Permeability and fabric compaction in forming of fiber metal laminates

Significant fluid-structure interaction is present in fiber metal laminate forming with a low viscous matrix. A modular, process-inspired test setup is presented for one-dimensional saturated and unsaturated infiltration experiments for fiber metal laminates. Permeability measurements for different fabric orientations, fabric layers, and fiber volume contents show low scatter and good repeatability for fiber volume contents up to 65%. Fiber metal laminate specimens were formed by exchanging the mid-segment of the test setup with a punch and die. The stiffness differences between metal and fabric lead to remarkably high compactions in the bending radii, significantly reducing the flow during infiltration. Contrary to resin transfer molding processes, no formation of resin-rich zones along bending edges occurs due to the high normal pressures from metal forming. A numerical forming simulation was developed to predict the local fiber volume content. Comparing the experimental results with the numerical simulation shows that the high fiber volume content in the radii almost exclusively impacts the overall permeability. Implications for fiber metal laminate processing and modeling are outlined.