Mechanisms of Hydrodynamically Induced In-Plane Deformation of Reinforcement Textiles in Resin Injection Processes

Abstract

The effects of hydrodynamically induced textile deformation during resin injection in Liquid Composites Molding processes have been experimentally investigated for various fiber volume fractions in a rectangular flow channel with linear injection gate. For layups from bi-directional ±45° engineered glass fiber fabric, three deformation effects have been identified: Wrinkling of the topmost fabric layer for low fiber volume fractions, instantaneous in-plane compression of the layup during fiber wetting for intermediate fiber volume fractions, delayed in-plane compression of the wetted part of the fabric for high fiber volume fractions. The deformation behavior is determined by the fabric stiffness and the fixation in the flow channel due to clamping. The fabric has been experimentally characterized with respect to compressibility and coefficient of static friction in order to understand the clamping effect. The injection pressure, which is critical for deformation, has been determined as function of the fiber volume fraction, i.e. as function of the clamping pressure. The characteristics of the function have been correlated with the three observed deformation effects. A simple mechanical model for description of layup displacement and compression, implying visco-elastic behavior of the fabric and clamping with friction on the flow channel walls for various impregnation states, is presented.