Cumulative Creep Damage for Polycarbonate and Polysulfone

The literature for creep-to-failure cumulative-damage laws are reviewed. Creep-to-failure tests performed on polycarbonate and polysulfone under single- and two-step loadings are discussed. A semiempirical cumulative-damage rule or modified time-fraction rule is developed, using as the starting point a power law for transient creep response. Experimental results are approximated well by the new rule. Damage and failure mechanisms associated with the two materials are suggested.