Look beyond datasheets for isochronous stress-strain curves and visco-plastic models in CAE programs. Use special designs to battle heat and stress.

Design engineers with considerable experience in metals may overlook the effect creep can have on the long-term performance of a plastic part, particularly when applications involve high operating temperatures. When a stress is applied over a long time, the observed strain is greater than that predicted by the short-term modulus. This additional strain is called creep. It occurs in metals, but is a much more significant design factor in plastics. It can generally be stated that the closer the applied stress is to the ultimate stress (or failure point), the more significant creep becomes for plastics.