Papers by Keyword: Interface Debonding

Abstract: The paper presents aspects observed during classic three-point test bending of various sandwich materials. These aspects outline the need to spare special attention to such test, in connection with the particular material and service life conditions it will endorse. Such special care is needed in conditions of scarcity of dedicated standards and some evasive formulations in the existing ones.

Abstract: In this study, the local stress of unidirectional fiber reinforced marine composites under transverse direction tension is conducted by using a representative volume element (RVE). With the application of fracture mechanics theory, the strength and debonding evolution of the fibre-matrix interface is analyzed and simulated by cohesive elements in FEA. The modeling results fit the experimental results in quasi-static conditions well, which demonstrates a proper simulation method for assessing the transverse mechanical properties of marine composites. Considering the complex work environment in ocean, transverse mechanical behaviors of marine composites under different strain rates is investigated, which would provide guidance for the marine composite designers.

Abstract: The bonding of fiber reinforced polymer (FRP) plates or sheets to the concrete structures has been found to be an effective technique to improve the capacity. As a result, a large number of studies have addressed debonding failures in FRP-strengthened RC structures, with many of them being focussed on understanding the behaviour of simple FRP-to-concrete bonded joints in which an FRP plate/sheet is bonded to a concrete prism and is subject to a tensile force. With the help of features of FRP–concrete interface and experimental data in the literatures, a non-linear mode II interface law is presented. The proposed interface law includes non-linear contributions of adhesive and concrete cover at high shear stresses. The numerical results presented in this study show that FRP strains, shear stresses, slips and values of delamination force in the bonded region are in good agreement with experimental results. The agreement verifies the validity of the proposed interface law.

Abstract: The bonding of fiber reinforced polymer (FRP) strips and plates to the concrete structures has been found to be an effective technique for flexural strengthening. The FRP is then under both pulling and peeling forces, resulting in a combination of shear sliding and opening displacement along the FRP/concrete interface. A novel experimental set-up is studied that a peeling load is applied on the FRP sheet by a circular rod placed into the central notch of the beam. Based on the linear-elastic fracture mechanics approach, a theoretical analysis is conducted on specimens representing the peeling behavior. From the numerical analysis, the load–displacement curves, load–stiffness of FRP sheet curves, and load–fracture energy curves affected by different variables are discussed. The peel load is related to the FRP sheet stiffness and to the interfacial fracture energy. Therefore, only two material parameters, the interfacial fracture energy of FRP–concrete interface and stiffness of FRP sheets, are necessary to represent the interfacial fracture behavior. The theoretical load–deflection curves of specimens agree well with the corresponding experimental results in the literatures.

Abstract: Nanocomposite tool materials are very important in engineering field for their advantage in mechanical properties and have a good foreground in the coming years. However, there are lots of puzzles in the materials design theory. So in this paper, a new nanocomposite tool materials design method is proposed based on the interface debonding theory. The wild phase content can be fixed by calculating the debonding interface rate and the strength requirement of the tool materials. Therefore, an experiment is carried out to fabricate WC based nanocomposite tool materials under the guider of the interface debonding theory. Results show that the experimental data is in accordance well with the calculation and the model is proved to be correct.

Abstract: This paper is devoted to studying influences of matrix/particle interface debonding and particulate size in micromechanical predictions of the effective moduli of particulate reinforced polymer composites (PRPC). The PRPC is regarded as a three-phase composite that includes the matrix, particle and interphase. The formulation for the effective moduli of the interphase is derived by the cohesive zone model, and combined with the Mori-Tanaka method, the micromechanical model for the effective moduli of the PRPC is formulated with emphasis on the effects of the matrix/particle interface, particulate size and volume fraction. The numerical example shows that the interface debonding, the particulate size and volume fraction have significant influences on the effective moduli of PRPC. The effective moduli of the PRPC can be used to characterize its damage degree.

Abstract: A micro-mechanical model and simulation for the damage behavior of short fiber interleaves (SFIs) were developed based on Mori-Tanaka method and an equivalent approach to interface debonding (Fitoussi etc 1990). The damage evolution and the stress-strain relation of SFIs have been predicted in the cases of interlaminar shear, out-of and in-plane tension, respectively. The simulation indicates that the damage always starts from the interface debonding of fibers perpendicular to load and the matrix cracking in the direction parallel to fibers, and then rapidly spreads to more fibers during loading. The strength and the ultimate strain in out-of-plane tension are much lower than that in interlaminar shear and in-pane tension. The strength and failure probability of interface bonding are the most considerable factors to affect the damage and failure of SFIs. The comparison of the simulation with the interlaminar shear test shows a good agreement.

Abstract: Based on Mori-Tanaka’s concept of average stress in the matrix and Eshelby’s equivalent inclusions theory, the stress or strain of the matrix, the reinforced particles and the composite are derived under a prescribed traction boundary conditions. The plastic strains and strains due to thermal mismatch between matrix and reinforced phase are considered as eigenstrains. The matrix and composite are postulated isotropic and the matrix satisfies isotropic hardening law. The interface debonding is decided by the tensile strength of the particles whose debonding probability is described by Weibull distribution function. Then the overall elastoplastic constitutive relation of spherical particle-reinforced metal matrix composite is derived by secant modulus method considering the interface debonding. The theoretical uniaxial stress-strain bebavior of the composite agrees well with the experimental curves.

Abstract: NiTi shape memory alloy fiber-embedded denture-base-resin matrix smart composites were developed as a new denture base material for a “smart denture”, whose shape could be recovered simply by heating after fracture. Three types of fiber surface treatment were applied for the composites and their properties were evaluated by the fiber-pull-out test and bending test, and shape change after repair was examined. A high interface debonding strength increased the fracture strain but did not affect bending strength, and a low interface sliding strength minimized shape change after repair. These results indicate that the fiber-matrix interface with a strong bonding but easy sliding after debonding could improve the preciseness of “smart repair”.