The DEMONSTRATE research program comprises some critical research activities, which primarily involve:
- The special design of the proposed test bench, which enables the reliable application of the fully representative tension / compression, bending, torsion and shear loads, simultaneously with pressure differential loads, at a cost and time efficient manner,
- The development of a virtual test methodology and an optimization algorithm to define loading and boundary conditions for the stiffened panels testing, which are fully representative of the full fuselage section in flight.
- The application of advanced metrology and non-destructive inspection equipment, comprising advanced full-field DIC methods (i.e. acoustic cameras, high accuracy IR cameras, Acoustic Emission techniques, etc)
- The development and validation of advanced FE models, both for the metallic and the thermoplastic panels, which will also include the main test rig components, in order to enable the fit-for purpose adaptation of the test bench.
The overall project comprises two core concepts, i.e. the “advanced test bench design, manufacturing and instrumentation” and the “advanced simulation methodologies” concepts, which are supported by a number of satellite concepts, namely the “Loads Definition at panel level”, “Digital Image Correlation”, “Novel damage detection”, Absolute Accurate methodology”, “Simulations Validation” and “Fatigue Spectrum” concepts that are adopted to address the project objectives.
a) Definition of test boundary and loading conditions at panel level
In order to de-risk the development process and enable almost right first-time designs, novel fuselage structural concepts are validated at a lower level of the test pyramid, i.e., at the level of a typical fuselage panel, which should include all critical and complex structural features of the fuselage barrel. Such experimental campaigns at the stiffened panel level include quasi-static testing at various loading combinations up to ultimate load final failure, as well as fatigue tests at loading conditions representative of the operational conditions of the selected aircraft flight profile.
To achieve this ambitious goal, the DEMONSTRATE concept is based on the virtual testing at both the “full-scale fuselage barrel” level, as well as the “curved stiffened panel” level. Detailed simulations of the physical tests of both the “fuselage barrel” and the “stiffened panel”, considering all crucial features of the test rig, will be performed using detailed Finite Element (FE) models.
b) Advanced test bench design and manufacturing concept
An innovative approach will be followed for the design and realization of the boundary and loading conditions to simulate the behaviour of a complete fuselage, despite having a curved segment of the full cylinder.
An innovative testing concept is suggested in DEMONSTRATE, using two distinct functions of the dummy structure:
- Pressure introduction at the inner side of the panel by an air-pressurized chamber.
- Replacement of missing fuselage section stiffness by a simple and adaptable bar structural assemply.
