Fatigue Behavior of Some Filled Polymers

A Maxwell rotating beam apparatus was used to measure the dynamic mechanical properties as well as the fatigue life of nylon 6 filled with glass beads or fine silica powder, a nylon 66 filled with calcined clay, an epoxy filled with glass beads, and high-impact polystyrene. Attempts to monitor damage by changes in the dynamic mechanical properties failed; the prop-erties remained essentially constant until only a relatively few cycles before failure occurred. The decrease in modulus and increase in damping with increasing maximum cyclic stress were due mostly to heat build-up rather than to any permanent damage. The fatigue life can be drastically de-creased by small surface scratches. ATIGUE LIFE is an important mechanical property of polymers and composite Fmaterials in most structural applications in which the load varies with time. The mechanism of fatigue failure is not well understood for composite materials an