Papers by Keyword: Interfacial Shear Stress

Abstract: If the attention is not paid to the crack in a structure, then it could suddenly propagate at a rapid rate and rip apart the structures. A small crack needs urgent attention and repair since replacing the parts with a small crack is not economically feasible at all the time. Repairs were used to be carried out through rivets, welding and nut-bolts, but recently composite materials are showing promising results in this field. Since composite material are anisotropic in nature their application needs careful study about the loading pattern on the repaired structure. In this study, Carbon Fiber Reinforced Polymer (CFRP) was used as a composite material to repair Aluminium alloy specimens. These specimen were subjected to a three-point bending load to investigate the effectiveness of CFRP. By using innovative ply drop technique and design of experiment a configuration was selected to sustain three-point bending load. To suppress the CFRP’s peeling off tendency, attention was given to the interfacial shear stress rather than to the fracture toughness parameter.

Abstract: The collaborative work between FRP plate and concrete is achieved through the binder, so the interface of them is the weak links. Under external loading, the relative slip occurred on the interface between FRP plate and concrete causes the redistribution of stress and then the bearing capacity of the member will be reduced. Especially the FRP plate is a kind of resin material and its physical and mechanical properties will change with temperature and time. Based on energy variation principle, the differential equations of interfacial shear stress meanwhile to considering temperature and creep effect of concrete beams strengthened with FRP plate are established, in which the strain-energy of concrete beam, FRP plate and glue layer are calculated. And the calculated formulas of interfacial shear stress for a single point load are given.

Abstract: The shear stress transfer of prestressed anchor is the key for anchor performance and engineering design. The interface bonding strength between soil and induration has a very important role in supporting capacity of the soil anchor. It is presumed that the deformation between the soil layer rod and induration is compatible after the sliding section. Based on the Mindlin solution of a force act on the interior of a semi-infinite solid, a theory solution for the shear load of anchorage section is solved by considering the part of slip characteristics of interface in the loading process. On this basis, the shear stress of anchorage section is tested from anchor pullout test on site. Contrasted with the tests result, it is proved that the theoretical analysis is consistent with the tests. Theoretically, the research of shear stress transfer will enrich and develop anchor cable theory.

Abstract: Interfacial stress due to thermal mismatch in layered structure has been considered as one of the major causes of mechanical failure in electronic packaging. The mismatch due to the differences in coefficient of thermal expansion (CTE) of the materials in multi-layered structure may induce severe stress concentration to the electronic composites namely interfacial delamination and die cracking. Therefore, the studies and evaluation of interfacial stress in electronic packaging become significantly important for optimum design and failure prediction of the electronic devices. The thermal mismatch shear stress for bi-layered assembly can be analyzed by using the mathematical models based on beam theory. In this study, Finite Element Method (FEM) simulation was performed to an electronic package by using ANSYS. The shear stress growth behavior at the interface of the bonded section was studied with the considerations of continuous and partial bond layers in the interfaces. Based on the analysis, it can be observed that the partial bond layer with small center distances can be simplified as a continuous bond layer for bi-layered shearing stress model analysis.

Abstract: The ability of carbon nanotubes (CNTs) to consider as the strongest and stiffest elements in nanoscale composites remains a powerful motivation for the research in this area. This paper describes a finite element (FE) approach for prediction of the mechanical behavior of polypropylene (PP) matrix reinforced with single walled carbon nanotubes (SWCNTs). A representative volume element is proposed for modeling the tensile behavior of aligned CNTs/PP composites. The CNT is modeled with solid elements. Modified Morse potential is used for simulating the mechanical properties of an isolated carbon nanotube. The matrix is modeled as a continuum medium by utilizing an appropriate nonlinear material model. A cohesive zone model is assumed between the nanotube and the matrix with perfect bonding until the interfacial shear stress exceeds the bonding strength. Using the representative volume element, a unidirectional CNT/PP composite was modeled and the results were compared with corresponding rule-of-mixtures predictions. The effect of interfacial shear strength on the tensile behavior of the nanocomposite was also studied. The influence of the SWCNT within the polymer is clearly illustrated and discussed. The results showed that polymer's Young's modulus and tensile strength increase significantly in the presence of carbon nanotubes.

Abstract: Thermo-mechanical stresses have been considered one of the major concerns in electronic Packaging assembly structural failure. The interfacial stresses are often caused by the thermal mismatch stresses induced by the coefficient of thermal expansion (CTE) difference between materials, typically during the high temperature change in the bonding process. This research work examined the effect of bond layer on thermal mismatch interfacial stresses in a bi-layered assembly. The paper verified the existing thermal mismatch solder bonded bi-layered analytical model using finite element method (FEM) simulation. The parametric studies were carried out on the effect of change of bond layer properties in order to provide useful references for interfacial stress evaluation and the electronic packaging assembly design. These parameters included CTE, temperature, thickness, and stiffness (compliant and stiff bond) of the bond layer. The recent development on lead free bonding material was being reviewed and found to have enormous potential and key role to address the future electronic packaging assembly reliability.

Abstract: A designed measuring device of soil interfacial shear stress is introduced in this paper. We used the device for measuring the shear stress between the soil interface, of which the moisture content was 30% and the clay content were 5%, 9%, 15%, 21%, 30% respectively. The results show that the shear strength of experimental soil and friction between the layers decreases with the clay content increasing when the moisture content is 30% and clay content is more than 15%, and the results increase with the clay content increasing when the clay content is less than15%. Based on the study of the laminar soil interfacial shear stress, it provides the basis for the future research of the laminar motion of the sediment and the deposition of the liquefied motion soil.

Abstract: Waterproof bonding layer is an important component for permeable asphalt pavement. BISAR was used to analysis the interfacial stress under different conditions, and the rules of the tensile zone, the maximal tensile stress, the maximal interfacial shear stress and the corresponding point were obtained, which should be considered in selecting the WBL materials.

Abstract: Basalt fiber has the advantages of non-pollution and omnipotence, and expected to be widely used in the 21st Century. Therefore, more and more attention is paid on experimental research of the basalt fiber in the world. Firstly, according to the type selection principles and requirements of the fibers used in the hydraulic concrete, the contrast testing of the plastic shrinkage between fiber cement mortar and pure mortar is made. The experimental results showed that basalt fiber, polypropylene fiber and polyacrylonitrile fiber can be preliminarily chosen as reinforced fibers in high performance hydraulic concrete. Secondly, the impacts of the suggested three sorts of fibers on the interfacial shear stress of the fiber concrete are analyzed by numerical simulation，which showed that maximum interfacial shear stress of the basalt fiber concrete is minimum. So, the bond strength between basalt fiber and concrete is the best. Finally, taking both characteristics of basalt fiber and the increase of concrete costs into account, it can be concluded that top priority should be given to the basalt fiber rather than to other fibers for high performance hydraulic concrete.

Abstract: In order to investigate the debonding failure mechanism,the distributions of interfacial shear stress between cracks and the influence of preload of on the ultimate load and interfacial shear stress,one reference beam and five beams strengthened with CFRP and steel plate at different level of perload were tested and analyzed.The experimental result indicated that the perload level has less influence on the ultimate capacity.Moreover,when debonding failure of sheet-end interface of concrete beams strengthened with CFRP and steel plate is avoided,the debonding failure of reinforced beams at perload level will occur in the position of midspan.At last,on the basis of cross-sectional equilibrium and compatiable conditions,an analytical model of interfacial bond shear stress is obtained, meanwhile the analytic model favorably matched with the experimental results.