An efficient method for fiber bridging traction identification based on the R-curve: Formulation and experimental validation

Fiber bridging is one of the main toughening mechanisms in mode I interlaminar and intralaminar fracture of laminated composites. Intact fibers exert closing forces on both faces of the crack, restraining crack propagation. An effective identification procedure is required to characterize bridging tractions and to develop accurate prediction models. The method proposed in this work is based on the resistance (R)-curve and assumes fiber bridging tractions decreasing non-linearly with respect to the crack opening displacement, following a parametric function. The distribution parameters are identified by a fixed-point iterative procedure where the energy release rate computed in a numerical model is matched with the values obtained experimentally in two points of the R-curve. The method is applied and validated through three cases, from low bridging intensity in thin-ply delamination to high bridging intensity in intralaminar fracture.