Mechanics of micro-architected carbon- and polymer-based interpenetrating phase composites

Abstract

Composite materials are known for their superior mechanical performance as a result of efficient load transfer between the reinforcing and matrix phases. However, the two-dimensional structure of laminated composites reduces their robustness to shear and out-of-plane loads, also enabling failure mechanisms such as interlaminar failure and fiber pull-out. Meanwhile, unique structure–property relations in architected materials have led to tunable mechanical properties, deformation, and failure mechanisms. While some architected materials have reached near-theoretical limits, the majority of current work focuses on describing the response of an unfilled single-material network, and the effect of a load-bearing second phase to a three-dimensional architecture is not well understood. Here, we develop facile fabrication methods for realizing centimeter-scale polymer- and carbon-based architected interpenetrating phase composites (IPC), consisting of a continuous 3D architecture surrounded by a load-bearing matrix, and determine the effect of geometry and constituent material properties on the mechanics of these architected IPCs. Using experiments together with computational models, we show that the matrix phase distributes stress effectively, resulting in a high-strength, stable response to loading. Notably, failure delocalization enhances energy dissipation of the composite, achieving specific energy absorption values comparable to those of wound fiber tubes. Finally, we demonstrate that the stress state in an IPC can be tuned using geometric design and introduce an example of optimized mechanical response in an architected composite. Altogether, this work bridges the gap between mechanically efficient composites and tunable architected materials, laying the foundation for a new class of strong, resilient, and programmable materials.