Due to their good osteostimulative and osteoconductive properties, bioglasses are a common material for bone replacement applications.

The ‘Bio Anti-fatigue’ project aims on enhancing the fatigue properties of technical materials by adopting anti-fatigue principles derived from natural materials. In one subproject, gradient glass and glass ceramic materials are developed, mimicking the anti-fatigue properties of corals. To our current knowledge the most relevant coral properties in this respect seem to be porosity and crystallinity, beside general geometry and composition.

Two bio-glasses, 45S5 and 13-93, were selected as the respective crystallization onset temperatures differ considerably (45S5 around 610 °C, 13-93 around 750°C). This enables the production of crystalline and amorphous layers.

Before producing glass samples with customized, anisotropic and gradient properties, the range of respective processing and sintering parameters for the two bio-glasses was determined. This comprises heating rate, sintering temperature and dwell times.

The present study correlates the structural properties, i.e. porosity and crystallinity, with the static mechanical properties of homogeneous glass samples. Crystallinity is determined using X-ray diffraction, and porosity is analyzed by µCT imaging. For mechanical testing, both 3-point bending and biaxial flexural strength are measured. This requires different sample geometries, straight beams for 3-point bending, round discs with a diameter to thickness ratio between 10 and 50 for biaxial flexural strength. Thus, both tests have a completely different zone of influence of the stresses, resulting in different values.

Dipl.-Ing. Marco Bartosch