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A-Z guide to reinforcements, resins and raw materials

Aramid

Strong aromatic polyamide organic fibre with high strength-to-weight ratio. Often used for applications requiring high impact resistance.

 

"B" Stage Resin

The condition of a partially cured resin polymer when it is only partially soluble in monomer or acetone but still plastic and still heat fusible.

 

Bismaleimides (BMI)

Primarily used in aircraft composites where operation at higher temperatures (230°C wet/250°C dry) is required. e.g. engine inlets, high-speed aircraft flight surfaces.

 

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.

 

Ceramic Matrix Composites (CMC)

Materials that use a ceramic as the matrix and reinforce it with short fibres, or whiskers such as those made from silicon carbide and boron nitride. Used in very high temperature environments.

 

CFRP

Carbon fibre-reinforced plastic

 

Chopped Strand

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

 

Chopped Strand Mat (CSM)

E-glass, nonwoven structures consisting of non-aligned glass fibers, sliced from a spinning cake. The glass fibers have been chemically bonded (by an emulsion or powder based binder).

 

Composite

A homogeneous material created by the synthetic assembly of two or more materials (a selected filler or reinforcing elements and compatiblematrix binder) to obtain specific characteristicsand properties. For the purposes of this study, a composites is a long-fibre reinforced polymeric material, where the reinforcement is greater than 7.5mm in length prior to processing (BS EN ISO 10350-2).

 

Continuous Filament

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

 

Continuous Roving

Parallel glass 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 highstrength moulding components. It also can be chopped (see Chopped Strand).

 

Conventional (Assembled) Roving

Glass roving that is assembled from several forming packages using a creel and a roving winder. Typical characteristics are multiple ends, 3-inch diameter centres, a tube core and some catenary (A term describing the uniformity of strand length in a specified length of roving stretched under tension).

 

Cyanate Esters

Primarily used in the aerospace industry. The material's excellent dielectric properties make it very suitable for use with low dielectric fibres such as quartz for the manufacture of radomes. The material also has temperature stability up to around 200°C wet. Typical costs: £40/kg.

 

Direct (Wound) Roving

A glass roving made directly at the bushing that does not go through a roving process. Typical characteristics are: single-end roving, coreless, 6-inch diameter centers and no catenary.

 

E-Glass

A borosilicate glass widely used in the manufacture of glass fibres for reinforced plastics. Suitable for electrical laminates because of its high resistivity.

 

Epoxy

A thermoset polymer containing one or more epoxide groups and curable by reaction with amines, alcohols, phenols, carboxylic acids, acid anhydrides, and mercaptans. An important matrix resin in composites and structural adhesives. Epoxies generally out-perform most other resin types in terms of mechanical properties and resistance to environmental degradation, which leads to their use in aircraft components. As a laminating resin their increased adhesive properties and resistance to water degradation make these resins ideal for use in applications such as boat building.

 

Fabric, Nonwoven

A material formed from fibres or yarns without interlacing (e.g., stitched bonded, nonwoven broadgoods).

 

Fabric, Woven

Woven fabrics are constructed produced by the interlacing of yarns, fibres or filaments in a regular pattern or weave style. The fabric's integrity is maintained by the mechanical interlocking of the fibres.

 

FRP

Fibre-reinforced plastic or polymer.

 

Gel Coat

A resin applied to the surface of a mould and gelled prior to lay-up. The gel coat becomes an integral part of the finished laminate, and is usually used to improve surface appearance and protect the laminate from the environment.

 

GFRP

Glass fibre-reinforced plastic, polymer or polyester.

 

Glass Fibre

Reinforcing fibre made by drawing molten glass through bushings. The predominant reinforcement for polymer matrix composites, it is known for good strength, processability and low cost.

 

Graphite Fibres

This term is used interchangeably with carbon fibres throughout the industry.

 

Glass Mat Thermoplastic (GMT)

A ready-to-mould glass fibre reinforced polypropylene material primarily used in compression moulding.

 

GRP

Glass-reinforced plastic, polymer or polyester.

 

Laminate

A product made by bonding together two or more layers of material or materials. Primarily means a composite material system made with layers of fibre reinforcement in a resin. Sometimes used as a general reference for composites, regardless of how made.

 

Matrix

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

 

Metal Matrix Composites (MMC)

Increasingly used by the automotive industry, these materials use a metal such as aluminium as the matrix, and reinforce it with fibres such as silicon carbide.

 

Multi Axial Fabrics

These fabrics consist of one or more layers of long fibres held in place by a secondary non-structural stitching tread used in the construction of composite components. The main fibres can be any of the structural fibres available in any combination. The stitching thread is usually polyester due to its combination of appropriate fibre properties (for binding the fabric together).

 

Non-Woven Fabric

A textile structure produced by bonding or interlocking of fibres, or both, accomplished by mechanical, chemical, thermal, or solvent means and combinations thereof.

 

PET

Polyethylene Terephthalate (Thermoplastic Polyester Resin).

 

Phenolics

Primarily used where high fire-resistance is required, phenolics also retain their properties well at elevated temperatures. The nature of their curing process tends to lead to the creation of some voids and surface defects, and the resins do not have high mechanical properties.

 

Polyamide

A polymer in which the structural units are linked by amide or thioamide groupings. Commonly called Nylon.

 

Polyesters

Thermosetting resins, produced by dissolving unsaturated, generally linear, alkyd resins in a vinyl-type active monomer such as styrene, methyl styrene, and diallyl phthalate. Cure is effected through vinyl polymerisation using peroxide catalysts and promoters, or heat, to accelerate the reaction. Other additives can include thixotropic additives, pigments, fillers and flame retardants. Polyester resins are the most widely used resin systems, particularly in the marine industry.

 

Polyimides

Used where higher temperatures operation preclude the use of bismaleimides (up to 250°C wet/300°C dry). Typical applications include missile and aero-engine components. Extremely expensive resin which also tends to be hard to process due to their condensation reaction emitting water during cure.

 

Polymer Matrix Composites (PMC)

Materials that use a polymer-based resin as the matrix, and a variety of fibres such as glass, carbon and aramid for the reinforcement. Also known as FRP - Fibre Reinforced Polymers (or Plastics).

 

Polyurethanes

High toughness materials, sometimes hybridised with other resins, due to relatively low laminate mechanical properties in compression. Uses harmful isocyanates as curing agent.

 

PPO

Polyphenylene Oxide (Thermoplastic Resin).

 

PPS

Polyphenylene Sulfide (Thermoplastic Resin).

 

Preform

A preshaped fibrous reinforcement formed by distribution of chopped fibres by air, water flotation, or vacuum over the surface of a perforated screen to the approximate contour and thickness desired in the finished part. Also, a preshaped fibrous reinforcement of mat or cloth formed to desired shape on a mandrel or mock-up prior to being placed in a mould press. Also, a compact "pill" formed by compressing premixed material to facilitate handling and control of uniformity of charges for mould loading.

 

Prepreg

Ready-to-mould material in sheet form which may be cloth, mat, or paper pre-impregnated with resin and stored for use. The resin is partially cured to a 'B' stage and supplied to the fabricator who lays up the finished shape and completes the cure with heat and pressure. SMC prepreg is made from glass strands chopped to lengths of 25 or 50mm, sandwiched between two layers of film, onto which the resin paste has already been applied. The prepreg passes through a compaction system that ensures complete strand impregnation before being wound into rolls. These are stored for a few days before moulding, to allow the prepreg to thicken to a mouldable viscosity.

 

Reinforcement

A material added to the matrix to provide the required properties; ranges from short fibresthrough complex textile complex textile forms.

 

Release Agents

Release agents are incorporated into the resin matrix (internal) or applied externally to the mould surface (external), correct selection can not only help optimise cycle time, but also the consistency of surface finish and  minimising post mould operation.

 

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.

 

RTP

Sometimes used to distinguish reinforced thermoplastic from reinforced thermoset plastic.

 

S Glass

Magnesium-alumina-silicate glasses with higher tensile strength and modulus than E glass, with better wet strength retention. Developed for aerospace and defence industries, and used in some hard ballistic armour applications.

 

Thermoplastic

Capable of being repeatedly softened by an increase of temperature and hardened by adecrease in temperature. Applicable to thosematerials whose change upon heating issubstantially physical rather than chemical andthat in the softened stage can be shaped by flow into articles by moulding or extrusion.

 

Thermoset

A material that will undergo a chemical reaction caused by heat, or initiated by a catalyst, leading to the formation of a solid. Once it becomes a solid, it cannot be softened and remoulded.