Experimental and Numerical Analysis of the Deformation Behavior of Adaptive Fiber-Rubber Composites with Integrated Shape Memory Alloys

Abstract

Fiber-reinforced rubber composites with integrated shape memory alloy (SMA) actuator wires present a promising approach for the creation of soft and highly elastic structures with adaptive functionalities for usage in aerospace, robotic, or biomedical applications. In this work, the flat-knitting technology is used to develop glass-fiber-reinforced fabrics with tailored properties designed for active bending deformations. During the knitting process, the SMA wires are integrated into the textile and positioned with respect to their actuation task. Then, the fabrics are infiltrated with liquid silicone, thus creating actively deformable composites. For dimensioning such structures, a comprehensive understanding of the interactions of all components is required. Therefore, a simulation model is developed that captures the properties of the rubber matrix, fiber reinforcement, and the SMA actuators and that is capable of simulating the active bending deformations of the specimens. After model calibration with experimental four-point-bending data, the SMA-driven bending deformation is simulated. The model is validated with activation experiments of the actively deformable specimens. The simulation results show good agreement with the experimental tests, thus enabling further investigations into the deformation mechanisms of actively deformable fiber-reinforced rubbers.

Hinged Adaptive Fiber-Rubber Composites Driven by Shape Memory Alloys—Development and Simulation

“…As already shown in [ 6 ], the geometrical relationships of this mechanism yield three main parameters that determine the achievable deformations: beam thickness, beam length and maximum SMA contraction. Since the SMA contraction is limited by the material, thickness and length of the beam remain as parameters.…”

“…In recent works, Shape Memory Alloys (SMA) have proven to be highly suited for the creation of adaptive structures [ 1 , 2 , 3 , 4 , 5 , 6 ]. Their thermomechanically induced shape change properties enable their use as actuators, thereby the reducing size, complexity and cost of actuation-based applications by replacing conventional actuators such as electrical motors, hydraulics and pneumatics [ 7 , 8 , 9 ].…”

“…In order to further improve the deformation behavior of such soft adaptive structures, solid-body hinges can be introduced by varying the bending stiffness across the specimen [ 13 , 14 ], thus concentrating the SMA-induced deformation in smaller areas. In past work by the authors [ 6 ], wire-shaped SMA were integrated into tailored reinforcement textiles by means of flat knitting technology and processed into interactive fiber-rubber composite (IFRC) specimens capable of large deformations. Additionally, a simulation model was developed, to describe the deformation behavior of the IFRC.…”

“…Therefore, a mesoscopic FEM modeling approach for IFRC with integrated SMA wires was developed in ANSYS ® as part of a previous work by the authors [ 6 ]. In mesoscopic modeling, the reinforcement fiber yarns are described as discreet geometry integrated within the surrounding matrix.…”

“…However, the level of detail is higher and allows for more concise investigations of the composite behavior and the interactions of its components. As shown in [ 6 ], the modeling approach overestimates the bending stiffness of the fiber-rubber composite without SMA (FRC) and therefore requires calibration with experimental data. The existing model is briefly explained below.…”