Experimental investigation of the effect of crosslinking fibers on mechanical properties of deer's antlers

Abstract

Flexural behavior of red deer's (Cervus Elaphus) antler is managed by not only orientation of osteons but also age, number density of fully fledged Cross-Linking Fibers (CLFs) and mineralization. Although crack propagation is affected by all these factors, a possible role of CLFs during the deformation remains rather disguised. The aim of this study was to enlighten the effect of dimensions, micro skeleton and mineral content of CLFs on plastic deformation. Therefore, mechanical properties, microarchitecture and mineralization of fracture sites of deer antlers were investigated using three-point bending tests in 32 specimens followed by high resolution scanning electron microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The bending tests show that maximum bending strength is in the range of 150-177 MPa, and elastic modulus approximates to 5-6 GPa. Furthermore, fracture toughness of the test specimens examined for all branching groups of antlers was 8-9 MPa.m(1/2). Age and the number of branching albeit are main reasons for differentiating microarchitecture and varying mechanical properties. SEM analyses show that a hierarchical architecture from bottom to up exists, in which some feathers and nano-sized fibrils are attached to larger fibrils that brings CLFs altogether. Antlers of adolescent deers are supposed to have shorter and thinner cross-linking fibers than elder ones. Some feathered micro-fibrils were identified across the CLFs connecting osteons. The thickness (270.0-320.0 nm) and length (700 nm) of feathers were strictly proportional to the microfibrils' size (10.0 mu m in length and 1.0 mu m in thickness). Furthermore, weight percentages of minerals varies along the CLFs that taking root on osteons by a bundle of many smaller fibrils whereas Pb, Cd and Hg have the highest values at the tip of broken CLFs. Such high values of these brittle elements lead to cracked ligament bridging as well.