Mixed-Mode Delamination Behavior of Carbon/Epoxy Composites

Abstract

The mixed-mode bending (MMB) test was employed in an investigation of delamination fracture behavior in static and fatigue loading for carbon/epoxy composites 1300/M10 and HTA/6376. As specimens were loaded at different ratios of alL for different mixed-mode ratios, both investigated composites exhibited brittle unstable or brittle stable behavior of crack growth. Mixed-mode delamination fracture toughness was determined at a IL = 0.5. Fracture surfaces of MMB specimens were examined using scanning electron microscopy to distinguish fracture features. Stable crack growth was observed over the entire range of crack lengths investigated in the cyclic tests. A consistent relation of crack growth per cycle to the cyclic strain energy release rate was obtained. The trend of reduction in crack growth rate data with diminution in cyclic strain energy release rate suggests the presence of a threshold strain energy release rate.