Experimental activities in the structural field consist primarily of research into the robustness of design solutions under static and dynamic loading and the validation of numerical solutions to complex problems. Computer-controlled servo-hydraulic testing machines are used to load test pieces and actual structural components to the load values encountered in operational service. A range of experimental techniques, such as ultrasound, x-ray, eddy current, laser interferometry, strain gauges etc., are used to verify component stress distributions and to study in detail the origination and propagation of defects. Results are used for the detailed design of test objects, for example the choice and design of mechanical bolt fastenings, verification of the computation data, and as a step in the certification work for new aircraft.
Special activities, such as firing at loaded wing structures containing tanks filled with liquid resembling aircraft fuel, can be carried out at FOI for the purpose of studying the occurrence and repair of weapon damage.
The material characterisation of typical aircraft materials, such as high strength aluminium alloys, titanium and ferrous alloys as well as a range of composite materials, is also carried out in FOI’s laboratories. In particular, the basic mechanisms involved in damage initiation and propagation under operational loading conditions are studied. The results are used as fundamental input data in computational models for verification of the structural strength of the aircraft as a whole.