In this paper the various failure modes which occur in long fibre composites are described and discussed. The significance of each of these fracture mechanisms, in terms of their energy-dissipating capacity as well as their effect on the residual load-bearing properties, is considered. A brief review of both the destructive and non-destructive techniques used for detecting and characterizing defects and damage is presented. The ability of each technique to identify the various fracture mechanisms involved in the failure of long fibre reinforced composites is discussed and their overall suitability for damage detection evaluated.

The significance of damage and defects and their detection in composite materials: A review:

The paper focuses on the moire phenomenon as a tool of experimental mechanics. The properties of moire patterns are outlined. The application of these properties to the measurement of displacements of the points of a surface (intrinsic moire), contours or deflections (projection moire) and slopes (reflection moire) is discussed. Observation methods, recording methods, data-processing techniques are outlined and practical aspects are stressed. Sensitivities and precisions that have been achieved are reviewed. Finally, some typical applications to problems in areas of interest are briefly described.

The moiré method—A review

Improved Moiré Interferometry and Applications in Fracture Mechanics, Residual Stress and Damaged Composites

High sensitivity moire interferometry is now a technique in fairly general use. Its development arose from the efforts of a number of workers over a period of nearly 40 years. This progress is reviewed in the ligh of the individual contributions that have led to the presentday accurate and user-friendly systems. In the first instance, the story is related in approximate chronological order; the contributions of individuals and groups are outlined in more detail in a series of appendices. It will become apparent that moire has not developed in a smooth, linear fashion—rather, a number of people reacted to the problems they were asked to solve, in a particular manner, and using methods and equipment available at the time. This view of the progress of science and technology as the creation of a climate of opinion and opportunity is very much in line with modern analyses of the history of science.

A historical review of moiré interferometry

https://www.civil.iitb.ac.in/~tkant/papers/TKant-IITB-JP027.pdf

Performance of heterosis element for bending of skew rhombic plates

A laser interferometer system is used to record two mutually perpendicular diffraction gratings on a photoresist coated specimen. When either grating is re-illuminated by the fringe pattern used to form it, real-time observations can be made of moire fringes corresponding to surface displacements which occur as a tensile load is applied to the specimen. The technique has been used to study the in-plane deformations of carbon-fibre composites, and typical results are given.

http://sdj.sagepub.com/content/9/1/36.full.pdf

An interference technique for the measurement of in-plane displacements of opaque surfaces

A technique is presented for accurate determination of the flexural stiffness of thin plates using optical holography. Measurements of the interference fringes on thin rhombic plates in anticlastic bending are used to calculate the components of curvature by a simple numerical method Control experiments on a metal plate give good agreement with the results of small deflection bending theory. The method appears ideally suited to the measurement of anisotropic flexural stiffness properties.

M Marchant

Papers

An interference technique for the measurement of in-plane displacements of opaque surfaces

Determination of the flexural stiffness of thin plates from small deflection measurements using optical holography

Heat-resistant gratings for the interferometric observation of in-plane surface displacements: