Multiscale analysis of elastic properties of 3D-printed carbon fiber-reinforced nylon-based composites: Numerical approach

This paper reports the investigation of the elastic properties of 3D-printed carbon fiber-reinforced nylon-based composites (CFRNCs) using experiments and multi-scale numerical modeling. Short-cut carbon fiber-reinforced nylon-based composites (sCFRNCs) and continuous carbon fiber-reinforced nylon-based composites (cCFRNCs) laminates were printed, and a comprehensive set of experimental data for their elastic properties was obtained. Some data were used to calibrate the material parameters of the printed filaments, and the rest were employed to assess the predictive capability of the multi-scale numerical model at determining the elastic parameters of macroscale 3D-printed laminates. Also, the elastic parameters of microscale printed filaments and mesoscale unidirectional laminas were determined. Unlike conventional models, this model considered the structural characteristics of the 3D-printed laminates, where each layer of the laminates was divided into a wall zone, edge zone, and unidirectional laminate zone at the macroscale. The results showed that the reinforcement in both the carbon fiber (CF) filaments and Onyx filaments was T300 CF monofilaments, while the matrix was different types of nylon materials. The predicted tensile modulus of CF filaments closely matched the experimental values reported in the literature, with an error of −0.95 %. Similarly, the predicted elastic properties of 3D-printed laminates agreed well with the experimental results, while the multi-scale model performed better for the 0° cCFRNCs laminates than the multi-directional cCFRNCs laminates. For the 0° laminates, the absolute error was less than 5.5 %, but for the multi-directional laminates, the absolute error was less than 9 %, with a few exceptions. In addition, a linear relationship was found between the tensile modulus and the mesoscale fiber volume fraction in 0° laminates, similar to the rule of mixtures (ROM) model. The results revealed that the ROM model served as a simplified model to replace the multi-scale numerical model for 0° cCFRNCs laminates when the influence of the edge zone was appropriately considered. An attempt was also made to employ a coordinate transformation (CT) method to simplify the multi-scale numerical model for off-axis multi-directional laminates. The results indicated that this method was ineffective when the edge zone was not considered.