Multiscale design of <scp>CFRPC</scp> sandwich structures with foam core: Microcellular optimization and compressive property evaluation

Abstract Microcellular foam cores are commonly incorporated into composite sandwich structures in aerospace and automotive applications due to superior energy absorption properties, contributing to lightweight design. However, traditional manufacturing techniques, like mold pressing and hot‐press molding, entail multiple stages, require intricate tooling, and incur high costs, constraining the designs of advanced sandwich structures. This study aims to develop a novel manufacturing technique that facilitates the integration of microcellular foam cores and continuous fiber‐reinforced polymer composite panels or reinforcements for sandwich structures. First, integrating in‐situ microcellular foaming and CFRPC with additive manufacturing facilitates the efficient and effective production of sandwich structures with complex designs. Then, the design incorporated three scales: macroscopic sandwich structures, unit‐cells, and microcellular. Subsequently, various unit‐cell configurations (honeycomb, square, rhombus, and re‐entrant honeycomb) were manufactured, and compressive properties were evaluated through experimentation. Finally, the study revealed the effect of temperature on foam density and compression modulus, finding that 230 °C optimizes foam expansion, improving properties. A 10 mm rhombus unit‐cell structure exhibited the highest compression modulus (40.38 MPa) and specific energy absorption (59.02 mJ·m 3 /kg), making it the optimal choice for load‐bearing applications. Lattice‐web reinforcements within the foam core significantly enhance compressive strength and energy absorption. The findings suggest that the proposed multiscale design and production methodologies facilitate the development of innovative and high‐performance multiscale sandwich structures and reinforcements, which are unattainable through conventional techniques. These structures have potential applications in the aerospace and automotive industries, where lightweight, energy‐absorbing materials are crucial. Highlights CFRP AM integrates online foaming and unit‐cell design for multiscale sandwiches. High‐throughput tests modeled parameters, controlling microcellular foam. Rhombus‐10 maximized stiffness; re‐entrant absorbed energy efficiently. Vertical/Y lattices improved stiffness; cylindrical reduced foam crush. A process‐structure–property method supports multiscale sandwich composites.