The effect of fiber volume fraction and aspect ratio on the creation of internal stress in the matrix and deformation for short-fiber shape memory alloy composite

Abstract

In recent years, some researchers have studied about shape memory alloy composites (SMACs) which consist of a shape memory alloy (SMA) reinforcement and polymer or metal matrix. In particular, considerable attention has been paid to the creation of internal stress in a matrix of SMAC. Internal stress in a matrix can be created when a deformed SMA fiber recovers its original shape in a composite. On the other hand, deformation of the composite appears when internal stress is created in matrix. Therefore, an interaction exists between the creation of internal stress in the matrix and deformation of the composite. The main purpose of the present research is to investigate the effect of fiber volume fraction and aspect ratio (l/d: length divided by diameter of fiber) on the creation of internal stress in the matrix and deformation for a short-fiber SMA reinforced composite (S-SMAC) under thermal loadings. In the present paper, a constitutive relation of S-SMAC is proposed on the basis of the shear-lag model. Then, the effects of fiber volume fraction and aspect ratio on the creation of internal stress in the matrix and deformation of the composite are investigated by using the proposed constitutive relation for S-SMAC under thermal loadings. The main conclusions are as follows: composite shrinkage and compressive residual stress in the matrix increase with increasing aspect ratio and fiber volume fraction after heating. Also, the composite strain history and residual stress history in the matrix are different according to the fiber volume fraction and aspect ratio during heating. The change of aspect ratio has a small effect on the creation of internal stress in the matrix and deformation of the composite. The performances of S-SMAC come close to that of long-fiber SMA reinforced composite (L-SMAC) when the aspect ratio is >25. Also, residual stresses in the fiber and matrix before heating influence the creation of internal stress in the matrix and deformation of the composite during heating.

Static and vibration properties of randomly oriented shape memory alloy short wires reinforced epoxy resin

“…The presented values are the desired aspect ratios for SMA/epoxy composites. This result is consistent with the results reported by Murasawa et al 28 They reported that the SMA wire aspect ratio should be greater than 25 for effective short SMA wire composites.…”

Intelligent Shape Memory Actuators

“…The dependence of rigidity and strength on temperature is therefore quite opposite between SMA and SMP elements. If the composite materials with SMA and SMP having different properties are developed, the new actuation properties of the material can be obtained (Murasawa et al 2004(Murasawa et al , 2006Tobushi 2006).…”

Review and perspectives: shape memory alloy composite systems

“…The results indicate substantial variation in stress distribution profiles for different activation and loading scenarios. In the work of Murasawa et al [306], a constitutive relationship was proposed for SMA composites based on the shear-lag model. The main conclusions of this work were the following: composite shrinkage and compressive residual stress in the matrix increase with increasing aspect ratio and fiber volume fraction after heating.…”