Tuesday, 1 August 2017

Autoclave or out-of-clave composites

Autoclave curing of structural composite components for aerospace applications is associated with some advantages that out-of-clave processing cannot deliver. This is why many people still prefer buying autoclave carbon fiber sheets and autoclave composites. However, the differences are minor as we shall see.

Nonautoclave curing has a knockdown factor for laminate properties such as the volume of fiber, and these are not realized with autoclave composite processing.

For instance, it is possible to achieve a 62 and 58 percent of fiber volumes with unidirectional fabrics and woven products respectively, while the out-of-autoclave process can achieve a 60 and 56 percent respectively. Thus there will be a 3 to 4 percent knockdown.

However, product quality should never be seen in the eyes of performance knockdowns; there is the overall weight, part count, manufacturability, processing time, surface quality and cost that must be included in this equation.

However, there has been a rise in autoclave component curing alternatives such as the VARTM. VARTM is a variety of resin infusion processes that are common in the marine, transportation and infrastructure markets.

The process involves laying up fiber reinforcements and core materials in one-sided mold and vacuum bagged.

Aero companies have been moving from autoclave composite processing, for instance using pre-preg materials to make aerospace grade parts. The resulting out-of-autoclave component curing turns out to satisfy the strict requirements for aerospace grade parts.

This has brought some doubt on the previous assumption that autoclave composite curing is superior. However, although some people claim that their out-of-autoclave products were much stronger, no difference exists when you test the weight, stiffness and safety history of these products and those produced in the autoclave composite processing.

In other words, for those needing out-of-autoclave and autoclave composites material, these two methods are just two different methods used to achieve similar results. What you should insist is a company that knows the processes very well and how to select the materials for each of the processes. However, you still can get products manufactured through autoclave processes.

This has been demonstrated in a number of tests even by renowned companies in the composite manufacturing area.