CONTINUUM DAMAGE MECHANICS APPLIED TO CYCLIC BEHAVIOR OF A GLASS-FIBER COMPOSITE PULTRUSION

Stress-controlled fatigue tests have been carried out on pultruded 60 vol % ECR-glass/polyester rods. Damage evolution was monitored continuously using stiffness decay and replication techniques. When the cyclic stresses corresponded to those within the linear portion of the monotonic stress/strain curve, fatigue damage accumulated linearly, whereas damage developed non-linearly at higher stresses. Using continuum damage mechanics, a strain energy model was developed to predict life, and then verified with the experimental results. The constants for the strain energy model were related to the slope of the S/N curve and stress-axis intercept at a half-cycle, according to a Basquin-type relationship.