Core compression in sandwich beams under contact loading

Failure of the core in sandwich structures under concentrated loading is of potential concern, and it is difficult to compute the core compressive stress by simple means. Contact loading adds additional complexity, as surface displacements are imposed and the contact zone size and pressure distribution is initially unknown. However contact loading is important as it is widely used in three or four point bend tests to determine failure properties, and is also typically involved in impact loading. The calculation of core compressive stress was addressed in the present work by utilizing an elasticity solution due to Pagano and Srinivas and Rao for transverse loading of layered orthotropic materials. Contact pressure distributions were obtained by systematically varying pressures and comparing the computed surface displacements with the indentor profile. The results show that the pressure distribution for an orthotropic half-space is applicable to sandwich beams over a wide range of variables. A beam-on-elastic-foundation model was found to be useful in correlating the analysis results for core compressive stress.