SEDL / STP / STP1436-EB / STP38420S

Assessment of Damage in a Unidirectional Off-axis Carbon-Epoxy Composite Under Cyclic Loading

Sorenser, LK
Research Assistant and Professor, University of Waterloo, Waterloo, Ontario

Plumtree, A
Research Assistant and Professor, University of Waterloo, Waterloo, Ontario

Pages: 13    Published: Jan 2003

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Abstract

Cyclic tests were conducted on unidirectional HTA/6376 specimens in order to isolate and describe the degradation of an off-axis composite, resulting in matrix dominated failure. Specimens were loaded at 45° to the fibre axis and tested first under quasi-static conditions and then under tension-tension fatigue. Resulting stress-life curves for the 45° off-axis carbon fibre-reinforced epoxy were shallow, resulting in a large amount of scatter.

Damage was monitored using strain gauge rosettes in the loading and transverse directions, as well as perpendicular to the fibres. Hysteresis loops were described by different definitions of modulus and strain accumulation, thus providing models based on dynamic, cyclic creep and total fatigue damage. Although the cyclic creep model described damage, including that in the first cycle, the total fatigue modulus is preferred based on its ability to collapse all damage curves into one. Use of this master curve permits accurate prediction of fatigue lives.