Why Prepreg Tooling is a Reliable Choice for Composites Processing
In composites manufacturing, a prepreg can be any combination of fabric or fiber reinforcement that is impregnated with a type of resin. At CAMX 2021, technical experts from Composites One demonstrated prepreg processing using an epoxy prepreg with a carbon fiber woven product.
The Technical Team discussed how prepreg is manufactured and demonstrated the use of prepreg materials in the production of parts. First, the product is rolled up and stored in a freezer to slow down the chemical process for storage and to ensure shelf life. Prepregs are cured with pressure and heat, either out of an autoclave under atmospheric pressure in a vacuum or in an autoclave with intense pressure applied. While there are various temperatures and rates to cure at, the demonstration showed a variable temperature cure.
Why use prepreg for tooling?
Prepreg is the most reliable way to control the variables that are involved in composites production, including the resin content, which is typically around 40% for structural composites. Prepreg also enables control of the thickness of the laminate with an even distribution of resin throughout the prepreg.
What should you consider when choosing material for composite tools?
It is critical that the tool has excellent dimensional stability. This is important at room temperature as well as in the curing cycle. As you apply heat, parts will expand, which is known as coefficient of thermal expansion (CTE). Composite materials, like prepregs, are good tooling materials because the CTE match between the tools and parts enables more precise composite parts.
As you cure parts in oven or autoclave, it is important to keep a uniform consistent temperature throughout the part and the tool itself. Product data sheets will typically include a ramp rate, or how fast you can heat the product to keep an even temperature throughout as it is curing. You should also consider the part thickness, which affects heat capacity. Thicker products will require more heat to reach the required temperature.
Aerovac process materials play a significant role in prepreg tooling
There are many manufacturing and supply process materials used in composites production. Aerovac provides innovative process materials like the Quick Draw vacuum bagging film, which is used in the CAMX video demonstration. The film goes down quickly and without the need for a breather material.
Vacuum bag material is used specifically for debulking multilayer prepreg parts. It is embossed to allow the air to exit through a valve while flattening the material and extracting air. Other consumables used in a prepreg layup against the tool include peel plies, breather material, vacuum bags, and sealant tape, all available from Aerovac and Composites One.
There are many choices to make in composites production when it comes to prepreg tooling. Composites One is here to guide you through the decision-making process from product selection to the successful manufacturing of parts.
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