High strain rate mechanical behavior of seashell-mimetic composites: Analytical model formulation and validation

Seashells (esp. Nacre, or mother-of-pearl) have attracted a substantial attention of the scientific community over the last decade. What makes it as a role model for bio-inspiration is its strength and specifically, superior toughness owing to the synergistic effect of its inorganic and organic components and its unique architecture at its most elementary level, i.e., brick and mortar architecture. Note that preponderance of the studies in literature is limited to quasi-static loading scenario. This is intriguing given the fact that both these materials are fundamentally used as a basic structural material for synthesizing and in orchestrating complex load bearing/shielding structures against predatory impact/crush attack. In our current investigation, an attempt has been made to predict the strength of these types of composites under dynamic regime by development of an analytical model, followed by experimental verification under high-strain rates using Split Hopkinson Pressure Bar (SHPB). Two types of ceramic–polymer composites were tested which were prepared via freeze casting technique. A reasonable agreement has been observed between the analytically predicted and experimentally observed values. Manifestation of dynamic self-stiffening behavior by these types of composites will find particular relevance in application of these types of composites as protective material when subjected to ballistic impact. Understanding the mechanical behavior of these types of composites under dynamic rates of loading will provide insights on the applicability of hybrid bio-inspired composites as protective materials.

► Analytical model formulation defining behavior of brick and mortar composites under impact loading.
► Experimental validation in a Split Hopkinson Pressure Bar (SHPB).
► For a fixed ceramic weight fraction, strain levels increase with increasing strain-rate.
► Manifestation of dynamic self stiffening behavior.