Evaluation of residual stresses and adhesion in polymer composites

A procedure to evaluate residual thermal stresses in polymer matrix composites is proposed, which takes into account the viscoelastic properties of the matrices. The viscoelasticity of the polymers was investigated by shear relaxation or dynamic mechanical tests. The influence of processing temperatures and cooling rates on the radial residual stresses acting around a carbon fibre was estimated both for thermoplastic and thermoset matrices. The importance of the radial stresses on the adhesion at the fibre-matrix interface was experimentally evaluated by fibre-matrix adhesion tests at different temperatures and after different cooling cycles.