Chapters authored
Mechanical Properties of Biomaterials Based on Calcium Phosphates and Bioinert Oxides for Applications in Biomedicine
Part of the book: Advances in Biomaterials Science and Biomedical Applications
Investigation of Mechanical Behaviour of a Bioceramic
In order to find a convincing method to measure bioceramics fracture toughness, tensile strength and modulus, a novel configuration of the Brazilian test was applied and described in the experimental work. The flattened Brazilian specimens, which are in the shape of discs having parallel flat ends, are subjected to compression for determination of opening mode I fracture toughness KIC. Experiments were done by using tricalcium phosphate-fluorapatite composites, which were tested by compressive loading on the parallel flat ends. The loading angle corresponding to the flat end width is about 2α = 20° in order to guarantee crack initiation at the centre of the specimen according to the Griffith criteria. Fracture toughness was also performed by using semi-circular bend “SCB”. Finite-element program, called ABAQUS, is used for numerical modelling for finding stress intensity factors. The effects of fluorapatite additives and fracture toughness were studied. Fracture toughness values of tricalcium phosphate-fluorapatite composites were found to increase with increasing addition of fluorapatite until an appropriate value. It is shown that there is a good agreement among the experimental, analytical and numerical results.
Part of the book: Fracture Mechanics
Effect of Titania Addition on Mechanical Properties and Wear Behavior of Alumina-10 wt.% Tricalcium Phosphate Ceramics as Coating for Orthopedic Implant
The aim of this study is to determine the effect of Titania on mechanical properties and wear behavior of Alumina-10 wt.% TCP ceramics and to evaluate the performance of Titania in improving their resistance to these effects. Al2O3–10 wt.% β-TCP mingled with TiO2 to obtain a mixture which is considered as a bioactive coating that may be used in orthopedic implants. Representative bioceramic samples of such blends were prepared with different percentages of Titania and then tested using different methods and techniques. Mechanical properties, fracture toughness were evaluated using the modified Brazilian, semi-circular bending specimens. A pin-on-disk tribometer was retained to study the wear behavior. Based on the obtained results, it was found that the best mechanical properties and wear resistance was displayed for Alumina-10 wt.% TCP-5 wt.% Titania composite. This composite presents a good combination of flexural strength (σf ≈ 98 MPa), compressive strength (σc ≈ 352 MPa), fracture toughness (KIC ≈ 13 MPa m1/2) and micro-hardness (Hv ≈ 8.4 GPa). In terms of tribological properties, the lowest wear volume and wear resistance was recorded for Al2O3–10 wt.% TCP − 5 wt.% TiO2 composition.
Part of the book: Titanium Dioxide
Combination of Numerical, Experimental and Digital Image Correlation for Mechanical Characterization of Al2O3/β-TCP Based on CDM Criterion
Cracks in engineering materials and structures can undergo different modes of deformation. This chapter presents a numerical and experimental approaches aimed to assess the fracture toughness and the Fracture behavior under tensile and shear loading of bioceramics based on commercial Alumina (Al2O3), synthesized Tricalcium phosphate (β-TCP). Conditioning was conducted at different percentages of TCP. After a sintering process at 1600°C for 1 hour, The Crack Straight Through Brazilian Disc were performed by image correlation during a mechanical test and numerical tests were carried out in order to find the angle where the pure mode II. A CDM based constitutive model was selected and implemented into a finite element code to study the damage of our bioceramics. The result of this combination was compared with the direction of crack propagation obtained experimentally. The directions of crack propagation found numerically were found in good agreement with those experimentally obtained by a mechanical test. Alumina-10 wt.% Tricalcium phosphate composites displayed the highest values of the fracture toughness. This value reached 8.76 MPa m1/2 MPa. The same optimal composition for the mode I and mode II stress intensity factor with maximum values of 7.6 MPa m1/2 and 8.45 MPa m1/2 respectively.
Part of the book: Advances in Fatigue and Fracture Testing and Modelling