A new method to study the fiber-matrix interface in unidirectional composite materials: Application for carbon fiber-epoxy composites

Numerous studies have been done on the nature of the fiber-matrix interface and on the role of this interface in mechanical properties of epoxy-carbon fiber composite materials. In this study, we describe a new test to study the fiber-matrix interface in unidirectional composites by dynamic shear testing along the fiber axis. This method, based on three scans with increased dynamic displacement amplitude, enables us to study the recovery of mechanical properties and appearance of damage in the material. For carbon fiber-epoxy unidirectional composite materials, it is possible to distinguish two ranges in the amplitude of dynamic displacement: a first for which a recovery for G′ and tan σ is observed and a second for which permanent damage appears. The influences of fiber surface treatments such as oxidation and/or sizing on dynamic behavior are clearly displayed by this test.