Most high performance polymer matrix woven composites are manufactured with resins that require curing at elevated temperatures. Once curing is completed, the composites are cooled down to the room temperature. Due to the significant difference in coefficients of thermal expansion between the resin and the reinforcement, intrinsic residual stresses develop in carbon fiber reinforced composites during cooling. These residual stresses have been observed to depend on the reinforcement configuration, even leading to microcracking in highly constrained three-dimensional (3D) woven composites. At this time, there are no standard experimental techniques for measuring distribution of residual stresses in 3D woven composites or comprehensive studies on the effects of such stresses on their long-term performance. Therefore, high fidelity numerical simulations of composite manufacturing processes validated by experimental observations are necessary.
In this paper, residual stress predictions based on different constitutive time- and temperature-dependent resin properties are compared. In particular, elastic, variable time pseudo-viscoelastic and linear viscoelastic approaches are examined. Finite element analysis is performed using the unit cell model of the “1x1 orthogonal” 3D woven composite previously developed based on direct x-ray computed microtomography observations. In addition to the analysis of residual stress distributions, hole drilling experiment is numerically simulated and the resulting surface displacements are compared with experimental measurements performed via electronic speckle pattern interferometry.