Influence of Strain Rate on the Mechanical Behaviour of Human Interstitial Bone at the Microstructural Level
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0898-L09-02.1
Influence of Strain Rate on the Mechanical Behaviour of Interstitial Bone at the Microstructural Level. M. Vanleene1, P.-E. Mazeran2 and M.-C. Ho Ba Tho1, 1 Laboratoire de Biomécanique et Génie Biomédical, UMR 6600, Université de Technologie de Compiègne, BP 20529, 60205 Compiègne Cedex, France, 2 Laboratoire Roberval Unité de Recherche en Mécanique, FRE UTC-CNRS 2833, Université de Technologie de Compiègne, BP 20529, 60205 Compiègne Cedex, France, ABSTRACT Investigation of bone mechanical properties is of importance for bone pathology and development of biomaterials and prosthesis. Due to the bone complex multi-scale structure, assessment of bone microstructure is an important step to understand bone mechanical behaviour. In this study, we performed dynamic nanoindentation tests to investigate visco-plastic and visco-elastic properties of bone interstitial lamellae. INTRODUCTION Mechanical properties of bone are important in understanding bone pathologies, development of biomaterials, and development of in vivo bone characterization devices. Cortical long bone is a complex material and its mechanical behaviour is determined by its intrinsic matrix composition (organic and mineral components) and its multi-scale hierarchical architecture. Bone microstructure is described as a haversian system, composed of osteons and interstitial lamellae. Macroscopic mechanical behaviour has been investigated using mechanical and ultrasonic methods. The recent development of nanoindentation allows the characterization of bone at the micro-scale [1-10]. The mechanical properties of osteon and interstitial lamellae of human cortical bone have values between 17.7 to 24.9 GPa and 19.3 to 25.8 GPa, respectively. Heterogeneity of osteon lamellae was observed within and between osteons [4, 7, 10]. The results are strongly dependent on sample preparation (dry or wet, embedded or not), and nanoindentation test parameters (indentation depth, quasi static or dynamic tests, strain and loading rates) [3, 8, 9]. According to our knowledge, the first investigation on strain rate and time dependence was performed by Fan et al. [8] on human bone. In this study, 88 indentations were performed on osteon lamellae in one tibial cortical bone sample using a quasi-static protocol and different constant loading rates. Multiple loading- unloading tests and a load holding period was used, and visco-plasticity was minimized in order to obtain accurate Young’s modulus values. The strain rate appeared to affect Young’s modulus of the osteon lamellae. The objectives of the present work are to simultaneously investigate visco-plastic and visco-elastic behaviours of human interstitial lamellae bone. MATERIALS AND METHODS Measurements were performed on polished samples of healthy human femur cortical bone (70 years-old). A lateral and medial specimens (5*5*4 mm) were obtained from a cross-section of the femur diaphysis. Specimens were dried in air at room temperature.
0898-L09-02.2
Figure 1: ESEM imaging of the nanoindentation matrix in the inter
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