Dynamic behavior of an automotive polyurethane foam under multiple compression cycles

Polyurethane foams developed for interior automotive applications were tested to determine their mechanical response to uniform dynamic compression. Specimens 50x100x100 mm were compressed to 25%, 50% or 75% strain at nominal strain rates of 0.14-14/s. From 1 to 100 compression cycles were imposed on the specimens. A recovery period was provided between cycles. In all cases, the foam undergoes cyclic softening. The percent reduction in stress response varies with strain, and is greatest at the low strain levels within each compression cycle.