Damage development, property degradation, and life prediction in composite laminates

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:7202668

Lee, J W

Damage mechanisms and accumulation and associated stiffness reduction in cross-ply graphite/epoxy laminates subjected to quasi-static and tension-tension fatigue loadings were investigated. Damage development consists of transverse matrix cracking, followed by longitudinal matrix cracking, local delaminations at crack intersections, and ultimately longitudinal fiber fractures of the primary load-carrying plies. The initiation of longitudinal matrix cracking was observed at approximately 65% of the normalized logarithmic lifetime (log n/log N). The reduction in axial modulus, even in normalized form, is a function of the cyclic stress level. The characteristic features of the typical axial modulus curve are: (1) initial drop due to first cycle damage, (2) gradual reduction or plateau due to transverse crack multiplication or saturation up to the characteristic damage state (CDS), (3) accelerated reduction corresponding primarily to fiber fractures. The in-plane shear modulus was more sensitive to longitudinal matrix cracking than the axial modulus of the laminmate. A model, based on static and fatigue properties of the single lamina, was developed for predicting the fatigue life of cross-ply laminates.

• Research Organization: Northwestern Univ., Evanston, IL (USA)
• OSTI ID: 7202668
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
CARBON
COMPOSITE MATERIALS
CRACKS
DAMAGE
DEFORMATION
ELEMENTAL MINERALS
ELEMENTS
EPOXIDES
FATIGUE
GRAPHITE
MATERIALS
MATHEMATICAL MODELS
MATRIX MATERIALS
MECHANICAL PROPERTIES
MINERALS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
TENSILE PROPERTIES