Papers by Keyword: Effective Modulus

Abstract: Effective moduli of fiber-reinforced polymer matrix composites filled with nanoparticle considering the effect of linear change of interphase are presented in this paper. The three-phase inclusion problem for matrix-interface-particle is equivalent to the Eshelby two-phase inclusion problem. According to the result of the Eshelby inclusion problem, the effective modulus tensor of unit cell of equivalent particle is derived. The effective moduli of equivalent matrix are given based on Mori-Tanaka method. Using two fundamental equation of micromechanic theory, the three-dimensional bridged formulation of unidirectional composites is derived. The quantitative relationship between the macroscopic elastic parameters and the structural parameters of the fiber-reinforced polymer composites filled with nanoparticles is investigated. Effects of the thickness of interfacial layer, the particle size and the volume fraction of nanoparticles on the effective elastic moduli of the composites are also discussed.

Abstract: The research methods of Cohesive Zone Model (CZM) are introduced and the parameters of cohesive zone model in ABAQUS software are calibrated based on the cohesive constitutive model determined by the fracture energy. Besides adopting exponential cohesive zone model, this paper applies a bilinear one to simulate the crack propagation of a simply supported single-edge notched concrete beams SE(B) (Mode I) and make comparisons with experimental result. Finally, the results represent effectiveness of the effective modulus and the special advantage in term of failure of fracture based on the cohesive zone model, which is of directly guiding significance for achieving a deep going understanding of crack propagation.

Abstract: Cord-rubber composites are usually subjected to cyclic deformation for the tire applications. Due to the hysteretic nature of the rubber, heat generation in the rubber component under dynamic cyclic loading often causes a rise in temperature, which can deteriorate the physical properties of the composites. Therefore, better understanding of the cord-rubber composites under thermal aging conditions is of great importance for the lifetime prediction. In the present work, the effective modulus of polyester cord- and steel cord-rubber composites at different aging conditions was studied by means of the mechanics of composite materials and the Arrhenius relationship based on the properties of components. It is found that the Halpin-Tsai relation with introducing the effect of thermal aging is also valid for the aged cord-rubber composites.

Abstract: A new 3D unit cell model is developed for homogenization calculation of composites containing randomly dispersed ellipsoid inclusions. The new unit cell is constructed using the Ansys Parameter Design Language (APDL), taking the inclusion volume fraction, inclusion orientation and spatial dispersion as variables. A series of unit cells containing multiple ellipsoids, showing random distributions in particle size and position, were constructed and used for finite element calculation at microscale, the effective modulus of the composites with periodic microstructures, which modeled by the unite cells, were then estimated by homogenization. The influences of particle volume fraction and the particle stiffness on the effective elastic modulus of the composites were examined. The estimated results were compared with different particle volume fractions were calculated, and the calculated data was compared with other classic models.

Abstract: A simplified approach for calculating the stress field of the fiber-reinforced composites is developed to improve the work of Theocaris et al. (1985) in this paper. This approach considers that the main factor affecting the stress field of composites is the existence of interphase between fiber and matrix, which possesses different Young’s modulus than those of the constituent phase. A parabolic law is adopted for the variation of Young’s modulus of graded interphase, versus the polar radius from fiber to matrix, while the Poisson’s ratio of the interphase is assumed as constant. Space axisymmetric model is applied to the Representative Volume Element (RVE) of the fiber-reinforced composites to evaluate stress field of the composites. Also, the effective longitudinal modulus of the fiber-reinforced composite can be obtained.

Abstract: Owing to their superior mechanical and physical properties, cCarbon nanotubes (CNTs) seem to hold a great promise as an ideal reinforcing material for composites of high-strength and low-density. HOWEVER, In most of the experimental results to date, however, only modest improvements in the strength and stiffness have been achieved by incorporating carbon nanotubeCNTs in polymers. There are many factors that influence the overall mechanical property properties of CNT-reinforced composites, e.g. the weak bonding between CNTs and matrix, the waviness and agglomeration of CNTs. In the presentis paper, we use the Mori-Tanaka method to evaluate the effects of these factors on the moduli stiffness of CNTs-CNT-reinforced composites are examined. It is established found that the waviness and agglomeration may significantly reduce the stiffening effect of CNTs, while the interface adhesion between the matrix and CNTs has little influence the moduli of CNTs-reinforced composites little.