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Aviation is under constant threat from the risk of explosive devices onboard commercial planes. Terrorists have proven that they might be able to circumvent security scans both by carrying explosive devices on board themselves, hidden in a piece of luggage, or by sending parcel bombs via mail. Security scans are essential and very efficient, but the risk that dangerous items would arrive undetected inside a commercial aircraft cannot be completely neglected, as past events have proven.
American and European airports are, nowadays, on alert over fears that terrorists would be plotting attacks using “human bombs,” improvised explosive devices that could be assembled onboard from liquid explosives and non-metallic detonating devices, or could be surgically implanted into would-be bombers or hidden in electrical devices or clothes (e.g., shoes) with little possibility of detection.
Since 2009, Al Qaeda and its affiliated groups have unsuccessfully plotted at least three attacks with bombs carried on board US bound flights by its operatives or planted in cargo. One was foiled by passengers who overpowered “Underwear bomber” Umar Farouk Abdulmutallab, after his trousers caught fire on a flight from Amsterdam to Detroit. Al-Asiri was believed to be behind the attack. He also designed the powerful bomb hidden in printer ink cartridges which was intercepted at a UK airport en route to the U.S. in 2010, where it was timed to detonate over the east coast (Lyons & Bucktin, 2014).
A further threat that must be taken into account is that of unfaithful security personnel: on August 24, 2004, two airplanes exploded in mid-air shortly after their departure from Moscow Domodedovo airport, killing all 89 onboard. Investigations found that the two suicide bombers were able to bribe personnel at the airport to let them onboard without scanning (NEWSru.com, 2006).
At present, quite rightly, a lot of effort is focused on prevention. However, this alone cannot secure full safety from an explosive device getting on board, as instances testify this. A way to increase air transport safety against these types or risks is of providing complementary protective structures for the cargo hold and passenger cabin areas within an aircraft, which would be able to attenuate the effects of an in-flight explosion. Existing solutions for blast containment, based on phase-changing materials or thick reinforced plates, have considerable drawbacks (weight, cost, and bulkiness) which have prevented their wider diffusion. On the contrary, technical textiles, combined in an innovative way and with addition of functional coatings, can represent an effective solution. Considering this field of research, the European Commission (EC) co-funded the collaborative project FLY-BAG, which are “Blastworthy textile-based luggage containers for aviation safety” and is state-of-the-art for blast mitigation solutions for the protection of civil aircraft (narrow-body; Community Research and Development Information Service, 2012).
The idea beyond FLY-BAG was to use a textile envelope as luggage container, where an internal high strength layer made of ballistic textiles is designed to stop hard fragments from the blast, coupled with an external layer designed to deform in a controlled way during the explosion, fully containing the blast pressure. In particular, the focus of the project was to validate the applicability of the developed prototypes within their destination environment. Also thanks to the presence within the project Consortium of the airline Meridiana, it provides support and guidance on compliancy with aviation procedures.
The project team designed, manufactured, and successfully blast-tested a luggage container based on a multilayer textile structure (see Figure 1), coupled with composite sandwich elements used to protect those areas of the airframe which are in direct contact with the container. The composite elements have the twofold function of spreading the impulsive blast load over a larger area of the textile bag and of contributing to energy absorption by crushing of the foamy core (Zangani, Ambrosetti, Bozzolo, Dotoli, et al, 2011; Zangani, Ambrosetti, Franitza, Illing-Guenther, & Koenig, 2010; Dotoli, Bozzolo, Fay, & Bardaro, 2010).
Figure 1. FLY-BAG prototype for narrow body aircraft