Mechanical and electromechanical characterization of a novel composite cellular solid for orthopaedic applications

Abstract

This document presents investigations concerning the feasibility of manufacturing a novel active composite cellular structure to be used in surgical applications such as spinal fusion. The development of a biomimetic spinal fusion implant was motivated by two main factors. The population of patients whose metabolic conditions jeopardize the success of this surgical operation keeps increasing. Current implants and techniques present financial, technical, and health drawbacks. The new medical device would feature enhanced mechanical and electromechanical properties that would overcome these issues and could accelerate bone healing. A simple one-dimensional piezoelectric re-entrant structure was created from piezoceramic plates positioned between metallic bowtie open cells. Various sizes of this structure were prepared by hand and by a solid free-form process. These ductile cellular solids were tested to verify if they presented a nonlinear mechanical behavior at small strains along with mechanical parameters and an electromechanical behavior that could be tailored for orthopaedic applications. The tensile strength of a gradual composition material used as an interface between the metallic and ceramic elements of the structure was also evaluated. Despite the small number of specimens and limitations in the current manufacturing process, the investigations showed that the mechanical and electromechanical properties of the re-entrant structure can be controlled and tailored via their relative density. Also, the gradual composition interfacing material presented a linear change in tensile strength that could eliminate the problems of stress concentration in the structure. This work provides base data for future finite element analyses of such and evolved versions of the piezoelectric re-entrant structure.