The Effect of Moisture, Matrix and Ply Orientation on Delamination Resistance, Failure Criteria and Fracture Morphology in CFRP

摘要

The objective of this work was to relate damage mechanisms, gleaned through electron microscopy, to delamination loci generated using fracture toughness (Mixed-Mode Bend) tests. From this, mixed-mode criteria were ranked using the x~2 method (goodness of fit). The shapes of the failure loci (G_T versus %G_I) were related to the damage mechanisms, and to the moisture content, fibre type and ply orientation. Due to cusp formation, the delamination toughness increased as the proportion of Mode Ⅱ increased. A further finding was that a 'hump' which was observed in the failure loci under Mode Ⅰ dominated loading was due to fibre bridging. Ply orientation also had a significant effect on the toughness; 0°/90° interface was about 45% tougher than the 0°/0° interface due to secondary matrix cracking parallel to the crack front. The presence of such additional mechanisms indicates that delamination toughness is not a material property but is dependent on ply orientation.