Experimental investigation of process induced strain during cure of epoxy using optical fibre bragg grating and dielectric analysis

In order to investigate how cure cycles for composites can be optimized for improved fatigue life of composites, an experimental set-up which measures temperature, process induced strain and level of cure, is presented. The experimental set-up measures strain in a neat epoxy sample using optical Fibre Bragg Grating sensors in a single glass fibre, combined with a thermo-couple used to compensate for thermal effects. The degree of cure in the neat epoxy sample is measured in the same sample using a dielectric sensor working simultaneously with the temperature and strain measurements. The combined measurements allows for quantification of a number of important parameters required for understanding how the temperature profiles used in processing of composites affects the level of process induced strains in the neat polymer material and thereby the level of residual stresses in the final composite materials.