Comparison between 1D and 2D delamination growth in composite laminates: An experimental and numerical investigation

Delamination growth in composite laminates is essentially two-dimensional (2D), indicating a multidirectional spreading of interlaminar damage. However, the evaluation and prediction of delamination growth mainly relies on the quantification of one-dimensional (1D) growth using unidirectional specimens. In this study, the discrepancies and similarities between 1D and 2D delamination behaviours of composite laminates are investigated, both experimentally and numerically. The fracture toughness of mode II delamination, measured experimentally through 1D tests, is compared with the numerically fitted critical Energy Release Rate (ERR) in 2D delamination using Cohesive Zone Modelling (CZM) method. The fracture mechanisms involved in 1D and 2D delamination growth are investigated through fractography at the delamination interfaces. Although similar damage mechanisms are present in 1D and 2D tests, using the fracture toughness measured from 1D tests to predict 2D growth is proven to be insufficient due to distinct extrinsic toughening effects. Variations in local stress states significantly influence delamination growth, necessitating different cohesive constitutive models to accurately describe 1D and 2D delamination processes.