The largest number of reinforced plastics composite products are produced by the hand lay-up process. A few examples of this processes uses are: boats, portable toilets, picnic tables, car bodies, diesel truck cabs, hard shell truck bed covers and air craft skins and interiors. The hand lay-up process is labor intensive plus the plastic resins produce toxic fumes requiring well ventilated facilities and protective equipment for workers. And, since the workers seem to want to be paid more when around toxic things, they may want more pay.
The hand lay-up process produces parts from an open, glass reinforced, mold. The mold surface is treated with several layers of release wax and then spray coated with a pigmented polyester resin called a gel coat. The surface of the mold will be duplicated by the gel coat. Over the gel coat, glass fiber is layered. Each layer is saturated with polyester resin that is specifically formulated to cure at room temperature. The polyester resin must be catalyzed 2% by weight. The catalyst is a toxic and corrosive peroxide. Each glass layer is pressed by hand with rollers to work the polyester resin into the glass fiber. Three to nine layers are added and allowed to cure depending on the desire strength of the part. Once the polyester is cured, the part is removed from the mold. The part requires trimming and post mold surface preparation. In the production of the high performance airplane, both carbon fiber and epoxy plastic are used.
Hand lay-up parts can consist of any size or configuration. Moreover, the process does not require any special tools. Parts can be easily fabricated as a weekend backyard project. Molds can be easily modified, cut into part for prefabrication and applied to create various surface textures. The rigid properties of the final product require that under cuts and straight wall be eliminated. Any openings must be machined in post molding operations. All corners must have somewhat large radius. The structure is often stiffened with the additions of honeycomb, balsa or rigid foam blocks.
Composites are one of the strongest materials around. When you consider the density of the material, composites are much stronger than most other building materials. It’s no surprise they are the material of choice for everything from airplanes to automobiles.
Composites materials are both strong and light. That’s a winning combination. Who wouldn’t want to work with a material that’s simple to ship and carry? Lightweight composites can save you money and manpower.
Products made from composites provide long-term resistance to severe chemical and temperature environments. Composites are often the material choice for outdoor exposure, chemical handling applications and other severe environments.
Composites pack a powerful one-two punch with their ability to be molded into complex shapes at a relatively low cost. This offers designers, engineers and architects a freedom not typically found with other competing materials.
Composite structures have an exceedingly long life span. Combine this with their low-maintenance requirements and composites become the material of choice for a host of applications.
- Widely used for many years.
- Simple principles to teach.
- Low cost tooling, if room-temperature cure resins are used.
- Wide choice of suppliers and material types.
- Higher fibre contents, and longer fibres than with spray lay-up.