Composite molding handbook (hand lay-up)

The molding or hand lay is the easiest part of preparing a fiber reinforced method. The process is carried out in a duly conditioned open mold (polished and release agents). The resin used is mixed with a catalyst or hardener, otherwise, curing may take days or even weeks. Then the mold is wetted with the mixture by pouring or brushes (initially can be applied a layer of gelcoat in the mold, which gives a better finish to the finished part). The sheets of glass or carbon fiber is placed over the mold and set in the mold with steel rolls.

Placing reinforcement

The material must be compacted firmly against the mold, air must not be trapped in the middle of the fiberglass and the mold. Additional resin applied and possibly additional fiberglass sheets. The resin and fiber is usually 60 to 40 by weight, but varies by product. The resins used are of low viscosity, in order to improve the impregnated fibers. The rolls are used to make sure all the resin layers between which the fiber is wetted throughout the thickness of the laminate and that the air bubbles are removed. The work must be done quickly enough to complete the job before the resin begins to cure.

Compacted by rollers

Can achieve different curing times by altering the amount of catalyst employed . It is important to use the correct amount of catalyst into the resin to assure proper curing time . A 1% catalyst is a slow cure , 2% is the recommended ratio , and 3% give rapid cure . The addition of more than 4% may result in the resin to cure before terminating the application. Optionally and to complete the process , a weight is applied from the top to expel excess resin and trapped air . Buffers are used ( such as coins ) to maintain the thickness because, otherwise , the weight may be compressed beyond the desired limit. By using cutting tools are removed excess material at the edges ( before curing ) . Once cured, the material was the demolding of the part. If required the workpiece can be adjusted to the final shape by a cutting process ( shaping, grinding , drilling , cutting, etc. . ) To give the tolerance to the piece finish . The pieces can be painted or lacquered ( in general, when not used gelcoat ) .

Process scheme

A variant consists in applying hand molding reinforced resin layer to a preformed core, generally of polyurethane foam. In this process, no mold is used as the core and having the form of the finished product. The outer composite laminate confers rigidity to the part while the polyurethane core makes it is very light. An example of this method is the molding of surfboards. Upon completion of applying the reinforcement and resin, the entire assembly is wrapped tightly in a PE film and a vacuum is applied, to compact the reinforcement against the core and eliminate bubbles. Subsequently, the PE is removed and get the finished product.

Carbon Fiber Fiberglass Aramid Fiber
Cores: Any (regular: polyurethane foam, honeycomb type panels, balsa wood)
Bee nest Core Polyurethane Foam Core
Typical applications manual molding composites are manufacturing wind turbine blades, boat production, architectural moldings, panels, bodies, molds, tanks, etc..
Part: container Part: of the bus