Papers by Author: Bao Lai Wang

Abstract: By the macroscopic tensile tests of the 3D four-directional braided composites, the failure pattern and fracture morphology of specimens with different geometric sizes have been observed. It is obtained that the different failure mechanisms and the material properties are relevant to the geometric sizes of samples under tensile states. The elastic properties of the braided composites are obtained by volume average method. The variation of shear modulus and Poisson ratio is obtained as well. It is shown that the elastic modulus increases with the increase of number of interior cells. The predicted results are in agreement with the experimental results. The results may provide experimental basis for further study on strength prediction and the establishment of strength criterion for 3D four-directional braided composites.

Abstract: Based on changing the braid angle and geometrical sizes, the compressive experiment of 3D braided four-directional Carbon/Epoxy braided composites is researched. It is found that failure of the braided composites exhibits compressive and shear failure mode. The failure crack propagates mainly in one or two 45º shear direction. Epoxy matrix among braid yarns of the braided composites is squeezed out to form epoxy band. The stress-strain relations of the braided composites with 45º and 30º braid angles all appear nonlinear apparently. Meanwhile the correlation of failure modes and constitutive relation with geometrical sizes of the braided composites is obtained. The compressive stress-strain relations of the braided composites are not great affected by the geometrical sizes. The compressive strengths with great discrete behaviors do not have obvious rules with height of the braided composites.

Abstract: Carbon-carbon composites are widely applied in the area of astronautics and aeronautics. As a kind of advanced composites, its properties are known to depend essentially on the technological regimes of its manufacturing processes. This paper is devoted to the modeling of manufacturing processes of the composites and focuses on establishing the processing-microstructure-property relation to enable design of internal architecture to predict and optimize properties.

Abstract: Recently, people devote to the development of beta titanium alloys which have better biocompatibility because of the addition of Mo, Nb, Ta, Zr, Sn, et al. In this paper, the effects of heat treatment and cold roll deformation on the mechanical properties of the Ti-11.3Mo-6.6Zr-4.3Sn alloy (TMZS) are investigated by tensile test. The results show that the excellent combination of strength and ductility can be obtained by heat treatment or cold deformation. The TMZS alloy can obtain intermediate modulus, stronger than nickel titanium, weaker than stainless steel. The corrosion resistance of this alloy in the Hank's solution, 0.9% NaCl physiological solution and artificial saliva with different pH values at 37
are investigated by means of open-circuit potential (OCP), Tafel and potentiodynamic anodic polarization techniques. All the test results suggest that the TMZS alloy has excellent corrosion resistance in the three simulated solutions especially in the artificial saliva and has a large potential for biomedical application. In addition, the pH value and simulated solutions have some influence on the corrosion resistance of the TMZS alloy.

Abstract: Recently, people devote to the development of Ni-free shape memory alloys in order to avoid the Ni-hypersensitivity and toxicity and pursue absolute safety. The shape memory effect and superelasticity have been reported in the biomedical Ti-Nb based alloys. The purpose of this paper is to report the phase constitution, tensile property, shape memory effect and corrosion resistance of the Ti-Nb alloys. The phase constitutions of the Ti-Nb alloys are investigated by means of X-ray diffraction (XRD). The results reveal that β+α′′ phases are presented in the Ti-35Nb alloy and only β phase in the Ti-52Nb alloy at room temperature. The tensile test and bending tests indicate that the Ti-35Nb alloy exhibits shape memory effect. The shape recovery ratio is near to 80% when the bending strain is 4.4% and decreases with the increase of the total bending strain. The corrosion resistance of the Ti-Nb alloys in the Hank's solution and artificial saliva (pH=7.4) at 37
are investigated by OCP, Tafel and anodic polarization methods. The results indicate that the Ti-35Nb alloy has a better corrosion resistance in the artificial saliva and can replace the Ti-Ni alloy in the dental application. In the non-oral condition, the Ti-52Nb alloy may be preferable.