Pure Mode I, II and Mixed Mode Interlaminar Fracture of Graphite/Epoxy Composite Materials

Abstract

Pure mode I, II and mixed mode fracture tests were performed to characterize the delamination of unidirectional graphite/epoxy composite. Double cantilever beam specimens were used for the pure mode I test and end loaded split specimens were used for the pure mode II test. The critical strain energy release rates were evaluated by beam theory and compliance method and the values were 333 J/m 2 and 1105 J/m 2 respectively. Modified mixed mode bending tests were performed to investigate the mixed mode I/II delamination. Various mixed mode ratios could be produced by simply changing the applied load position on the loading lever and the bending load position on the specimen. A new analytical method was presented that can decompose the total strain energy release rate into mode I and mode II components. Experimental and finite element results agreed well with the theoretical ones.