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Probabilistic Simulation for Combined Cycle Fatigue in CompositesA methodology to compute probabilistic fatigue life of polymer matrix laminated composites has been developed and demonstrated. Matrix degradation effects caused by long term environmental exposure and mechanical/thermal cyclic loads are accounted for in the simulation process. A unified time-temperature-stress dependent multifactor interaction relationship developed at NASA Glenn Research Center has been used to model the degradation/aging of material properties due to cyclic loads. The fast probability integration method is used to compute probabilistic distribution of response. Sensitivities of fatigue life reliability to uncertainties in the primitive random variables (e.g., constituent properties, fiber volume ratio, void volume ratio, ply thickness, etc.) computed and their significance in the reliability-based design for maximum life is discussed. The effect of variation in the thermal cyclic loads on the fatigue reliability for a (0/+/- 45/90)s graphite/epoxy laminate with a ply thickness of 0.127 mm, with respect to impending failure modes has been studied. The results show that, at low mechanical cyclic loads and low thermal cyclic amplitudes, fatigue life for 0.999 reliability is most sensitive to matrix compressive strength, matrix modulus, thermal expansion coefficient, and ply thickness. Whereas at high mechanical cyclic loads and high thermal cyclic amplitudes, fatigue life at 0.999 reliability is more sensitive to the shear strength of matrix, longitudinal fiber modulus, matrix modulus, and ply thickness.
Document ID
20100015630
Acquisition Source
Glenn Research Center
Document Type
Technical Memorandum (TM)
Authors
Chamis, Christos C. (NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
August 24, 2013
Publication Date
March 1, 2010
Subject Category
Composite Materials
Report/Patent Number
NASA/TM-2010-216104
E-16950
Funding Number(s)
WBS: WBS 432938.11.01.03.02.03.01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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