Characterization of stress in reinforcements in magnesium based squeeze infiltrated cast hybrid composites

Characterizing residual stresses in the reinforcement of cast composites has been studied in the present work. Micro Raman Spectroscopy is a unique tool for determining the strain on the reinforced fibres in ceramic/polymer/metal matrix composites. Stress induced Raman shifts can be used to determine the stress/strain in films, fibres and particulates in composites. In this paper, the application of Micro Raman Spectroscopy as a non-destructive technique in providing information on the compressional/tensile strain in reinforcements in metal matrix composites is investigated. Examples are taken from hybrid Mg based composites reinforced with carbon fibres, Mg2Si in situ reinforcement, formed by the addition of Si in to the matrix and SiC particles. The studies on the strain measurements in as-cast condition and its comparison after thermal cycling of the composites using the bandwidth measured are discussed. Analysis of the bandwidth offers a tool to understand that the wavenumber shift is strain induced. With this, the compressional state of the fibres embedded in the matrix can be analysed.