ANALYSIS OF VARIABLE STRESS HISTORY ON POLYMERIC COMPOSITE-MATERIALS WITH PHYSICAL AGING

The long-term viscoelastic behavior of polymeric materials below their glass transition temperatures is greatly affected by physical aging. This effect also extends to polymeric matrix composites. The understan ding of the effect of physical aging is necessary to allow designers t o predict the long-term performance of composites structures. This pap er combines an integral-type constitutive law with lamination theory t o describe the viscoelastic response of a composite material. The effe ct of physical aging on the response is included via a reduced time pa rameter in the integration. Results of composite response to variable load history are examined and aging effects illustrated.