Mechanically-prestressed bistable composite laminates with weakly coupled equilibrium shapes

Fiber-reinforced asymmetric laminates fabricated at elevated temperatures may exhibit bistability at room temperature. The magnitude of deformation in each shape depends primarily on the curing temperature. This paper presents a novel asymmetric bistable laminate that is fabricated at room temperature and whose stable shapes are analogous to those of a thermally cured fiber-reinforced polymeric composite. The proposed laminate is composed of a stress-free isotropic core layer sandwiched between two asymmetric, mechanically-prestressed, fiber-reinforced elastomeric layers. Its stable shapes can be independently tuned by varying the prestress in each elastomeric layer. The mechanics of the laminate are studied using an analytical laminated-plate model that includes the geometric and material nonlinearities associated with large deformations caused by highly-strained elastomers. The effects of core modulus, core thickness, elastomer-core width ratio, and laminate size are examined through a parametric study. Laminate samples are fabricated in the 90°/core/0° configuration for model validation. The simulated stable shapes of the laminate are in agreement with the measured shapes. The dynamic response of the laminate during shape transition is measured using a motion capture system.