Apparently a plane is a piece of metal which flies. But appearances many times deceive: Current aircrafts are not made of metal but of composite materials (glass and carbon fibers, honeycomb…) that are heated to high temperatures in an autoclave furnace and lead to very strong, lightweight and very expensive materials. Inevitably there are always parts that have to be made of metal, but it is intended to use strong and light materials in order to save fuel or transport more passengers/load.
Imagine you are an aircraft manufacturer and you receive a batch of composite parts (very expensive, as we mentioned before) and you suspect that some of them have defects. The first inspection you have to do is simply visual, i.e., check if apparently the piece has a defect. However, aviation sector is very intolerant with quality defects so you should subject them to different treatments to determine if they can entry or not to the manufacturing phase.
Quality tests are called “Material Testing” and serve to determine the mechanical properties possessed by these materials. Tests may be of two types: destructive and nondestructive. For obvious reasons we are interested in nondestructive tests to check if the piece can be used in the manufacturing process. Remarks:
- Liquid penetrant inspection (LPI): a special liquid is applied
to penetrate the cracks if any, then the excess of the liquid is removed and the defects are at sight. One of the most used is the fluorescent mode because they are more easily detectable when ultraviolet light is applied. - Ultrasonic testing: Very useful when we want to detect faults which cannot be seen. This is the case of detection of small air pockets that may appear at the time of forge of composites. These parts are formed from the overlapping layers of material, if placing a sheet over another remain some air, it could reduce the quality and therefore be fragile by the place where the accumulation is.
- Radiography test: As same as in hospitals with people, you can make radiographs materials to detect any anomaly.
The materials science applied to the aviation industry is very interesting because it is closely linked to the most advanced technology. The downside is that when the material price is very high it impacts on the entire value chain of the good that is being built.
Sources:
- “Desarrollo de un sistema de detección de fallas de materiales compuestos”, UFSC, Argentina, 2012.
- Personal compilation
Alfonso,
Tech For Space Editor