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Boeing's 787 Dreamliner uses composites for various airframe components.  (Source: Boeing)

UV Light Shows Resin Bleeding into Fracture  (Source: Gizmag)
Future composite aircraft could have a circulatory system filled with the resin

Miniscule cracks and flaws in the airframe of commercial and private aircraft can lead to catastrophic failure of the aircraft leading to loss of life and property. Commercial airlines routinely inspect their aircraft for damage and issues that could lead to an accident. The problem is that small cracks and light damage can be difficult to detect and impossible to see with the naked eye.

Aerospace engineers from Bristol University have developed a new method to complement routine visual inspections of commercial aircraft made from composite materials such as the Boeing 787 Dreamliner.

The researchers have devised a way to fill the hollow parts of composite aircraft with a self hardening resin. When the airframe is damaged the resin would bleed out of the hollow spaces into the crack and seal the damaged area with enough strength to maintain flight and safely land. The engineers also say that future aircraft could have the resin moving continuously through a circulatory system built-in to the airframe.

The resin doesn’t return the airframe to 100% of its strength, but the researchers say that the resin would allow the damaged area to regain 80% to 90% of its former strength. The process used by the engineers is likened to the process the human body uses to heal after a cut. In the body, blood leaks into the damage tissue where platelets form clots to stop bleeding and a scab forms to aid in healing and protect the area. In the engineers system the resin is the blood and the hardened resin is like a clot and scab protecting the area.

The resin the engineers propose to use would have a blue color allowing ground crews to readily identify areas where the resin has affected repairs to small areas of damage. Project leader Dr. Ian Bond said, “This approach can deal with small-scale damage that’s not obvious to the naked eye but which might lead to serious failures in structural integrity if it escapes attention. It’s intended to complement rather than replace conventional inspection and maintenance routines, which can readily pick up larger-scale damage, caused by a bird strike, for example.”

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By Amiga500 on 5/31/2008 8:14:34 AM , Rating: 2
Interesting work.

I'm not quite sure how they intend to get the resin to the target area though.

Typically failure of composites will be within the composite, and is characterised by delamination of the laid-up layers - this is usually the result of a surface impact event.

That is why composites must undergo a lot of ultrasound and similar NDT analysis when on aircraft as by definition, the "cracks" within a composite cannot be detected using visual inspection.

Ok, so, it is proposed to have a liquid resin within the... structure... I guess, that can be transported to the delaminated section.

1. How does it know where the delaminated bit is? Does the resin have to be stored under pressure?

2. How does it get there?

3. What is the hardening mechanism once it gets there - and what stops it hardening before it gets there?

4. Fundamental to the strength of composites used on aircraft is the manufacturing process required when making the part. This resin will not be bonding under pressure, and the strength of its bonding between the layers will be minimal at best. I am highly skeptical of recovering to 80% or 90% ultimate tensile strength.

5. Since the failure is within the composite, and the repair will also be within the composite, no blue dye will be visible on the component surface.

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