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 both experimentally and numerically under remote quasi-static loading. The hybrid laminates are classified into two groups: one featuring alternative overlaying of steel and composite, and the second consists of symmetric cross-ply and angle-ply configurations overlaid within steel layers. These hybrid configurations allowed to examine the effects of layup sequence and composite-layer ply orientation on the laminate's fracture behaviour. Experimental results revealed that layup sequence and composite ply orientation affected the overall fracture behaviour and load-carrying capacity of the hybrid laminates. Additionally, a semi-analytical framework was developed to determine the interlaminar stresses and investigate the different interfaces susceptible to delamination. This provided insights in whether interlaminar stresses were a primary or a secondary (combined with other fracture modes) factor in fracture mechanisms observed experimentally in the laminates considered. Angle-ply laminates, known for exhibiting mode III delamination at dissimilar interfaces, were also considered. Furthermore, these laminates additionally served as a baseline configuration to establish a “characteristic distance”, a parameter required for average stress fracture criterion. Therefore, the fracture criterion was first utilised to predict mode III delamination in angle-ply laminates. Subsequently, the same characteristic distance in quadratic average stress criterion for mixed mode I/III delamination in hybrid laminates was utilised which was observed to exhibit mixed-mode behaviour at the hybrid steel/composite interface. The obtained prediction of fracture stresses against experimental results are in close agreement.