Failure Behavior of Unidirectional AS4/3501-6 Carbon/Epoxy Laminates

The work is aimed at improved understanding of deformation and failure mechanisms of unidirectional carbon fiber reinforced plastics. Monotonic tension and compression experiments are conducted on 3501-6 epoxy resin and AS4/3501-6 carbon/epoxy composite at temperatures ranging from room temperature to 200°C. The goal is to better resolve the matrix modulus and matrix strength influence on the compressive strength and associated failure mechanisms. Two compressive failure mechanisms are observed. At temperatures below 100°C, the failure is governed by formation of longitudinal matrix cracks followed by transverse shear failure. Above this temperature, the failure is governed by localized kinking of fibers. The tensile and compressive strengths of both materials decreased with increasing temperature, the sensitivity to temperature was higher in compression versus tension. A deformation model based on Eshelby's equivalent inclusion theory is utilized to investigate the local and mean field stresses in the matrix as a function of fiber misalignment angle, fiber/matrix modulus mismatch and fiber volume fraction. Deformation maps are constructed to illustrate the link between local stresses and failure mechanisms. The results are compared to the models proposed by Argon and Budiansky.