Glossary of terms
A B C D E F G H I J K L M N O P R S T :: Abbreviations
These terms are frequently used in the reinforced plastics and allied industries:
A
- Ablative:
- material that absorbs heat through decomposition process called pyrolysis at or near the exposed surface
- Accelerator:
- accelerates cure of a resin
- Additives:
- the term used for a large number of specialist chemicals which are added to resins/compounds to impart specific properties, for example, flame retardancy, and UV resistance
- Adhesive:
- substance applied to mating surfaces to bond them together by surface attachment. An adhesive can be in liquid, film or paste form.
- Aramid:
- high-strength, high-stiffness aromatic polyamide fibres
- Aspect ratio:
- the length/diameter ratio of a fibre
B
- Blister, blistering:
- undesirable raised areas in a moulded part caused by local internal pressure, due usually to rapped air, volatile reaction by-products or water entering by osmosis.
- Bulk Moulding Compound (BMC):
- polyester resin/glass fibre premix, for injection or transfer moulding, also known as dough moulding compound (DMC)
C
- Carbon fibre:
- reinforcing fibre known for its light weight, high strength and high stiffness.
- Catalyst (also called hardener):
- a chemical compound (usually an organic peroxide) which initiates polymerisation of a resin
- Chlorinated paraffins:
- flame-retardant additives for polyester resins
- Chopped strands:
- short strands cut from continuous filament strands of reinforcing fibre, not held together by any means
- Coefficient of thermal expansion:
- a material’s fractional change in length corresponding to for a given unit change in temperature
- Composite: a material made up of resin and reinforcement (usually fibre)
- Compression strength:
- the crushing load at failure of a material, divided by cross-sectional area of the specimen
- Contact moulding:
- moulding of fibre-reinforced resins without application of external pressure
- Core:
- in sandwich construction, the central component to which inner and outer skins are attached. Foam, honeycomb and wood are all commonly used core materials.
- Corrosion resistance:
- the ability of a material to withstand contact with ambient natural factors without degradation or change in properties. For composites, corrosion can cause crazing.
- Coupling agent:
- a substance, which promotes or establishes a stronger bond at the resin matrix/reinforcement interface
- Cracking:
- actual separation of moulded material, visible on opposite surfaces of a part ad extending through the thickness (fracture)
Crazing:- fine cracks, which may extend in a network on or under the surface of a moulded part
- Cure:
- the process of hardening of a thermosetting resin (by cross-linking of the molecular structure), under the influence of heat
- Curing agents:
- chemical compounds used to cure thermosetting resins
- Curing time:
- the time taken for a resin to cure to its full extent
- D
- Delamination:
- splitting, physical separation or loss of bond along the plane of layers of a laminated material
- Direct roving:
- roving produced by winding a large and determined number of filaments direct from a bushing
- Dough moulding compound (DMC):
- polyester/resin fibre premix, for injection or transfer moulding, also known as bulk moulding compound (BMC)
F
- Fibre:
- a unit of matter of relatively short length, characterised by a high ratio of length to thickness or diameter
Filament: - a unit of matter of relatively short length, characterised by a high ratio of length to thickness or diameter
- a single textile element of small diameter and very long length considered as continuous
- Filler:
- material (usually low cost) added to a resin to extend it, or give special properties
- Finishing:
- application of coupling agent to textile reinforcements to improve the fibre/resin bond
- Flexural strength:
- the strength of a material in bending expressed as the stress if a bent test sample at the instant of failure.
- Flow:
- the movement of a resinous material, thermosetting or thermoplastic, under pressure, to fill all parts of a closed mould
- Fracture:
- cracks, crazing or delamination resulting from physical damage.
G
- Gate:
- the opening through which a moulding compound is injected into a closed mould; the size, geometry and positioning of the gate can strongly influence properties of the finished moulding
- Gel:
- the state of a resin, which has set to a jelly-like consistency
- Gelcoat:
- a thin layer of unreinforced resin on the outer surface of a reinforced resin moulding; it hides the fibre pattern of the reinforcement, protects the resin/reinforcement bond, gives smooth external finish and can also provide special properties; it is usually pigmented
- Glass fibre:
- reinforcing fibre made by drawing molten glass through bushings. The predominant reinforcement for polymer composites, it is known for its good strength, processability and low cost.
H
- Hardener:
- see catalyst
- HET acid anhydride:
- saturated dicarboxylic acid anhydride, containing chlorine
- Honeycomb:
- light weight cellular structure made from either metallic sheet materials or non-metallic materials and formed into hexagonal nested cells, similar in appearance to the cross-section of a beehive
- Hybrid:
- a resin or reinforcement made from two or more different polymers or reinforcement materials
I
- Impact strength:
- a material’s ability to withstand shock loading as measured by fracturing a specimen
- Impregnation:
- saturation of reinforcement with liquid resin
- In-mould coating (IMC):
- a process used with SMC (and recently developed also for thermoplastics) in which a liquid/melt coating layer is applied to the exterior of a moulding while still in the mould, as part of the moulding cycle
- Interface:
- the contact area between reinforcement and resin
L
- Laminate:
- the structure resulting from bonding multiple plies of reinforcing fibre or fabric
- Lay-up:
- a resin-impregnated reinforcement in the mould, prior to polymerisation
M
- Mat:
- a widely used sheet-type reinforcement made up of filaments, staple fibres or strands, cut or uncut, oriented or random, lightly bonded together
- Monomer:
- a compound containing a reactive double bond, capable of polymerising
P
- Polyester:
- usual term for an unsaturated polyester resin
- Polymer:
- a long-chain molecule, consisting of many repeat units
- Porosity:
- numerous air pockets or voids in a moulded product
- Porosity:
- Post-cure:
- application of external heat to bring a resin to a stable state of cure in the shortest possible time
- Preform:
- reinforcement pre-shaped to the general geometry of the intended moulded part; it is used on more complex and deep-draw mouldings, to optimise distribution and orientation of fibres
- Premix:
- a moulding compound prepared prior to, and apart from, the moulding operation, containing all components necessary for moulding
- Prepreg:
- a factory-made combination of reactive resins and reinforcing fibres, plus other necessary additive chemicals, ready to be moulded
R
- Reactive resins:
- liquid resins which can be cured by catalysts and hardeners to form solid materials
- Release agent:
- a substance which prevents a moulding from sticking to the mould surface; it may be a chemical compound or a solid material such as a cellulose or plastics film
- Reinforcement:
- key element added to resin (matrix) to provide the required properties; ranges from short fibres and continuous fibres through complex textile forms
- Resin:
- polymer with indefinite and often high molecular weight and a softening or melting range that exhibits a tendency to flow when subjected to stress. As composite matrices, resins bind together reinforcement fibres
- Resin transfer moulding (RTM):
- a moulding process in which catalysed resin is injected into a closed mould already containing the pre-formed reinforcement
- Roving:
- endless glass fibre bundles; a collection of parallel strands (assembled roving) or parallel filaments (direct roving) assembled without intentional twist
S
- Sandwich structure:
- composite composed of lightweight core material to which two relatively thin, dense, high strength, functional or decorative skins are adhered
- Sheet moulding compound (SMC):
- a flat pre-preg material, comprising thickened resin, glass fibre and fillers, covered on both sides with polyethylene or nylon film, ready for press-moulding
- Size:
- a coating applied to glass fibres or filaments during manufacture, to improve handling and protect from abrasion
- Strand:
- an assembly of parallel filaments simultaneously produced and lightly bonded
T
- Thermoplastic:
- a plastic, which softens each time it is heated
- Thermoset:
- a plastic which flows and then sets permanently on first heating, as s result of setting up a three-dimensional cross-linked molecular structure, and subsequently will not soften or dissolve
- Thick moulding compound (TMC):
- a compound similar to BMC, but continuously produced in sheet form with a thickness of 25mm or more
- Void:
- a pocket of gas or air trapped in a laminate or moulding
- Wet-out:
- complete wetting/saturation of a fibrous surface with a liquid resin
Abbreviations
- ACM:
- advanced composite material
- AFRP:
- aramid fibre reinforced polymer
- BMC:
- bulk moulding compound
- CFRP:
- carbon fibre reinforced polymer
- DMC:
- dough moulding compound
- GFRP:
- glass fibre reinforced polymer
- FRP:
- fibre reinforced polymer
- SMC:
- sheet moulding compound
- TMC:
- thick moulding compound