6 months Internship Offer 2025: Development of polymeric alveolar structures for aerospace impact applications – IMT Mines Albi (17/11/2024)

Sandwich structures are widely used in lightweight applications due to their exceptional strengthto-weight ratio, achieved by placing a low-density core between two rigid skins (such as composites or metals). Various core configurations have been explored in the literature, including Nomex® and aluminum honeycombs, lattice structures and similar designs [1]. Among these, alveolar structures, and more particularly polymeric foams, offer a promising and customizable solution. This class of materials provides a versatile approach to integrate multiple functions within the sandwich structure without significantly increase its mass [2]. A particularly interesting application is the use of foam-cored sandwich panels in impactresistant design. Impact loads primarily produce out-of-plane strains, which are largely dependent on the core material rather than the skins. This has led to an extensive body of research focusing on the properties of core materials for impact applications [3]. One of the primary challenges in this field is developing foams with exceptionally low density while retaining mechanical performances, as density and mechanical properties are typically inversely related. A promising approach involves using in-situ expandable reactive foams, which allow the alveolar structure to form directly during the manufacturing process, rather than assembling pre-formed cores with the skins. However, these materials are particularly challenging to manage because the foaming and solidification steps are highly dependent on processing conditions. This method offers advantages such as tunable manufacturing processes and the ability to incorporate specific fillers and short fibers, enhancing the mechanical properties of the foam. Additionally, it enables the integration of outof-plane stiffening elements directly during processing, which can further improve the structural response of the sandwich panel. However, the integration of expandable cores within composite structures remains particularly complex, highlighting the need for further innovation in both manufacturing techniques and material design.

Publié le 17/11/2024