A unique dual pendulum system was developed to measure single-impact
compression responses of foamed polymers. The data, complemented with a
mathematical model of impact, led to measures of the material’s energy absorption,
compression modulus, and damping. Results are presented for a class of
open-celled foamed polymers specifically developed for shock mitigation.
The experiments employed such materials of four different densities, with
impact times ranging in the 1 to 5 ms range and mean impact stresses up to
160 kN/m.
The results for these materials showed: (1) energy losses of up to 50%
of incident energy, with a peak energy absorption per unit volume of
18 kJ/m; (2) peak compression
modulus of 880 kN/m with
strain rates approaching 200 s;
(3) a mean damping factor of 0.258 with a standard deviation of 0.029. Such data are
of practical importance in many shock-mitigating applications, including prostheses,
floor pads and cushions, gloves for hand-held vibrating tools, grips for hockey sticks
and tennis rackets, and soles for sports shoes.
