Development and validation of modified constitutive model for carbon fiber reinforced polymer composites under impact loading

Carbon fiber reinforced polymer (CFRP) laminates, specifically T700/Epoxy 648, are known for their excellent mechanical properties in both high and low temperatures, making them suitable for spacecraft structures. This study investigates the mechanical behavior of CFRP laminates with various lay-up designs through quasi-static and dynamic mechanical tests. The laminates demonstrated linear behavior under longitudinal and transverse tensile loads, with maximum stress corresponding to strain ranges of 1.6 % to 1.9 % for longitudinal loads and 0.7 % to 0.9 % for transverse loads. In contrast, nonlinear behavior emerged during transverse compression and longitudinal shear tests, attributed to progressive material damage. The maximum load in compression tests was reached at strains of 2 % to 3 %, while shear tests peaked at strains of 17 % to 19 %. Based on the uniaxial test outcomes, we developed a modified constitutive model utilizing continuum damage mechanics. This model incorporates damage tensors and strain rate sensitivity constants and was implemented as a VUMAT subroutine in Abaqus using fortran. Validation was conducted through numerical simulations of a harpoon impacting CFRP laminates to simulate space debris capture. The simulation results aligned closely with experimental data, confirming the model's accuracy. Furthermore, damage modes observed on both the front and rear sides of the laminates showed consistency between numerical simulations and experimental results. The findings indicate that increasing impact velocity significantly affects the delamination area of the CFRP laminates, with higher velocities resulting in more extensive interlayer delamination failure.