Transverse deformation of unidirectional fiber-reinforced metal matrix composites

The use of forging as a forming or fabrication process for metal matrix composites (MMCs) requires an understanding of the plastic behavior of MMCs during transverse compression. The current study focuses on the effects of fiber packing array, fiber volume fraction, aspect ratio, and friction condition at the die/workpiece interface on the debonding and cavity-formation at the fiber/matrix interface, which severely limits height reduction of MMCs in forging. Rigid-plastic finite element simulation is used to determine the global strain distribution and local interfacial stress distribution in MMCs as a function of various geometric configurations and friction conditions. In order to verify the finite element simulation and investigate debonding/crack formation around fibers experimentally, MMC specimens with periodic arrays of stainless steel fibers embedded in tin-bismuth alloy are fabricated using a vacuum-casting technique developed for this study. MMC samples with various geometric configurations are compressed at different friction conditions to document the debonding/cracking behavior. The experimental results are compared with the finite element simulation to establish the relationship between actual physical debonding/cracking of MMC samples and the stress and strain distributions. The deformation of MMCs is associated with global shear planes, which depend on the fiber packing array and fiber volume fraction. Depending on the MMC configuration, application of friction can localize fiber/matrix debonding or cause premature fracturing during compression.