The greater the difference between thermal and mechanical properties of the fibre and matrix, the more residual stress is created. Nevertheless, the amount of residual stress depends on the layers structure, laminate lay-up and the fabrication process. In addition to the contraction of polymer during curing cycles, polymerization creates a kind of contraction induced by cross-linking of polymer molecules and therefore intensifies the residual stress creation. Such a phenomenon is important and must be taken into account (Callister, 1994).