Experimental and numerical assessment of fracture initiation in laser-welded webcore sandwich panels

We present experimental study on penetration resistance of all-steel laser-welded webcore sandwich panels. A low weight-to-stiffness ratio of these panels provide the means to develop cost and energy efficient and sustainable ships, when service, ultimate and fatigue limit states are considered. However, the response for accidental limit state remains uncertain as the failure of weld is often excluded from the analyses. In addition, the modelling effort in the conceptual design stage can be prohibitive, especially when considering accidental loads and fracture propagation. Therefore, clamped sandwich panels with dimensions of 1.2x1.2 m were penetrated with rigid indenter until onset of fracture. In parallel, tensile coupon tests were made with material extracted from the panels. The behaviour of panels was simulated using FEM with explicit, simplified consideration of welds. The assumptions and limitations of our modelling approaches is discussed with respect to fidelity of the simulations. It is also shown that the failure of sandwich panels is complex phenomenon where local bending of unit cells has significant effect to the failure mode predicted.