Making Your Own Prepregs
Composite materials that are used as reinforcements can be impregnated with resin ahead of time, are called prepregs. You use a prepreg in manufacturing different composite parts by cutting it out and laying it onto your mold, shaping as required. Since it has already been impregnated with resin, there are not any concerns with spreading the resin and curing agents on the dry materials while they are in the mold.
Pre-impregnated materials can be purchased from a composites supplier, or they can be made yourself. Woodward Aerospace shows us how.
Carbon Fiber Pipe Wrap
Carbon Fiber can be used to wrap the outside or the inside of pipelines as a way to reinforce and strengthen them. Carbon Fiber is lightweight yet extremely strong. It can be field-installed on pipelines that are clean and non-pressurized.
Repairs to pipelines can be extremely expensive if they need to be dug out of the ground, cut out, and replaced with new sections. This is time-consuming work requiring long shutdowns. Composites repairs can be accomplished by professionals that can access the work area and have a line that is non-pressurized and clean.
These carbon fiber reinforcements help to restore structural integrity that has been lost through age, damage, or other new design requirements. There are many advantages to repairing existing pipelines and other structures rather than replacement.
Interior repair from ABC 10 News in California demonstrates an interior pipeline repair:
An external pipeline repair is shown here in an instructional video. I do have a few concerns about the use of all of the unreinforced resin that is used to cover the carbon fiber wrap. I am not sure what the purpose there is, other than maybe to protect the carbon fiber from future damage.
Custom Fiberglass Speaker Boxes
Fiberglass materials allow for custom shapes and features. A very popular Do It Yourself project is custom speaker boxes for automobiles.
To accomplish this, it is important to begin with a solid foundation material. Very often this is wood, which allows for screwing and stapling. Next, the speaker mounts need to be properly attached. Orientation of the mounting surface is established for the speaker that will be used in the finished installation.
Fleece fabric material is one method that is used to span the surfaces and transition across the different areas. This material allows for smooth transition, holds staples, is easy to work with, and is inexpensive. Once it is in place it can be covered with resin and fiberglass to establish a solid surface. This can be sanded smooth and painted for full effect.
WestCoastCustomsTV demonstrates how the fleece is applied in the video below:
Compression Molding Large Vehicle Parts
Compression molding with composite resins can yield very durable, strong, and well-engineered parts.
Placing reinforcements (usually fibered glass) and resin in a heated metal mold before compressing it under high temperatures will result in a finished piece with very unique properties. The parts made in these matched metal molds have very repeatable properties, high strength to weight ratios, and are corrosion and chemically resistant. The parts can be painted, and have many positive design attributes.
Ashley Industrial Molding is a company that manufactures such parts. These large parts are made with compression and RIM molding for customer such as John Deere and Case tractors. They have a good video demonstrating their equipment, processes, and finished parts.
Making a Small Mold
There are many methods and materials that can be used for making a fiberglass composite mold.
I found a video from Eastbay Composites that demonstrates a method for making small molds in a very quick an inexpensive fashion.
As you see from watching this, the basic construction materials are tooling gelcoat and inexpensive bondo for the support structure.
This mold construction technique certainly has drawbacks, but also has several advantages. None of the materials required spray equipment, which is messy. Brushes are inexpensive and easily disposed. A disadvantage of this method is that surface finish might suffer from a lack of consistency on the coating thicknesses for the gelcoat and the release agents.
Using bondo as the support structure is quick and easy compared to glass and resin, but can cause problems as well. It is more likely to crack, and can warpage issues as it cures and may be hotter in some areas than others. Bondo may have some difficulty maintaining dimensional tolerance as it shrinks during cure. Industrial resins used to create molds have minimal shrinkage in their chemistry and are placed on slower to minimize heat from the chemical reaction.
For quick, inexpensive and easy parts, this method from Eastbay Composites may work well for you. What has not been discussed yet is that the mold model can be the most difficult part. Off the shelf items are easy, but custom ones may be difficult. Creating a shape or surface is time consuming and tenuous. After that is complete, you can make your mold and final production parts!
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