Micro-Raman Spectroscopy in Micromechanics; The Giant Awakes

The recent evolution of micro-Raman spectroscopy as micromechanical experimental technique had a profound effect on the field of solid mechanics in general and composite micromechanics in particular. MicroRaman spectroscopy (MRS) is the only technique capable of measuring local stress in a wide range of composite materials with a spatial resolution of 1 μm. This capability has been utilized in the field of fibrous composites to provide accurate measurements of axial and interfacial stress distributions along individual fibers and at fiber/matrix interface. Such experimental measurements shed light on and strengthened our understanding of crucial events taking place during composite loading such as damage initiation, propagation, and stress concentration. In addition, the effect of composite constituents (fiber, matrix, and interphase) on such events was better understood. This resulted in more accurate models capable of predicting composite behavior and fracture more closely. This paper reviews our recent work in the field of micro-Raman spectroscopy in composite micromechanics. The paper will emphasize two main areas; 1- Interfacial behavior in composites, and the effect of a brittle interphase on interfacial damage initiation and propagation, and 2- stress concentration phenomenon and the possibility of tailoring an interphase to control composite toughness. Future potential of the MRS technique to investigate mechanics of functionally graded materials (FGM) and mesoscopic stress fields in polycrystalline materials will also be discussed