A comprehensive review of the mechanisms and structure of interpenetrating phase composites with emphasis on metal-metal and polymer-metal variants

Interpenetrating phase composites (IPCs) have gained increasing attention over the past 25 years due to their intriguing mechanical and functional properties arising from their interconnected, interlocking, and co-continuous structure. While early IPC research predominantly focused on ceramic-based systems, the last decade has witnessed a remarkable surge of interest in polymer and metal-based IPCs. This surge can be attributed to the rapid adoption of additive manufacturing in research and renewed interest in diverse phase combinations. Despite this surge, our review reveals a compartmentalized development of different IPC branches, even within the same phase combinations. To address this, we present a comprehensive compilation and categorization of relevant IPC research based on phase combinations and IPC designs. Within each IPC category, we extensively explore the synergistic mechanisms between material choice and preform design, shedding light on the resulting mechanical and functional properties of IPCs. Moreover, based on our review, we identify challenges and essential considerations for specific phase combinations and manufacturing methods. Our review aims to provide a holistic perspective on the current state of IPC research and inspire novel IPC designs.