Finite Element Assisted Modelling of the Microscopic Impregnation Process in Thermoplastic Preforms

Abstract

Fibre reinforced composite materials incorporating thermoplastic matrices are gaining increasing popularity in many industrial applications. One of the potential preforms for the manufacture of technical components is commingled yarn composed of reinforcement and matrix in fibre form. These are often employed in the pultrusion process. Another innovative preform consists of polymer powder preimpregnated sheath surrounding fibre bundles. To achieve adequate mechanical properties of the final product it is essential, when producing laminates by a process such as pultrusion with both types of preform, that sufficient matrix impregnation is achieved. The prevention of voids and dry-spots in the laminate requires a theoretical understanding of the mechanisms involved. On a microscopic scale, several finite element (FE) models can be used to simulate the progress of the matrix flow into the interstitial spaces between the single reinforcement fibres. In the present simulations, a hexagonal and a square arrangement account for two of the various fibre packings occurring in a laminate. It permits an estimation of the impregnation performance of commingled and powder impregnated yarns. For each preform the shear rate, to which the polymer matrix is subjected during the impregnation and consolidation process, can be predicted.