Manufacturing and morphing behavior of high-amplitude corrugated laminates

Unidirectionally fiber-reinforced materials are highly orthotropic with respect to stiffness, strength, or thermal expansion. Flat and unsymmetric laminates made of such materials will become curved when temperature changes. As fiber reinforced plastics (FRP) are typically processed at elevated temperatures, i.e. curing of thermoset and melting of thermoplastic materials, the temperature-induced curvature will appear at service temperatures. This chapter explains in Sections 15.2 through 15.8 how the effect can be used to create corrugated laminates where the corrugation shape consists of circular sections with or without undercuts. The deformations occurring after releasing the cured laminates from the flat lamination surface, as well as the morphing behavior, imply large deformations which we address with an analytic nonlinear morphing model explained in Sections 15.9 through 15.11. All modeling relies on periodicity of the corrugation pattern and large extension along the direction transverse to the corrugations. The nonlinear deformations within one representative unit cell are found by integration of curvature and strain that depend on internal line reactions, and these in turn must be in equilibrium with external morphing force. The equilibrium residual is removed by using the Newton minimization method. The verified model is used to simulate morphing deformation and to study the influence of laminate thickness and corrugation amplitude on line-force-stretch diagrams.