A new mixed mode test for carbon/epoxy composite systems

The present research examines analytically and experimentally the mixed mode interlaminar fracture toughness of a resin film infused (RFI) carbon fiber/epoxy laminate, namely a IM7-AS4/3501-6 hybrid composite system. The inability to develop representative interlaminar failure in composites with current mixed mode test configurations motivated this particular investigation. The paper is part of a more extensive research effort concerned with the effects of stitching upon the mixed mode fracture toughness of a RFI composite. A new mixed mode test configuration is suggested, the Single Leg Four Point Bend (SLFPB), which provides a robust method with small specimens and a simple apparatus. Closed form fracture mechanics-based strain energy release (SERR) calculations have been established for this configuration. Finite element analysis was conducted to validate the closed form solution. Results show a very good agreement between analytical solutions, numerical simulation and the newly designed SLFPB experimental test. (C) 2003 Elsevier Ltd. All rights reserved.