Effect of expansion rate on interfacial mechanical properties and failure mechanism of sandwich composites prepared via thermal expansion molding process

Abstract

Based on its ability to integrate foam expansion into rapid prototyping products, the Thermal Expansion Molding Process (TEMP) of foam sandwich composites has shown great application prospects. The influence of the Expansion Rate (ER) on the interfacial mechanical features and failure mechanism of foam sandwich composites has always been a crucial concern in product development during thermal expansion foam forming. Herein, Carbon Fiber Reinforced Polymer (CFRP) foam sandwich panels were fabricated via TEMP, using expansion ratios of 2x, 4x, 6x, and 8x. The relationship between the expansion ratio and mechanical performance of two key interfaces was investigated: The CFRP/foam interface (Interface I) and the fiber/foam interface within the foam (Interface II). The average peel strength of Interface I gradually decreased with increasing expansion ratio: 21.48 N·mm/mm (2×), 19.41 N·mm/mm (4×), 18.92 N·mm/mm (6×), and 17.30 N·mm/mm (8×). Furthermore, the Double cantilever beam-uneven bending moment (DCB-UBM) test revealed that the initial strain energy release rate of Interface II gradually decreased with increasing ER. Finally, a three-point bending test was performed to explore the failure mode of four kinds of ER foam sandwich panels. The findings revealed that the 4x ER was the most suitable for making foam sandwich composites via TEMP. This paper offers a vital reference for developing foam sandwich composite products using TEMP technology.