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The final stage of the curing of a thermosetting resin in which the material has become infusible and insoluble in common solvents.

Cabled Yarn

Yarn that is plied more than once; yarn made by plying two or more previous plied yarns.


A term applied to the glass package that is produced in the forming department. Also used as forming cake package, forming cake and cake package. All terms are synonymous.

Carbon Fibre

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


A composite of carbon fibre in a carbon matrix.


The process of untangling and partially straightening fibres by passing them between two closely spaced surfaces which are moving at different speeds, and at least one of which is covered with sharp points, thus converting a tangled mass of fibres to a filmy web.


A substance that changes the rate of a chemical reaction without itself undergoing permanent change in composition or becoming a part of the molecular structure of the product. A substance that markedly speeds up the cure of a compound when added in minor quantity as compared to the amounts of primary reactants.


A measure of the difference in length of the strands in a specified length of roving as a result of unequal tension; the tendency of some strands in a taut horizontal roving to sag lower than the others.

Caul Plates

Smooth metal, plastic, or rubber plates free of surface defects, used in contact with the lay-up during the curing process to transmit normal pressure and provide a smooth surface on the finished part. A caul plate must be the appropriate size and shape for the composite lay-up with which is will be used.


he space inside a mould in which a resin or moulding compound is poured or injected. The female portion of a mould. That portion of the mould that encloses the moulded article (often referred to as the die). Depending on the number of such depressions, moulds are designated as single cavity or multiple cavity.


In honeycomb core, a cell is a single honeycomb unit, usually in a hexagonal shape.


Carbon fibre-reinforced plastic.

Chemical Size

A surface finish applied to the fibre that contains some chemical constituents other than water.


The ease of chopping/cutting the glass fibres to a uniform length.

Chopped Strand

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

Chopper Gun

A special piece of equipment used in the manufacture of reinforced plastic parts, which chops glass and sprays resin and catalyst simultaneously onto a moulded surface.


Cured and simultaneously bonded to another prepared surface.


A resin produced by copolymerisation, the process where unlike molecules are arranged in alternate sequence in a chain.

Co-Woven Fabric

A reinforcement fabric woven with two different types of fibres in individual yarns; for example, thermoplastic fibres woven side by side with carbon fibres.


The application of a temporary vacuum bag and vacuum to remove trapped air and compact the lay-up.


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 fibres; 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 moulding thermoset plastics in which a part is shaped by placing the fibre and resin into an open mould cavity, closing the mould, and applying heat and pressure until the material has cured or achieved its final form.

Compression Mould

A mould which is open when the material is introduced and which shapes the material by heat and by the pressure of closing. Also ‘compression moulding’.


Subjecting a material to a prescribed environmental and/or stress history before testing.


Ability of the mat to conform to difficult shapes without causing wrinkles or leaving excessively resin-rich or glass-rich radii, which may craze.

Contact Moulding

A process for moulding reinforced plastics in which reinforcement and resin are placed on a mould, cure is either at room temperature using a catalyst-promoter system or by heat in an oven and no additional pressure is used.

Continuous Filament

An individual, small-diameter reinforcement that is flexible and indefinite in length.

Continuous Roving

Parallel filaments coated with sizing, gathered together in single or multiple strands and wound into a cylindrical package. It can be used to provide continuous reinforcement in woven roving, filament winding, pultrusion, prepregs or high-strength molding components. It also can be chopped (see Chopped Strand).

Conventional Roving

Roving that is assembled from several forming packages using a creel and a roving winder. Typical characteristics are multiple ends, 3-inch diameter centers, a tube core and some catenary.


The central component of a sandwich construction to which the sandwich faces or skins are attached; also, part of a complex mould that forms undercut parts.


For fabric, number of warp and filling yarns per inch in woven cloth. For yarn, size based on relation of length and weight.

Coupling Agent

Any chemical substance designed to react with both the reinforcement and matrix phases of a composite material to form or promote a stronger bond at the interface; a bonding link.


Fine cracks that may extend in a network on or under the surface of a plastic material.


A device for holding the required number of roving balls or supply packages in desired position for unwinding onto the next processing step.


A fiber’s waviness, which determines the capacity of the fibre to cohere.

Cross Laminated

Material laminated so that some of the layers are oriented at various angles to the other with respect to the laminate grain. A cross-ply laminate usually has plies oriented only at 0/90 degrees.


The setting up of chemical links between molecule chains. This occurs in all thermosetting resins. Styrene monomer is a crosslinking agent in polyester resins.


To change the properties of a thermosetting resin irreversibly by chemical reaction, i.e., condensation, ring closure, or addition. Cure may be accomplished by addition of curing (cross-linking) agents, with or without catalyst, and with or without heat.

Cure Cycle

The time/temperature/pressure cycle used to cure a thermosetting resin system of prepreg.

Cure Stress

A residual internal stress produced during the curing cycle of composite structures. Normally, these stresses originate when different components of a wet lay-up have different thermal coefficients of expansion.

Curing Agent

A catalytic or reactive agent that brings about polymerisation when it is added to a resin.

Curing Temperature

Temperature at which a cast, moulded, or extruded product, a resin-impregnated reinforcement, an adhesive, etc., is subjected to curing.

Curing Time

The period of time during which a part is subjected to heat or pressure, or both, to cure the resin; interval of time between the instant of cessation of relative movement between the moving parts of a mold and the instant that pressure is released. (Further cure may take place after removal of the assembly from the conditions of heat or pressure.)


The complete, repeating sequence of operations in a process or part of a process. In moulding, the cycle time is the period (or elapsed time) between a certain point in one cycle and the same point in the next.