Thermally induced mechanical work and warpage compensation of asymmetric laminates

The thermal warpage of asymmetric laminates can be converted into mechanical work. However, thermal warpage is usually unwanted, and can be mitigated with compensatory tool designs. This paper investigates both concepts, focusing on monostability, bistability and the transitional behaviour between the two. Numerical and experimental results showed that the maximum achievable mechanical work goes through a local maximum and then a local minimum as the laminate transitions from bistability to monostability with a decreasing edge length to thickness ratio. The local maximum was correlated with the appearance of the second principal curvature, while the local minimum took place just before reaching the bifurcation point. We successfully manufactured laminates from the monostable region flat using tools with two significant principal curvatures. Laminates from the bistable region were successfully transformed to monostable laminates with similar tools, implying that successful warpage compensation of bistable laminates requires tools that include both principal curvatures.