  The mechanical response of interpenetrating phase composites (IPCs) with
stochastic spinodal topologies is investigated experimentally and numerically.
Model polymeric systems are fabricated by Polyjet multi-material printing, with
the reinforcing phase taking the topology of a spinodal shell, and the
remaining volume filled by a softer matrix. We show that spinodal shell IPCs
have comparable compressive strength and stiffness to IPCs with two
well-established periodic reinforcements, the Schwarz P triply periodic minimal
surface (TPMS) and the octet truss-lattice, while exhibiting far less
catastrophic failure and greater damage resistance, particularly at high volume
fraction of reinforcing phase. The combination of high stiffness and strength
and a long flat plateau after yielding makes spinodal shell IPCs a promising
candidate for energy absorption and impact protection applications, where the
lack of material softening upon large compressive strains can prevent sudden
collapse. Importantly, in contrast with all IPCs with periodic reinforcements,
spinodal shell IPCs are amenable to scalable manufacturing via self-assembly
techniques.
