Influence of Physical, Thermal and Mechanical Parameters on Micro Residual Stresses in Polymeric Composites

The effects of physical, thermal and mechanical parameters on curing micro-thermal residual stresses are studied, based on the energy method, to present a theoretical solution for prediction of residual stress felds. A fnite element analysis is developed to compare the theoretical and numerical results together. There is found to be a good agreement between the results of the two methods. However, due to the edge effect, the fnite element method is not able to satisfy the boundary conditions at the composite ends. An increase in the fber length leads to a signifcant increase in axial and shear stresses. In addition, for long fber composites the axial and shear residual stresses distribution become more uniform along the fber length and suddenly decrease to zero at the composite edge. The results of the two methods demonstrate that besides the physical characteristics of composites, the order of mismatch in thermal and mechanical properties of the fber and matrix has a considerable infuence on the axial and shear residual stress felds. It must be noted that the radial stress distribution is approximately independent of these parameters and only its maximum value is changed at fber end. The presented analytical solution not only satisfes all governing boundary conditions, but also yields the residual stress felds according to longitudinal and radial coordinates. A shear stress concentration occurs at vicinity of composite edge that signifcantly intensifes due to increasing the mismatch in thermal and elastic properties of the fber and matrix. High mismatch in coeffcient of the thermal expansion and Young’s modulus of the fber and matrix causes a substantial increase in the axial and shear stresses, while the difference between the Poisson’s ratios of the composite constituents has not any signifcant effect on the residual stress feld.