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To optimize the optical fiber temperature sensor employing the deep-grooved process, a novel scheme was proposed. Fabricated by the promising CO2 laser irradiation system based on the two-dimensional scanning motorized stage with high precision, the novel deep-grooved optical fiber temperature sensor was obtained with its temperature sensitivity of the transmission attenuation −0.107 dB/°C, which was 18.086 times higher than the optical fiber sensor with the normal depth of grooves while other parameters remained unchanged. The principal research and experimental testing showed that the designed temperature sensor measurement unit had the ability of high sensitivity in transmission attenuation and insensitivity to the wavelength, which offers possible applications in engineering.

This work derives an interaction integral for the computation of mixed-mode stress intensity factors (SIFs) in three-dimensional (3D) nonhomogeneous materials with continuous or discontinuous properties. The present method is based on a two-state integral by the superposition of actual and auxiliary fields. In 3D domain formulation of the interaction integral derived here, the integrand does not involve any derivatives of material properties. Furthermore, the formulation can be proved to be still valid even when the integral domain contains material interfaces. Therefore, it is not necessary to limit the material properties to be continuous for the present formulation. On account of these advantages, the application range of the interaction integral can be greatly enlarged. This method in conjunction with the finite element method (FEM) is employed to solve several representative fracture problems. According to the comparison between the results and those from the published lectures, good agreement demonstrates the validation of the interaction integral. The results show that the present interaction integral is domain-independent for nonhomogeneous materials with interfaces.

Considering the material properties to be one-dimensionally dependent, this paper studied an anti-plane problem for an embedded crack and edge crack perpendicular to the boundary of a functionally graded magneto-electro-elastic strip. The crack is assumed to be either magneto-electrically impermeable or permeable. Integral transform and dislocation density functions are employed to reduce the problem to the solution of a system of singular integral equations. Numerical results show the effects of the loading combination parameter, material gradient parameter and crack configuration on the field intensity factors and the energy release rates of the functionally graded magneto-electro-elastic strip.

The purpose of the present work is a numerical study of the interaction between a crack and second phase particles in a reinforced composite material. Simulations are accomplished using the extended finite element method (XFEM) without tip-enriched functions, a new domain expression of an interaction integral for evaluating stress intensity factors, and the maximum hoop stress criterion for crack-growth direction prediction. Crack deflection mechanisms and the associated energy release rate variations are investigated. It is found that although the energy release rate is affected by the particle at relatively large distances, the crack trajectory is not substantially altered until the crack is very close to the particles. A pre-existing interface crack is also observed by introducing adaptive enriched functions in the XFEM. By this method, expensive meshing strategies can be avoided and considerable flexibility is obtained. The results show that the flaw could attract the main crack and increase the energy release rate.

Piezoelectric materials and structures contain more or less electromechanical interfaces in engineering applications. It is difficult to obtain the fracture parameters efficiently of the piezoelectric materials with complex interfaces. This paper presents a domain-independent interaction integral for material nonhomogeneity and discontinuity which can be used for solving the stress intensity factors (SIFs) and the electric displacement intensity factor (EDIF) of piezoelectric materials with complex interfaces efficiently. The interaction integral is based on the J-integral by superimposition of two admissible states and the present formulation does not involve any derivatives of mechanical and electric properties. Moreover, it is proved that the interface in the integral domain does not affect the value of the interaction integral and thus, the present method does not require electromechanical parameters of piezoelectric materials to be continuous. The interaction integral method combined with the extended finite element method (XFEM) is used to investigate the influences of material continuity on the SIF and the EDIF and the results show that the material parameters and their first-order derivatives affect both the SIF and the EDIF greatly, while the higher-order derivatives affect both of them slightly.

In the present study, the highly efficient composite lattice structures were filled with silicon rubber in their enormous space, to enhance their mechanical property and energy absorption capacity. Out-of-plane compression tests were carried out to evaluate the enhancement. The initial response and failure mode of the newly developed structure kept the same as that before filling. However, a higher stress level region was appeared which benefited to its energy absorption.