Effect of laminate parameters on the bistability of CFRP laminates and predicting the bistability of laminates through bistability charts

The bistable carbon fiber reinforced polymer (CFRP) laminates are used in aerospace and morphing structures due to the shape-changing capability. And their bistability is influenced by parameters such as side length, ply thickness, ply orientation and material properties. However, it’s time-consuming to determine if a laminate is bistable through the conventional numerical approaches. This study first investigates the effect of laminate side length, ply thickness, layup and material properties on the bistability of laminates through a numerical model backed up by FEA simulation and experiments. It was found that the critical laminate length which causes the laminate to become bistable is linearly proportional to the laminate’s ply thickness, and each laminate with a specific layup and material properties has a particular critical length-to-ply-thickness ratio R c . Under free boundary condition, the R c of the laminates is significantly affected by the number of plies when the total number of plies in the laminate is below 8, whilst the effect of ply orientation becomes more critical as the number of plies increases further, the effect of the in-plane modulus and the thermal expansion coefficient of the lamina on the bistability of the laminate was also investigated. After obtained the R c of various laminates, the bistability of the laminates can be determined efficiently through the “bistable charts” proposed in this study.