Papers by Keyword: Stress Transfer

Abstract: This paper shows a mathematical model of shear stress transfer at the interface between fiber and matrix composite. The stress transfer is a key parameter determining the quality of fiber-matrix interface, which directly correlates with the composite performance as load-bearing structures. The model is derived from the energy balance approach in prior and post fiber cracking. The debonding process is included in the model by implementing traction-separation law. The results show the developed model can predict the shear stress along with the interface. There are significant differences in shear stress by considering the debonding process compared with conventional models. The debonding process must be regarded to assure an accurate evaluation of the interface quality.

Abstract: The simple percolation model, in which critical indices are defined by the form of a reinforcing component of nanostructured composite structure, was proposed for the description of reinforcement degree for nanostructured composites polymer/2D-nanofiller. The indicated critical indices are close by absolute values to standard percolation indices. The form of reinforcing component controls the type of nanostructured composite. It has been shown that reinforcement degree of these nanomaterials is independent on modulus of elasticity of nanofiller, but is defined by its structure (aggregation level), created in polymer matrix. The percolation indices of a percolation model, which are due to the form of reinforcing component and nanocomposite type, are defined by its main characteristic – the fraction of phases division surface in overall sample volume and are the basic factor, controlling reinforcement degree of nanostructured composites.

Abstract: The coal 8210 big mining height of the Datong mine Jin hua gong face in the process of mining airport coal pillar fried state a, floor deformation intense, serious kick drum, eventually leading to rock failure .In the severe cases, easily induced by shock pressure and other disasters ,these have serious impact on the efficient production of face security in the large mining height. by the airport side of roadway roof pressure relief, combined with roadway bolting reinforcement technology effectively control the deformation of surrounding rock of roadway, Test results show that the security measures taken can meet the well production safety requirements.

Abstract: Stress transfer in the carbon nanotube reinforced nanocomposites is investigated in this work. The model consists of two concentric cylinders, namely, a single-walled carbon nanotube cylinder (SWCNT) and a matrix cylinder, as the representative volume element (RVE). The stress analysis is performed using the shear lag model for the axisymmetric RVE. Analytical solutions for the axial normal stresses in the SWCNT and matrix, and the interfacial shear stress across the SWCNT/matrix interface are obtained. Numerical results show that using a large volume fraction improves the efficiency of the stress transfer from the matrix to the carbon nanotubes.

Abstract: From 2006, authors started a series of experimental and analytical studies to establish a design method for a new connection system of concrete filled steel tube (CFT) by using built-in reinforcing steel bars (CFTR). Among the series, a pullout test of the built-in steel bars from the CFTRs has been early performed, which is orientated as a fundamental study for the connections of CFTR [1]. In the pullout test study, it is clarified that the influence of tube shapes (square and circular), the stress transfer capacities of bond by steel bars, ring bands in steel tubes and anchor plates of steel bars. The new connection system of CFTR may apply to an exposed-type CFT column base, where the built-in high strength steel bars contribute to transfer the axial force, bending moment and shear force from a CFT column to the foundation [2, 3]. The column base strength is much increased by the built-in steel bars. In other words, the built-in steel bars make the base plate and anchor bolts compact without any strength reduction in the column base. A stable elastic-plastic behavior is observed in the CFTR column base, and an evaluation method of the ultimate strengths is proposed for that. A further improved CFTR column base is the base without any base plate (non-base-plate CFTR column base), so that all of the stresses can be transferred through the built-in high strength steel bars [4]. A stable hysteretic behavior is observed in the column base, and the evaluation method of the ultimate strength is also proposed. It is noteworthy that the non-base-plate CFTR column base is applicable to the super high strength steel, because the base system does not require any full penetration welding, which sometimes causes brittle fracture in super high strength steel.

Abstract: Effective combination and carry-loading together between steel and concrete play important roles for the steel-concrete composite structure. The steel-concrete composite joint decides the constructing safety and life-cycle performance as the key member for the steel-concrete composite arch bridge. The stress distribution in the steel-concrete composite joint was studied by model test under pressure-bending load. And the stress transfer was probed in the steel box, composite joint and reinforced concrete box. The result shows that the steel and reinforced concrete boxes are under elastic compression in the steel-concrete composite joint. The bearing plate can effectively reduce the stress in concrete and steel boxes. This plate and stiffener can smoothly transfer and scatter the stress from steel box to concrete box. The failure mode is concrete cracking near the interface between steel box and concrete box under large eccentric compression.

Abstract: In this paper, the stress distribution of short-fiber-reinforced composites (SFRC) using representative volume element (RVE) approach based on the finite element analysis (FEA) was presented. A three-phase model was built, in which loads were applied to the matrix. The influences of interphase parameters like Young’s modulus and thickness were studied. The FEA confirms that interphase Young’s modulus and thickness control stress distribution in SFRC. The stress concentration at the fiber interface becomes greater with high interphase Young’s modulus and thin interphase thickness. The FEA results were also compared with those obtained by analytic method.

Abstract: The paper presents a new design concept for evaluating the mechanical strength of unidirectional composite material with shape memory alloy (SMA) fiber in the presence of matrix crack. NiTi SMA fiber with both ends knotted is used to actively control the composite strength instead of straight fiber for purpose of better ensuring stress transfer from the matrix to the fiber. Experiment is conducted to verify the effectiveness of this new design concept.

Abstract: An improved shear-lag analytical model has been established to study stress transfer in carbon nanotube (CNT) reinforced polymer matrix composites with and without debonding interface. The Poisson’s effect and radial effect of matrix is considered in the model for the first time, and a simplified 2D representative volume element (RVE) is modeled using a four-phase composite composed of matrix, nanotube, bonded, and debonded interfaces in this analysis, and the axial stress for CNT and matrix and interfacial shear stress along the CNT is predicted. The results show that load transfer efficiency in CNT reinforced composites is affected by the debonding length, and the abrupt change of shear stress is existent at the tip of debonding interface.

Abstract: In this paper, the experimental investigation into the enhancement of mechanical strength in shape memory alloy (SMA) fiber composites is made by using knotted fiber at the two ends instead of straight fiber. TiNi SMA fiber with both ends knotted is used for purpose of better ensuring stress transfer from the matrix to the fiber than straight fiber. Tension test is carried out above the austenitic finish temperature in air. Specimens are heated by means of electrical resistive lamplight heating. The results indicate that the mechanical strength is larger in the knotted fiber composite than in the straight fiber composite. Knotted fiber exerts the superiority of TiNi SMA fiber composite.