Abstract
Flocked energy absorbing material, or FEAM, is a novel form of pseudo-composite material that has potential relevance in a wide range of engineering applications. FEAM consists of monofilament fibers of different deniers flocked onto substrates in varying densities to form single or double-sided layers that are separated by fabric dividers. When used for impact protection, FEAM absorbs energy through the buckling and bending of the fibers. Because this class of materials is relatively new, much of its mechanical behavior is not understood. This study aims to address that by investigating the dynamic viscoelastic and in-plane shear properties of FEAM in various configurations. The tan(δ) of FEAM was determined with a purpose built DMA while varying flock length, density and denier, along with temperature and frequency. These results were validated through batch-to-batch testing and calibration with Sorbothane®. The in-plane shear properties were determined at medium strain rates with a purpose-built double-lap shear jig placed inside a guided weight drop tower. DMA revealed that increasing the frequency of loading on FEAM tends to increase its tan(δ), increasing the aspect ratio of the constituent fibers in FEAM tends to decrease tan(δ), and increasing the density of the fibers tends to increase tan(δ). Shear testing revealed that FEAM samples absorb more energy per unit volume than VN600 foam when sheared at medium strain rates. These tests were made possible by funding provided by the NFL through the Head Health Challenge.