Shape memory effect in cross-linked polyethylene matrix composites: the effect of the type of reinforcing fiber

Abstract

The recovery stress of shape-memory polymers is often low; therefore their field of application is limited. In this study, we compared the effects of different fiber reinforcements on the shape memory characteristics of cross-linked polyethylene (X-PE) matrix. We used fiber reinforcement to increase the recovery stress of the shape memory polymer and compared the results of different fiber reinforcements to find the ones that confer the best shape memory properties. We investigated glass, carbon, Kevlar®, and Dyneema® fibers to find the fibers that increase the recovery stress of the composites most. The deformed shape was created by three-point bending, and then heat-activated shape recovery was examined. All reinforcements increased the recovery stress and decreased the shape fixity ratio and the shape recovery ratio. The samples had similar characteristics, except for the low recovery stress Kevlar® fibers and the low recovery ratio of the composite reinforced with glass fibers. With the polyethylene Dyneema® fibers, the composite was self-reinforced and did very well by all metrics. They increased the maximum recovery stress from 0.3 to 2.4 MPa, through having excellent adhesion to the matrix and high strength in their own right. Our research proved that self-reinforced composites could measure up to conventional composites in shape memory applications. Aside from the Dyneema® fibers carbon fibers work best in the X-PE matrix, and should be the preferred conventional reinforcement materials.