Fatigue behaviour of composite adhesive lap joints

This paper is concerned with a fatigue study of composite adhesive lap joints produced from a bi-directional woven E-glass fibres and polypropylene. The adhesive used was a Bostik 7452 (Rubber & Plastics Grade) ethyl cyanoacrylate type. The effects of layer orientation, lap joint length and water immersion on the fatigue behaviour were studied. The specimens were immersed in water during periods until ninety days for controlled temperatures of 20, 40 and 70 °C. The results are presented in the form of curves of stress amplitude versus number of cycles to failure and also in the form of number of cycles to failure against time to exposure in water for fixed stress amplitudes. The fatigue damage and failure mechanisms were analysed and discussed. The joint shows that creep deformation within the temperature range of this study was probably the mainly cause of the dynamic stiffness reduction observed.