Thermal residual stress and interface binding effects on fiber reinforced composites

The properties of fiber composites change with increasing the temperature, which generates the different thermal stresses and thermal expansion coefficients for fiber and matrix. The existence of a force makes the fiber and matrix maintain a bonding state in the process of expansion, and this force is fundamental for the equation of stress and strain. For a flexible substrate, the shear stress of matrix is inversely proportional to the distance to fiber, and the internal axial shear stress equation is obtained in this study. The deformation compatibility condition of interface could be also defined if the fiber and matrix are without debonding. Because the residual stress is a kind of balance of internal stress, the balance formula is proposed, and then the thermal residual stress expression could be finally obtained. It is found that the value of thermal residual stress varies with the length of fiber, and the effect of fiber length-diameter ratio on thermal residual stress is also discussed.