It’s an interesting concept when one thinks of composite materials. By now, you’re most likely somewhat familiar with—and may have heard about—the benefits that these combined materials, such as carbon fibers, can result in. Referred to as Carbon Fiber Reinforced Plastics (CRP), or simply “Composite” materials, this raw material has become wide-spread in civil aircraft after being used for years in the defense industry. And why not? The benefits are huge. Composite materials allow producing lightweight structures which in turn reduce fuel bills and emissions.
According to a 2014 report, Aerospace & Defense applications are now the largest consumers of carbon fiber (30% of demand) and generate 50% of global carbon fiber revenues.
Industry analysts expect an annual growth of between 8 and 13% for carbon composites revenue in the passenger aircraft segment and between 6 and 12% in the defense segment [source]. See Figure 1.
Figure 1: Development of carbon composite revenues in US$ million in A&D
New Processes, New Issues
There is a variety of processes used to manufacture composite materials:
Figure 2: CRP market share by manufacturing process (2013); view source.
Prepregs, which account for 37%, are reinforcement materials that are pre-impregnated (hence the term “prepreg”) with a resin. The prepregs are laid up by hand or machine onto a mold surface, vacuum bagged and then heated to typically 120-180°C /248-356°F.
Autoclaves and materials have a high cost, but because of the quality and lightness of the material obtained, prepeg layup with autoclave has been until now the primary choice for the Aerospace and Defense industry.
However, new materials bring new challenges. And one major challenge is the unexpected occurrence of defects during the manufacturing of these costly composite parts.
The prepregs require storage at a controlled temperature and present certain inherent problems (variability of the raw material, variability of the processing methods used for the prepreg rolls, sensitivity of the raw material to the prevailing temperature and humidity rate in the production environment, etc.).
As a result, up to 20% of the parts may exhibit defects such as porosity and delamination which, albeit invisible to the naked eye, are nonetheless present in the mass. These faults weaken the resistance of a part, and when there are too many such faults, the part is discarded. See Figure 3 as an example of a defective production process.
Figure 3: Example of delamination issue at a leading edge of a wing
Just as new materials require new production processes, so too are new IT systems required to manage the new level of complexity that is tied to this type of material – especially when faced with a 20%+ scrap rate! A great deal of production process tracking must be done to ensure each process has been completed appropriately, and accurately. And, considerable data must also be extracted to build intelligence that can help with continuous process improvement.
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