Visoelastic behavior of carbon epoxy composites by creep tests

Abstract

One of the main requirements for the use of fiber-reinforced polymer matrix composites in structural applications is their evaluation during service life, which demands a study of the time dependent behavior due to viscoelastic response of the polymeric matrix. In the present study, creep and creep rupture test in constant load were performed in specimens of unidirectional carbon fiber-reinforced epoxy composites with fibers orientations of 90º, at temperatures of 25 and 70 ºC. The aim is the viscoelastic characterization of the material through the creep curves to some levels of constant load during periods of 1000 h, the attainment of the “creep rupture envelope” by the creep rupture curves and the determination of the transition from linear to non-linear behavior through isochronous curves. In addition, comparisons of creep compliance curves with a viscoelastic behavior prediction model based on Schapery equation were also performed. It was noted a modification of the material behavior regarding the strength, stiffness and deformation, showing that these properties were affected for the time and tension level, especially above the room temperature. The prediction model was capable to represent the creep behavior, however the equations components may change with the applied tension and the elapsed time of test.