Scientists Working to Improve Carbon Fiber Aircraft Repair

1. Scientists Working to Improve Carbon Fiber Aircraft Repair You're on your way to work when the car in front of you kicks up a pebble that flies into your windshield and cracks it on impact. The crack is pretty small, so it's no big deal. You call the auto glass company who comes right to your workplace and fixes the crack without having to replace your windshield. Wouldn’t it be nice if repairing damaged carbon fiber were that simple? Technology has gotten to the point where we can apply heat and pressure to fix minor cracks in windshields without sacrificing the integrity of the glass. We can even affect repairs to carbon fiber components in much the same way. But such repairs do not work very well on large pieces. Thus, what does an airline do when minor damage is detected in the body of a plane? Scientists at the Singapore Institute of Manufacturing Technology (SIMTech) are working on a system they say could lead to better on-site repairs to aircraft exhibiting minor damage. If their system proves successful, it will save airlines a ton of time and money. How to Repair Carbon Fiber Repairing carbon fiber is by no means new. It has been around for quite a while, and it has proven to be effective. The only problem is that current repair methods are not practical when it comes to something as big as a Boeing 787. Standard practice for repairing damaged carbon fiber is pretty straightforward. Technicians cut away the damaged carbon fiber, insert a wedge-shaped patch, add epoxy, and then put the part into an autoclave to cure. An autoclave is essentially a high-heat oven that removes volatile gases and cures the adhesive. This repair process works quite well. But you cannot build an autoclave big enough to house a commercial jetliner. And even if you could, exposing an entire airplane to that much heat over a prolonged amount of time would invariably damage it. So traditional repair processes just do not work well for jetliners. The Proposed Solution SIMTech is proposing a new repair process that utilizes double vacuum debulking to accomplish much the same thing that high heat autoclaves accomplish. The process is not yet ready for prime time, but scientists are testing it rigorously in Singapore. They hope to have a viable process ready to go in relatively short order.

2. The process starts with the same fundamental practice of cutting away damaged carbon fiber and gluing in a replacement patch. But instead of putting the entire airliner into an autoclave, this process involves placing a rigid box over the repaired area. Inside the box is a flexible vacuum bag that is subsequently placed over the patch. When activated, the vacuum bag removes the volatile gases that would otherwise make the carbon fiber material too porous to be structurally sound. Temperature inside the box is tightly controlled as well, allowing the patch to be cured in place. Highly Technical Work What we have described here is merely a simplistic overview of the double vacuum debulking process. In reality, it is highly technical work that requires the right combination of skill, knowledge, and technique. It is by no means something that just any composite fabricator can handle. SIMTech scientists are working with the best of the best in Singapore to figure this all out. They have let it be known that the industry needs to start training repair technicians in order to support the demand for repairs once their process is perfected. In the meantime, they will keep working to better understand carbon fiber repairs for the aviation industry.