Sensitivity of bistable laminates to uncertainties in material properties, geometry and environmental conditions

Under certain conditions asymmetric composite laminates can have a bistable response to mechanical loading. A transition between the two stable states provides opportunities to produce large deflections or shape changes from relatively low energy inputs that do not need to be maintained to sustain a specific shape. Such laminates are attracting interest in aerospace applications, deployable structures and energy harvesting. Accurate modelling predictions of bistable laminate shapes has proven challenging, in part due to uncertainties in geometry, material properties and the operating environment of the laminates. In this paper a detailed sensitivity analysis of the influence of each of these properties on laminate curvature is undertaken and demonstrates that bistable laminates are most sensitive to uncertainties in the Young's moduli, thermal expansion coefficients, ply thickness and the temperature change from the elevated cure temperature. Accurate characterisation of these properties and quality control during manufacture can reduce the discrepancies between analytical models and experimental results and allow the models to be used as viable tools for the design of bistable laminates. It is also shown that laminates are highly sensitive to moisture absorption and temperature changes, especially when changes in material properties due to temperature were included in the modelling.