Long-term creep deformation of carbon fiber/epoxy composites with physical aging: Experimental investigation and constitutive modeling

The tensile creep tests for two kinds of epoxy resin matrix composite laminates were performed under 25 degrees C and 50 degrees C. Results indicate that these materials deform in a time-dependent manner, that is, the tensile strain increases within a short time after the tests began, and then decreases during most of the loading period. Such increase and decrease trends reflect the creep characteristic and effect of physical aging, respectively. A linear viscoelastic model is developed to include both the creep temperature effect and physical aging effect, starting from the Boltzmann superposition principle. In modeling, these two effects both contribute to the transient compliance and result in the increase and decrease of the transient compliance. Time-temperature/aging time superposition principle is adopted to deal with the influences of temperature and physical aging. This theoretical model is further implemented numerically within a finite element framework. To verify the newly proposed model, not only the experimental and numerical results of the tensile deformations of laminates are compared, but also the bending deformations of structural components made from the above laminates are analyzed.HighlightsTensile creep tests were done for carbon fiber/epoxy laminates.The strain shows creep temperature and aging effect (TE and AE).New constitutive relation was proposed to describe the TE- and AE-caused strains.Structural-level flexure creep tests and simulation analyses were conducted. Tensile Creep Testing of CF/EP Composites and Structural-Level Flexural Creep Testing.image