A MICROMECHANICAL APPROACH TO STUDY THE DAMAGE EVOLUTION OF EPOXY BASED COMPOSITES UNDER FATIGUE LOADING

Abstract

In this contribution, a novel approach to study the matrix crack evolution on a micromechanical level is introduced. For the micromechanical analysis, material models for the fibers, the matrix, and the fiber-matrix-interface are needed. In uniaxial mechanical tests, the epoxy based resin is found to behave viscoplastically. A rheological model is developed and calibrated using cyclic tensile test data. Uniaxial fatigue tests are used to derive a direction-independent failure criterion based on the hysteresis energy. While the interface properties are set to be equal with the neat resin ones, the fibers are idealized to behave elastically and with no damage. Utilizing a cycle jump and degradation framework, an RVE of a fiber-reinforced composite is created. The damage observed in the RVE shows a single, dominant crack perpendicular to the loading direction with a distinct degradation of the effective stiffness in the loading direction. Further investigations regarding the element, and cycle jump size as well as the fiber architecture (volume fraction, radius, RVE size, …) are identified as next steps.