A flight approved system for FBG interrogation for Structural Health Monitoring (SHM) will be developed and tested. The design of the new system is revolutionary (light weight, compact and solid-state). SHM includes all monitoring aspects which have a direct link to structure integrity. SHM offers reduced cost of ownership through condition-based maintenance, extended service life (Fatigue Life Assessment), and reduced risk of failure. Automated inspection means time savings and a reduction of the Human Factor.
Fibre optical systems are lightweight, small, and easy to integrate into/onto composites and other materials. Due to the fact that many sensors can be integrated into one optical fibre, the sensor network becomes much simpler when compared to electrical sensor networks. Fibre optical sensors are EMC insensitive and safe. These sensor systems can be used for predictive health monitoring and realtime monitoring during flight.
SHM and impact detection for primary aircraft structures
High-speed, synchronous interrogation using multiple fibre bragg grating sensors enables design and delivery of robust inspection and analysis systems. The increasing use of thermoplastic carbon fibre-reinforced plastic (CFRP) materials in the aerospace industry for primary aircraft structures, such as wing leading-edge surfaces and fuselage sections, has led to rapid growth in the field of structural health monitoring (SHM).
Second Test Flight
TFT-FOS and the Dutch National Aerospace Laboratory (NLR) made a first successful flight test with the Deminsys C interrogator on October 24th 2008. This first flight was performed with the PH-NLZ test aircraft, a Fairchield Metro II twin turboprop aircraft with pressurised cabin. It demonstrate the initial feasibility, or Proof of Concept, of the FBG sensor technology and especially the Deminsys interrogator for use in an aircraft environment.
First Test Flight
Technobis Fibre Technologies and the Dutch National Aerospace Laboratory (NLR) made a first test flight with the Deminsys optical fibre measurement system using the NLR test aircraft PH-NLZ on October 24th 2008. The NLR’s PH-NLZ test aircraft is a Fairchield Metro II, a twin turboprop aircraft with pressurised cabin. The PH-NLZ is equipped with independent electrical circuits and has special adaptations and accommodations for testing of measurement equipment and sensors.
Over the last 9 months, a complete redesign of Deminsys electronics and firmware has taken place. The first stage of the process involved collecting requirements from various sources. It soon became clear that it would not be feasible to incorporate all of the elements suggested, and so a clear set of requirements was selected. It was agreed that the remaining requirements would follow at a later stage, with a particular customer or clear roadmap as guideline.
Damage identification with optical fibres in composites
During the last year considerable effort has been put in the application of optical fibres with Fibre Bragg Grating sensors for damage identification in composite structures. This is a collaboration between TFT-FOS, the National Aerospace Laboratory (NLR) and the University of Twente.
Aircraft require regular costly inspections to guarantee their safety. This currently mainly relies on manual non-destructive inspection methods.
During the last century, a lot of research has been dedicated to more automated systems called Structure Health Monitoring (SHM), which consists of a network of sensors to detect changes in the physical and/or geometric properties of a structure from data gathered at two different states, a reference state, considered as the undamaged state, and the current state. Changes can be caused by damage present in the structure. SHM techniques can be operated on-line during the flight or off-line on the ground and can be focused on global inspection of large surface areas or on local inspection of highly critical areas (hot spots). The main objectives of SHM are to reduce the cost of ownership and to improve the system operational availability.