Experimental and numerical investigation of fracture characteristics in hybrid steel/composite and monolithic angle-ply laminates

This study investigated the fracture characteristics of hybrid laminates consisting of CorTen steel and carbon fibre-reinforced polymer composites under quasi-static loading, both experimentally and numerically. The hybrid laminates are classified into two groups: one featuring alternative overlaying of steel and composite, and the other with symmetric cross-ply and angle-ply configurations overlaid within steel layers. The effects of layup sequence and composite-layer ply orientation on the fracture behaviour are examined. Experimental results revealed these factors influenced the fracture behaviour and load-carrying capacity. A semi-analytical framework is developed to determine the interlaminar stresses and assess interfaces susceptible to delamination, identifying whether these stresses are primary or secondary factors (combined with other fracture modes) in the experimentally observed fracture mechanisms. Angle-ply laminates, known for exhibiting mode III delamination at dissimilar interfaces, served as a baseline configuration to establish a “characteristic distance” for the average stress fracture criterion. This criterion is first utilised to predict mode III delamination in angle-ply laminates and subsequently, using the same characteristic distance in the quadratic average stress criterion, for mixed-mode I/III delamination in hybrid laminates. The predicted fracture stresses closely agreed the experimental results.