Some Insights Into The Impact Fatigue Damage Behaviour In Laminated Composites
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Y. Ouroua, K. Azouaoui, A. Mesbah, N. Ouali & T. Boukharouba
An experimental method for impact fatigue of low energy was devised to provide some insights into the impact fatigue damage behaviour and characterize the response of laminated glass/polyester composites under conditions of increasing impact energy and increasing number of impacts. The impact frequency and subsequent projectile velocity of an impact fatigue apparatus specially designed and fabricated was varied to provide a spread of incident energies. The internal damage as a consequence of repeated impacts was investigated at five different levels of incident impact energy in the range of 3 – 7J, with the laminated specimens. The results indicated that the laminates suffered severe microstructural damage under impact fatigue, including cracking of the resin, delaminations, crushing and fracture of the glass fibres. Macroscopic failure mode can also be observed, such as; formation of spherical crater and propagating crack at the back face of plates, formed by the tensileshearing failure of fibre bundles at the weaving level. The delamination behaviour in the laminated specimens depended largely upon the level of incident energy. Well-defined impact fatigue (E-Nf) behaviour, showing an endurance limit at above 104 impact cycles, has been demonstrated. Keywords: impact fatigue, endurance curve, glass/polyester, delamination area, low velocity, life duration, cumulative impact energy. 1 Introduction Composite materials have a behaviour beyond elasticity marked by the presence of local microscopic phenomena which is called damage. The impact damage mechanisms remain still badly understood because of the various fracture
impact fatigue, endurance curve, glass/polyester, delamination area, low velocity, life duration, cumulative impact energy.