Abstract

In this work, the oblique impact response of sandwich structures, with carbon/epoxy face-sheets and aluminium honeycomb core, is analysed by implementing a 3D numerical model in Abaqus/Explicit finite element code. The numerical model was validated with data taken from the scientific literature for a normal impact, and numerical results showed good correlation with experimental data. The validated model was used to study the variation of the ballistic limit and the residual velocity with the impact angle of the projectile.  In order to determine the contribution of the core in the impact process, another finite element model was developed, corresponding to that of a laminated spaced plates a distance equivalent to the thickness of the composite sandwich core. It was found that both ballistic limit values ​​and residual velocity are affected by the presence of the core in the sandwich plates and by the obliquity of the impact angle.

Abstract

Composite sandwich structures with core cellular materials are widely used in diverse industries such as the aerospace, marine, car, and wind industries due to their good mechanical properties on bending. The growing environmental awareness has increased the interest in the use of materials from biodegradable and renewable sources. During recent years, there has been an increasingly growing interest in the use of agglomerated cork as a core material in sandwich structures, replacing synthetic polymeric foams in specific applications.

Among its remarkable combination of properties, we can find a hyperelastic behaviour, low thermal conductivity, low permeability, and good energy absorption and vibration damping properties. Additionally agglomerated cork is produced from the waste of the cork industry, being a renewable and biodegradable material that is environmentally sustainable.

The aim of this work is to address the quasi-static and dynamic compression testing of two types of agglomerated cork of different densities, using a servo-hydraulic testing machine and drop weight tower. The mechanical behaviour and energy absorption properties at different strain rates are evaluated from the contact force measurements and estimations of impact kinetic energy. Additionally, Digital Image Correlation (DIC) is used to estimate the variability in the local strain through the test specimen.