MECHANICAL CHARACTERIZATION OF CARBON-EPOXY AND GLASS-EPOXY COMPOSITES BY INDENTATION TESTING

The indentation technique has been developed to perform surface mechan ical characterization of materials. This technique consists in monitor ing the penetration of a diamond indenter in the material to be charac terized while the displacement and the force are continuously measured . Modelling loading and unloading curves allows estimation of plastic and elastic properties of the material. Linking this technique with an optical sighting system permits the characterization of various phase s of the composite materials with a displacement accuracy better than 0.1 mu m. The mechanical behaviour of carbon or glass fibre reinforced polymer under various solicitations is mainly related to the behaviou r of its 'phases': the matrix, the fibres and the fibre-matrix interfa ce. Several techniques have been developed giving information about me chanical properties of the composite, particularly for the interfacial strength. Modelling static and dynamic indentation curves on fibres a llows computation of the interfacial strength and fibre mechanical pro perties. This paper presents our indentation technique and the model t hat we have developed to study glass fibre-epoxy matrix and carbon fib re-epoxy matrix composites with a fibre diameter of 5-20 mu m.