ISSN: 0884-6804
Page Count: 6

Stiffness Change of a Graphite Epoxy Laminate Under Reverse Fatigue Loading
Rotem, A
Professor, Technion-IIT,

Abstract

The stiffness of a flat specimen, made of graphite epoxy (T300/934), was measured during reverse fatigue loading. Laminates of basic layup, unidirectional cross-ply and angle-ply, as well as multidirectional (isotropic) layup, were tested. It was found that all the laminates exhibit rapid stiffness degradation on the last (third) fatigue stage. Except for the [0°] unidirectional laminate, the last stage starts at about 70 to 80% of the fatigue life, regardless of the load level and the final mode of failure (tension or compression). It is shown that for this material, stiffness degradation is a result of crack accumulation, mainly along the fibers, even for the fiber dominated laminates. This general phenomenon can serve to predict usable safe life of laminates under fatigue loading.

Keywords:
composite fatigue, stiffness of laminates, graphite epoxy

Paper ID: CTR10153J
DOI: 10.1520/CTR10153J
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