Meeting Abstract

P1.136  Monday, Jan. 4  Building a Biological Hammer BERGAM, Brittany A.*; FRIEDMAN, Alex; SWANSON, Brook O.; Gonzaga University; Gonzaga University; Gonzaga University bbergam@gonzaga.edu

The stomatopod dactyl is a powerful spring-loaded appendage that is used for smashing hard shelled prey, producing point forces in excess of 1000 N and cavitations at the strike point. The dactyl cuticle can survive thousands of these strikes with minimal damage. Here we describe the unique biomaterial and structural features that allow this extreme material performance. The dactyl cuticle is much thicker and has much higher mineral content than other parts of the cuticle. We expect this higher mineral content to lead to increased stiffness and hardness at the expense of toughness. Nanoindentation and bulk impact toughness were used to describe the properties of the dactyl. Two species, Odontodactylus scyllarus and Gonodactylaceus falcatus were used in this study. In nanoindentation we find that the surface of the dactyl has high resistance to permanent deformation, hardness, and very high resistance to elastic deformation, stiffness. The hardness of the O. scyllarus was 2.028 ±0.7616 GPa with a stiffness value of 84.12 ±17.73 GPa while the G. falcatus averaged a 1.510 ±0.7775 GPa for the hardness and a stiffness value of 66.06 ±26.29 GPa. In both of these cases the property values drop precipitously with increasing depth so that the hard and stiff striking surface is backed with much more compliant material. Charpy impact toughness was used to determine the absorbed energy of dactyls under dynamic loading. It was found that the dactyl had an average toughness of 19.3 KJ/m2. We hypothesize that this high toughness can be achieved because of the fibrous organic component in the low-stiffness interior of the dactyl. This combination of high surface stiffness (a bit higher than tooth enamel) and high toughness (a bit higher than wood) place the dactyl in the realm of metals instead of biomaterials.