R

REINFORCED MOLDING COMPOUND

Compound consisting of a polymer and a reinforcement fiber or filler supplied by raw material producer in the form of ready-to-use materials.

 

REINFORCEMENT

A fiber that when encapsulated in a polymer resin matrix forms a composite or fiberglass laminate. Also refers to a structural member designed to stiffen a molded part.

 

RELEASE AGENT

A compound used to reduce surface tension or adhesion between a mold and apart.

 

RELEASE FILM

A non-stick film layer that does not bond to the composite during cure.

 

RESIN

A liquid polymer that when catalyzed cures to a solid state.

 

RESIN RICH

Excess resin in a laminate.

 

RESIN STARVED

Insufficient resin in a laminate.

 

RESIN TEARING

Separation of pigments in a gel coat effecting cosmetic appearance.

 

RESIN TRANSFER MOLDING (RTM)

Molding process in that catalyzed resin is pumped into a two-sided, matched mold where a fibrous reinforcement has been placed. The mold and/or resin may or may not be heated.

 

ROVING

A collection of bundles of continuous filaments in untwisted strands. Used in the spray-up (chopping) process.

 

S

 

SANDWICH CONSTRUCTION

A laminate with two composite skins separated by, but bonded to, a structural core material. Used to create, rigid, lightweight structures.

 

SECONDARY BONDING

Bonding to a previously cured laminate surface.

 

S-GLASS

High strength glass fiber, commonly used in high-performance parts. S-Glass has high compression strength.

 

SELF EXTINGUISHING

Ceases to burn when the source of flame is removed.

 

SHEAR

Stress resulting from applied forces. It is caused by two contiguous parts of a body sling, relative to each other, in a direction parallel to their plane of contact.

 

SHEET MOLDING COMPOUND (SMC)

A molding compound consisting of a B-staged resin and chopped glass fiber, used in compression molding.

 

SHELF LIFE

The allowable storage time before a product must be used.

 

SHIP LAP

Method of joining two panels together by means of one panel having a recessed shelf to receive the other panel on top of it leaving a flush surface.

 

SKIN COAT

The first layer of laminate next to the gel coat, generally, one ply of chopped strand mat.

 

 SLAVE PUMP

A catalyst pump that is driven by the resin pump through a pair of level arms.

 

SPECIFIC GRAVITY

The ratio between the density of a given substance and the density of water.

 

SPLIT MOLD

An open mold made in two or more pieces.

 

SPRAY-UP

The process of spraying glass fibers, resin and catalyst simultaneously into a mold using a chopper gun.

 

STIFFNESS (RIGIDITY) 

Material’s ability to resist bending. Relationship of load to deformation for a particular material.

 

STRAIN

Deformation resulting from stress.

 

STRANDS

A primary bundle of continuous filaments combined in a single compact unit without twist.

 

STRESS

External force applied to an object, expressed in force per unit area.

 

STRESS CRACK

External or internal cracks in a composite caused by tensile stresses; cracking may be present internally, externally or in combination.

 

STYRENE MONOMER

 

SURFACING MAT

 

SURFACING VEIL

 

SURFACTANT

 

SYNTACTIC FOAM

T

 

TACK

Surface stickiness.

 

TACK FREE

A surface that is not sticky after cure.

 

TAPE

A narrow width reinforcing fabric or mat.

 

TENSILE LOAD

A pulling load applied to opposite ends of a given sample.

 

TENSILE ELONGATION

An engineering term referring to the amount of stretch a sample experiences during tensile strain. ASTM D-638

 

TENSILE STRENGTH

A measurement of the tensile load a sample can withstand. ASTM D-638.

 

THERMAL COEFFICIENT OF EXPANSION

Measures dimensional change

 

THERMAL CONDUCTIVITY

Measures the transfer of heat through a material.

 

THERMOPLASTICS

A group of plastic materials that become elastic or melt when heated and return to their rigid state at room temperature. Examples are PVC, ABS, polystyrene, polycarbonates, nylon, etc.

 

THERMOSETS

Materials that undergo a chemical cross-linking reaction going from liquid to solid or semi-solid. This reaction is irreversible. Typical thermosets are polyesters, acrylics, epoxies and phenolics.

 

THIXOTROPIC

A term describing the rehology (or flow characteristics) of a liquid that resists flowing or drainage during application.

 

THIXOTROPIC INDEX (T.I.)

A measure of thixotroy using a Brookfield Viscometer. The low speed viscosity divided by the high-speed viscosity.

 

TOOLING GEL COAT

A gel coat formulated for mold surfaces.

 

TRANSLUCENT

Permits a percentage of light to pass but not optically clear like a window glass.