A novel approach to measure local strains in polymer matrix systems using polarised Raman microscopy

A novel approach to measure local strains in amorphous polymers is described. The method is based on the identification of changes in the molecular orientation with strain. Molecular orientation is quantified through a series expansion of Legendre functions where the coefficients of the series are determined from the Raman scattering intensities by varying the polarizations of incident and scattered light. The relations between the elements of the strain tensor and the coefficients of the Legendre functions are obtained from a set of simple uniaxial strain tests. The experimental technique is applied to measure the thermal strain field in the matrix around an embedded fibre in a single fibre model composite. The experimental results indicate that local shear yielding takes place within the matrix. This conclusion was supported by measurements of strain distribution in the fibre.