Dynamic mechanical behavior of flocked layer composite materials

A custom designed dynamic mechanical apparatus was constructed to measure the tan(δ) (loss tangent) properties of Flocked (layer) Energy Absorbing Materials (FEAM). Flocked Impact Energy Absorbing (IEA) materials derive their dynamic mechanical impact absorbing properties from the compressional deformation (bending, buckling) and inter-fiber friction of nominally upright flocked fibers in the flock fiber composite assembly. The reported work summarizes the dynamic mechanical, low strain, linear viscoelastic tan(δ) properties of FEAM composite layer structures at frequencies from 25 to 100 Hz and a temperature range of 0 °C-50 °C. The effect of tan(δ) at various flock densities (fibers/mm2) was also measured. These studies were carried out to gain information and insight into the role that a material's dynamic mechanical properties have on the overall IEA performance of sport (and military) apparel pad structures. Results show that the tan(δ) of FEAM materials increases as the measuring frequency and flocked layer's flock density increase. Tan(δ)'s behavior at various temperatures (0 °C-50 °C) did not follow an expected trend; the highest tan(δ) value was observed to occur at room temperature. Nevertheless, the obtained tan(δ) information on these various FEAM configurations should provide some guidance in designing optimized FEAM sport (and military) pad IEA composites.