Coupling resonance effect of interface delamination of laminates excited by horizontal shear wave sources on the surface

Coupling resonance effect of interface delamination of laminates excited by horizontal shear wave sources on the surface is studied by analytical methods based on forced propagation solutions deduced by surface perturbation methods, integral transformation methods and global-matrix methods. The influence of excitation sources on the interface shear stress is investigated. It is found that coupling resonance frequencies of interface shear stress are intrinsic properties of structures and are independent of excitation sources, at which even a very small perturbation can also lead to the interface stratification. The results provide the theoretical basis for layered and/or anti-layered design of laminates.

Coupling resonance mechanism of interfacial fatigue stratification of adhesive and/or welding butt joint structures excited by horizontal shear waves

Coupling resonance mechanism of interfacial fatigue stratification of adhesive and/or welding butt joint symmetric and/or antisymmetric structures excited by horizontal shear waves are investigated by forced propagation analytical solutions derived by plane wave perturbation methods, integral transformation methods and global matrix methods. The influence of materials on the coupled resonance frequency is analyzed and discussed by the analytical methods. Coupling resonance of interface shear stress is a structure inherent property. Even a very small excitation amplitude at the coupling resonance frequency can result in interface shear delamination. The coupling resonance frequency decreases with the increase of interlayer thickness or shear wave velocity difference between substrate and interlayer. The results could be applied to layered and/or anti-layered structural design.

Temperature-Dependent Fatigue Damage Evolution of Fiber-Reinforced Ceramic-Matrix Composites

In this paper, the temperature-dependent fatigue damage evolution of fiber-reinforced ceramic-matrix composites (CMCs) is investigated. The fatigue loading/unloading constitutive model considering the effect of temperature is developed based on the damage mechanisms of matrix cracking, interface debonding, and repeated sliding between the fiber and the matrix. The relationships between the fatigue loading/unloading hysteresis loops, testing temperature, applied cycle number, peak stress, and fiber/matrix interface debonding and sliding are established. The evolution of fatigue loading/unloading hysteresis loops, interface debonding and sliding length with applied cycle number is analyzed. The effects of temperature, peak stress level, applied cycle number, interface shear stress, and interface debonding energy on the fatigue damage evolution are discussed based on the developed temperature-dependent fatigue loading/unloading constitutive model. The experimental fatigue damage evolution of SiC/SiC composite at 600°C, 800°C, and 1000°C in inert atmosphere, 1000°C in air and in steam atmosphere, and 1300°C in air atmosphere are predicted. The interface shear stress of SiC/SiC composite decreases with temperature, and the degradation rate of interface shear stress increases with temperature.

Acceptance Criteria for the Mechanical Integrity of Clad/Base Metal Interface for High Temperature Nuclear Reactor Cladded Components

The existing Class A metallic materials qualified in the ASME Section III, Division 5 rules for high temperature nuclear reactors do not have optimal corrosion resistance for some reactor coolants such as liquid lead, lead/bismuth eutectic, and molten salts which is a major constraint on long life designs. A near term solution to this limitation is the use of cladded components — overlay the Class A materials with a thin layer of some corrosion resistant material. However, this necessitates the development of a design method for cladded components without requiring long-term testing of clad materials in order to support the near-term deployment of these advanced reactor systems. In two other PVP papers [PVP2020-21469, PVP2020-21493], the development of such design method along with a complete set of design rules and clad selection criteria are presented. However, the developed design rules and clad selection criteria are based on a priori assumption of perfect bonding between the clad and base materials. In practice the clad/base debonding may occur before the end of the design life of the component. Therefore, this paper focuses on developing a general acceptance test for checking whether the mechanical integrity of the clad/ base metal interface will be retained till the end of the design life. This work proposes to perform temperature cycling tests on cladded buttons of 12.7 mm diameter and a few mm thickness. A simple analytical expression is provided to determine the temperature range for the temperature cycling tests so that the clad/base interface shear stress intensity at the edge of the cladded button mimics the maximum interface shear stress intensity experienced by the component during the design transients. The paper also provides a method to determine the clad/base interfacial shear stress from finite element structural analysis of components.

Analysis of the Elastic-Plastic Theoretical Model of the Pull-Out Interface between Geosynthetics and Tailings

Aiming at the strain-hardening and strain-softening phenomena between geosynthetics and tailings during pull-out tests, bilinear and trilinear shear stress-displacement softening models were proposed. The pull-out process of the hardening reinforcement was divided into the elastic stage, elastic-hardening transition stage, and pure hardening stage. The pull-out process of the softened reinforcement was divided into the elastic stage, elastic-softening transition stage, pure softening stage, softening-residual transition stage, and pure residual stage. The expressions of the interface tension, shear stress, and displacement at the different stages under a pull-out load were derived through the interface basic control equation. At the same time, the evolution law of the interface shear stress at different pull-out stages was analysed, and the predicted results of the two elastic-plastic models were compared with the experimental results. The results show that the predicted results are in good agreement with the experimental data, which verifies the validity of the proposed two elastic-plastic models for the progressive failure analysis of reinforcement at the pull-out interface. During the process of pull-out, the transition stage is not obvious. When the reinforcement is in the elastic stage, the nonlinearity and maximum value of the interface shear stress increase with an increase in the elastic shear stiffness, while the tensile stiffness shows the opposite trend. When the reinforcement is in the hardening or softening stage, the larger the hardening (softening) shear stiffness is, the larger the change range of shear stress is and the more obvious the hardening (softening) characteristics of the reinforcement are. The results comprehensively reflect the progressive failure of reinforcement-tailing interfaces with different strain types and provide theoretical support for the study of the interface characteristics of geosynthetic-reinforced tailings.

Modeling matrix fracture in fiber-reinforced ceramic-matrix composites with different fiber preforms

In this paper, the stress-dependent matrix multiple fracture in silicon carbide fiber-reinforced ceramic-matrix composites with different fiber preforms is investigated. The critical matrix strain energy criterion is used to determine the matrix multiple fracture considering the interface debonding. The effects of the fiber radius, fiber elastic modulus, matrix elastic modulus, fiber volume, interface shear stress, and interface debonded energy on the matrix multiple fracture and the interface debonding are analyzed. The experimental matrix multiple cracking and interface debonding of minicomposite, unidirectional, and two-dimensional woven SiC/SiC composites with different fiber volumes and interphases are predicted. The matrix cracking density increases with the increasing of the fiber volume, fiber elastic modulus, interface shear stress, and interface debonded energy, and the decreasing of the fiber radius and matrix elastic modulus.