Mechanical behaviour of hybrid FFRP/aluminium honeycomb sandwich structures

The combination of lightweight properties and high energy absorption capacity makes sandwich structures suitable for applications in transportation industry, such as automotive, aerospace, and shipbuilding industry. In these fields, the gas emissions reduction, fuel saving, vehicle safety and load capacity increase are currently important requirements. This research deals with the study of the mechanical behaviour of a "green" hybrid honeycomb sandwich structure made by an aluminium honeycomb core and flax fibres reinforced skins. Specific interest has been addressed to their mechanical behaviour in terms of bending properties and low-velocity impact response. For the impact tests, two indenters having hemispherical geometry with a diameter of 10 mm (H10) and 20 mm (H20) were selected. The results were compared with other hybrid structures analysed in previous studies. The static three-point bending tests produced different collapse modes, depending on the support span distance. Non-destructive evaluation was carried out for failure mode analysis by optical microscopy and digital radiography (DR). In the aluminium-flax hybrid sandwich structures it is found an increase in the impact strength of 25 % compared to the unreinforced aluminium honeycomb sandwich structures. In terms of specific energy absorption (SEA), it is interesting to underline an increase of 50 % compared to traditional AHS structures.