Manipulating impact damage modes in composite laminates by helical pitch angle and ply thickness

The low compressive strength after impact (CAI) of composite laminates greatly limits their industrial application. At present, mainstream research focuses on material modification, especially resin toughening. In this paper, we consider a different research thinking: microstructure design. If impact damage modes in laminate are inevitable, which kinds of impact damage modes (or combinations) are less harmful to CAI strength? If some impact damage modes are less harmful, then we can manipulate these specific impact damage modes by microstructure design. In this paper, to manipulate specific impact damage modes, we adopted two design strategies: using thin-ply and bouligand structure, and realized four typical impact damage modes. We found a relatively harmless combination of impact damage forms to maximize the CAI strength, namely, t = 0.12 mm; gamma = 30 degrees. The numerical results revealed that when the ply thickness or the pitch angle is too large or too small, impact damage becomes more serious and extreme, which greatly reduces the CAI strength.