Bistable prestressed buckled laminates

The bistability of cross-ply [0n/90n]T laminates has already been investigated, both experimentally and analytically, in much detail. Bistability occurs due to geometric non-linearity and the mismatch between the thermal expansion coefficients of the constituent fibre and matrix materials. In this current work a new type of bistable laminate is presented which has a symmetric lay-up. Its bistability derives from careful manipulation of the residual stresses across the width of the laminate. This is done by applying a prestress to selected fibres in [0/90/90/0]T FRP prepreg laminates prior to curing. Once cured and cooled down this prestress is released and the resulting laminate then buckles. This buckling creates two bistable bowing geometries with two edges remaining relatively flat. Analytical and finite element modelling is also carried out to better understand this buckling mechanism. Potential applications of these new bistable composites include morphing aircraft skins.