Investigating the uniaxial compressive mechanics of graded polymer foams via in-situ synchrotron X-ray microtomography

Graded polymer foams are emerging as transformative materials for structural applications, outperforming uniform foams due to their spatially tailored density and microstructural features. However, harnessing their full potential requires a deep understanding of how their macroscopic mechanical behavior relates to their complex microstructure evolution. In this study, we elucidate the uniaxial compressive response of graded foams using in-situ synchrotron X-ray microtomography, complemented by comparative experiments on uniform foams of varying densities. Our findings reveal that graded foams exhibit both qualitatively and quantitatively distinct mechanical behavior, driven by unique microscale deformation mechanisms. We evaluate and discuss their superior energy absorption performance and demonstrate how the density, cell size and circularity profile evolves under increasing macroscopic strain. Notably, the graded architecture enables precise control over the localization and progression of densification bands, offering unprecedented design flexibility for advanced structural applications.