Tools of the Trade
All composite shops, small or large, need a basic selection of tools. For most hand layup projects, you need tools for mixing, cutting, and laying. Other processes require more specialized tools, and I'll be discussing those in a future column. For this week, we'll take a look at the most common tools almost every shop should have.
Most of the tools mentioned below can be purchased from an online Catalog seller. Prices vary widely, so do some comparison shopping.
Mixing
Unless you're working with prepregs, you will need tools for mixing resins. Your most expensive purchase will be a scale for weighing resin components. Most shops use an analytical balance accurate to 0.1 or 1.0 g. Get a clear plastic cover to protect the balance from spills. Mechanical balances or scales will also work, but the analytical balances are faster. Most lab supply companies have a good selection of balances, or look for a dealer of used equipment.
You can also get special mixing pumps which can be set for specific mix ratios. These are good for mixing large quantities of a few resin types, but they require more cleaning and are less flexible than balances.
Of course, you also need mixing containers and tools. Unless you're dealing with large quantities of materials, paper or metal buckets and wooden sticks work just fine. You can buy these from any of the composite suppliers, but you'll get the best price at a place like Home Depot or a warehouse club.
Cutting
Cutting tools are fairly simple, and in most cases you can use the same tools for both prepregs and dry cloths. A good pair of scissors is essential for either type of material. These you should buy from a composite supplier, because ordinary shears will wear out quickly. You will need one pair for Kevlar and another for glass and graphite. A decent pair will cost between $15.00 and $30.00, but you may want to splurge for a $60.00+ pair of ceramic shears for cutting Kevlar.
Rotary cutters (they look like pizza cutters) are also available. I haven't used these myself, but they are supposed to work especially well on dry fabrics. For prepregs, an ordinary carpet knife or razor blade will work well. They will be dulled quickly by Kevlar, but the blades are cheap, so you can afford to replace them often.
For any of these cutters, you will also need a cutting surface. Self-healing mats are very nice but expensive. A large sheet of plastic (like a kitchen cutting board) works fine, but the surface will become rough with scratches after a while.
Laying
Once you have your material cut and the resin mixed, it's time to layup the part. If you're working with prepreg, you place the composite on the tool and compact it. The best tool for compacting is a thin (3/8 in or so) teflon block with a rounded front end. Simply rub the block over the laminate to compact the ply.
For wet layups, you need to work the resin into the dry fabric, and at the same time remove any trapped air. Simply pour the resin onto the fabric and press it in using a plastic squeegee (they look like yellow paddles). If you press too hard, you may distort the fabric. You can buy squeegees from any composite supplier, but most automotive stores also sell them.
You can also work the resin in using a roller of some type. Fibre Glast, for example, offers over one dozen different types of rollers. Stippled rollers help to remove trapped air, and curved rollers can be used on curved parts. Smooth rollers can also be used for compacting prepreg. Personally, I like to use a squeegee to start, because it spreads the resin faster and removes excess resin. I then use a roller to remove trapped air.
Miscellaneous
Many suppliers offer mixing kits which include an assortment of squeegees, rollers, brushes, gloves, buckets, and sticks. These can be a good deal if you need small quantities of these materials, or you want to try a variety of tools. However, it will still usually be less expensive to buy from a local store (automotive, hardware, or warehouse club).
Squeegees and mixing buckets are disposable, but you'll want to keep your other tools clean. Solvents like acetone or alcohol, available from stores like Home Depot, work best. For large quantities, go through a chemical supply company. These solvents are considered hazardous waste, so be sure to dispose of them properly. I've tried Simple Green, but it just doesn't dissolve resins.
Resins themselves are hazardous, but only in their uncured state. Let any unused resin cure in its mixing container (along with the squeegees), then dispose of it like any other non-hazardous material.
Finally, you will want to protect your hands when working with uncured resins (either mixed or prepreg). Resins are a skin sensitizer, which means that you will eventually become allergic to them if you handle them. There are many other hazards associated with resins, so be sure to read the Material Safety Data Sheet (MSDS) for the particular system you are using.
For your hands, simple latex gloves work fine for most cases. Buy them in bulk from a hardware store or lab supply company. Lined gloves are more comfortable, but also more expensive. Avoid powdered gloves because they will contaminate your layups. Also, latex dissolves in acetone, so these won't protect you during cleanup.
Prepregs are usually tacky. Plain latex gloves will stick to the prepreg, making it difficult to work with the material. Also, the fingertips will eventually tear off. Thus, I prefer to use the Layup Glove from Comasec Safety (800-333-0219). The glove is lined for comfort, the material is thicker for strength, and the surface is textured for so it doesn't stick easily to prepregs.
Finally, you can purchase protective hand creams. I don't have any experience with these, but they are supposed to protect your hands if you should come in contact with epoxy.