Topologically Optimized Graded Foams

The adoption of Nature-inspired strategies to improve materials has fostered the introduction of cavities. But how to mass-produce structures in which a complex architecture of cavities is point-to-point fine-tuned to the local and global application requirements? To this aim, the use of a procedure based on topology optimization and gas foaming is herein reported. As an example case, a polymeric foamed beam whose density map is optimized in 3D for three-point bending is designed and produced by gas foaming a purpose-designed preform. The preform is produced with polypropylene and by a high pressure autoclave with CO2 as blowing agent. Optical and scanning electron microscopy as well as X-ray microscopy are used to analyze the 3D optimized foamed structures and show the effectiveness of the foaming design protocol in producing the finite element method-optimized structures. A remarkable twofold increase in the stiffness of the optimized structures is measured with respect to that of the uniformly foamed counterpart with equal overall mass. With the use of a single recyclable material in a single processing step, this method allows one to conceive the mass production of optimized, therefore more sustainable, plastic parts.