An Experimental Investigation of Combined Symmetric Asymmetric Composite Laminates

It has been found that certain asymmetric composite laminates exhibit bistability, and are thus called bistable composite laminates. A bistable composite laminate is a composite laminate that exhibits multiple stable static equilibrium states. If the bistable composite is actuated it will snap to its secondary equilibrium state and then remain there without any further actuation. This unique behavior of bistable composites has made them the subject of much research in the areas of morphing structures as well as energy harvesting. Much of the research done on bistable laminates has been focused on the fundamental characterization of the bistable behavior and of the laminate equilibrium shapes. Little investigation has been done on how the boundary conditions affect the bistable behavior and this study investigates how the amount of symmetry in a partially- symmetric partially-asymmetric rectangular laminate under an imposed clamped edge boundary condition affects the bi-stability and the curvature of the laminate. A simple design of experiment was developed and 5 sets of 41 laminates with varying amounts of asymmetry were fabricated. These laminates were measured using a profilometer to capture the post cure and snap through curvatures of the laminates with a fixed edge boundary condition. The results showed that up to 20% symmetry can be introduced in the laminate without a substantial loss in snap through curvature, and that up to 83% symmetry can be introduced in the laminate before bistability is lost. Finite element simulations were conducted in Abaqus CAE 6.14 and the results showed good correlation with the experimental results