CFRP Structures Having Shape Memory-Like Properties Fabricated with Embroidery Technique

Abstract

Some asymmetrically laminated CFRP (Carbon Fiber Reinforced Plastic) structures are known to show a "bistability", having two stable shapes. This property allows them to maintain a stable shape without any energy supply and achieve relatively large deformations between the two shapes. Therefore, the bistable CFRP structures are expected to be applied to morphing wings etc. Furthermore, using an embroidery machine to place reinforcing carbon fibers the bistable CFRP structures could deform into more complex desired shapes. As a preliminary study, we examined the bistability of a simple [0°/90°] CFRP plate fabricated by the embroidery technique and Vacuum assisted Resin Transfer Molding method. In the study it was found that the CFRP plate have one stable shape at the curing temperature and two stable shapes at lower temperatures, and that th is two-layer bistable CFRP plate exhibit asymmetric deformation due to difference in the amount of threads and resin in each layer coming from the fabrication method. From this observation result, we hypothesized that one of the two shapes would be stabler and that cooling from the curing temperature the plate would necessarily take the stabler shape. This property could give the CFRP structures shape memory-like effect. Therefore, in this study, we investigate the shape memory-like effect of the bistable CFRP plate fabricated with the embroidery technique. To clarify the mechanism of the deformation behavior, a five-point bending test is performed at several temperatures through experiment and finite element analysis. The finite element analysis is in qualitative agreement with the experiment and their results support the hypothesis.