In this paper, the effect of the variations of material combinations on the fracture behaviour of an arbitrarily inclined crack terminated at a bimaterial interface was investigated. By using the complex variable method, a comprehensive analysis of the state of stress and stress intensity factors (SIFs) was performed. The digital photoelastic technique was also employed to verify the analytical results. To ensure the accuracy in the process of determining SIFs, a visual check between experimentally obtained images and theoretically reconstructed images was performed. It was concluded that far-field effects usually found in the homogeneous case had to be included in the stress equations.

Electronic speckle pattern interferometry (ESPI) was used to perform nondestructive evaluation of carbon-fiber reinforced plastic (CFRP) laminate plates containing various sizes and shapes of defects located at different depths. A specially designed vacuum box was used to provide the deformation of the test specimen. Not the same as the traditional ESPI, the decorrelation between two speckle patterns was used to determine the size, and shape of a defect. By using the speckle decorrelation, the location, size and shape of a defect can be easily determined. A series of computer programs was developed on the ESPI system to acquire and analyze the interferometric patterns. Although the detected shape and size do not match well with the originally embedded one, the ESPI procedures developed in this paper should still be a potentially quantitative nondestructive method for detecting the location and size of the defect in composite materials.

From high-tech industry to consumer electronics, thermoelectric cooler (TEC) has been widely used. Basically, TEC is a sandwich structure. An array of small bismuth telluride cubes is placed between two ceramic plates and bonded to them. When a DC is applied, thermal deformation occurs because of the temperature gradient produced between the two ceramic plates of the device. To ensure the safety of the TEC, it is therefore important to investigate the thermal deformation induced. However, because of the complexity of the TEC structure, numerical simulation cannot be easily performed. In this study, digital speckle pattern interferometry (DSPI) was employed to measure the real-time full-field thermal deformation in TECs. Variations of thermal deformations versus magnitudes of DC were obtained. The obtained experimental results will be very useful for building the numerical model. KEY WORDS: digital speckle pattern interferometry (DSPI), thermal deformation, thermoelectric cooler (TEC) 232 Ó

In this paper, both photoelasticity and moiré interferometry were successively incorporated with finite element method to investigate the predicted thermal stresses and lateral displacement of bonded structures calculated from different theories. It was found that the distributions of moment and transverse force play significant roles in making different values of thermal stresses in the adherends by authors’ and Suhir's 1986 theories. On the other hand, the values of lateral displacement obtained from different theories are almost identical.

A general transfer matrix method (GTMM) is developed to derive the characteristic equation for the multi-material junction and wedge problems. Using complex variable techniques, the boundary conditions can be represented by a matrix equation. The matrix itself can be simpli®ed to be a square matrix of order 4, for both the junction and wedge problems. In the case of a uniform temperature ®eld, non-homogeneous terms occur on the interface of different kinds of materials. Including the logarithmic terms of potential for temperature, the GTMM can also be applied in this case. Since the derivation of the method involves only a matrix of order 4 or less, the GTMM is much more convenient in the implementation of computer programs. IntroductionIn general, the derivation of a characteristic equation for the multi-material junction and wedge problems (Fig. 1) is a tedious work. There are several methods to obtain the characteristic equation. Williams (1952) used the Airy's stress function to derive this equation. Bogy (1968) and Dunders (1969) adopted the Mellin transformation technique to determine the order of singularity. Theocaris (1974) solved an n-material junction problem, using the Kolosov-Muskhelishvili (1953) stress functions. All of the aforementioned works derived a set of equations from the boundary conditions, which can be rewritten in the form of a homogeneous matrix equation. However, the dimension of the matrix increases, as the number of material interfaces increases. Then, it is a rather dif®cult task to derive the characteristic equation, and obtain the eigenvectors. Dempsey and Sinclair (1979) proposed two methods of expanding the determinant for an n-material wedge; the ®rst by an expansion by the complementary minors, and the second, by a transfer matrix approach. The ®rst method was used for the wedge problems, and the transfer matrix method was applied to the junction problems. The advantage of the transfer matrix method is that, only square matrices of order four appear in the process. It should, however, be pointed out here, that a large size matrix was built up in the beginning stages, for both the problems. A general method that reduces the order of the matrices, as could be applied equally well for both the problems might be worth pursuing. Chen and Nisitani (1993) applied the transfer matrix method to a closed trimaterial wedge. Ying and Katz (1987) followed Willams' approach, and established a formulation for multi-material wedges. The boundary conditions, which they dealt with, were free and clamped. It should be noted that the square matrix of the characteristic equation is of order two. Although the order of the matrix is greatly reduced, it is not compatible with the undetermined constants or eigenvectors. Techniques of matrix manipulation were well used in the anisotropic bimaterial problem by Boem and Atluri (1995). The concept of a transfer matrix was implicitly applied in their work. Two real matrices, denoted as a and b, which were extensions of the Dunders parameters to the aniso...