Local Weakening of Honeycomb Core for Improved Surface Quality and Bonding in Co-Cured Sandwich Panels

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 strengthened panels without further processing of the core leads to higher flatness tolerances 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 process for the reduction of the residual stresses in strengthened areas, as well as improved bonding between core and face sheets is presented. The process is based on local reduction of the compressive strength in the surface area of the honeycomb core, which allows for controlled, irreversible deformation at curing pressure. For the reduction of compressive strength, a concept based on a robot guided tool with multiple blades is presented. The process parameters impacting the compressive strength after weakening are derived based on a model based analysis. A testing tool was built, and a series of tests was performed, in order to quantify the impact and to select suitable parameters. It was found that the remaining compressive strength depends mainly on the cutting pattern, the blade distance and the cutting depth. A Further reduction of compressive strength was achieved by bending the remaining structures after the cutting process. In order to validate the process, surface flatness, as well as bonding strength between core and face sheets have been measured. In addition to the flat integration of a large amount of additional prepreg layers it has been found that the bonding strength increases up to 30% due to increased bonding surface of the honeycomb core

Flexible and automated production of sandwich panels for aircraft interior

The demand for aircraft interior equipment is constantly growing due to general increase of personal air travel, individualization of design and limited life cycles. This especially poses challenges to the manufacturing of sandwich panels as a main component of interior parts. The current processes need to adapt to the increasing demand for individualized parts in small batches. In this paper, we propose a concept for the automated production of planar sandwich panels consisting of NOMEX honeycomb core and fiber reinforced prepreg sheets. The concept consists of an optimized process chain, concepts for automated honeycomb potting and automated sandwich laying. A novel approach for modelling of the potting process is developed to ensure completely filled cells without air entrapment. Simulations and time analysis show the general feasibility and give a first estimation of achievable production rates. The conclusion of the paper outlines the focus of further research.The work presented in this paper is being carried out in projects funded by BMWi - Germanys Federal ministry for Economic Affairs and Energy

Automated installation of inserts in honeycomb sandwich materials

Threaded inserts are a standard connecting element for sandwich components, which are widely used for aircraft interior. Therefore, inserts are installed in large quantities. However, installation is mostly done manually. An automation of the insert installation process yields high potentials for cost savings, increased output and increased productivity. Tight joining tolerances, highly individual components and quality requirements, however, pose challenges for insert placement, component referencing and program generation. In this paper a system for automated installation of potted inserts is presented. An automation concept is developed based on an analysis of the inserts, sandwich components and joining tolerances. For validation the concept is implemented in a demonstrator. Achievable accuracy, the system’s robustness, as well as the joining process are examined. Further optimizations are discussed and future steps presented

Towards semi automated pre-assembly for aircraft interior production

The growing aviation market puts first tier suppliers of aircraft interior under great pressure. Cabin monuments, not only consist of various assemblies with a wide range of parts, they are also highly customized by the airliners. Historically grown, poorly optimized manual processes offer the required flexibility, but limit the production rate of the individual products. The aviation industry responds with an increased use of automation technology. Recent standardization and automation approaches for efficient manufacturing, lead to an increase in productivity of these low volume products. However, complementary approaches to increase the degree of automation during assembly of aircraft interior components are missing. To reach a higher degree of automation this paper presents a derivation of cabin specific assembly processes with a varying degree of automation. First the range of components and processes in pre-assembly is analyzed with respect to automation. Based on the analysis, components and processes are classified in standardized groups. Fully automated and flexible automation processes are introduced to develop a semi-automated system. Furthermore, the required flow of information is described. Discussion of the results shows that the presented solution allows a flexible pre-assembly of low-volume interior parts and sets a baseline for further digitalization approaches.Bundesministerium für Wirtschaft und Energie - BMW

Augmented and virtual reality for inspection and maintenance processes in the aviation industry

Maturity of augmented and virtual reality devices has considerably grown recently. As processes in the aviation industry are error prone and time consuming, efforts are made to implement these technologies to support human workers during inspection and maintenance. Nevertheless, varying process and device characteristics impede the selection of a suitable technology. A concept is presented to evaluate the potential of inspection and maintenance processes in the aviation industry regarding the use of mixed reality systems. Four different use cases are discussed applying augmented or virtual reality devices in an industrial context