: An overview of the virtual crack closure technique is presented. The approach used is discussed, the history summarized, and insight into its applications provided. Equations for two-dimensional quadrilateral elements with linear and quadratic shape functions are given. Formula for applying the technique in conjuction with three-dimensional solid elements as well as plate/shell elements are also provided. Necessary modifications for the use of the method with geometrically nonlinear finite element analysis and corrections required for elements at the crack tip with different lengths and widths are discussed. The problems associated with cracks or delaminations propagating between different materials are mentioned briefly, as well as a strategy to minimize these problems. Due to an increased interest in using a fracture mechanics based approach to assess the damage tolerance of composite structures in the design phase and during certification, the engineering problems selected as examples and given as references focus on the application of the technique to components made of composite materials.

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Virtual crack closure technique: History, approach, and applications

Structural health monitoring and damage detection techniques are tools of great importance in the off-shore, civil, mechanical and aeronautical engineering communities, both for safety reasons and because of the economic benefits that can result. The need to be able to detect damage in complex structures has led to the development of a vast range of techniques, of which many are based upon structural vibration analysis. In the present article, some of the latest advances in Structural Health Monitoring and Damage Detection are reviewed, with an emphasis on composite structures on the grounds that this class of materials currently has a wide range of engineering applications. FOREWORD-It should be noted that this review is not intended to be a general, all-encompassing review covering the whole range of structural health monitoring (SHM); it was planned as the starting point for a study focusing on damage detection, localization and assessment for certain kinds of structure. Thus, the line of thought behind the search and the structure of this review is a result of objectives beyond the scope of the paper itself. Nevertheless, it was considered that, once the above was understood, an updated synopsis such as this could also be useful for other researchers in the same field. ©2006 SAGE Publications.

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A review of vibration-based structural health monitoring with special emphasis on composite materials

The problem of impact damage in laminated composite structures, and the consequent reduction in residual strength, has been a topic of continual research for over two decades. The number of journal papers on the subject now runs into four figures and most have been conscientiously reviewed by Abrate(1991, 1994, 1998). This review is not intended to be in the academic tradition, with emphasis on acknowledging the authorship of all the various research initiatives. Instead we present our opinions so that the reader can appreciate our current understanding of the problem, our capability of predicting by analysis, and the scope of the design tools for avoiding structural damage, or at least designing damage tolerant aerospace structures.

Impact on composite structures

Discrete cohesive zone model for mixed-mode fracture using finite element analysis

Characterization and analysis of delamination fracture in composites: An overview of developments from 1990 to 2001

This paper describes a damage accumulation mechanism in cross-ply CFRP laminates [02/902]2S subjected to out-of-plane loading Drop-weight impact and static indentation tests were carried out, and 

Damage propagation in CFRP laminates subjected to low velocity impact and static indentation

On Failure Mechanisms of Composite Laminates with an Open Hole Subjected to Compressive Load

Compressive buckling stability of composite panels with through-width, equally spaced multiple delaminations are investigated analytically and experimentally. An analytical method is formulated on the basis of Rayleigh-Ritz approximation tech nique. Timoshenko type shear effects are included. An experiment and a finite element analysis are also conducted on the present model. The analytical results agree very well with the experimental and finite element results. The buckling load, which is the com pressive strength of the panel in the case of the present model, reduces significantly due to the existence of multiple delaminations. The mechanism causing the significant loss of the compressive buckling load due to the delaminations is well explained.

Effects of multiple delaminations on compressive buckling behaviors of composite panels

Instability problem of multiple penny-shape interlaminar delaminations in circular axisymmetric plates subjected to a transverse concentrated loading is theoretically studied. The authors consider a case that all the delaminations located at the same intervals have a same size and propagate simultaneously. Then, they consider two cases that one of the delaminations is larger or smaller than the rest. The energy release rates are obtained in closed forms and the results are compared with those obtained numerically via a finite element analysis. The present solutions agree excellently with the finite element results. When the load is constant, the energy release rate is constant regardless of the size of the delaminations and increases linearly with the number of the delaminations. When one of the delamination is larger or smaller than the others, the energy release rate of the shorter delamination or delaminations become much larger than that of the longer delamination(s), that is, only the smaller delamin...

Hiroshi Suemasu

Papers

Damage propagation in CFRP laminates subjected to low velocity impact and static indentation

On Failure Mechanisms of Composite Laminates with an Open Hole Subjected to Compressive Load

Effects of multiple delaminations on compressive buckling behaviors of composite panels

Multiple Delaminations and their Severity in Circular Axisymmetric Plates Subjected to Transverse Loading

A numerical study on compressive behavior of composite plates with multiple circular delaminations considering delamination propagation