Experimental and numerical investigation of the relationship between material defects and elastoplasticity behavior of 3D-printed carbon-fiber-reinforced thermoplastics under compressive loading

Abstract

In this study, the compressive properties of 3D-printed carbon-fiber-reinforced thermoplastics (3DP-CFRTPs) were experimentally and analytically investigated. Non-hole compression (NHC) and cross-ply open-hole compression (OHC) experiments were conducted to investigate their material properties and damage initiation and propagation. The results of OHC tests at different open hole diameters were divided into "delamination buckling," a conventional failure mode, and "layer buckling," a failure mode that does not lead to complete rupture. In the numerical analysis, a novel periodic cell (PUC) model was developed that considers fiber waviness and voids to analyze nonlinear behavior, including elastoplasticity. The PUC analysis results for the 45° and 90° samples predicted the equivalent stiffness with high accuracy and reproduced the nonlinear behavior well. Sensitivity analysis with material defects (fiber waviness and voids) as variables showed that the voids decreased the elastic modulus and promoted plastic deformation. In contrast, fiber waviness significantly decreased the elastic modulus in the fiber direction, slightly increased the shear properties, and suppressed plastic deformation. Moreover, sensitivity analysis of the mesoscale analysis suggested that "layer buckling" occurs when fiber waviness and voids are considered, which may be a unique failure mode for 3DP-CFRTPs.