Progressive Failure Analysis Method of a Pi Joint with Uncertainties in Fracture Properties

In this presentation, the structural performance of fiber reinforced composite laminate Pi joints is studied through a progressive failure analysis (PFA) method. The bonded joint area that is the weakest link of the Pi joint structure is modeled using the discrete cohesive zone method (DCZM). The damage growth and failure of the bonded interface is modeled through an exponential decaying traction-separation law that governs the behavior of DCZM elements. This interface model is implemented into a non-linear finite element (FE) code for modeling the progressive failure of the composite Pi joint structures. The present PFA framework is incorporated with a probabilistic analysis module to consider material variability and manufacturing inconsistencies. The proposed PFA methodology is demonstrated for a 2D Pi-shaped laminate composite structure adhesively bonded through a Pi joint, and subjected to a pull-off load. Nomenclature G IC = Mode I critical strain energy release rate G IIC = Mode II critical strain energy release rate C σ = critical cohesive strength of Mode I C τ = critical cohesive strength of Mode II iC δ = critical relative displacement fields ( i =1 and 2) i δ = relative displacement fields ( i =1 and 2) i α = softening rate of a traction separation law ( i =1 and 2) ) ( ~ mn i K = initial stiffness of a DCZM subelement