11th World Congress on Computational Mechanics (WCCM) / 5th European Conference on Computational Mechanics (ECCM) / 6th European Conference on Computational Fluid Dynamics (ECFD), Barcelona, Spain, 20 - 25 July 2014, pp.3703-3714
In wind energy and aerospace industries, new advances in composite manufacturing technology enable to produce primary load carrying elements as composite materials in wide variety of shapes large such as an L-shape. However, due to the geometry, Interlaminar Normal Stresses (ILNS) are induced once a moderately thick laminate takes highly curved shape. In the curved part of the L-shaped structure, the development of ILNS promotes mode-I type of delamination propagation which is the weakest fracture mode. This is a problem that has recently risen to the forefront in in-service new composite civil aircrafts. This study focuses on experimental and computational investigation of dynamic delamination in a 12-layered woven L-shaped CFRP laminates subjected to quasi-static shear loading. Delamination initiation and propagation processes were captured with a million fps high speed camera. A single delamination is found to initiate in the curved region at the 5th interface during a single drop in the load. The delamination is then observed to propagate at intersonic speed of 2200m/s. The experiments are simulated using cohesive elements by implementing bilinear cohesive model into ABAQUS/Explicit. The experiments and computations are found to be in good agreement, at the macroscale in terms of load-displacement behavior and the failure load, and at the mesoscale in terms of the location of delamination nucleation and delamination crack tip speeds. Shear Mach waves emanating from the crack tips are also observed in the simulations during intersonic crack propagation.