A Green Solution in Out of Autoclave Manufacturing


by dewi susanti

Composite materials find applications in various industries right from the aerospace industry to automotive components to the manufacture of musical instruments. Composites are the perfect raw material for these manufacturing processes primarily because of their high strength to weight ratio. Autoclave curing is the most commonly used material for fabricating composites. However, of late, consultants have started recommending Out of Autoclave (OOA) processes for the same purpose. The reasons are the time and cost advantages and the ability to get autoclave quality materials outside the autoclave.

Out-of-Autoclave Alternatives to the Autoclave

1. Resin Transfer Molding (RTM):

It features a two-part, closed mold. The mold is made of metal mainly aluminum. Dry fiber reinforcement is placed into the lower half of the mold, following which it is closed and clamped. Epoxy or resin is pumped into the mold via injection ports under pressure. The low-viscosity, catalyzed resin spreads out and fills the mold, displacing the air in the process. After the initial layout the curing process starts with the heating of the mold. The resin polymerizes and forms the new compound.

Resin transfer molding is most suitable in the manufacture of light weight components that demand a high strength to weight ratio and low void content. It creates a smooth finish and is well-suited for the production of components with complex shapes and large surfaces.

2. Vacuum Assisted Resin Transfer Molding (VARTM):

Vacuum Assisted Resin Transfer Molding is the second of the autoclave curing alternatives. The technique is applied in the production of high-grade composites used for boat hulls, rail cars and turbine blades. The process is similar to resin transfer molding. The distinguishing point however, is that after the dry fiber reinforcement is laid out into the mold and the mold is sealed, it is vacuum bagged. A VARTM cure session dispenses with the use of high heat or pressure used in an autoclave or for that matter even in Resin Transfer molding. A vacuum is created between the reinforcement sheet and the preform to remove any existing air pockets. The process is relatively inexpensive and therefore the best option for mass production of composites.

Out of Autoclave Quality: Expect nothing less

Composite materials processed in a high pressure autoclave stand out for their superior quality. Hence, aerospace, marine and automotive industries always opt for an autoclave cure. If quality is what bothers you, the quality of composites processed outside an autoclave is at par with that of materials processed in an autoclave. The materials produced are of the desired fiber concentrations and free of voids trapped in the fabric. Out of autoclave methods are less expensive and faster. They dispenses with the need of pre and post processing steps.

Out of Autoclave: The Green Solution

Out of autoclave processing comes across as a very promising solution not only because of its cost advantages but also because of its eco-friendly nature. Greenhouse gases generated during industrial production processes are causing damage to the earth and global warming is just one of the repercussions. Unlike autoclave processing, out of autoclave manufacturing of composites keeps greenhouse gas emissions to the minimum. To add, energy consumption expenses are also a cost against a company’s profit. Out of autoclave processing for large scale manufacturing reduces energy consumption drastically. It shortens cycle times and reduces tooling costs. Thus, it’s win-win situation for the manufacturer.