Bone-inspired composite: manufacturing and characterization

This paper presents the design, manufacturing and mechanical characterization of a biologically inspired composite structure. Classical laminated plates, made of different layers, often present typical kinds of damage, such as delamination, which are related to the same nature of fibers layup. The present structure, instead, aims to reproduce some particular toughening mechanisms occurring in the microstructure of bone. Human bone, indeed, is composed of different sub-parts having multiple functionalities: among these, repeating cylindrical structures, called osteons. One of the osteon main features is related to crack deviation: indeed, cracks in bone tend to be deviated by the osteons, while propagating. Thus the global energy, required to make the crack propagating, is partially spent in deflection. This offers an increased toughness to the bone. Based on these considerations, a composite material is developed, bio-mimicking human bone. A characteristic manufacturing process and a suitable equipment is developed to prepare the composite plates, made of both glass and carbon fibers and epoxy resin. From these plates, experimental static tests are performed to fully characterize the obtained material in two directions (longitudinal and transversal to the osteon axis): 1) tensile, 2) compressive; 3) bending; 4) fracture toughness tests. Moreover, a classic laminate made of the same fiber content is also manufactured and tested, for comparison. The results of these tests highlight higher mechanical performances for the bio-mimetic composite, in the longitudinal direction, but shortcomings in the transversal direction, and show crack deviation and splitting, similarly to what occurs in human bone.