulate the impact performance. This model has been accomplished by forming a user established subroutine (VUMAT) and executing it in ABAQUS software. Finally, the effect of CNTs amount on dynamic properties of laminated composites was discussed.

Local Guided Wavefield Analysis for Characterization of Delaminations in Composites

NASA Technical Reports Server (NTRS)

Rogge, Matthew D.; Campbell Leckey, Cara A.

2012-01-01

Delaminations in composite laminates resulting from impact events may be accompanied by minimal indication of damage at the surface. As such, inspection techniques are required to ensure defects are within allowable limits. Conventional ultrasonic scanning techniques have been shown to effectively characterize the size and depth of delaminations but require physical contact with the structure. Alternatively, a noncontact scanning laser vibrometer may be used to measure guided wave propagation in the laminate structure. A local Fourier domain analysis method is presented for processing guided wavefield data to estimate spatially-dependent wavenumber values, which can be used to determine delamination depth. The technique is applied to simulated wavefields and results are analyzed to determine limitations of the technique with regards to determining defect size and depth. Finally, experimental wavefield data obtained in quasi-isotropic carbon fiber reinforced polymer (CFRP) laminates with impact damage is analyzed and wavenumber is measured to an accuracy of 8.5% in the region of shallow delaminations. Keywords: Ultrasonic wavefield imaging, Windowed Fourier transforms, Guided waves, Structural health monitoring, Nondestructive evaluation

Ewing sarcoma gene EWS is essential for meiosis and B lymphocyte development

PubMed Central

Li, Hongjie; Watford, Wendy; Li, Cuiling; Parmelee, Alissa; Bryant, Mark A.; Deng, Chuxia; O’Shea, John; Lee, Sean Bong

2007-01-01

Ewing sarcoma gene EWS encodes a putative RNA-binding protein with proposed roles in transcription and splicing, but its physiological role in vivo remains undefined. Here, we have generated Ews-deficient mice and demonstrated that EWS is required for the completion of B cell development and meiosis. Analysis of Ews–/– lymphocytes revealed a cell-autonomous defect in precursor B lymphocyte (pre–B lymphocyte) development. During meiosis, Ews-null spermatocytes were deficient in XY bivalent formation and showed reduced meiotic recombination, resulting in massive apoptosis and complete arrest in gamete maturation. Inactivation of Ews in mouse embryonic fibroblasts resulted in premature cellular senescence, and the mutant animals showed hypersensitivity to ionizing radiation. Finally, we showed that EWS interacts with lamin A/C and that loss of EWS results in a reduced lamin A/C expression. Our findings reveal essential functions for EWS in pre–B cell development and meiosis, with proposed roles in DNA pairing and recombination/repair mechanisms. Furthermore, we demonstrate a novel role of EWS in cellular senescence, possibly through its interaction and modulation of lamin A/C. PMID:17415412

Constitutive modeling of the rheological behavior of platelet suspensions

NASA Astrophysics Data System (ADS)

Sommer, Drew E.

Compression molding of chopped fiber composites is used to manufacture complex 3D geometries with high fiber volume fractions of 50-60% and long, discontinuous fibers and thermoplastic matrices. When prepreg, chopped into platelets, is used as a charge material, the individual platelets remain intact during the molding process and flow relative to one another, as experimental observations show. Heterogeneity of the platelet/resin suspension cannot be considered at the structural scale of molding simulation. Instead, the suspension should be idealized into the homogenized anisotropic and viscous system which obeys the prescribed anisotropic stress-strain rate constitutive relation. The viscosity tensor of the aforementioned constitutive law was analytically evaluated in this work through the representative volume element (RVE) based analysis. An idealized microstructure of platelets was developed to perform such an analysis. The platelets were aligned and arranged in a planar configuration with periodic boundary conditions. Analytic expressions for the effective, anisotropic viscosities were derived by micromechanical analysis for the idealized microstructure of rigid platelets. In this analysis, the load transfer mechanisms and their contribution to the viscosity of the platelet assembly were investigated. The kinematic assumption of linear velocity distributions consistent with the mechanism of shearing rate was adopted. While the platelets were assumed to be rigid, the resin was taken as an incompressible, isotropic fluid which provided for the platelet-to-platelet load transfer. Strain rate and temperature dependence were included by modeling the polymer matrix as a Carreau fluid. Shear strain in the resin was developed due to the relative motion of adjacent platelets. The resin shear strain rate was expressed in terms of the corresponding platelet velocities. Equilibrium of the platelet was used to relate the applied far-field stress to the average strain rate through the viscosity of neat resin and geometric parameters of the RVE constituents. When combined, these parameters defined the effective homogenized viscosities of an anisotropic system equivalent to the platelet/resin suspension. The expressions for the effective viscosities were found to be dependent on the platelet geometry, stack geometry, the platelet volume fraction and the viscosity of neat resin. In this study, the platelet volume fraction was defined as the volume of platelets within the RVE divided by the RVE volume and discriminated from the fiber volume fraction within a platelet. An approach using the "viscous solid analogy'' was developed to leverage structural finite element methods to predict homogenized viscosities of the platelet assembly. A finite element model was constructed to develop a comparison to the analytic expressions for rigid platelets and include the effect of deformation within the platelets. To compare with the analytic expressions, large viscosities were prescribed for the platelet to approximate rigidity. The properties of the deformable platelets were determined by an approach proposed by Pipes and co-workers. The assumption of rigidity was found to be approximate except in the case of elongation along the fiber direction. A laminate analogy was implemented as a homogenization tool to include the effect of orientation on the apparent viscosities of a multi-axial platelet assembly. The aligned platelet suspension was used to predict the `pseudo-ply' properties. Pseudo-laminates, which were assumed to approximate the microstructure, were developed. The effective `pseudo-laminate' viscosities were predicted with classical lamination theory.

Prediction of Size Effects in Notched Laminates Using Continuum Damage Mechanics

NASA Technical Reports Server (NTRS)

Camanho, D. P.; Maimi, P.; Davila, C. G.

2007-01-01

This paper examines the use of a continuum damage model to predict strength and size effects in notched carbon-epoxy laminates. The effects of size and the development of a fracture process zone before final failure are identified in an experimental program. The continuum damage model is described and the resulting predictions of size effects are compared with alternative approaches: the point stress and the inherent flaw models, the Linear-Elastic Fracture Mechanics approach, and the strength of materials approach. The results indicate that the continuum damage model is the most accurate technique to predict size effects in composites. Furthermore, the continuum damage model does not require any calibration and it is applicable to general geometries and boundary conditions.

Compression of laminated composite beams with initial damage

NASA Technical Reports Server (NTRS)

Breivik, Nicole L.; Gurdal, Zafer; Griffin, O. H., Jr.

1993-01-01

The effect of isolated damage modes on the compressive strength and failure characteristics of laminated composite test specimens were evaluated experimentally and numerically. In addition to specimens without initial damage, specimens with three types of initial damage were considered: (1) specimens with short delaminations distributed evenly through the specimen thickness, (2) specimens with few long delaminations, and (3) specimens with local fiber damage in the surface plies under the three-point bend contact point. It was found that specimens with short multiple delamination experienced the greatest reduction in compression strength compared to the undamaged specimens. Single delaminations far from the specimen surface had little effect on the final compression strength, and moderate strength reduction was observed for specimens with localized surface ply damage.

Fatigue delamination onset prediction in tapered composite laminates

NASA Technical Reports Server (NTRS)

Murri, Gretchen Bostaph; Salpekar, Satish A.; Obrien, T. Kevin

1989-01-01

Tapered (0 deg) laminates of S2/CE9000 and S2/SP250 glass/epoxies, and IM6/1827I graphite/epoxy were tested in cyclic tension. The specimens usually showed some initial stable delaminations in the tapered region, but these did not affect the stiffness of the specimens, and loading was continued until the specimens either delaminated unstably, or reached 10(exp 6) to 2 x 10(exp 7) million cycles with no unstable delamination. The final unstable delamination originated at the junction of the thin and tapered regions. A finite-element model was developed for the tapered laminate with and without the initial stable delaminations observed in the tests. The analysis showed that for both cases the most likely place for an opening (Mode 1) delamination to originate is at the junction of the taper and thin regions. For each material type, the models were used to calculate the strain energy release rate, G, associated with delaminations originating at that junction and growing either into the thin region or tapered region. For the materials tested, cyclic G(sub Imax) values from DCB tests were used with the maximum strain energy release rates calculated from the finite-element analysis to predict the onset of unstable delamination at the junction as a function of fatigue cycles. The predictions were compared to experimental values of maximum cyclic load as a function of cycles to unstable delamination from fatigue tests in tapered laminates. For the IM6/1827I and S2/SP250 laminates, the predictions agreed very well with the test data. Predicted values for the S2/CE9000 were conservative compared to the test data.

Multiscale Static Analysis of Notched and Unnotched Laminates Using the Generalized Method of Cells

NASA Technical Reports Server (NTRS)

Naghipour Ghezeljeh, Paria; Arnold, Steven M.; Pineda, Evan J.; Stier, Bertram; Hansen, Lucas; Bednarcyk, Brett A.; Waas, Anthony M.

2016-01-01

The generalized method of cells (GMC) is demonstrated to be a viable micromechanics tool for predicting the deformation and failure response of laminated composites, with and without notches, subjected to tensile and compressive static loading. Given the axial [0], transverse [90], and shear [+45/-45] response of a carbon/epoxy (IM7/977-3) system, the unnotched and notched behavior of three multidirectional layups (Layup 1: [0,45,90,-45](sub 2S), Layup 2: [0,60,0](sub 3S), and Layup 3: [30,60,90,-30, -60](sub 2S)) are predicted under both tensile and compressive static loading. Matrix nonlinearity is modeled in two ways. The first assumes all nonlinearity is due to anisotropic progressive damage of the matrix only, which is modeled, using the multiaxial mixed-mode continuum damage model (MMCDM) within GMC. The second utilizes matrix plasticity coupled with brittle final failure based on the maximum principle strain criteria to account for matrix nonlinearity and failure within the Finite Element Analysis--Micromechanics Analysis Code (FEAMAC) software multiscale framework. Both MMCDM and plasticity models incorporate brittle strain- and stress-based failure criteria for the fiber. Upon satisfaction of these criteria, the fiber properties are immediately reduced to a nominal value. The constitutive response for each constituent (fiber and matrix) is characterized using a combination of vendor data and the axial, transverse, and shear responses of unnotched laminates. Then, the capability of the multiscale methodology is assessed by performing blind predictions of the mentioned notched and unnotched composite laminates response under tensile and compressive loading. Tabulated data along with the detailed results (i.e., stress-strain curves as well as damage evolution states at various ratios of strain to failure) for all laminates are presented.

Finite element model correlation of a composite UAV wing using modal frequencies

NASA Astrophysics Data System (ADS)

Oliver, Joseph A.; Kosmatka, John B.; Hemez, François M.; Farrar, Charles R.

2007-04-01

The current work details the implementation of a meta-model based correlation technique on a composite UAV wing test piece and associated finite element (FE) model. This method involves training polynomial models to emulate the FE input-output behavior and then using numerical optimization to produce a set of correlated parameters which can be returned to the FE model. After discussions about the practical implementation, the technique is validated on a composite plate structure and then applied to the UAV wing structure, where it is furthermore compared to a more traditional Newton-Raphson technique which iteratively uses first-order Taylor-series sensitivity. The experimental testpiece wing comprises two graphite/epoxy prepreg and Nomex honeycomb co-cured skins and two prepreg spars bonded together in a secondary process. MSC.Nastran FE models of the four structural components are correlated independently, using modal frequencies as correlation features, before being joined together into the assembled structure and compared to experimentally measured frequencies from the assembled wing in a cantilever configuration. Results show that significant improvements can be made to the assembled model fidelity, with the meta-model procedure producing slightly superior results to Newton-Raphson iteration. Final evaluation of component correlation using the assembled wing comparison showed worse results for each correlation technique, with the meta-model technique worse overall. This can be most likely be attributed to difficultly in correlating the open-section spars; however, there is also some question about non-unique update variable combinations in the current configuration, which lead correlation away from physically probably values.

Thermoplastic coating of carbon fibers

NASA Technical Reports Server (NTRS)

Edie, D. D.; Lickfield, G. C.

1991-01-01

Using a continuous powder coating process, more than 1500 meters of T 300/LaRC-TPI prepreg were produced. Two different types of heating sections in the coating line, namely electrical resistance and convection heating, were utilized. These prepregs were used to fabricate unidirectional composites. During composite fabrication the cure time of the consolidation was varied, and composites samples were produced with and without vacuum. Under these specimens, the effects of the different heating sections and of the variation of the consolidation parameters on mechanical properties and void content were investigated. The void fractions of the various composites were determined from density measurements, and the mechanical properties were measured by tensile testing, short beam shear testing and dynamic mechanical analysis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Price, H.L.

Much of the polymer composites industry is built around the thermochemical conversion of raw material into useful composites. The raw materials (molding compound, prepreg) often are made up of thermosetting resins and small fibers or particles. While this conversion can follow a large number of paths, only a few paths are efficient, economical and lead to desirable composite properties. Processing instrument (P/I) technology enables a computer to sense and interpret changes taking place during the cure of prepreg or molding compound. P/I technology has been used to make estimates of gel time and cure time, thermal diffusivity measurements and transitionmore » temperature measurements. Control and sensing software is comparatively straightforward. The interpretation of results with appropriate software is under development.« less

An Enhanced Vacuum Cure Technique for On-Aircraft Repair of Carbon-Bismaleimide Composites

NASA Astrophysics Data System (ADS)

Rider, Andrew N.; Baker, Alan A.; Wang, Chun H.; Smith, Graeme

2011-06-01

Carbon/bismaleimide (BMI) composite is increasingly employed in critical load carrying aircraft structures designed to operate at temperatures approaching 180°C. The high post-cure temperature (above 220°C) required to fully react the BMI resin, however, renders existing on-aircraft prepreg or wet layup repair methods invalid. This paper presents a new on-aircraft repair technique for carbon/BMI composites. The composite prepregs are first warm-staged to improve the ability to evacuate entrapped air. Then the patch is cured in the scarf cavity using the vacuum bag technique, followed by off-aircraft post-cure. The fully cured patch then can be bonded using a structural adhesive.

Field Performance of Three-Phase Amorphous Metal Core Distribution Transformers at Pearl Harbor, Hawaii

DTIC Science & Technology

1990-08-01

transformer core, such as loose or fractured core laminations . A sound level meter with an A- weighting frequency network was used for the...loaded on flatbed trucks as shown in Figure 2 and permanently installed at various sites throughout the Pearl Harbor complex. Figure 3 shows the final

Ballistic Missile Propellant Evaluation Test Motor System (Super BATES)

DTIC Science & Technology

1974-11-25

and laminated parts are debulked and 75 cured in a hydroclave at 950 psi (minimum) and 3000 F, and machined to final dimensions. All molded parts are...to pick dlf- ferent lengths of motors simply hy relocating and pinning the cross arms. flatbed truck with forklift will be i adequate for moving

A Forest Products Technology Program for Washington Community Colleges. Final Report.

ERIC Educational Resources Information Center

Grotefend, Robert T.

This report describes a project to develop a forest product technology curriculum that prepares students at the technical level, junior management, to work in the manufacturing of wood and bark into lumber, plywood, particle board, laminates, and pulp chips. Chapter 1 describes project objectives and procedures followed. In chapter 2 the history…

Control of formaldehyde and TVOC emission from wood-based flooring composites at various manufacturing processes by surface finishing.

PubMed

Kim, Sumin

2010-04-15

This paper assesses the reproducibility of testing formaldehyde and TVOC emission behavior from wood flooring composites bonded by urea-formaldehyde resin at various manufacturing steps for surface finishing materials. The surface adhesion step of laminate flooring for this research was divided into two steps; HDF only and HDF with LPMs. In the case of engineered flooring, the manufacturing steps were divided into three steps; plywood only, fancy veneer bonded on plywood and UV coated on fancy veneer with plywood. Formaldehyde and VOCs emission decreased at the process of final surface finishing materials; LPMs were applied on the surface of HDF for laminate flooring. Although emissions increased when fancy veneer was bonded onto plywood in the case of engineered flooring, emission was dramatically reduced up to similar level with plywood only when final surface finishing; UV-curable coating was applied on fancy veneer. This study suggests that formaldehyde and VOCs emission from floorings can be controlled at manufacturing steps for surface finishing. 2009 Elsevier B.V. All rights reserved.

Thermo-mechanical characterization of a thermoplastic composite and prediction of the residual stresses and lamina curvature during cooling

NASA Astrophysics Data System (ADS)

Péron, Mael; Jacquemin, Frédéric; Casari, Pascal; Orange, Gilles; Bailleul, Jean-Luc; Boyard, Nicolas

2017-10-01

The prediction of process induced stresses during the cooling of thermoplastic composites still represents a challenge for the scientific community. However, a precise determination of these stresses is necessary in order to optimize the process conditions and thus lower the stresses effects on the final part health. A model is presented here, that permits the estimation of residual stresses during cooling. It relies on the nonlinear laminate theory, which has been adapted to arbitrary layup sequences. The developed model takes into account the heat transfers through the thickness of the laminate, together with the crystallization kinetics. The development of the composite mechanical properties during cooling is addressed by an incremental linear elastic constitutive law, which also considers thermal and crystallization strains. In order to feed the aforementioned model, a glass fiber and PA6.6 matrix unidirectional (UD) composite has been characterized. This work finally focuses on the identification of the material and process related parameters that lower the residual stresses level, including the ply sequence, the fiber volume fraction and the cooling rate.

Optimization of wall thickness and lay-up for the shell-like composite structure loaded by non-uniform pressure field

NASA Astrophysics Data System (ADS)

Shevtsov, S.; Zhilyaev, I.; Oganesyan, P.; Axenov, V.

2017-01-01

The glass/carbon fiber composites are widely used in the design of various aircraft and rotorcraft components such as fairings and cowlings, which have predominantly a shell-like geometry and are made of quasi-isotropic laminates. The main requirements to such the composite parts are the specified mechanical stiffness to withstand the non-uniform air pressure at the different flight conditions and reduce a level of noise caused by the airflow-induced vibrations at the constrained weight of the part. The main objective of present study is the optimization of wall thickness and lay-up of composite shell-like cowling. The present approach assumes conversion of the CAD model of the cowling surface to finite element (FE) representation, then its wind tunnel testing simulation at the different orientation of airflow to find the most stressed mode of flight. Numerical solutions of the Reynolds averaged Navier-Stokes (RANS) equations supplemented by k-w turbulence model provide the spatial distributions of air pressure applied to the shell surface. At the formulation of optimization problem the global strain energy calculated within the optimized shell was assumed as the objective. A wall thickness of the shell had to change over its surface to minimize the objective at the constrained weight. We used a parameterization of the problem that assumes an initiation of auxiliary sphere with varied radius and coordinates of the center, which were the design variables. Curve that formed by the intersection of the shell with sphere defined boundary of area, which should be reinforced by local thickening the shell wall. To eliminate a local stress concentration this increment was defined as the smooth function defined on the shell surface. As a result of structural optimization we obtained the thickness of shell's wall distribution, which then was used to design the draping and lay-up of composite prepreg layers. The global strain energy in the optimized cowling was reduced in2.5 times at the weight growth up to 15%, whereas the eigenfrequencies at the 6 first natural vibration modes have been increased by 5-15%. The present approach and developed programming tools that demonstrated a good efficiency and stability at the acceptable computational costs can be used to optimize a wide range of shell-like structures made of quasi-isotropic laminates.

Tack Measurements of Prepreg Tape at Variable Temperature and Humidity

NASA Technical Reports Server (NTRS)

Wohl, Christopher; Palmieri, Frank L.; Forghani, Alireza; Hickmott, Curtis; Bedayat, Houman; Coxon, Brian; Poursartip, Anoush; Grimsley, Brian

2017-01-01

NASA’s Advanced Composites Project has established the goal of achieving a 30 percent reduction in the timeline for certification of primary composite structures for application on commercial aircraft. Prepreg tack is one of several critical parameters affecting composite manufacturing by automated fiber placement (AFP). Tack plays a central role in the prevention of wrinkles and puckers that can occur during AFP, thus knowledge of tack variation arising from a myriad of manufacturing and environmental conditions is imperative for the prediction of defects during AFP. A full design of experiments was performed to experimentally characterize tack on 0.25-inch slit-tape tow IM7/8552-1 prepreg using probe tack testing. Several process parameters (contact force, contact time, retraction speed, and probe diameter) as well as environmental parameters (temperature and humidity) were varied such that the entire parameter space could be efficiently evaluated. Mid-point experimental conditions (i.e., parameters not at either extrema) were included to enable prediction of curvature in relationships and repeat measurements were performed to characterize experimental error. Collectively, these experiments enable determination of primary dependencies as well as multi-parameter relationships. Slit-tape tow samples were mounted to the bottom plate of a rheometer parallel plate fixture using a jig to prevent modification of the active area to be interrogated with the top plate, a polished stainless steel probe, during tack testing. The probe surface was slowly brought into contact with the pre-preg surface until a pre-determined normal force was achieved (2-30 newtons). After a specified dwell time (0.02-10 seconds), during which the probe substrate interaction was maintained under displacement control, the probe was retracted from the surface (0.1-50 millimeters per second). Initial results indicated a clear dependence of tack strength on several parameters, with a particularly strong dependence on temperature and humidity. Although an increase in either of these parameters reduces tack strength, a maximum in tack was predicted to occur under conditions of low temperature and moderate humidity.

Mid-pregnancy maternal leptin levels, birthweight for gestational age and preterm delivery

PubMed Central

Shroff, M.R.; Holzman, C.; Tian, Y.; Evans, R. W.; Sikorskii, A.

2014-01-01

Summary Objective Maternal blood leptin levels are positively associated with adiposity. Recent studies suggest that leptin is also abundantly produced by the placenta and may function as a regulator of fetal growth. Our goal was to examine mid-pregnancy levels of leptin in maternal blood in relation to birthweight for gestational age (BW/GA) and timing of delivery after accounting for maternal pre-pregnancy body mass index (prepreg-BMI) and pregnancy complications. Patients Data were from 1,304 sub-cohort mother/infant pairs who participated in the Pregnancy Outcomes and Community Health (POUCH) Study (1998–2004). Measurements Leptin levels, measured at 16–27 weeks’ gestation, were log-transformed. Geometric mean (GMean) leptin levels were estimated by weighted linear regression with gestational age at blood draw as a covariate. GMean was re-transformed to the original scale for reporting. Results Using the GMeans leptin in mothers of term appropriate-for-gestational age (AGA) neonates as the referent (25.2 μg/L), we observed lower levels in mothers of preterm AGA (21.9 μg/L), term small-for-gestational age (SGA) (20.3 μg/L), and preterm SGA neonates (21.7 μg/L). Results were largely unchanged after adjustment for prepreg-BMI. Leptin levels were higher in mothers who delivered large-for-gestational age (LGA) neonates, both preterm (33.6 μg/L) and term (29.1 μg/L), but the GMeans were markedly attenuated after adjustment for prepreg-BMI. Conclusion The association between BW/GA and maternal leptin levels after adjustment for prepreg-BMI may represent: 1) a residual effect of maternal adiposity that is not fully captured by BMI; and/or 2) variation in placental leptin levels entering the maternal circulation. In conclusion, mid-pregnancy maternal blood leptin levels may be an early indicator of fetal growth status. PMID:22934578

Mid-pregnancy maternal leptin levels, birthweight for gestational age and preterm delivery.

PubMed

Shroff, Monal R; Holzman, Claudia; Tian, Yan; Evans, Rhobert W; Sikorskii, Alla

2013-04-01

Maternal blood leptin levels are positively associated with adiposity. Recent studies suggest that leptin is also abundantly produced by the placenta and may function as a regulator of foetal growth. Our goal was to examine mid-pregnancy levels of leptin in maternal blood in relation to birthweight for gestational age (BW/GA) and timing of delivery after accounting for maternal prepregnancy body mass index (prepreg-BMI) and pregnancy complications. Data were from 1304 subcohort mother/infant pairs who participated in the Pregnancy Outcomes and Community Health (POUCH) Study (1998-2004). Leptin levels, measured at 16-27 weeks' gestation, were log-transformed. Geometric mean (GMean) leptin levels were estimated by weighted linear regression with gestational age at blood draw as a covariate. GMean was re-transformed to the original scale for reporting. Using the GMeans leptin in mothers of term appropriate-for-gestational age (AGA) neonates as the referent (25·2 μg/l), we observed lower levels in mothers of preterm-AGA (21·9 μg/l), term small-for-gestational age (SGA) (20·3 μg/l) and preterm-SGA neonates (21·7 μg/l). Results were largely unchanged after adjustment for prepreg-BMI. Leptin levels were higher in mothers who delivered large-for-gestational age (LGA) neonates, both preterm (33·6 μg/l) and term (29·1 μg/l), but the GMeans were markedly attenuated after adjustment for prepreg-BMI. The association between BW/GA and maternal leptin levels after adjustment for prepreg-BMI may represent: (i) a residual effect of maternal adiposity that is not fully captured by BMI; and/or (ii) variation in placental leptin levels entering the maternal circulation. In conclusion, mid-pregnancy maternal blood leptin levels may be an early indicator of foetal growth status. © 2012 Blackwell Publishing Ltd.

Out-of-Autoclave Manufacturing of Aerospace Representative Parts

NASA Astrophysics Data System (ADS)

Cauberghs, Julien

The use of carbon fibre reinforced composites for aerospace structures has seen a high increase in recent years, and is still growing. The high stiffness-to-weight ratio of these materials makes them ideal for primary structures on airplanes, satellites, and spacecrafts. Nevertheless, the manufacturing of composites remains very costly since it requires equipment investment such as an autoclave, and very qualified workers. Out-of-autoclave manufacturing technology is very promising since it only requires a traditional oven, while still aiming at similar part quality. However, the absence of positive pressure compared with an autoclave makes it more difficult to achieve low porosity parts. This research investigates the manufacturing of complex features with out-of autoclave prepreg technology. The features studied are tight-radius corners with a curvature change, and ply drop-offs. Ply drop-offs tests were conducted to identify if porosity is higher at ply terminations. In corners, the bagging arrangement was modified to achieve the most uniform thickness in areas of curvature change, even with small radii. The conclusions from these studies provided us with guidelines to manufacture larger representative parts, which included these features. The representative parts were tested for porosity, thickness uniformity, mechanical performance, and glass transition temperature (Tg). A total of four representative parts were manufactured with out-of-autoclave technology, and one more was manufactured with an autoclave to allow for a proper comparison between the two processes. The materials used were MTM45-1 5 harness satin and CYCOM5320 plain weave for the out-of-autoclave parts, and CYCOM5276-1 plain weave for the autoclave part. The effect of ply drop-offs on porosity was found to be negligible. Thickness deviation in corners was attributed to a combination of consumable bridging, prepreg's bulk factor and inter-ply shear. Overall, out-of-autoclave prepregs showed performance similar to autoclave prepregs.

Analysis of delamination related fracture processes in composites

NASA Technical Reports Server (NTRS)

Armanios, Erian A.

1992-01-01

This is a final report that summarizes the results achieved under this grant. The first major accomplishment is the development of the sublaminate modeling approach and shear deformation theory. The sublaminate approach allows the flexibility of considering one ply or groups of plies as a single laminated unit with effective properties. This approach is valid when the characteristic length of the response is small compared to the sublaminate thickness. The sublaminate approach was validated comparing its predictions with a finite element solution. A shear deformation theory represents an optimum compromise between accuracy and computational effort in delamination analysis of laminated composites. This conclusion was reached by applying several theories with increasing level of complexity to the prediction of interlaminar stresses and strain energy release rate in a double cracked-lap-shear configuration.

Evolutionary changes in lamin expression in the vertebrate lineage

PubMed Central

Stick, Reimer; Peter, Annette

2017-01-01

ABSTRACT The nuclear lamina is involved in fundamental nuclear functions and provides mechanical stability to the nucleus. Lamin filaments form a meshwork closely apposed to the inner nuclear membrane and a small fraction of lamins exist in the nuclear interior. Mutations in lamin genes cause severe hereditary diseases, the laminopathies. During vertebrate evolution the lamin protein family has expanded. While most vertebrate genomes contain 4 lamin genes, encoding the lamins A, B1, B2, and LIII, the majority of non-vertebrate genomes harbor only a single lamin gene. We have collected lamin gene and cDNA sequence information for representatives of the major vertebrate lineages. With the help of RNA-seq data we have determined relative lamin expression levels for representative tissues for species of 9 different gnathostome lineages. Here we report that the level of lamin A expression is low in cartilaginous fishes and ancient fishes and increases toward the mammals. Lamin B1 expression shows an inverse tendency to that of lamin A. Possible implications for the change in the lamin A to B ratio is discussed in the light of its role in nuclear mechanics. PMID:28430006

Analysis of interlaminar stresses in thick composite laminates with and without edge delamination

NASA Technical Reports Server (NTRS)

Whitcomb, J. D.; Raju, I. S.

1984-01-01

The effect of laminate thickness on the interlaminar stresses in rectangular quasi-isotropic laminates under uniform axial strain was studied. Laminates from 8-ply to infinitely thick were analyzed. Thick laminates were synthesized by stacking (45/0/-45/90) ply groups, rather than grouping like plies. Laminates with and without delaminations were studied. In laminates without delaminations, the free-edge interlaminar normal stress distribution in the outer ply groups was insensitive to total laminate thickness. The interlaminar normal stress distribution for the interior ply groups was nearly the same as for an infinitely thick laminate. In contrast, the free-edge inter-laminar shear stress distribution was nearly the same for inner and outer ply groups and was insensitive to laminate thickness. In laminates with delaminations those delaminations near the top and bottom surfaces of a thick laminate have much larger total strain-energy-release rates (G sub t) and mode I-to-total (G sub t/G sub t) ratios than delaminations deep in the interior. Therefore, delaminations can be expected to grow more easily near the surfaces of a laminate than in the interior.

Structural integrated sensor and actuator systems for active flow control

NASA Astrophysics Data System (ADS)

Behr, Christian; Schwerter, Martin; Leester-Schädel, Monika; Wierach, Peter; Dietzel, Andreas; Sinapius, Michael

2016-04-01

An adaptive flow separation control system is designed and implemented as an essential part of a novel high-lift device for future aircraft. The system consists of MEMS pressure sensors to determine the flow conditions and adaptive lips to regulate the mass flow and the velocity of a wall near stream over the internally blown Coanda flap. By the oscillating lip the mass flow in the blowing slot changes dynamically, consequently the momentum exchange of the boundary layer over a high lift flap required mass flow can be reduced. These new compact and highly integrated systems provide a real-time monitoring and manipulation of the flow conditions. In this context the integration of pressure sensors into flow sensing airfoils of composite material is investigated. Mechanical and electrical properties of the integrated sensors are investigated under mechanical loads during tensile tests. The sensors contain a reference pressure chamber isolated to the ambient by a deformable membrane with integrated piezoresistors connected as a Wheatstone bridge, which outputs voltage signals depending on the ambient pressure. The composite material in which the sensors are embedded consists of 22 individual layers of unidirectional glass fiber reinforced plastic (GFRP) prepreg. The results of the experiments are used for adapting the design of the sensors and the layout of the laminate to ensure an optimized flux of force in highly loaded structures primarily for future aeronautical applications. It can be shown that the pressure sensor withstands the embedding process into fiber composites with full functional capability and predictable behavior under stress.

Energy Saving Glass Lamination via Selective Radio Frequency Heating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allan, Shawn M; Baranova, Inessa; Poley, Joseph

2012-02-27

This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates overmore » the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North America. The second task dealt with a study of current lamination processes in the various laminate industries, and development of concepts for integrating RF lamination into new or existing processes. The third task explored the use of a non-destructive technique for analyzing laminate adhesion with the University of Illinois at Urbana-Champaign. The fourth task focused on developing concepts for curved glass lamination using RF lamination. The fifth and sixth tasks together comprised an analysis of laminate product markets, ranking for applicability and commercialization potential, and the development of commercialization strategies for those products. In addition, throughout the project as new experimental data and conventional process data were obtained, the benefits analysis of RF lamination was refined. The goals of the project described above were achieved, positioning RF lamination for the next stage growth envisioned in the original Industrial Grand Challenge proposal. Working with Pilkington North America, lamination of flat autoglass with PVB was achieved, meeting all 16 stringent industry tests. In particular, PVB laminates made with RF lamination passed environmental tests including the high temperature, 120°C bake test, without significant formation of bubbles (defects). The adhesion of PVB to glass was measured using the pummel method. Adhesion values ranging from 1 to 7 out of 10 were obtained. The significant process parameters affecting the environmental and adhesion performance were identified through a designed experiment. Pre-lamination process variables including PVB storage humidity and the de-airing process (vacuum or nip rolling) were significant, as well as the level of pressure applied to the laminate during the RF process. Analysis of manufacturing with RF lamination equipment, based on the processes developed indicated that 3 RF presses could replace a typical auto-industry autoclave to achieve equal or greater throughput with possibly less capital cost and smaller footprint. Concepts for curved lamination identifying castable molds for prototyping were developed, which allowed Ceralink to obtain commitment to begin curved tooling development. The project significantly helped to advance RF lamination past the feasibility and novelty stage and into the realm of commercial acceptance as a viable alternative to autoclaves. The demonstration of autoclave-quality autoglass produced in just 1 minute with RF lamination, with validation by Pilkington, has fueled industry motivation to seriously consider RF lamination. The industry and other contacts and outreach made in the study of laminate markets (including 3 technical publications and 5 conference presentations), has resulted in a recent surge in RF lamination activity.« less

Energy Saving Glass Lamination via Selective Radio Frequency Heating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allan, Shawn M.

2012-02-27

This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates overmore » the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North America. The second task dealt with a study of current lamination processes in the various laminate industries, and development of concepts for integrating RF lamination into new or existing processes. The third task explored the use of a non-destructive technique for analyzing laminate adhesion with the University of Illinois at Urbana-Champaign. The fourth task focused on developing concepts for curved glass lamination using RF lamination. The fifth and sixth tasks together comprised an analysis of laminate product markets, ranking for applicability and commercialization potential, and the development of commercialization strategies for those products. In addition, throughout the project as new experimental data and conventional process data were obtained, the benefits analysis of RF lamination was refined. The goals of the project described above were achieved, positioning RF lamination for the next stage growth envisioned in the original Industrial Grand Challenge proposal. Working with Pilkington North America, lamination of flat autoglass with PVB was achieved, meeting all 16 stringent industry tests. In particular, PVB laminates made with RF lamination passed environmental tests including the high temperature, 120 C bake test, without significant formation of bubbles (defects). The adhesion of PVB to glass was measured using the pummel method. Adhesion values ranging from 1 to 7 out of 10 were obtained. The significant process parameters affecting the environmental and adhesion performance were identified through a designed experiment. Pre-lamination process variables including PVB storage humidity and the de-airing process (vacuum or nip rolling) were significant, as well as the level of pressure applied to the laminate during the RF process. Analysis of manufacturing with RF lamination equipment, based on the processes developed indicated that 3 RF presses could replace a typical auto-industry autoclave to achieve equal or greater throughput with possibly less capital cost and smaller footprint. Concepts for curved lamination identifying castable molds for prototyping were developed, which allowed Ceralink to obtain commitment to begin curved tooling development. The project significantly helped to advance RF lamination past the feasibility and novelty stage and into the realm of commercial acceptance as a viable alternative to autoclaves. The demonstration of autoclave-quality autoglass produced in just 1 minute with RF lamination, with validation by Pilkington, has fueled industry motivation to seriously consider RF lamination. The industry and other contacts and outreach made in the study of laminate markets (including 3 technical publications and 5 conference presentations), has resulted in a recent surge in RF lamination activity.« less

Development of an impact- and solvent-resistant thermoplastic composite matrix, phase 3

NASA Technical Reports Server (NTRS)

Delano, C. B.; Kiskiras, C. J.

1985-01-01

The polyimide from BTDA 1,6-hexanediamine and m-phenylenediamine was selected from a prior study for the present study. Methods to prepare prepreg which would provide low void composites at low molding pressures from the thermoplastic polyimide were studied. Cresol solutions of the polyimide were applied to a balanced weave carbon fabric and the cresol removed prior to composite molding. Low void composites were prepared from smoothed prepregs at high pressures (34.5 MPa) and temperatures as low as 260 C. Lower molding pressures lead to higher void composites. Need for a lower melt viscosity in the neat resin is suggested as a requirement to achieve low void composites at low pressures. Some mechanical properties are included.

Influence of quality control variables on failure of graphite/epoxy under extreme moisture conditions

NASA Technical Reports Server (NTRS)

Clements, L. L.; Lee, P. R.

1980-01-01

Tension tests on graphite/epoxy composites were performed to determine the influence of various quality control variables on failure strength as a function of moisture and moderate temperatures. The extremely high and low moisture contents investigated were found to have less effect upon properties than did temperature or the quality control variables of specimen flaws and prepreg batch to batch variations. In particular, specimen flaws were found to drastically reduce the predicted strength of the composite, whereas specimens from different batches of prepreg displayed differences in strength as a function of temperature and extreme moisture exposure. The findings illustrate the need for careful specimen preparation, studies of flaw sensitivity, and careful quality control in any study of composite materials.

Diode Laser Assisted Filament Winding of Thermoplastic Matrix Composites

PubMed Central

Quadrini, Fabrizio; Squeo, Erica Anna; Prosperi, Claudia

2010-01-01

A new consolidation method for the laser-assisted filament winding of thermoplastic prepregs is discussed: for the first time a diode laser is used, as well as long glass fiber reinforced polypropylene prepregs. A consolidation apparatus was built by means of a CNC motion table, a stepper motor and a simple tensioner. Preliminary tests were performed in a hoop winding configuration: only the winding speed was changed, and all the other process parameters (laser power, distance from the laser focus, consolidation force) were kept constant. Small wound rings with an internal diameter of 25 mm were produced and compression tests were carried out to evaluate the composite agglomeration in dependence of the winding speed. At lower winding speeds, a strong interpenetration of adjacent layers was observed.

[Development of denture base resin. 2. Manufacturing of visible-light cured prepreg and physical properties of FRP].

PubMed

Kimura, H; Yu, P Y; Teraoka, F; Sugita, M

1989-09-01

To develop the visible light-cured FRP denture base, we investigated the physical properties and the warp of FRP plate by using various combinations of matrix resin and reinforcement. From the results of the bending test, hardness test and manipulation processing, the matrix resin of Bis-GMA/UDMA/3 G at 48/48/4 wt% was determined. The sateen weave's glasscloth as the reinforcement of the prepreg was used. The maximum plies included FRP of 0.5 mm, 0.8 and 1.0 mm thickness have the same maximum bending strengths of 45 kgf/mm2, which is about 5 times larger than that of conventional acrylic resin. The warp of these FRP plates were not found.

Utilization of Induction Bonding for Automated Fabrication of TIGR

NASA Technical Reports Server (NTRS)

Hinkley, Jeffrey A.; Johnston, Norman J.; Hulcher, A. Bruce; Marchello, Joseph M.; Messier, Bernadette C.

1999-01-01

A laboratory study of magnetic induction heat bonding of titanium foil and graphite fiber reinforced polymer prepreg tape, TiGr, demonstrated that the process is a viable candidate for low cost fabrication of aircraft structure made of this new material form. Data were obtained on weld bonding of PIXA and PETI-5 prepreg to titanium. Both the foil and honeycomb forms of titanium were investigated. The process relies on magnetic susceptor heating of titanium, not on high frequency heating of graphite fiber. The experiments showed that with a toroid magnet configuration, good weld bonds might be obtained with heating times of a few seconds. These results suggest the potential is good for the induction heating process to achieve acceptable commercial production rates.

Sonic Fatigue Design Techniques for Advanced Composite Aircraft Structures

DTIC Science & Technology

1980-04-01

AFWAL-TR-80.3019 AD A 090553 SONIC FATIGUE DESIGN TECHNIQUES FOR ADVANCED COMPOSITE AIRCRAFT STRUCTURES FINAL REPORT Ian Holehouse Rohr Industries...5 2. General Sonic Fatigue Theory .... ....... 7 3. Composite Laminate Analysis .. ....... ... 10 4. Preliminary Sonic Fatigue...overall sonic fatigue design guides. These existing desiyn methcds have been developed for metal structures. However, recent advanced composite

76 FR 13429 - Notice of Availability of Final Environmental Impact Statement for the Proposed Blackfoot Bridge...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-11

... 1B would incorporate a layer of impermeable material called a laminated geosynthetic clay liner, or... inches of topsoil; 1 foot of weathered alluvium cover material; 6 inches of drainage/protective layer material; GCLL; 6 inches of a protective sub-grade layer (weathered alluvium or other earthen material...

Status review of PMR polyimides

NASA Technical Reports Server (NTRS)

Serafini, T. T.

1978-01-01

The current status of first and second generation PMR polyimides are reviewed. Synthesis, processing, and applications were considered, using prepreg materials based on processable, high temperature resistant polyimides.

Strength and stiffness of small glued-laminated beams with different qualities of tension laminations

Treesearch

Catherine M. Marx; Russell C. Moody

1981-01-01

A total of 180 small Douglas Fir–Larch (DF-L) or Southern Pine (SP) glued-laminated beams were evaluated to determine the tension lamination quality necessary to obtain desired design stresses. The test beams had either the regular laminating grades of L1 DF-L/No. 1D SP or the special 302-24 laminating grade as tension laminations. Because an initial set of SP beams...

Lamination cooling system

DOEpatents

Rippel, Wally E.; Kobayashi, Daryl M.

2005-10-11

An electric motor, transformer or inductor having a lamination cooling system including a stack of laminations, each defining a plurality of apertures at least partially coincident with apertures of adjacent laminations. The apertures define a plurality of cooling-fluid passageways through the lamination stack, and gaps between the adjacent laminations are sealed to prevent a liquid cooling fluid in the passageways from escaping between the laminations. The gaps are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. The apertures of each lamination can be coincident with the same-sized apertures of adjacent laminations to form straight passageways, or they can vary in size, shape and/or position to form non-axial passageways, angled passageways, bidirectional passageways, and manifold sections of passageways that connect a plurality of different passageway sections. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.

Residual stresses in angleplied laminates and their effects on laminate behavior

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1978-01-01

Evidence of the presence of lamination residual stresses in angleplied laminates were transply cracks and warpage of unsymmetric laminates which occur prior to application of any mechanical load. Lamination residual strains were measured using the embedded strain gage technique. These strains result from the temperature differences between cure and room temperature and vary linearly within this temperature range. Lamination residual stresses were usually present in angleplied fiber composites laminates; they were also present in unidirectional hybrids and superhybrids. For specific applications, the magnitudes of lamination residual stresses were determined and evaluated relative to the anticipated applied stresses. Particular attention was given to cyclic thermal loadings in applications where the thermal cycling takes place over a wide temperature range.

Lamins of the sea lamprey (Petromyzon marinus) and the evolution of the vertebrate lamin protein family.

PubMed

Schilf, Paul; Peter, Annette; Hurek, Thomas; Stick, Reimer

2014-07-01

Lamin proteins are found in all metazoans. Most non-vertebrate genomes including those of the closest relatives of vertebrates, the cephalochordates and tunicates, encode only a single lamin. In teleosts and tetrapods the number of lamin genes has quadrupled. They can be divided into four sub-types, lmnb1, lmnb2, LIII, and lmna, each characterized by particular features and functional differentiations. Little is known when during vertebrate evolution these features have emerged. Lampreys belong to the Agnatha, the sister group of the Gnathostomata. They split off first within the vertebrate lineage. Analysis of the sea lamprey (Petromyzon marinus) lamin complement presented here, identified three functional lamin genes, one encoding a lamin LIII, indicating that the characteristic gene structure of this subtype had been established prior to the agnathan/gnathostome split. Two other genes encode lamins for which orthology to gnathostome lamins cannot be designated. Search for lamin gene sequences in all vertebrate taxa for which sufficient sequence data are available reveals the evolutionary time frame in which specific features of the vertebrate lamins were established. Structural features characteristic for A-type lamins are not found in the lamprey genome. In contrast, lmna genes are present in all gnathostome lineages suggesting that this gene evolved with the emergence of the gnathostomes. The analysis of lamin gene neighborhoods reveals noticeable similarities between the different vertebrate lamin genes supporting the hypothesis that they emerged due to two rounds of whole genome duplication and makes clear that an orthologous relationship between a particular vertebrate paralog and lamins outside the vertebrate lineage cannot be established. Copyright © 2014 Elsevier GmbH. All rights reserved.