Intro to Lay-up and Spray-up Molding 140

advanced composite

A composite made from specially formulated resins and high performance fibers. Advanced composites are used for applications that require a customized mixture of resins and reinforcements to produce specific properties in the composite.

autoclave

A pressure vessel that promotes faster curing through a combination of vacuum and heat.

binder

An ingredient used to bind together two or more other materials in a composite. Binders promote adhesion and cohesion.

bleeder

The part of a vacuum bagging system that absorbs excess resin.

breather

The part of a vacuum bagging system that allows air circulation throughout the assembly.

ceramic

A hard, brittle material that can withstand high temperatures and resist corrosion.

chopped strand mat

A sheet of material covered with discontinuous fiber reinforcements.

chopper gun

The part of a spraying device that chops continuous strands of fiber so that they may be sprayed on to a surface.

composite

A material that is made by combining a binding resin with small filaments of solid material. Composites have the strength of metal, the light weight of plastic, and the rigidity of ceramics.

compression stress

The internal load that a part is subjected to when a force squeezes or pushes down on it.

continuous strand mat

A sheet of material covered with long, continuous fiber reinforcements.

drape

A measure of the suppleness of a fabric. A prepreg must have an adequate amount of drape in order to be shaped.

extrusion

A molding process during which material is pushed or drawn through a die to create objects of a fixed cross-sectional profile.

fabric

Material made by weaving fibers together.

fiber

A reinforcing material whose length is greater than its height or width. Fibers are longer than whiskers or particles.

fiberglass

Reinforcement material made from extremely fine strands of glass. Fiberglass is the most commonly used composite reinforcement.

fiberglass reinforced plastic

FRP. A polymer that cannot be remelted or reformed once it has cured, due to a molecular process called cross-linking that occurs during curing.

filament

A long, thin, hair-like material. Filaments are combined to form fibers.

flexural stress

The internal load that a part is subjected to when a force causes an object to bend perpendicular to the object's long axis.

gel coat

The protective outer coating of a composite material.

hand lay-up molding

A manual molding process during which reinforcement in the form of a fabric or a mat is positioned manually into the mold and saturated with a resin.

initiator

An ingredient used to facilitate chemical reactions.

injection molding

A molding process during which resin is heated in a barrel and then injected into a mold by a reciprocating screw. The resin then cools in the mold and is ejected as a solid part.

lay-up molding

A manual molding process during which reinforcement in the form of a fabric or a mat is positioned manually into the mold and saturated with a resin.

load

The overall force applied to a material or structure. In a composite, the matrix transfers the load to the reinforcement fibers.

mat

A sheet of material covered with fiber reinforcements. Reinforcements can be discontinuous (chopped) or continuous.

matrix

The material that binds together the reinforcing fibers of a composite. The matrix is usually a viscous material that hardens to give shape to the composite part and to protect the fibers from damage.

metal

A naturally occurring material with high electric and thermal conductivity, luster, density, and strength. Examples of metal include copper, iron, nickel, and lead.

mil gage

A device used to measure the thickness of gel coat.

open molding

A molding process during which fibers are placed into a single-sided or open mold. Resin is added to the fibers until they are fully wetted. The resin is then cured.

openness

A measure of the open space between woven fibers in a fabric.

plastic

A synthetic polymer that can be molded and hardened into a variety of shapes.

polyester

A type of thermoset that is commonly combined with other polymers for numerous commercial uses. Polyester is light, strong, and resistant to weather and corrosion.

polypropylene

A type of thermoplastic known for being very lightweight.

polyvinyl alcohol

A water-soluble synthetic polymer used as a release material in open molds. Polyvinyl alcohol has excellent film forming, emulsifying, and adhesive properties and is resistant to oil, grease, and solvent.

pre-impregnated fiber

A ready-to-mold sheet of fiber reinforcement that has been preimpregnated with resin. Also known as a prepreg.

prepreg

A ready-to-mold sheet of fiber reinforcement that has been preimpregnated with resin. Also known as pre-impregnated fiber.

reinforcement

The part of the composite that provides strength, stiffness, and the ability to carry a load. In manufacturing, fibers are the most commonly used reinforcement.

release material

A substance that is applied to a mold surface to make it easier to release a molded part.

resin

A substance made from either synthetic or natural polymers and used for composite matrices. In essence, a resin is a polymer that has not been processed into its final form.

sealant

The part of a vacuum bagging system that adheres to the vacuum bag and creates an airtight assembly.

shear stress

The internal force that causes a material to slide against itself or its internal components.

spray-up molding

A manual molding process during which an operator uses a spray machine to simultaneously apply resin and chopped fiberglass strands to a mold.

strength-to-weight ratio

The relationship between a material's strength and its weight. To find the ratio, the strength of a material is divided by its density.

tensile stress

The internal load that a part is subjected to when pulled apart by an applied force.

thermoforming

A plastic shaping process that shapes heated plastic sheets around a mold. Thermoforming is a lower-volume process that produces detailed parts with close tolerances.

thermoplastic

A polymer in which the molecules are not cross-linked, or they are cross-linked to a weaker degree. A thermoplastic polymer can be reshaped or reformed by reheating the polymer.

thermoset

A polymer that cannot be remelted or reformed once it has cured, due to a molecular process called cross-linking that occurs during curing.

traditional composite

A composite that uses a relatively consistent combination of resin and fiberglass reinforcement. Traditional composites are low-cost and are processed by traditional methods.

vacuum bag

The part of a vacuum bagging system that forms an airtight seal over an entire assembly.

vacuum bagging

A type of compression molding during which a bag is placed over the mold and the vacuum compresses the bag and squeezes out any air or excess resin.

veil

A thin fiberglass fabric made of very fine strands. Veil is used to cover any exposed fiberglass strands on the composite and create a smoother surface.

vinyl ester

A type of polymer used in engineering composite resins. Vinyl esters have mechanical properties that are between those of polyesters and epoxies.

wetting

Applying a liquid to a solid surface. In composites, wetting allows the matrix to bond with the reinforcement.

woven roving

A thick, heavy fiberglass fabric made by loosely weaving large strands of fiber.