The response of a woven graphite fiber/polyimide composite to aging in nitrogen

Rupnowski, P.; Gentz, M.; Armentrout, D.; Sutter, James K.; Kumosa, M.

doi:10.1016/j.actamat.2005.06.010

Cited by 5 publications

(24 citation statements)

References 32 publications

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“…12) [13][14][15][16][17][18][19][20]22,23,25,[27][28][29][31][32][33][34][35][38][39][40]. The composite manufacturing conditions, visco-elastic properties of the polyimide resin, orthotropic properties of the graphite fibers and composite architecture (weave type, fiber 17 distribution, etc.)…”

Section: Failure Predictions; Modeling Of Micro-and Meso-stressesmentioning

confidence: 99%

“…1) are advanced materials that are widely used in aerospace applications, which require high temperature capabilities up to approximately 400°C . However, one of the limitations of such composites is their low strength under biaxial shear dominated loading conditions at room and elevated temperatures [2,[3][4][5]9,11,14,16,17,[20][21][22][23][24]28,30,34,[38][39][40]. Under these loading conditions, intralaminar and interlaminar cracks develop in the composites at relatively low applied loads ( During manufacturing of graphite/polyimides, large residual thermal stresses are generated in the composites [6][7][8][11][12][13][14][15][16][17][18][19][20][22][23][24][26][27][28][29]34,38,40].…”

Section: Introductionmentioning

confidence: 99%

“…Although the maximum stresses are not significantly affected by fiber architecture, the volume fraction of fibers has a considerable effect on the aging and cooling stress. The residual stresses in a woven 8HS T650-35/PMR-15 subjected to aging at 315°C in nitrogen have been determined using the finite element model of a woven unit-cell [38,40]. The aging stresses in the composite were predicted on a meso-scale for the aging times up to 1000 hours.…”

mentioning

confidence: 99%

“…However, one of the limitations of such composites is their low strength under biaxial shear dominated loading conditions at room and elevated temperatures [2,[3][4][5]9,11,14,16,17,[20][21][22][23][24]28,30,34,[38][39][40]. Under these loading conditions, intralaminar and interlaminar cracks develop in the composites at relatively low applied loads ( During manufacturing of graphite/polyimides, large residual thermal stresses are generated in the composites [6][7][8][11][12][13][14][15][16][17][18][19][20][22][23][24][26][27][28][29]34,38,40]. A greater discrepancy between the thermal expansion coefficients of the fibers and that of the resin, and a larger temperature difference between the manufacturing and in-service temperatures leads to the generation of higher residual thermal stresses.…”

mentioning

confidence: 99%

“…The T650/PMR-15 composite was tested as supplied, whereas the high stiffness composites based on either M40J or M60J graphite fibers with PMR-H-50 resin were tested as supplied and after thermal conditioning with and without moisture added. To explain the effect of temperature, residual thermal stresses and biaxial loads on the failure process of the composites, the visco-elastic computations of micro-and meso-stress distributions in the composites have been performed [13][14][15][16][17][18][19][20]22,23,25,[27][28][29][31][32][33][34][35][38][39][40]. …”

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confidence: 99%

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Fundamental Issues Regarding the High Temperature Failure Properties of Graphite/Polyimide Fabric Composites

Kumosa¹

2004

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the tingathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments rega of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters S (0704-01881, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control, PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS PERFORMING ORGANIZATION NAME{S) AND ADDRESS(ES)Center for Advanced Materials and Structures Department of Engineering University of Denver 2390 South York Street Denver CO 80208 SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)USAF SPONSOR/MONITOR'S ACRONYM(S) AFOSR SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTDistribution Statement A. Approved for public release; distribution is unlimited. SUPPLEMENTARY NOTES ABSTRACTIn this work, a method based on X-ray diffraction (XRD) measurements of internal stresses in embedded metallic ellipsoidal inclusions is briefly described. The method has been recently developed for the determination of residual thermal stresses in high temperature graphite/polyimide composites. The effects of external bending loads and aging on the measurements of the internal stress in unidirectional and woven graphite fiber (T650-35)/polyimide (PMR-15) composites were examined in addition to several other factors which could influence the accuracy of the stress measurements. Such factors as the volume fraction of inclusions, their aspect ratios and the interaction between individual embedded inclusions were also evaluated in this study. It has been showi that despite its complexity the proposed method can be successfully applied to the evaluation of residual stresses in high temperature polymer matrix composites subjected to external loads and aging. EXECUTIVE SUMMARYGraphite/polyimide composites are advanced materials that are widely used in aerospace applications at temperatures up to approximately 400°C . A major limitation of woven fiber/polyimide systems is the inability of these materials to resist intralaminar and interlaminar damage initiation and propagation under shear-dominated biaxial loading conditions. Therefore, failure analyses of unidirectional and woven graphite/polyimide composites based on medium (T650-35) and high (M40J and M60J) modulus graphite fibers with PMR-15 and PMR-II-50 polyimide resins have been performed experimentally and numerically in this study [1-5,9-11,14-17,20-25, 27,28,30,31-35,37-40]. The composites were subjected to biaxial shear dominated stress conditions over a temperature range from 20°C to 316°C. Particular attention was given to the evaluation of damage development and its effect on the shear strengths of the woven composites using the Iosipescu shear and ±45° tensil...

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Section: Failure Predictions; Modeling Of Micro-and Meso-stressesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Fundamental Issues Regarding the High Temperature Failure Properties of Graphite/Polyimide Fabric Composites

Kumosa¹

2004

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Effects of prior aging at 288°C in air and in argon environments on creep response of PMR‐15 neat resin

Ruggles‐Wrenn¹,

Broeckert²

2008

J of Applied Polymer Sci

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The creep behavior of PMR-15 neat resin, a polyimide thermoset polymer, aged in air and in argon environments at 2888C for up to 1000 h was evaluated. Creep tests were performed at 2888C at creep stress levels of 10 and 20 MPa. Creep periods of at least 25-h in duration were followed by 50-h periods of recovery at zero stress. Prior isothermal aging increased the elastic modulus and significantly decreased the polymer's capacity to accumulate creep strain. The aging environment had little influence on creep and recovery behaviors. However, aging in air dramatically degraded the tensile strength of the material. Dynamic mechanical analysis revealed an increase in the glass transition temperature from 3308C to 3368C after 1000 h in argon or in air at 2888C. The rise in the glass transition temperature with aging time is attributed to an increase in the crosslink density of the PMR-15 polyimide. Increase in the crosslink density due to aging in both air and argon environments is likely behind the changes in the elastic modulus and the decreased capacity for inelastic straining. A visibly damaged surface layer of 0.16 mm thickness was observed in specimens aged in air for 1000 h. Results indicate that the unoxidized core material governs the overall mechanical response, whereas the oxidized surface layer causes a decrease in tensile strength by acting as a crack initiation site and promoting early failures.

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Effects of prior aging at 288°C in argon environment on time‐dependent deformation behavior of a thermoset polymer at elevated temperature, part 1: Experiments

McClung

Ruggles‐Wrenn

2009

J of Applied Polymer Sci

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The inelastic deformation behavior of PMR‐15 neat resin, a high‐temperature thermoset polymer, aged at 288°C in argon environment for up to 2000 h was investigated. The experimental program was designed to explore the inﬂuence of prior isothermal aging on monotonic loading and unloading at various strain rates. In addition, the relaxation response and the creep behavior of specimens subjected to prior aging of various durations were evaluated. All tests were performed at 288°C. The time‐dependent mechanical behavior of the PMR‐15 polymer is strongly influenced by prior isothermal aging. The elastic modulus increased and the departure from quasi‐linear behavior was delayed with prior aging time. Stress levels in the region of inelastic flow increased with prior aging time. Furthermore, prior aging significantly decreased the polymer's capacity for inelastic straining, including the material's capacity to accumulate creep strain. Conversely, the relaxation response was not affected by the prior aging. © 2009 Wiley Periodicals, Inc.† J Appl Polym Sci, 2009

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The response of a woven graphite fiber/polyimide composite to aging in nitrogen

Cited by 5 publications

References 32 publications

Fundamental Issues Regarding the High Temperature Failure Properties of Graphite/Polyimide Fabric Composites

Fundamental Issues Regarding the High Temperature Failure Properties of Graphite/Polyimide Fabric Composites

Effects of prior aging at 288°C in air and in argon environments on creep response of PMR‐15 neat resin

Effects of prior aging at 288°C in argon environment on time‐dependent deformation behavior of a thermoset polymer at elevated temperature, part 1: Experiments

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