Interlaminar Fracture of Composite Materials

Interlaminar fracture characteristics of a graphite/epoxy composite material (AS1/3501-6) are investigated under the opening, shearing and mix ed mode conditions. The Arcan test fixture was modified to accomodate the composite specimen containing an embedded interlaminar crack. Both critical stress intensity factor and strain energy release rate data were deter mined and the quadratic interaction for mixed mode behavior was compared to experimental data. Results of over sixty tests showed that the test fixture yielded results which compare favorably with results from contemporary test fixtures. Critical fracture parameters for the opening and shearing modes were shown to differ by a factor of 9.1. Further, the test results showed general agreement with the quadratic interaction relation.