Meeting Abstract

25.4  Jan. 5  The Effect of Blade Design on Fracture Toughness in Biological Materials ANDERSON, Philip S. L.; Univ. of Chicago andersps@uchicago.edu

Dental structures capture, retain and fragment food for ingestion. The morphology of gnathostome dentition should be viewed in light of the material properties of the prey. Animal muscle and skin are tough materials which inhibit fragmentation unless energy is continually applied directly to the tip of the fracture. Using a sharp blade greatly reduces the fracture toughness (the work required to bisect an item) of such materials. Despite the variation of bladed tooth morphology in gnathostomes, few studies have experimentally examined the effects of different blade designs on cutting efficiency. I test the effects of different blade morphologies on the fracture toughness of select biological materials. I cut pieces of raw, unprocessed biological tissues (fish and shrimp) with a double guillotine device. The testing machine accommodated straight blades, and blades angled and paired to create bladed notches and matching bladed triangles, and permitted measurement of the work required to cut the material. I hypothesized that the bladed notches and triangles would require less work to fragment the biological materials than straight blades. Blade design does have a large effect on the work required to fragment biological tissues. A notched blade reduced the work to fracture of biological tissues tested by up to 300 J/m² (25% reduction). Biological specimens that contained multiple materials with different properties (shrimp covered in cuticle) showed greater reduction (50%) in work to fracture when more acutely angled blades were used. A bladed triangle matched to a notch reduced work to fracture by another 200 J/m². Strain patterns seen using photoelastic gelatin show that the reduction in work to fracture when using triangular and notched blades arises from an overall reduction in the strain placed on the material when cut.