Mechanics of interface debonding in fiber-reinforced materials

The evaluation of damage in multiphase materials plays a crucial role in their safety assessment under service mechanical actions. In this context, the quantification of the damage associated to fibre–matrix detachment is one of the most important aspects to be carried out for short fibre-reinforced materials. In the present article, the problem of progressive fibre–matrix debonding is examined and a mechanics interpretation of such a phenomenon is developed by relating the shear-lag and the fracture mechanics approach in order to determine the fibre–matrix interface characteristics. A multiscale approach is employed: at macroscopic level, composites with dilute dispersed fibres, arranged in a undirectional or in random orientation, are analysed through a homogenization approach, whereas the problem of axisymmetric debond growth in short fibres is examined at microscopic level. Moreover, a ‘structured’ linear elastic interface framework model for crack propagation analysis is applied by defining a microscopic truss structure, enabling to relate each other the classical shear strength approach and the fracture mechanics approach. Finally, a fibre pull-out test and some simple fibre-reinforced structural components are examined. This new proposed point of view on the debonding phenomenon allows a deep understanding of the mechanics of the fibre–matrix interface and enables to characterize such an interface layer that has a relevant role in mechanics design of composites materials.