Characterization of Layered Hybrid Foam Formed by Aluminum Foam/EPS-Filled Syntactic Foam: Flexural Test Results

This research was designed to carry out the production, testing, and analysis of new layered hybrid foams obtained by joining closed-cell aluminum foam with expanded polystyrene (EPS)-filled syntactic foams. The mechanical properties of these new, layered hybrid foams make it quite a suitable candidate for engineering applications. In the study, three different EPS with densities of 10 kg/m3, 18 kg/m3 and 30 kg/m3 were used. To analyze the flexural properties, three-point flexural tests (2 mm/min) were performed on closed-cell aluminum foam, EPS-filled syntactic foams, and layered hybrid foams. These tests were conducted according to the ASTM C393/C393M-20 standard. The flexural modulus and strength of the layered hybrid foams were then compared to those of closed-cell aluminum foam and EPS-filled syntactic foams. EPS-filled syntactic foams exhibited higher flexural strength as the density increased, with the highest density sample reaching a maximum flexural strength of approximately 9 MPa. Flexural tests of closed-cell aluminum foam showed three different stages in the stress–strain curve: elastic, plateau and fracture regions. The plateau region demonstrates the impact energy absorption capacity of aluminum foam, making it suitable for impact protection applications. EPS-filled syntactic foams exhibited a more brittle structure, showing sudden fracture after the elastic region. In the flexural tests of layered hybrid foams, 103% higher flexural strength was obtained compared to closed-cell aluminum foam and 26% higher flexural strength was obtained compared to EPS-filled syntactic foams. Hybrid foams with thicker EPS-filled syntactic foam layers had higher deformation capacity and increased durability. This demonstrates the superior mechanical performance of layered hybrid foams and their potential for advanced engineering applications. Consequently, this study provides essential knowledge for the designing of new layered hybrid foams and offers insight into how to use these foams as core materials in sandwich structures. © The Author(s) 2025.