Prediction of energy absorption in composite stiffeners

The energy absorption behavior of composite stiffeners subjected to axial compression has been investigated. Flat plate, angle, and channel specimens were fabricated of T650-35/F584 graphite/epoxy plain-weave fabric and were crush tested under axial compression. A nonlinear finite element approach was used to model the sustained crushing of the flat plate specimens, and a progressive failure model was implemented as part of the finite element analysis to enable investigation of the fundamental mechanisms involved in the crushing behavior. The progressive failure model was based on linear elastic fracture mechanics for prediction of crack growth and a set of failure criteria for predicting fiber/matrix failures that occurred as a result of large deformations. Friction between the specimen and the crushing surface was included in the model. A semi-empirical analysis methodology was developed for prediction of the energy absorption capability of composite stiffeners based on crush tests of flat plate specimens and an understanding of the fundamentals of the energy absorption process.