Characterisation and testing of biomaterials

Abstract

The investigation of the structural mechanics of the entire body system is despite it’s rather long history in science, compared to more recently developed research field like genetics, still extremely important and by no means outdated. Improved innovative treatments of the musculoskeletal system will require specifically designed implants and implant materials to guarantee optimal function of the injured segment and fast rehabilitation. As the actual loading situation of the implant-biomaterial compound is highly sensitive to implant-induced changes in the specific in vivo situation, the mechanical properties of living biological materials still require intense research activities, especially due to the large scatter in terms of biological variation. Structural failure of biomaterials by plastic deformation or fracture is observed if thematerial dependent threshold strength is exceeded. This load inducing failure can be the result of a single load case or a superposition of different load combinations (i.e. monotonic or static loading). Furthermore, material failure can also be induced by repeated (cyclic) loading at loads which are significantly below the material or compound stability characterizing static strength. This failure type is generally the most common (already repeated load application in the order of 20 cycles can induce dynamic failure). It should be noted that the characteristic material or compound parameters are strongly affected and directly related to the material (micro-) structure. For biological materials this is generally described by biological scatter in terms of the mechanical morphogenesis. Therefore, any analysis concerning mechanical parameters or properties has to be interpreted in terms of the specific microstructure of the material. The focus of this chapter is to give an introduction into the basic principles of load induced material behavior and failure under static and dynamic conditions with respect to specific material structure. Further information can be found in standard text books on biomechanics and solid mechanics [4,10, 12–16,19,20,24].