Aramid
Aromatic polyamide fibers characterized by excellent high-temperature, flame-resistance, and electrical properties. (DuPont's brand is Kevlar)

BMC
Bulk Molding Compound. Thermosetting resin mixed with strand reinforcement, fillers, and so on, into a viscous compound for compression or injection molding.

Carbon Fiber
An important reinforcing fiber known for its light weight, high strength, and high stiffness that is commonly produced by pyrolysis of an organic precursor fiber (often polyacrylonitrile (PAN) or rayon) in an inert atmosphere.

Chopped Strand
Continuous roving that is chopped into short lengths for use in mats, spray-up or molding compounds.

Composite
A homogeneous material created by the synthetic assembly of two or more materials (a selected filler or reinforcing elements and compatible matrix binder) to obtain specific characteristics and properties. Composites are subdivided into classes on the basis of the form of the structural constituents; Laminar - Composed of layer or laminar constituents; Particular -The dispersed phase consists of small particles; Fibrous -The dispersed phase consists of fibers; Flake -The dispersed phase consists of flat flakes; Skeletal -Composed of a continuous skeletal matrix filled by a second material. 

Compression Molding
A technique for molding thermoset plastics in which a part is shaped by placing the fiber and resin into an open mold cavity, closing the mold, and applying heat and pressure until the material has cured or achieved its final form.

Hand Lay-Up
A fabrication method in which reinforcement layers are placed in mold by hand, saturated with resin and then cured to the formed shape.

Mat
A fibrous reinforcing material comprised of chopped filaments (for chopped-strand mat) or swirled filaments (for continuous-strand mat) with a binder to maintain form; available in blankets of various widths, weights, and lengths.

Matrix
The material in which the fiber reinforcements of a composite system are embedded. Thermoplastic and thermoset resin systems can be used, as well as metal and ceramic.

Prepreg
Ready-to-mold material in sheet form which may be cloth, mat, or paper pre-impregnated with resin and stored for use.

Resin
A material, generally a polymer that has an indefinite and often high molecular weight and a softening or melting range and exhibits a tendency to flow when it is subjected to stress. Resins are used as the matrices to bind together the reinforcement material in composites. 

Sheet Molding Compound (SMC)
A ready-to-mold glass fiber reinforced polyester material primarily used in compression molding. 

Thermoplastic
Capable of being repeatedly softened by an increase of temperature and hardened by a decrease in temperature. Applicable to those materials whose change upon heating is substantially physical rather than chemical and that in the softened stage can be shaped by flow into articles by molding or extrusion. 

Thermoset
A material that will undergo a chemical reaction caused by heat, catalyst, etc., leading to the formation of a solid. Once it becomes a solid, it cannot be reformed.

Wet-Out
The degree and/or rate at which each individual filament is "wet" or encapsulated by the matrix polymer resin in a composite sheet. Relates to the ability of the polymer matrix resin system to move through the glass fiber bed and to attain complete encapsulation of each individual filament. A measure of the wetability of the sized glass fiber surface.