Testing reinforced plastics

The tests used to characterize homogeneous plastics can be applied to a large extent to reinforced plastics (see the specialized articles in this treatise). However, particular care must be taken with sample preparation, experimental conditions and the processing of results, since, given the heterogeneous and often highly anisotropic nature of composite materials, small manufacturing, cutting and loading angle defects can lead not only to scattered results, but also to significant variations in stress states, even to the extent of modifying failure mechanisms.

Nevertheless, to take account of the particular characteristics of composite materials (heterogeneity, anisotropy, etc.), specific tests have been developed, notably to analyze their composition (reinforcement content and void ratio, quality of the reinforcement/matrix bond), measure their specific characteristics (delamination resistance), check their sensitivity to damage (fracture mechanics) and study the behavior of semi-finished products (pipes and fittings) and industrial parts (tanks and reservoirs). In addition, more traditional tests (traction, flexion, compression, etc.) have been adapted to these materials (modification of specimen geometries and test conditions, tests in the main directions of the composite, for example).

The following paragraphs describe the main specific techniques that can be used in industry, and which are the subject of standards or highly advanced developments in laboratories. We limit ourselves here to characterization tests on solid-state composites, as the control of raw materials (resins, reinforcements) and semi-finished products (prepregs) is covered in other specialized articles in this book.