Manual layup

Preliminary studies on the microwave curing of a polyester resin and composite material used in marine yacht industry showed that the microwave curing was an alternative method for the faster processing of laminated materials for structural applications. Laminates (10 cm x 10 cm) made by three layers of fiberglass and polyester resin were prepared by manual layup and cured under a microwave irradiation power output of 1800 W. When the samples were heated less than ll-12s, the... 

In noncontinuous hopper feeders or modern continuous metering hoppers, a high mixing precision with an error margin of less than 1% can be achieved. Blending by manual layup or with automated bale-reduction systems is less precise. 

The labour-intensive nature of the manual ply layup procedure both in terms of implementation and inspection to guarantee quality of the component... 

The ATL and AFP processes are thus a cross between filament winding with its elaborate automated patterns of fibre laydown and unidirectional prepreg layup with its reliance on the autoclave. The use of automated robotic machinery for the layup gives increased layup speed (vital to economically manufacture these large items in feasible timescale), consistency and freedom from errors compared with manual techniques, as well as ensuring precision in the placement of the tows and tapes. 

Manufacturing methods for composites vary from manual to fully automated processes, whereby the latter have better quality control than the former. Wet layup, pultrusion, and filament winding are all discussed in some detail, while other techniques such as pull-winding, resin transfer moulding, vacuum bag moulding, and injection moulding are left to specialized composite materials texts. 

Wet layup is a manual method in which the dry fabric, or mat fibres, are first laid onto the substrate or mould. Resin is then applied and rolled evenly over the surface to remove air pockets. This is repeated to obtain the required number of layers. The fabric can be pre-wetted before laying to allow for a better fibre/matrix ratio control. 

Hand layup. The oldest method is a purely manual operation. (1) The open female mold is first treated with mold release. (2) Optionally, a pigmented gel coat is applied 15 to 20 mils thick and partly cnred. (3) Glass fiber mat, or woven or knitted cloth, is hand-laid into the mold or onto the gel coat. (4) Thixotropic polyester/styrene liquid, containing MEK peroxide and activator, is impregnated into the cloth. (5) The assembly stands and cures at room temperature. This gives a product with one good surface and somewhat irregular thickness. 

Hand Layup (Contact Molding or Open Mold Process). The oldest and simplest technique is primarily manual. An open mold is waxed to lubricate it. The surface of the proposed product is applied to the mold, usually as an unreinforced gel coat or sometimes as a thermoformed plastic sheet. A layer of fabric is hand cut and hand laid into the mold. Catalyzed resin is poured over the fabric and worked into it with brush, roUer, and squeegee to eliminate air bubbles. Another layer of fabric is laid over this, often oriented in a specific direction to optimize properties. Again, catalyzed resin is poured over it and worked into it. The process is repeated as many times as required to build up the desired thickness and optimum orientation of the layers. If the cure reaction is inhibited by air, a wax may be dissolved in the resin it exudes to the surface and forms a barrier to exclude air and permit complete cure. The resin may be allowed to cure at room temperature, or the assembly may be heated to complete or hasten the cure reaction. 

Hand Lay-uplSpray up Spray up and open contact molding (hand lay-up) in one-sided molds is one of the cheapest and most common process for making fiber composite products. Typical products are boat hulls and decks, truck cabs and fenders. In a typical open mold application, the mold is first waxed and sprayed with gel coat and cured in a heated oven at about 49°C. In the spray up process, after the gel coat is cured, catalyzed resin (usually polyester or vinyl ester at 500-1,000 cP viscosity) is sprayed into the mold, along with chopped fiber. A secondary spray up layer imbeds the core between the laminates (sandwich construction). Then it is cured, cooled, and removed from the reusable mold. In hand layup processing, continuous fiber strand mat and other fabrics such as woven roving are manually placed in the mold. Each ply is sprayed with catalyzed resin (1,000-1,500 cP) and the resin is worked into the fiber with brush rollers to wet-out and compact the laminate. 

Lay-up method and tools Lay-up method (manual automated) maximum layup speed gap and orientation tolerances... 

UHMWPE fabric-reinforced UHMWPE homocomposites have also been investigated for orthopedic applications, but with mixed results [26, 28, 35], In a study by Suh et al.. Spectra 1000 fabrics were blended with GUR 415, resulting in a 60% fabric volume fraction [26]. The composite layup was produced manually by layering dry fabric sheets and powder in the mold. The authors noted lower wear of the fabric-based composite in dry, but not under bovine-serum lubricated, conditions in a unidirectional reciprocating wear tester [26]. 

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