Multiscale modeling of the mechanical behavior of 3D braided CFRP composites under uniaxial tension

An innovative multiscale modeling approach is developed to study the mechanical behavior of 3D braided CFRP composites under uniaxial tension. A microscale representative volume element (RVE) is established to compute the effective properties of the yarn. Two sets of mesoscale RVEs are constructed according to the actual braided architecture, namely the surface and interior RVEs, respectively. Damage behavior of the mesoscale models is predicted using a combined continuum damage mechanics (CDM) and cohesive zone modeling (CZM) approach. A local homogenization approach is developed to transform the braiding yarns and the attached resin into normalized subcells. Furthermore, an equivalent block-stacking based (EBSB) cell is established by assembling these subcells following the yarn distribution, to simplify the braided architecture. A macroscale model is constructed by extending the EBSB cell, to predict the tensile behavior of 3D braided composites. The predicted force–displacement curve, elastic modulus and tensile strength concur well with the experimental measurements, validating the reliability of the proposed multiscale modeling approach. The damage mechanisms of 3D braided composites are investigated via multiscale modeling and scanning electron microscope (SEM) observations. It reveals that the fiber breakage, matrix cracking and debonding are the dominant failure modes.