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Fellowship Description

Research program title

Analysis of Failure in Composite Materials and Structures

Reference number

2004

Supervisor

Program description

Composite materials and structures have found more and more applications in many industries. These include aerospace, automobile, naval, and energy generation industry such as wind turbines. For effective use of these materials, it is essential that some predictive capability is available for the prediction of their failures. There are many failure criteria proposed by previous researchers. However there is serious disagreement between them. The reason for this is due to the lack of efficient methods to detect failures in composites and their structures, in the initiation stage. Current methods to measure deformations include strain gages, fiber optics, Digital Image Correlation. Methods to detect failure include acoustic emission, thermography and visual observation. These methods can detect large deformation or failure that are well advanced. Early weaknesses or early stage failure such as those due to resin rich areas, or matrix cracks are very difficult to detect. Acoustic emission may indicate matrix cracks but the data is usually smeared by noise.

Over the past several years, Professor Hoa and his associates have developed a technique that can detect weak areas or early stage cracks in composite structures. This technique relies on the augmentation of the electrical conductivity of the material upon addition of carbon nanotubes. By incorporating a proper amount of CNTs into the epoxy matrix of the composite material, it is possible to not only detect, but also locate and quantify the damages. Composite materials have a large degree of variability, and the crack occurrence pattern does not follow the self- similar cracking behavior in metals. Rather the early cracks tend to jump from one location to another. With the ability to detect this, it is possible to come up with criteria for the prediction of failure. This program of research has profound fundamental importance, since it provides answers to a question that has obstructed the progress of composites for so many years.

Academic qualifications required

  • PhD in Mechanical Engineering with background work on polymer matrix composite materials and structures
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