Search

This paper investigates edge delamination in an orthotropic layered structure composed of a thin film and a substrate under a temperature change. An edge interface crack is analyzed for two configurations in which it emerges from an interior or corner edge of the film. Special attention is paid to the effects of orthotropic material constants on delamination cracking. The necessary material parameters involved in the energy release rate and mode mixity for the interface crack are found based on a modified Stroh formalism. The explicit dependence of the energy release rate and mode mixity on one orthotropic parameter for the film is discovered using an orthotropy rescaling technique. The effects of other material parameters on the energy release rate and mode mixity are examined numerically, and the growth and arrest of edge interface cracks are discussed based on an energy criterion. [ABSTRACT FROM AUTHOR]

Delamination between the layers of smart composite beams is a possible failure type. The effectiveness of active vibration control, when delamination appears, is investigated in this article. In particular, optimized fuzzy controllers are developed and tested on partially delaminated piezocomposites. A finite element model based on layerwise theory, which incorporates the electromechanical coupling and the adhesive layer, is first developed. Delamination is considered by nonlinear structural analysis techniques and is used for the creation of realistic partially delaminated structures. Fuzzy controllers are built and applied to the smart structure. The fine-tuning of the parameters of control is done using genetic algorithms. Based on the results obtained from the numerical investigation, the applicability of fine-tuned fuzzy controllers, even in the case of partial delamination, is shown. According to different delamination scenarios, which were tested in this work, the design of adaptive fuzzy controllers, robust against delamination, is feasible. [ABSTRACT FROM AUTHOR]

An incremental crack extension procedure is implemented for simulating the growth of an interface defect in an electronic flip-chip device subjected to fatigue temperature cycling. The distributions of fracture mechanics parameters including the strain energy release rate, the stress intensity factors and phase angles along the curvilinear front of an embedded corner defect on the interface of silicon die and underfill are estimated and substituted into a subcritical crack growth model to predict the evolution of the defect under cyclic loading condition. It is observed from the analysis that the corner defect is under crack faces contact condition during temperature cycling, and consequently, the delamination growth is under mode-II and mode-III driving forces. In addition, the crack growth rate is highest in the middle of the crack front, and the corner crack evolves from an initially concave front to a quarter-circular front under temperature cycling. [ABSTRACT FROM AUTHOR]