Load Capacity of Sandwich Panel With Core Foam Evaluated by 3-Point Bending Test

Abstract The classification society Bureau Veritas requires a structural assessment of composite materials structures to confirm the compliance with applicable rules, like 3-point bending tests. However, for sandwich panels with a low-density foam core, local phenomena like indentation and wrinkling may occur in the upper face sheet at the loading punch, thus the intended load capacity of the sandwich panel will not be reached. It is then proposed to perform complementary shear tests to capture the behaviour of the core of the sandwich panel. In the present paper, the load capacity in a 3-point bending test is simulated with emphasis on the influence of the constitutive modelling of the core foam, as calibrated against experimental results for shear tests. It is carried out as a benchmark exercise, with participation from three universities. The FE-simulations show that the shear test can be used to accurately model the load capacity of the core foam. However, for the 3-point bending test using specimen with a very high panel length / thickness ratio a large part of the load transfer is done in the upper face sheet with less involvement of shear in the core. Although core fracture is observed in the experiments, both the FE-simulated and experimentally found maximum load agree well with the load capacity as determined from analytical formula for local failure in the upper face sheet. The FE-simulated vertical displacement at maximum load differs though.