Papers by Author: Tie Jun Wang

Abstract: Split Hopkinson Pressure Bar (SHPB) experiments are carried out to study the deformation behavior of acrylonitrile-butadiene-styrene (ABS) resin at elevated temperature and high strain rate. The temperature and strain rate considered are 293K and 343K and 8.0×102s-1, 2.7×103s-1 and 1.0×104s-1, respectively. The curves of engineering stress and strain at different temperatures and different strain rates are experimentally obtained. The effects of temperature, strain rate and the fraction of ABS on the deformation behavior of ABS resin are discussed in detail. Then, a rate and temperature dependent phenomenological constitutive law for ABS resin is developed.

Abstract: The elastic field around a nanosized spheroidal cavity is derived on the basis of surface elasticity theory. The effects of surface energy, shape and size of the cavity are discussed. It is seen that the stress field near the nanosized cavity depends on the shape and the size of the cavity as well as the properties of the surface. These new characteristics are different from those predicted by the classical elasticity and may illuminate some new mechanisms at nanoscale.

Abstract: The objective of the work is to numerically study the meso-scale deformation of amorphous glassy polymer. A molecular polymerization algorithm is employed to generate three-dimensional (3D) random networks of polymer, in which the micro-parameters and meso-structures, such as entanglement point, sliding point, etc. are considered. Then, 3D unit cell model and finite element method are used to calculate the stress and deformation relations of polymer. The evolution of meso-structure of glassy polymer with deformation is obtained simultaneously. Further, variation of the orientation of polymer chain with deformation was quantitatively studied.

Abstract: As a direct and simple method, essential work of fracture has been widely used for fracture measurement of ductile polymers. In this paper, fracture toughness of PC and PC/ABS alloy is experimentally investigated. A series of double edge-notched tension (DENT) specimens and essential work method are employed to measure the fracture toughness of PC and PC/ABS alloy. By the way, the critical crack tip opening displacement is obtained. Moreover, the fracture surfaces of DENT specimens are examined by using a scanning electron microscope (SEM).

Abstract: A unified yield criterion is proposed in this paper, which is valid for the metallic sandwich sections with various core strength and geometrical dimensions and can reduce to the classical yield criteria for solid monolithic section and sandwich section with weak core, respectively. Then, the unified yield criterion is used to derive the analytical solution for the large deflection of fully clamped metallic sandwich beam subject to a transversely concentrated load, in which the interaction of bending and stretching is considered. Comparisons of the present solutions with experimental results are carried out and good agreements are found. It is seen that the axial stretching induced by large deflection has a significant effect on the deflection of sandwich structure in the post-yield regime, and the load carrying capacity of metallic foam core sandwich beam may be underestimated as the core strength is neglected in analysis.

Abstract: Dynamic Mechanical Analysis (DMA) and static relaxation tests are carried out to study the viscoelastic deformation of PC/ABS alloy with blending ratio of PC to ABS being 50/50. A modified approach is developed to calculate the relaxation modulus of PC/ABS alloy from the DMA experimental results of storage and loss moduli. Comparison of the results obtained from DMA and static relaxation tests is presented and good agreement is found.

Abstract: Large deformation performances of polycarbonate (PC) and PC/ABS (Acrylonitrile Butadiene Styrene) have been investigated experimentally in this paper. The displacement fields of these polymers are measured with a system based on digital image correlation (DIC) method. The variations of strains during tension are measured and the true stress-strain curves are presented. For these materials, it is observed that the contraction in thickness is larger than that in width during tension. No obvious stress softening is observed in the true stress-strain curves. The true stress-strain curves can be fitted well with three-stage model.

Abstract: The tensile property of PC/ABS was investigated with an optical image analysis method in the paper. With the consideration of polymer micro mechanism, a three-stage phenomenon based model is used to describe the true stress-strain curves. The regression constants obtained with the method could be described with definite physical meanings. It is shown that two lateral contractions are not identical at the later necking stages. The fracture strain could be used as a criterion to describe uniaxial tensile fracture.

Abstract: Effect of resin content on the mechanical properties of satin carbon fabric/epoxy composites is studied in this paper. Mechanical properties of the satin carbon fabric/epoxy composites are experimentally measured. The compressive strength and conversion ratio of strength of carbon fiber in the fabric composites are measured and compared with the experimental data of composite laminates reinforced by unidirectional fiber tape.

Abstract: Body-centered cubic unit cell models and three-dimensional finite element method are used to study the inelastic deformation of rubber particle modified polymers. Calculations are carried out for three loading conditions, i.e. uniaxial loading, plane strain deformation loading and the so-called 'equivalent shear' loading. Distributions of the localized shear deformation are presented to understand the microscopic deformation mechanisms of the polymers. Effects of particle size, particle volume fraction and loading conditions on the micro- and macroscopic deformation behavior of rubber particle modified polymers are discussed.