Characterization of the properties of anisotropic and inhomogeneous composite materials for use in demanding structural applications requires a wide range of mechanical tests. Furthermore, tests need to be conducted over a range of temperatures on materials conditioned in a variety of different environmental conditions. The measurement of strain is a key requirement in tests to determine and monitor tension, compression, and shear properties.
Currently, most approaches to strain measurement in composites coupon testing use contacting methods involving bonded strain gages or clip-on extensometers. Recent developments in noncontacting strain measurement mean these systems now offer similar performance to traditional contacting systems, as well as providing significant other benefits such as the ability to provide full field strain maps.