Journal Published Online: 01 December 1985
Volume 7, Issue 4

The Influence of Moisture and Toughened Resin on the Mixed Mode Fracture of Unidirectional Graphite/Epoxy Laminates



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 KI/KII 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 KI/KII ratios were observed.

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

Author Information

Blikstad, M
Linköping Institute of Technology, Linköping, Sweden
Johannesson, TR
Linköping Institute of Technology, Linköping, Sweden
Pages: 6
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Stock #: CTR10307J
ISSN: 0884-6804
DOI: 10.1520/CTR10307J