This study aims to investigate the effects of two testing parameters on the results of the nano-indentation experiment in the heterogeneous particle reinforced composites: (1) the particle distribution pattern, and (2) the methods for calculating the residual projected contact area of the sample under the indenter. For this purpose, several nano-indentation experiments were performed by using Berkovich indenter on the specimens prepared from Filtek Z350 XT dental nanocomposite as a particle reinforced composite with a volume fraction of 63.3 percent. Then, the nano-indentation procedure on the dental nanocomposite was simulated using the finite element (FE) method. In the FE simulation, several representative volume elements (RVEs) of the nanocomposite were modeled by modifying the Lubachevsky-Stillinger algorithm to distribute particles randomly with a volume fraction of more than 50 percent in a cubic volume. The hardness and elastic modulus of the nanocomposite were calculated from the results of the nano-indentation experiment and the simulation. In these calculations, the projected contact area of the indenter on the specimen was obtained using two different approaches of the Oliver-Pharr method and direct measurement of the area. The results indicated that the distribution of particles around the indenter has significant effects on the nano-indentation results. According to the simulation results, the heterogeneity of the material causes the projected contact area of the indenter on the sample to distort from its equilateral triangle shape, which is assumed in the Oliver-Pharr method. Therefore, the method of direct measurement of the indenter projected contact area on the specimen is proposed to obtain more precise results from the nano-indentation test on heterogeneous materials.

这项研究旨在研究两种测试参数对异质颗粒增强复合材料纳米压痕实验结果的影响：（1）颗粒分布模式，（2）计算聚合物颗粒残余投影接触面积的方法。压头下的样品。为此，使用Berkovich压头对由Filtek Z350 XT牙科纳米复合材料制成的颗粒增强复合材料样品进行了数个纳米压痕实验，复合材料的体积分数为63.3％。然后，使用有限元（FE）方法模拟了牙科纳米复合材料上的纳米压痕过程。在有限元模拟中 通过修改Lubachevsky-Stillinger算法对纳米复合材料的几个代表性体积元素（RVE）进行建模，以将体积分数大于50％的颗粒随机分布在立方体积中。从纳米压痕实验和模拟结果计算出纳米复合材料的硬度和弹性模量。在这些计算中，使用Oliver-Pharr方法的两种不同方法以及面积的直接测量来获得压头在样品上的投影接触面积。结果表明，压头周围的颗粒分布对纳米压痕结果有显着影响。根据仿真结果，材料的异质性导致压头在样品上的投影接触面积偏离其等边三角形形状，这在Oliver-Pharr方法中假设。因此，提出了一种直接测量试样上压头投影接触面积的方法，以从异质材料的纳米压痕试验中获得更精确的结果。