Fracture toughness of the tensile and compressive fibre failure modes in laminated composites

The fracture toughnesses associated with fibre tensile failure and compressive fibre kinking in a T300/913 carbon-epoxy laminated composite are measured using compact tension and ‘compact compression’ tests respectively. The specimen strain fields were monitored using a digital speckle photogrammetry system during the tests. The damage present in the specimens after the tests was investigated using C-scan and optical and scanning electron microscopy. The initiation and propagation values of the tensile fibre failure critical energy release rate were determined as 91.6 kJ/m2 and 133 kJ/m2 respectively. For fibre compressive kinking, an initiation value of 79.9 kJ/m2 was obtained, but no meaningful propagation values could be determined. In both cases, the test results showed low scatter.