ABSTRACT
This paper reports the application of a test procedure developed at the University of Liverpool Impact Research Centre to impart pulse pressure loading to riveted and laser welded, stiffened flat panels. A series of structural tests on 1m by 1m panels together with material and joint characterisation tests were performed to study the dynamic non-linear behaviour of the panels and identify particular modes of failure that could lead to catastrophic failure of the aircraft. Pulse pressure testing of the riveted panels has identified four principal modes of failure of the structure, namely (1) rivet shear/tension failure, (2) frame buckling, (3) stringer buckling and (4) frame rupture. The dynamic failure pressure ranged from 32 to 43 kPa for the panel geometry tested (131 to 262mm stringer spacing and 525mm frame spacing). Rivet failure and frame rupture generally occurred at larger stringer spacing and frame buckling generally occurred at smaller stringer spacing. For the laser-welded panels, failure pressures were between 28 and 32 kPa and failure was dominated by significant weld failure at the frame-skin interface. The material characterisation tests at different rates of loading have shown that the material is only mildly strain rate dependent. Joint characterisation tests demonstrated that the riveted joints had a higher energy absorbing capacity than the laser-welded joints.
