Correlation Between Mechanical Properties and Particle Size of Fiber-Reinforced Selective Laser Sintering–Precoated Sand Molds

When basalt fibers are evenly and layer-wise laid down in the laser sintering area, it can effectively enhance the bending strength and the tensile strength of the precoated sand mold prepared by selective laser sintering (SLS). However, the reinforcing effect of the fibers is influenced by the particle size of the precoated sand. Therefore, in this study, the same sintering parameters were used to prepare specimen of precoated sand with different particle sizes. Then, 0.05−0.20 wt% of basalt fibers was added to the precoated sand mold. The green/dry bending strength and tensile strength of the specimens were tested. And, in combination with the fracture morphology of the specimens, the reinforcing effect of the fibers in different particle sizes of the precoated sand was investigation. The results suggest that, as the precoated sand size decreased, the bending and tensile strengths of the specimens without fibers showed a trend of first decreasing and then increasing. This was influenced by the thickness of the resin layer on the surface of the precoated sand and the number of resin necks. The reinforcing effect of the fibers in the specimens is related to the pore diameter between the precoated sand. After calculation, the optimal amounts of fibers added to the specimen were found to be exponentially correlated with the particle size of the precoated sand, with a correlation coefficient of over 80%. That is, in the preparation of fiber-reinforced SLS-precoated sand molds, the larger the diameter of the precoated sand aggregate, the more fibers are required to be added, providing a certain theoretical basis for the subsequent production process.