Finite element analysis of the delamination crack propagation in laminated composites is presented. Fracture mechanics based Virtual Crack Closure Technique (VCCT), and the cohesive element technique, have been used to simulate the delamination initiation and propagation under Mode-I type loading. Detailed description of the parameter selection process for these two techniques with ABAQUS®/Stan...

This study characterizes the family ties of crack cocaine users cared for in a psychiatric emergency department in southern Brazil. It is a qualitative study with a series of cases carried out in the city of Maringá, PR, Brazil from April to June 2010. Data were collected through semi-structured interviews, analyzed using content analysis, and organized into two categories: family ties as facil...

This paper describes a framework to study the initiation and arrest of an interfacial crack, using a combination of experiment and computation. We consider a test configuration widely used in the microelectronic industry: a sample of two substrates bonded by a stack of thin films, with a pre-crack in one of the substrates, perpendicularly impinging upon the films. When the sample is loaded to a...

In multilayer ferroelectric actuators, electrode edges are the main source of fracture due to the generation of non-uniform electric fields in their vicinity. The electric fields, in turn, induce incompatible strain fields and hence concentrated stresses, which may cause the ceramic to crack. In this paper, the crack initiation from the electrode edges is simulated using a phase-field model. Th...

Debonding between core and facings is a common failure mode of sandwich structures that can severely damage the load-carrying capacity of the structure. The objective of this work is to study the effect of debonding in double cantilever beam specimens made of aluminum facings and PVC foam cores. The configuration follows the standard ASTM D5528-94a peel test. Four PVC foam core materials under ...

In many cases cracks leading to fracture occur at interfaces between two different constituents, e.g. a fiber and the matrix in a composite. The early solutions of such problems in the context of linear elastic fracture mechanics (LEFM) revealed the presence of an unsatisfactory behavior: rapid oscillations in the stress and displacement fields, implying the physically impossible phenomenon of ...

We compare experimental observations of a slow interfacial crack propagation along an heterogeneous interface to numerical simulations using a soft-clamped fiber bundle model. The model consists of a planar set of brittle fibers between a deformable elastic half-space and a rigid plate with a square root shape that imposes a non-linear displacement around the process zone. The non-linear square...

Partition of unity enrichment techniques are developed for bimaterial interface cracks. A discontinuous function and the two-dimensional near-tip asymptotic displacement functions are added to the finite element approximation using the framework of partition of unity. This enables the domain to be modelled by finite elements without explicitly meshing the crack surfaces. The crack-tip enrichmen...

The propagation of an interfacial crack front along the weak plane of a thin film stack is considered. A simple patterning technique is used to create a toughness contrast within this perfectly two-dimensional weak interface. The transparency of the specimens allows us to directly observe the propagation of the purely planar crack obtained during a DCB (Double Cleavage Beam) test. The effect on...

In flip-chip package, the mismatch of thermal expansion coefficients between the silicon die and packaging substrate induces concentrated stress field around the edges and corners of silicon die during assembly, testing and services. The concentrated stresses result in delamination on many interfaces on several levels of structures, in various length scales from tens of nanometers to hundreds o...