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Composites Terminology Database

This glossary is not an exhaustive list, however it does contain the majority of terms used in the composites industry and as part of the management of our website, it is updated on a continual basis.

The terms are accessed by clicking on the appropriate letter below, all the terms beginning with the letter R can be found below.

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Terms R

Click on a term and it will take you to the coresponding explanation.


reaction injection moulding (RIM)
A process for moulding polyurethane, epoxy, and other liquid chemical systems. Mixing of two to four components in the proper chemical ratio is accomplished by a high-pressure impingement-type mixing head, from which the mixed material is delivered into the mould at low pressure, where it reacts (cures).


reinforced plastics
Moulded, formed, filament-wound, tape-wrapped, or shaped plastic parts consisting of resins to which reinforcing fibres, mats, fabrics, and so forth, have been added before the forming operation to provide some strength properties greatly superior to those of the base resin.


reinforced reaction injection moulding (RRIM)
A reaction injection moulding with a reinforcement added. See also reaction injection moulding
"reaction injection moulding"


reinforcement
A strong material bonded into a matrix to improve its mechanical properties. Reinforcements are usually long fibres, chopped fibres, whiskers, particulates, and so forth. The term should not be used synonymously with filler.


relaxation time
The time required for a stress under a sustained constant strain to diminish by a stated fraction of its initial value.


relaxed stress
The initial stress minus the remaining stress at a given time during a stress-relaxation test.


release agent
A material that is applied in a thin film to the surface of a mould to keep the resin from bonding to the mould. See also mould release agent. Also called parting agent.
"mould release agent"


release film
An impermeable layer of film that does not bond to the resin being cured. See also separator
"separator"


residual gas analysis (RGA)
The study of residual gases in vacuum systems using mass spectrometry.


residual strain
The strain associated with residual stress.


residual stress
The stress existing in a body at rest, in equilibrium, at uniform temperature, and not subjected to external forces. Often caused by the forming and curing process.


resilience
The ratio of energy returned, on recovery from deformation, to the work input required to produce the deformation (usually expressed as a percentage). The ability to regain an original shape quickly after being strained or distorted.


resin content
The amount of resin in a laminate expressed as either a percentage of total weight or total volume.


resin pocket
An apparent accumulation of excess resin in a small, localised section visible on cut edges of moulded surfaces, or internal to the structure and non-visable. See also resin-rich area.
"resin-rich area"


resin system
A mixture of resin and ingredients such as catalyst, initiator, diluents, and so forth, required for the intended processing and final product.


resin transfer moulding (RTM)
A process whereby catalysed resin is transferred or injected into an enclosed mould in which the fibreglass reinforcement has been placed. "RTM"


resin-rich area
Localised area filled with resin and lacking reinforcing material. See also resin pocket.
"resin pocket"


resin-starved area
Localised area of insufficient resin, usually identified by low gloss, dry spots, or fibre showing on the surface.


resin
A solid or pseudosolid organic material, usually of high molecular weight, that exhibits a tendency to flow when subjected to stress. It usually has a softening or melting range and fractures conchoidally. Most resins are polymers. In reinforced plastics, the material used to bind together the reinforcement material: the matrix. See also polymer.
"polymer"


resistivity
The ability of a material to resist passage of electrical current either through its bulk or on a surface.


reverse helical winding
In filament winding, as the fibre delivery arm traverses one circuit, a continuous helix is laid down, reversing direction at the polar ends. In contrast to biaxial, compact, or sequential winding. The fibres cross each other at definite equators, the number depending on the helix. The minimum region of crossover is three.


reverse impact test
A test in which one side of a sheet of material is struck by a pendulum or falling object, and the reverse side is inspected for damage.


RGA
See residual gas analysis
"residual gas analysis"


rheology
The study of the flow of materials, particularly plastic flow of solids and the flow of non-Newtonian liquids. The science treating the deformation and flow of matter.


rib
A reinforcing member designed into a plastic part to provide lateral, horizontal, hoop, or other structural support. "ribs"


ribs
A reinforcing member designed into a plastic part to provide lateral, horizontal, hoop, or other structural support. "ribs"


RIM
See reaction injection moulding below
"reaction injection moulding"


reaction injection moulding (RIM)
A process for moulding polyurethane, epoxy, and other liquid chemical systems. Mixing of two to four components in the proper chemical ratio is accomplished by a high-pressure impingement-type mixing head, from which the mixed material is delivered into the mould at low pressure, where it reacts (cures).


rise time
In urethane foam moulding, the time between the pouring of the urethane mix and the completion of foaming.


Rockwell hardness
A value derived from the increase in depth of an impression as the load on an indenter is increased from a fixed minimum value to a higher value and then returned to the minimum value. Indenters for the Rockwell test include steel balls of several specific diameters and a diamond cone penetrator having an included angle of 120 degree with a spherical tip having a radius of 0.2 mm (0.0070 in.).

Rockwell hardness numbers are always quoted with a prefix representing the Rockwell scale corresponding to a given combination of load and indenter, for example, HRC 30.


room-temperature curing adhesive
An adhesive that sets (to handling strength) within an hour at temperatures from 20 to 30 degree C (68 to 86 degree F) and later reaches full strength without heating.


room-temperature vulcanising (RTV)
Vulcanisation or curing at room temperature by chemical reaction; usually applies to silicones and other rubbers.


roving ball
The supply package offered to the winder, consisting of a number of ends or strands wound to a given outside diameter onto a length of cardboard tube. Usually designated by either fibre weight or length in yards.


roving cloth
A textile fabric, coarse in nature, woven from rovings.


roving
A number of yams, strands, tows, or ends collected into a parallel bundle with little or no twist.


RRIM
See reinforced reaction injection moulding
"reinforced reaction injection moulding"


RTM
See resin transfer moulding
"RTM" "resin transfer moulding"


RTV
See room temperature vulcanising
"room-temperature vulcanising"


rubber
Cross-linked polymers with glass transition temperature below room temperature, which exhibit highly elastic deformation and have high elongation.


rupture
A cleavage or break resulting from physical stress. Work of rupture. The integral of the stress-strain curve between the origin and the point of rupture.

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