On the mechanical effect of stitch addition in sandwich panel

Monolithic stitched composite materials successfully inspired the addition of transverse reinforcements in the case of sandwich structures. Indeed, the gains are undeniable in term of ultimate stress and of modulus regarding the principal mechanical tests practiced on sandwich (bending, shearing and compression). These bonds reduce the impact of the inter-laminar shearing which tends to break the connection between the core and the skins. Moreover, such reinforcements finally increase mechanical properties in the thickness direction, thus solving the principal disadvantage of these sandwich structures. Although the mass of such stitched panels is higher than that of the unstitched ones, the specific performances remain considerable. The direct influence of the macro-structural parameters of the stitches (step and angle) on the mechanical behavior of the structure is presented. It was also clearly highlighted that it is necessary to find a compromise between the structural parameters and the mass in order to obtain the expected mechanical performances.