Glossary of Terms

• Additive
  A material added to a resin to modify its characteristics. Examples include pigments, UV inhibitors, fire retardants and fillers.

• Bi-directional
  A reinforcement arrangement where fibres are oriented at right angles to each other, providing strength in two perpendicular directions.

• Catalyst
  A substance that initiates or accelerates the curing reaction of a resin system without being permanently changed by the reaction itself.
• CFRP Manufacturing
  Carbon Fibre Reinforced Polymer manufacturing. The process of producing composite parts using carbon fibre as the primary reinforcement material.
• Chopped Strand Mat
  A mat of randomly oriented short glass fibres held together by a binder. Used as a reinforcement layer to provide multi-directional strength.
• CNC
  Computer Numerical Control. An automated machining process used for precision cutting, trimming and finishing of composite components.
• Composite
  A material made from two or more constituent materials with significantly different physical or chemical properties that, when combined, produce a material with characteristics different from the individual components.
• Compressive Strength
  The maximum compressive stress a material can withstand before failure. Measured as force per unit area under compression loading.
• Core
  A lightweight material placed between face sheets in a sandwich structure to increase stiffness and flexural strength while adding minimal weight.
• Cure
  The process of chemical cross-linking of a resin system, transforming it from a liquid or semi-liquid state to a solid, rigid material.

• Density
  The mass per unit volume of a material, typically expressed in kg/m³ or g/cm³.
• Dielectric Strength
  The maximum electric field that a material can withstand without electrical breakdown. FRP composites are excellent electrical insulators with high dielectric strength.

• Epoxy Resin
  A thermosetting resin system known for excellent adhesion, mechanical properties and chemical resistance. Widely used in high-performance composite applications.

• Fabrication
  The process of manufacturing composite parts, including lay-up, moulding, curing and finishing operations.
• Fibreglass
  Glass fibres with diameters typically ranging from 9-32 microns, used as the most common reinforcement material in composite manufacturing.
• Fibre Reinforcement
  The fibrous material embedded within the resin matrix to provide structural strength and stiffness to a composite. Common types include glass, carbon and aramid fibres.
• Fillers
  Particulate materials added to a resin to modify properties such as shrinkage, cost, weight or surface finish. Examples include calcium carbonate, alumina trihydrate and microspheres.
• Finish
  A surface treatment or coating applied to fibres to improve their compatibility with the resin matrix and enhance handling characteristics.
• Fire Retardants
  Additives incorporated into resin systems to reduce flammability and improve fire performance of composite products.
• Fire Retardant Resin
  A resin system formulated with fire retardant additives or inherently fire-resistant chemistry to meet specific fire performance requirements.
• Flammability
  The measure of a material's ability to support combustion. Composite fire performance is tested to standards such as ASTM E84 and BS 476.
• Foam
  A lightweight cellular material used as a core in sandwich structures. Common types include PVC, PET, polyurethane and phenolic foams.
• FRP
  Fibre Reinforced Polymer. Also known as GRP (Glass Reinforced Plastic), GFRP (Glass Fibre Reinforced Polymer) or RP (Reinforced Plastic). A composite material made of a polymer matrix reinforced with fibres.

• Gelcoat
  A pigmented resin coating applied to the mould surface before lay-up to provide a smooth, durable and weather-resistant exterior finish on the finished composite part.

• Hand Lay Up
  An open-mould manufacturing process where reinforcement fabrics are placed by hand into a mould and resin is applied manually using brushes or rollers.

• Laminate
  A composite structure made of multiple layers of reinforcement material bonded together with resin. Each layer may have different fibre orientations to achieve desired mechanical properties.
• Lay Up
  The process of placing reinforcement materials into or onto a mould in the required sequence and orientation prior to resin application and curing.

• Machine Tool
  Equipment used for precision machining, cutting, drilling or trimming of composite parts after moulding and curing.
• Matrix
  The resin component of a composite material that binds the reinforcement fibres together, transfers loads between fibres and protects them from environmental damage.
• Mould
  A shaped tool or form used to give the desired geometry to a composite part during the manufacturing process.

• Phenolic Resin
  A thermosetting resin with excellent fire, smoke and toxicity properties. Widely used in transportation and building applications where fire performance is critical.
• Pigment
  A colouring material added to resin or gelcoat to achieve a desired colour in the finished composite product.
• Polyester Resin
  The most commonly used thermosetting resin in the composites industry. Offers good mechanical properties, corrosion resistance and ease of processing at an economical cost.
• Porosity
  The presence of voids or air pockets within a cured composite laminate. Excessive porosity can reduce mechanical properties and is minimised through proper processing techniques.
• Print-through
  A surface defect where the pattern of the underlying reinforcement fabric becomes visible on the finished surface of a composite part.
• Pultrusion
  A continuous manufacturing process where reinforcement fibres are pulled through a resin bath and then through a heated die to produce constant cross-section profiles.

• Resin
  A polymer material in liquid or semi-liquid form that, when cured, forms the matrix of a composite material. Common types include polyester, vinylester, epoxy and phenolic resins.
• RTM
  Resin Transfer Moulding. A closed-mould process where dry reinforcement is placed in a mould cavity and resin is injected under pressure to impregnate the fibres.

• Sandwich
  A structural composite consisting of two thin, strong face sheets bonded to a thicker, lightweight core material. Provides exceptional stiffness and strength at minimal weight.
• Skin
  The outer face sheet of a sandwich composite structure. Also referred to as the face sheet or laminate layer.

• Tensile Strength
  The maximum tensile stress a material can withstand before failure. A key mechanical property for structural composite applications.
• Thermal Coefficient of Expansion
  The rate at which a material expands or contracts with changes in temperature. Composites can be engineered to have very low thermal expansion coefficients.
• Thermoplastic
  A polymer that softens when heated and hardens when cooled. Unlike thermosets, thermoplastics can be repeatedly remelted and reformed.
• Thermoset
  A polymer that undergoes an irreversible chemical reaction (curing) to form a rigid, cross-linked structure. Once cured, thermosets cannot be remelted or reformed.
• Tool
  The mould or form used to manufacture a composite part. Tools can be made from various materials including composites, metals and wood.

• Unidirectional
  A reinforcement arrangement where all fibres are oriented in a single direction, providing maximum strength along that axis.