Methods for adhesion/friction reduction of novel wire-shaped actuators, based on shape memory alloys, for use in adaptive fiber-reinforced plastic composites

Abstract

For fiber-reinforced plastic composites, fiber-matrix adhesion is a significant aspect of composite properties. While conventional lightweight structures are always aiming for high fiber-matrix adhesion, innovative and unconventional functional constructions require different concepts. The research work treating adaptive fiber-reinforced plastic composites with shape memory alloy wires presented here uses the approach of actuators freely movable within the composite. This is supposed to prevent mechanical tensions in the interfaces of actuator and composite structure, which would otherwise cause damages of the composite. This work examines hybrid yarns based on friction spinning technology, with shape memory alloy wires as their core component as well as glass fibers, and partly polypropylene, as their sheath component. Additionally, the surface properties of the shape memory alloy wires being used are modified by sanding and coating. The results of a characterization by pull-out testing clearly show that a coating of the shape memory alloy wires with an abherent causes considerable decrease in adhesion and friction in the interface and leads to the mobility of the shape memory alloy wires in the later composite. An even greater effect is attained by sheathing the hybrid yarns in an additional layer of polypropylene, compacting the yarn cross-section. Thus, the pull-out force could be reduced to 35-40% of the reference structure.

Development and mechanical properties of adaptive fiber-reinforced plastics

“…To ensure proper mobility of SMAs in AFRPs and to reduce the damage to the AFRP matrix during the thermal induced activation of SMAs, modifications were executed by converting SMA hybrid yarns (SMA-HYs) in the form of a core-sheath structure with glass and polypropylene using the friction spinning machine – DREF 2000 (Fehrer AG, Austria). The process descriptions and parameters for the production of SMA-HYs can be found in the scientific literature [23]. The produced SMA-HYs were applied for the subsequent development of adaptive reinforcement woven fabrics.…”

Development and testing of controlled adaptive fiber-reinforced elastomer composites

“…The covering is done with a DREF friction spinning machine. Details for this preparation and material specifications can be found in Kluge et al 24,25 The reinforcement textile in this study is a single-layer plain glass fiber weave, in which the covered SMA wires are integrated as weft yarns. In the resulting fabric, the SMA wires are on the upper side of the fabric with a distance of 8.2 mm between the SMA wires.…”

Electro-bending characterization of adaptive 3D fiber reinforced plastics based on shape memory alloys

“…Kluge et al [19] have shown a method to minimize the fixation of the SMA with the matrix by producing a coresheath hybrid yarn, where the core consists of the SMA. The sheath acts as a barrier for the infiltration of the matrix into the hybrid yarn, ensuring the maximum SME of the SMA into the FRP and less damage of the interface matrix.…”