Experimental and Computational Investigation of Thermal Stability and Mechanical Performance of HDPE/Nanoclay/Alumina Hybrid Composites

The study aims to prepare high-density polyethylene (HDPE) reinforced with nanoclay (NC) and alumina fillers by the melt‑mixing technique. The modulus of samples EC1 and EC2 before and after thermal aging is 665.4, 630.6, and 702, 674 MPa, respectively. The Halpin-Tsai and the Mori-Tanaka models closely predict the modulus values compared to experimental values. The Tsai-Pagano model, the Christensen-Waals model, and the ROM model overpredict the modulus of the composites compared to the experimental modulus. The critical stress‑intensity factor of the EC1 composite before and after aging is 1.07 and 1.09 MPa m0.5, respectively. The fracture energy release values of the EC1 composite before and after aging are 1.72 and 1.71 kJ/m2, respectively. The predicted elastic modulus of the 3% alumina-reinforced composite closely matches the experimentally measured value, indicating that the COMSOL accurately estimates the ultimate stress behavior. The thermogravimetric analysis test indicates that EC2, EC3, and ECA2 samples break down at higher temperatures than pure HDPE samples. The polymer composite ECA3 shows the slowest rate of mass loss at elevated temperatures compared to other composites in the derivative thermogram for polymer composites.