An Experimental Study of the Displacement and Strain Fields across Interphases in Thermoplastic Composites

The main purpose of this paper is to develop a set of improved micro-metrology system, which consists of a digital image-measuring device and a microscope with a long focal length, for the study of displacement fields, strain fields in the area across the interphases, and also the effect of temperature on the micro-mechanics properties of interphases in thermoplastic composites. Meanwhile, the precision of the micro-metrology system is assessed by using an extra solution within of the framework of infinitesimal strain in particular, the choice of the size of subset in the correlation technique is discussed when the displacements are not infinitesimal. Experimental results show that, under practical service conditions of thermo-mechanical coupled loads, a significant residual thermal stress mismatch due to the difference in coefficients of thermal expansion between the fiber and the matrix is balanced out.