Full-field optical techniques : applications to strain measurement and mechanical identification.

The paper aims at introducing basics on full-field optical methods applied to composites since those methods highly enhance the experimental characterisation of material and structure behaviour. Different classical methods are first introduced, focusing on their relative performances. The special interest of the grating shearography method is then emphasised. It is applied to a one-ply fabric coupon in uniaxial tensile loading. The comparison with strain gauges of different effective length shows the flexibility of the technique to perform adapted analysis. Since the method is capable to measure the surface slope and in-plane strain fields, it is shown that both those data are necessary to catch an in-depth understanding of the mechanical behaviour of the fabrics. Finally, the basic interest of these techniques coupled to numerical analysis is underlined. It is believed that such a coupling can lead to a complete renewal of the mechanical characterisation of materials and systems.