A New Finite Element Technique and a Study of Residual Stress in Composite Materials.

摘要

Two studies are presented in this report. The first is the development of a new finite element solution, and the second is an analysis of residual stress in filamentary composite material. The new feature of the finite element solution is in the formulation phase of the development; existing procedures are used for the numerical solution. The technique presented is restricted to problems usually described as quasistatic or creeping flow, but it is not restricted by small strain or rotation, nor is it specialized to a particular theory of constitutive behavior. Relative to existing codes the new technique may offer advantages for the study of solid-fluid interactions or for material behavior which fits neither of the concepts of solids or fluids. Four sample problems are studied. A comparison of numerical predictions with some exact analytic solutions is presented, and the comparison is excellent. The second study concerns residual stress. Its development in polymeric filamentary reinforced composite materials is discussed in terms of differential dimensional changes that occur during processing. Two phenomena which contribute to the development of residual stress are considered: dimensional change of the resin due to polymerization and differential thermal expansion of the resin and reinforcement upon cooling from the cure temperature to room temperature. Results of the study to date do not indicate that dimensional changes due to polymerization may be neglected in residual stress assessments. (Author)