Experimental and numerical investigation on the residual distortion and stress fields in un-symmetric hybrid composite laminates induced by the manufacturing process

Due to the high strength to weight ratio of composites, their applications are extending rapidly in many industries. Composites can be fabricated by using different constituent (including fiber and matrix) materials. Different curing cycles and thermal expansion coefficients of matrix and fibers in hybrid composites may lead to residual stresses and distortion. Residual stresses can decrease the durability of the part during commissioning, and distortion makes the assembly process more difficult or even impossible. In this study, different inter-ply hybrid laminates reinforced by carbon and glass fibers are fabricated by hand lay-up method. After curing, they are cooled by three different rates. Distortions of laminates are measured by coordinate measurement machine and their residual strains are measured by the incremental hole drilling method. Calibration factors are calculated by simulation and finally, residual stresses are determined. Also, residual stresses and distortion of laminates are predicted by classical lamination theory and finite element method. The obtained results are compared and acceptable conformity is seen. Comparison of experimental distortion results showed that cooling rates in the laminate which have more degree of un-symmetry will lead to 100 percent deviation of numbers.