What is the definition of "sheet molding compound"?
SMC. A rolled-up sheet in which the ingredients are not mixed together all at once. Instead, a pre-mixed, pre-initiated paste of resin and filler is applied to a moving sheet of film onto which strands of fiberglass are applied.

Learn more about sheet molding compound in the class Intro to Composites 110 below.


Composites Training


Class Information
Composites Training Tooling U-SME classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and will take approximately one hour to complete.
Class Name:Intro to Composites 110
Description:This class covers the basic materials used to make composites, how composites are processed, and the applications of composites in various markets.
Prerequisites: none
Difficulty:Beginner
Number of Lessons:12
Language:English, Spanish
 
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Class Outline
  • Objectives
  • Engineering Materials
  • What Is a Composite?
  • What Is a Matrix?
  • Thermoset and Thermoplastic Matrices
  • What Is a Reinforcement?
  • Reinforcement Forms
  • Product Fabrication
  • Composite Processing Methods
  • Pros and Cons of Composites
  • Composite Applications
  • Summary
  
Class Objectives
  • Describe the different types of engineering materials used in manufacturing.
  • Define a composite.
  • Define a matrix.
  • Distinguish between thermoset and thermoplastic matrices.
  • Define a reinforcement.
  • Describe reinforcement forms.
  • Describe how composites are used in product fabrication.
  • Distinguish between different composite processing methods.
  • List the pros and cons of composites.
  • Describe composite applications.

Class Vocabulary

Vocabulary TermDefinition
adhesive bonding The joining of two or more materials with a nonmetallic substance such as liquids, drops, or gels.
aerodynamic Having a design that reduces friction and resistance.
alloy A metal consisting of a mix of two or more elements, one of which must be a metal.
applied force The energy or effort provided to a machine to perform work.
aramid A type of fiber with strong heat resistance that is used primarily in aerospace and military applications.
boron A metallic element having a marked effect on hardenability even in minute quantities.
bulk molding compound BMC. A molding compound that combines a resin, initiator, filler, and reinforcement into a block of sticky dough-like material.
carbon A non-metallic chemical element used in composite reinforcements.
ceramic A hard, brittle material that can withstand high temperatures and resist corrosion.
chopped Discontinuous pieces of fiber that have been cut into lengths of 1-3 in. (2.5 to 7.6 cm).
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 molding A molding process in which reinforcement is saturated with resin and subjected to pressure and heat to create a finished part.
compression press The machine in which compression molding takes place.
continuous Covering the entire dimension of a part without a break or interruption. Continuous fibers are used in mat and cloth reinforcements.
cross-linking The development of primary bonds that form between polymer molecules. Thermosets are heavily cross-linked, while thermoplastics are not cross-linked, or they are cross-linked to a weaker degree.
cured Having permanently cross-linked molecules. Curing occurs in thermosets when they are heated to mold.
cutting A machining process that uses a tool to create chips and remove metal from a workpiece.
damping ability The ability to dissipate energy. Damping is usually used to absorb shock and reduce vibration.
discontinuous Chopped or cut. Discontinuous fibers can be applied to a mat or sprayed on to a surface with a special gun.
drilling The process of using a multi-point tool to penetrate the surface of a workpiece and make a round hole.
ductile Able to be drawn, stretched, or formed without breaking.
epoxy A high-strength adhesive, often made of two different materials that must be mixed together just prior to use.
fiber A reinforcing material whose length is greater than its height or width. Fibers are larger than whiskers or particles.
fiberglass Reinforcement material made from extremely fine strands of glass. Fiberglass is the most commonly used composite reinforcement.
filament An extremely thin strand of material. Filaments can be combined into a larger strand called a fiber.
filament winding A process in which strands of fiber are soaked in resin and wound around a core in the desired pattern to create a part.
finishing The treatment of a surface to remove roughness and irregularities and improve its appearance.
grinding The use of an abrasive to remove minor imperfections and bring a part to its final finish tolerance.
injection molding A molding process in 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 in which reinforcement in the form of a fabric or a mat is positioned 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.
mandrel The core around which resin-impregnated fiber is wound.
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.
mechanical fastening A process that joins two materials through the use of screws, bolts, and nails.
metal A naturally occurring material with high electric and thermal conductivity, luster, density, and strength. Examples of metal include copper, iron, nickel, and lead.
molding compound A type of ready-made composite in which the matrix and reinforcement have already been combined. Molding compound is available in bulk form and in sheet form.
molecule Two or more atoms joined together by chemical bonds. A molecule is the smallest amount of a specific chemical substance that can exist alone.
nylon An artificial material made from polymers. Nylon is extremely strong and resilient.
open molding A molding process in which fibers are put into a single-sided or open mold. Resin is added to the fibers and the part is cured at room temperature or with heat.
orientation The direction or lay of a reinforcement fiber.
particle An extremely small piece or part. Particles are smaller than whiskers or fibers.
petrochemical A compound made from petroleum or natural gas. Petrochemicals can be used to make matrix resins.
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.
polyetheretherketone PEEK. An organic thermoplastic polymer used to fabricate items for high-performance applications. PEEK is extensively used in the aerospace, automotive, teletronic, and chemical process industries.
polymer A group of molecules that are linked to each other in a chain-like structure. Polymers are used to create composite matrices.
polyphenylene sulfide PPS. A thermoplastic resin used primarily in compression and injection molding. PPS is extremely resistant to corrorsion.
polypropylene A type of thermoplastic known for being very lightweight.
polyurethane A type of plastic that is often chemically complex. Polyurethane is used for padding and insulation in furniture, clothing, and packaging, and in the manufacture of resins for adhesives, elastomers, and fillers.
pre-impregnated fiber Prepreg. Reinforcement material that has already been saturated with resin.
prepreg Pre-impregnated fiber. Reinforcement material that has already been saturated with resin.
pultrusion A molding process in which heated resin cures as it is pulled through a die. Pultrusion is a variation of the extrusion process, during which resin is pushed through a die.
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.
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.
resin infusion A type of molding in which a dry fiber preform is placed into a mold. Resin is injected into the mold until it saturates the preform and the part is cured.
rigid Unable to bend or resistant to bending.
sheet molding compound SMC. A rolled-up sheet in which the ingredients are not mixed together all at once. Instead, a pre-mixed, pre-initiated paste of resin and filler is applied to a moving sheet of film onto which strands of fiberglass are applied.
spray-up molding A manual molding process in which an operator uses a spray machine to simultaneously apply resin and chopped fiberglass strands to an open mold.
synthetic Not of natural origin. Artificial or human-made. Nylon is a synthetic material while cotton is a natural material.
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.
turning An operation performed on a lathe that feeds a cutting tool along the length of a cylindrical part to reduce its diameter.
vacuum bagging A type of compression molding in which a bag is placed over the mold and the vacuum compresses the bag and squeezes out any air or excess resin.
vinylester A synthetic resin that forms a chain of molecules around a fiber.
viscous Having a high resistance to flow. Viscous fluids tend to be sticky or syrupy.
wetted Having full contact between a fluid and a surface. Fiber reinforcement must be saturated with matrix resin in order to be fully wetted.
whisker A short, thin filament used for composite reinforcements. Whiskers are smaller than fibers.