Because of high stiffness and strength to weight ratios, composite sandwiches are being used increasingly, especially in aerospace applications. The main drawback of sandwich components is their relatively low resistance to impact damage and the extent to which their strength is reduced under compressive loading after impact. As part of a wider study aimed at increasing the impact resistance of sandwich panels, a continuum damage model is proposed. The model developed describes the compressive behaviour of honeycombs made from materials that are prone to elastic buckling. The material behaviour in compression is described by a combination of three distinct constitutive models, namely elastic, elastic continuum damage and an inelastic strain accumulation model. This has been interfaced with a commercial finite element package to model soft body impacts onto a minimum gauge honeycomb core sandwich. Results from analysis are compared to experimental data and the correlation is found to be very good.

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The assessment of damage due to impacts in composite sandwich panels and the component life reductions associated with such damage is becoming increasingly important within the aerospace industry. This study analyses minimum gauge, non-metallic honeycomb wing panels subject to impact damage. In all instances the damage is caused by ‘soft body’ impactors travelling at elevated velocities to simulate bird strike and other soft debris. The damage formed during these impacts is shown to be large in plan area but shallow and primarily causes crushing of the core in a thin layer. Loading of the panels after impact has been performed to determine the reduction in load carrying capacity and associated failure mechanisms. Damage due to soft body impact is shown to be very different to the classical rigid body impact upon which current repair schemes are based. As a result in many applications the use of current repair schemes may be inappropriate. The viability of new repair techniques is discussed with particular attention to the prevention of failure mechanisms due to loading after impact.