The compression of wood/thermoplastic fiber mats during consolidation

Secondary processing of non-woven wood and wood/thermoplastic fiber mats is generally performed using compression molding, where heated platens or dies form the final product. Although the study and use of wood-fiber composites is widespread, few research efforts have explicitly described the fundamentals of mat consolidation. In contrast, the wood composite literature has prolifically addressed the compression of wood-strand composites. Models developed for wood-strand composites and powders are reviewed and applied to experimental data for compression of wood and wood/polypropylene (PP) fiber mats. The compression response was monitored during consolidation with varying platen temperatures, densities, and PP content. A model developed from the relationship between the instantaneous modulus and relative density was found to fit the compression of the non-woven fiber mats. The consolidation behavior was analogous to previous work with wood-fiber composites and found to be influenced by the PP content and strain rate.