Analytical Investigation and Comparative Assessment of Interphase Influence on Elastic Behavior of Fiber Reinforced Composites

Interfacial interactions and interphases play a key role in all fiber reinforced composites. However, a clear distinction must be made between interface and interphase. Interphase becomes interface if its thickness decreases to zero. In most of the available micromechanical models the interface is considered perfect (no interphase). However, such a condition is hardly fulfilled in real composites. It is possible to find the volume of interphase by using DSC or identification of interphase region using SEM or some other sophisticated instrument techniques as it is a region created between the two main phase of a composite. All these techniques require special technical skill. In the present study attempt is made to identify the existence of the interphase region in fiber matrix composites using SEM. It was also decided to develop an equation for volume fraction and thickness of interphase by considering the composite as three-phase RVE. Developed equations of interphase volume fraction was used by considering the soft and stiff interphase parameters. Comparisons were made to study elastic behavior of fiber reinforced composites in longitudinal and transverse directions with available experimental data and published model in the literature and they are in good agreement.