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

摘要

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, all 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 oil 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.