NOTES ON THE MODELING OF PREFORM COMPACTION .2. EFFECT OF SIZING ON BUNDLE LEVEL MICROMECHANICS

Composite materials processed through the general class of Liquid Comp osite Molding schemes must essentially go through a two step process-f iber preforming, followed by resin infusion. Although the preform itse lf gives the basic skeleton of the structure, the compaction stage res ults in significant changes to the microstructure, resulting in flatte ning of weft yarn bundles and simultaneous reorientation and rearrange ment of those in the warp direction. The movement also results in nest ing and inter-layer packing resulting from significant inter-bundle mo vement. Sizings are generically used to assist in wet-out and to reduc e fiber damage during preforming and compaction. However, they also ab sorb volume in a dry preform, and indicate response similar to a two-p hase system consisting of a softer concentric shell surrounding a stif fer fiber, thereby causing changes in response of the preform and comp osite. In this paper we focus on the effect of sizing on behavior at t he bundle level, accounting for compaction effects including those und er shear deformation.