Accession Number : ADA302366

Title :   Residual Strength and Life Prediction of Composite Laminates.

Descriptive Note : Final rept.,

Corporate Author : VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF ENGINEERING SCIEN CE AND MECHANICS

Personal Author(s) : Subramanian, S. ; Reifsnider, K. L. ; Stinchcomb, W. W.

PDF Url : ADA302366

Report Date : JUL 1995

Pagination or Media Count : 98

Abstract : A systematic study was conducted to examine the influence of fiber-matrix interphase on the mechanical properties of composite laminates. Three material systems having the same carbon fibers and toughened epoxy matrix, but with different interphases were used in this study. The fibers used in the 810 A and 820 A systems received 100% and 200% surface treatments respectively, and were sized with epoxy material. The 8100 system was manufactured with 100% surface treated fiber that were sized with a thermoplastic material. Results indicate that the 810 0 system had significantly greater longitudinal tensile strength and failure Strain compared to the 810 A and 820 A systems. The 810 0 laminates have longer fatigue lives at higher load levels and shorter fatigue lives at lower load levels compared to the 810 A laminates. The 820 A laminates have longer life compared to the other two materials systems. The cross-ply laminates from the three material systems exhibit different damage mechanisms and failure modes under monotonic tensile and fatigue loading. A micromechanics model was developed to investigate the role of the interphase on the tensile strength of unidirectional laminates. A new parameter called the efficiency of the interface', is introduced in the model. A simple scheme that uses the experimentally determined tensile modulus of unidirectional laminates in a concentric cylinders model, is described to estimate the interfacial efficiency. The tensile fatigue performance of cross-ply laminates is predicted using this micromechanics model in a cumulative damage scheme. The predicted fatigue lives and failure modes agree well with experimental results. (MM)

Descriptors :   *COMPOSITE MATERIALS, *LAMINATES, *FIBER REINFORCED COMPOSITES, *STRENGTH(MECHANICS), STRESS STRAIN RELATIONS, TENSILE STRENGTH, LIFE EXPECTANCY(SERVICE LIFE), STIFFNESS, TENSILE PROPERTIES, CARBON FIBERS, MATRIX MATERIALS, CYLINDRICAL BODIES, AEROSPACE CRAFT, CREEP, THERMOPLASTIC RESINS, FATIGUE(MECHANICS), EPOXY COMPOSITES, FAILURE(MECHANICS), AEROSPACE INDUSTRY, MICROMECHANICS, UNIDIRECTIONAL.

Subject Categories : Laminates and Composite Materials

Distribution Statement : APPROVED FOR PUBLIC RELEASE