Buckling-driven deformation and failure mechanism of additively manufactured CFRP structures via micromechanics-based multi-scale modeling

Additively manufactured continuous fiber-reinforced polymer (CFRP) composites enable the fabrication of lightweight cellular structures with tunable mechanical properties, while process-dependent defects create challenges for accurately predicting their mechanical behavior under loading. A micromechanics-based multi-scale modeling approach considering the original defects is developed to investigate the deformation modes and failure mechanisms of AM-fabricated CFRP cellular structures. Stress amplification method and micromechanics of failure criteria (MMF) are adopted to identify the microscopic damage states, and ultimately manifested as the degradation of macroscopic stiffness. The representative geometrical features of nodes and cell walls and void in different scale are obtained by Micro-CT data reconstruction and SEM image analysis, respectively. The cellular structures exhibit a buckling-driven deformation and different failure modes as investigated by experimental and numerical studies. The basic deformation modes include elastic deformation, buckling, buckling with delamination, and node fracture, in which buckling mode shows the large capability to absorb loading energy. The proposed multi-scale model predicts energy absorption with high reliability, with a maximum deviation of 14.70 % from experiments. Notably, topological design markedly influences energy dissipation, with the Kagome structure achieving an experimental EA of 529.47 J, approximately 1.8 times that of the triangular configuration. The findings provide valuable insights into AM-driven design of CFRP cellular structures with engineerable mechanical performance.