PERMEABILITY CHARACTERIZATION .2. FLOW BEHAVIOR IN MULTIPLE-LAYER PREFORMS

Within the resin transfer molding (RTM) process, flow is generally cha racterized by the progression of a distinct, nonuniform flow front int o the preform as a function of time. The now front progression introdu ces unsaturated characteristics into RTM flow fields. As a result, the definition of an effective in-plane permeability (K-eff) is used to d etermine the permeability of actual preforms as they fill with fluid. This K-eff expression expands upon the original definition of Darcy's law by generalizing its applicability to unsaturated creeping flows. R esults of experimentally obtained K-eff for flow in single-layer prefo rms have been detailed for two common RTM materials, a random mat and a 3-D weave, in Part 1. In this paper (Part 2), we characterize the un saturated and saturated permeabilities of multiple-layer preforms cons tructed from the random mat and 3-D weave materials characterized In P art 1. This work identifies the apparent permeability characteristics of a specific unsaturated multiple-layer flow that demonstrates behavi or inherent to this important class of heterogeneous flows. Also, para llels are drawn between the unsaturated permeability behavior of compl ex 3-D weave materials and multiple-layer preforms.