Strain‐Rate‐Dependent Off‐Axis Failure of Unidirectional Carbon‐Fiber Composites via a Lattice Model

ABSTRACT A strain‐rate‐dependent triangular lattice model is presented for the off‐axis failure of unidirectional carbon‐fiber composites. Building on an anisotropic lattice with decoupled matrix–fiber damage, rate dependence is introduced in the matrix‐dominated bond stiffnesses and in the NU failure criterion, both driven by local strain rates computed from the lattice kinematics. The model is assessed against off‐axis compression tests on AS4/3501‐6 at , 1, and . The transverse modulus follows the logarithmic rate law to within . With the measured modulus ratio in the criterion, the predicted strengths deviate from the experiments by on average ( excluding ) and increase with the strain rate. The central‐force lattice underpredicts the strength at orientations misaligned with the bonds, and is not quantitatively reliable at . The peak strength is mesh‐objective, whereas the post‐peak energy dissipation is not.