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Eschen, Henrik
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Local Weakening of Honeycomb Core for Improved Surface Quality and Bonding in Co-cured Sandwich Panels

Hamburg University of Technology-Henrik Eschen, Thorsten Schüppstuhl
  • Technical Paper
  • 2019-01-1859
To be published on 2019-09-16 by SAE International in United States
Sandwich panels made of NOMEX honeycomb core and fiber reinforced face sheets are a major component of aircraft interior parts. A common way to locally increase the strength of such panels, e.g. for load introduction, is the local thickening of the face sheets with additional prepreg layers. Curing of such strengthened panels without further processing of the core leads to higher flatness tolerances due to the added thickness as well as residual stresses. Machining of the core in the strengthened areas is possible, but expensive due to high machine costs and additional cleaning processes. In this paper a new automated process for the reduction of the residual stresses in strengthened areas is presented. The process is based on a local reduction of the compressive strength in the surface area of the honeycomb core, which allows for a plastic deformation in thickened areas at curing pressure. For the reduction of compressive strength, a concept based on a robot guided tool with multiple parallel blades is presented. A model based analysis of the process parameters shows that…