FRACTURE AND FATIGUE OF HIGH-PERFORMANCE COMPOSITE-MATERIALS - MECHANISMS AND PREDICTION

The fracture and fatigue in high performance composite materials are of a quite different nature from those of metals. Damage due to fatigue is to be feared much less in the first case than in the second. However, compression loading is much more damaging in composite than in metallic materials, especially in cyclic loading. On the other hand, the most worrying causes of damage are the stress concentrations in the vicinity of notches and holds. Finally, it will be pointed out in this paper that the more important mechanism is delamination. The first part of this paper is devoted to a review of the fracture criteria in monotonic loading and to fatigue life prediction laws. The second part is about the different types of damage in tension, in shear, in torsion, in compression and in combined load applied at a cylindrical specimen. The effect of a notch on fracture and fatigue will be reviewed in the following part: toughness, damage and models will be discussed under axial loading and biaxial loading. The case of notch effect under compression will be considered. The subject of this paper is limited to glass or carbon long fibre-reinforced polymers including thermoset and thermoplastic matrices. The approach presented herein essentially concerns the study of fracture criteria and damage mechanics up to the microscopic scale. In both cases, the application of the concepts of fracture mechanics leads to analysis which allows one to suitably characterize the behaviour of materials.