Orientation-dependent tensile deformation and damage of a T700 carbon fiber/epoxy composite: A synchrotron-based study

Uniaxial tensile experiments are conducted on a T700 carbon fiber/epoxy composite along various off-axis angles. Stress–strain curves are measured along with strain fields mapped via synchrotron x-ray digital image correlation, as well as computerized tomography. Elastic modulus and tensile strength decrease with increasing off-axis angles, while fracture strain exhibits a nonmonotonic trend as a combined result of tensile strength decrease and fracture mode transition. At high off-axis angles, strain field mapping demonstrates distinct tensile and shear strain localizations and deformation bands approximately along the fiber directions, while deformation is mainly achieved via continuous growth of tensile strain at low off-axis angles. Roughness of fracture planes decreases exponentially as the off-axis angle increases. The stress–strain curves, strain fields, tomography and fractographs show consistent features, and reveal a fracture mode transition from mainly tension (fiber fracture) to in-plane shear (interface debonding).