Transient deformation and curvature evolution during the snap-through of a bistable laminate under asymmetric point load

Bistable carbon fiber composites, whose bistability arises from having asymmetric fiber layouts in different layers, have shown immense potential for using in shape morphing and adaptive structure applications. While many studies in this field focus on these composite laminates' external shapes at the two stable states, their snap-through behavior of shifting from one stable shape to the other remains a critical aspect to be investigated in complete detail. Moreover, symmetric loading conditions have been extensively studied based on the classical lamination theory, but the asymmetric loading conditions received far less attention. Therefore, this study examines an asymmetric, localized point load on a [0∘/90∘] bistable laminate and its complex transient deformation during the snap-through. Finite element simulation and experiment results reveal three uniquely different snap-through behaviors — two-step snap, one-step snap, and no snap — depending on the point load location. The localized initiation and propagation of a “curvature inversion zone,” calculated from finite element and digital image correlation results, are directly related to these snap-through characteristics. This study also explored the feasibility of using an extended analytical model of classical lamination theory to qualitatively reproduce the above findings. This model compares three polynomial functions of different orders to approximate the out-of-plane laminate displacement field. This study's results can offer valuable insights into the fundamental mechanics of snap-through behaviors and the actuation designs for the bistable composites for different loading scenarios. [Display omitted]