Effects of preform architecture on racetracking in liquid molding

摘要

This paper is concerned with preferential edge flow or racetracking, arising in liquid molding. The object of this paper is to understand the effect of preform architecture on the extent of racetracking, in terms of the mechanical characteristics of the preforms. Rectangular preforms with fiber volume fractions of around 0.4 to 0.47 were prepared with precision cutting from two different isotropic woven glass fabrics - Hexcel 7500 and Hexcel 7544. Experimental techniques have been developed for determining the sliding friction characteristics and effective stiffness of these preforms. Mold filling experiments were run in a rectangular mold with known starting edge gaps between the mold wall and the preforms. The injection pressure transients, the wetted area of the preform and the resin front in the edge gap were moitored. Greater sliding friction associated with a greater clamp force i nthe mold for one of the fabrics led to more controllable racetracking.