ISSN: 0884-6804
Page Count: 6

The Influence of Moisture and Toughened Resin on the Mixed Mode Fracture of Unidirectional Graphite/Epoxy Laminates
Blikstad, M
Research associate and professor of engineering materials, Linköping Institute of Technology,

Johannesson, TR
Research associate and professor of engineering materials, Linköping Institute of Technology,

Abstract

Hygrothermal effects on the fracture toughness of unidirectional graphite/epoxy laminates of two different grades have been investigated. The material systems used are Fiberite T300/1034 and the more ductile Fibredux T300/920.

The fracture toughness in terms of the critical strain energy release rate Gc was measured for mixed-mode crack propagation along the fibers in off-axis specimens and in rail shear tests. By varying the off-axis angle, crack propagation occurred under different K^I/K^II ratios. It was observed that both moisturization of T300/1034 and change to the more ductile epoxy resin increases the critical strain energy release rate. When the toughened resin laminate had absorbed moisture, its toughness, however, decreased substantially.

A scanning electron microscope was used to investigate the crack surfaces. Topographical differences caused by moisture and different K^I/K^II ratios were observed.

The results were analyzed in terms of the quadratic mixed-mode fracture criteria.

Keywords:
crack propagation, cracks, moisture, graphite/epoxy, unidirectional, fracture toughness, mixed mode, ductile matrix

Paper ID: CTR10307J
DOI: 10.1520/CTR10307J
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