Overview
Evonik proposed to contribute to the evaluation of the strength of foam sandwich structures, as demanded in the Call for Proposal (CfP), by providing a failure criterion, which has been designed specifically for ROHACELL® foams in cooperation with the German Institute for Polymers (DKI) in Darmstadt. This criterion had been proved to deliver very accurate results in static FE calculations and might be used as a basis for extension to calculate impact and fatigue loads.
Evonik has profound knowledge and experience in the field of manufacture and supply of raw and shaped foam core materials meeting the requirements of the aerospace industry, which Evonik proposes to supply as demanded in the CfP. Evonik has the facilities to produce raw foam cores as well as to shape these cores to the desired geometry, e. g. by using cutting and CNC machining equipment. Furthermore Evonik possesses the infrastructure needed for the quality control and documentation which is mandatory for aircraft applications. ROHACELL® foams offer superior heat and pressure stability up to 180°C and 7 bar as well as a one hundred percent closed cell structure, which eliminates excessive resin absorption and thus reduces overall weight. Evonik possesses an autoclave, which is proposed be used for the manufacture of sandwich panels, e.g. using prepreg face sheets. Evonik proposed to contribute to the development of special design rules considering SHM-requirements, as demanded in the CfP.
Funding
Results
Executive Summary:
The goal of the project was the design and manufacture of carbon fibre reinforced plastic (CFRP) sandwich structures with embedded Structural Health Monitoring (SHM) sensors. This goal was reached.
Suitable ROHACELL foam cores were designed and machined. An autoclave was used to manufacture demonstrator parts. Fibre optical bragg gratings (FOBG) were chosen as SHM system, the demonstrator parts were designed as profile stiffened shells with foam-filled omega profiles. The performance of the FOBG in the cured demonstrator parts was shown.
It was concluded that the implementation of SHM systems in profile stiffened shells is feasible. SHM systems integrated in structurally loaded aircraft parts can lead to a significant reduction of safety factors, thus reducing weight and decreasing fuel consumption. Furthermore SHM systems would allow for a reduction of maintenance effort.
The project consortium consisted of the single member Evonik Röhm GmbH, Kirschenalle, D-64293 Darmstadt.