Superior mechanical properties by exploiting size-effects and multiscale interactions in hierarchically architected foams

Dear Colleagues,

I invite you to read our recent paper on hierarchically architected foams published in Extreme Mechanics Letters: Read full article here.

Abstract

Protective applications in extreme environments demand materials with superior modulus, strength, and specific energy absorption (SEA) at lightweight. They must also have the ability to attenuate intense stress waves and absorb kinetic energy from impact while providing thermally stable functionality. However, these properties typically have a trade-off. Hierarchically architected materials—such as the architected vertically aligned carbon nanotube (VACNT) foams—offer the potential to overcome these trade-offs and achieve synergistic enhancement in mechanical properties because of their multiscale origins of bulk properties derived from structural features that span nano to millimeter scales. Such architected materials with complex hierarchical structures require careful investigation of the effects of multitier design parameters and their interactions on the resultant bulk mechanical properties. Here, we adopt a full-factorial design of experiments (DOE) approach to identify an optimal set of design parameters to achieve synergistic enhancement in SEA, compressive strength, and modulus at lightweight in VACNT foams with mesoscale cylindrical architecture. We exploit size effects from geometrically-confined synthesis and highly interactive morphology of the CNTs to enable higher-order design parameter interactions that intriguingly disrupt the diameter-to-thickness (D/t)-dependent scaling laws found in common architected materials having steel and composite tubular structures. We show that exploiting complementary hierarchical mechanisms in architected material design can lead to superior and synergistic enhancement of mechanical properties and performance desirable for extreme protective applications.