Glossary

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Adhesive

A thermoset resin (e.g., epoxy, phenolic or BMI) in the form of a thin film or paste, cured under heat and pressure to bond a wide range of composite, metallic and honeycomb surfaces.

Aramid
A high strength, high stiffness fiber derived from polymid. Kevlar™ and Nomex™ are examples of aramids.

Bismaleimide
Thermosetting matrix used for prepregs. Excellent resistance to temperature, high mechanical properties, good resistance to chemical agents and radiations.

Carbon Fiber
Fiber produced by carbonizing precursor fibers based on PAN (polyacrylonitrile), rayon or pitch. The term is often used interchangeably with graphite. However, carbon fibers and graphite fibers are made and heat treated at different temperatures and have different carbon contents.

Composite materials
Product made by combining two or more dissimilar materials such as fibers and resins to create a product with exceptional structural properties not present in the original materials.

Core
Central component of a sandwich structure, placed between two exterior skins.

Cowls or Cowling
The outside protective shell of a jet engine, traditionally made out of metal. Cowls mainly provide the engine with protection from the elements and with structural support..

Engineered Products
Completed composite components that typically are manufactured from prepregs, honeycomb, adhesives and assembled hardware. These parts are ready for direct attachment to a structure (e.g., aircraft) or to sub-assemblies. Emerging manufacturing processes allow the fabrication of engineered products directly from reinforcing fibers/fabrics and matrix resins.

Fairing
A secondary structure of an airplane providing enhanced aerodynamics. Typically, fairings are found where the wing meets the body or at various locations on the leading or trailing edge of the wing.

Fiberglass
Filaments made by drawing molten glass. Woven by Hexcel Schwebel into fabrics and commonly used as a composite reinforcement.

Filament Winding
A process to manufacture composite materials components such as rocket casings and cylinders. Fiber filaments are impregnated in a resin matrix and then wound in a predetermined pattern over a form of the desired component.

FRM
Fibre Reinforced Matrix: A combination of fibre and resin matrix as in Prepreg, RTM, RFI, etc.

Glass (fiber)
Thin filament made with melted glass. Good resistance to traction, good adherence to all resins, high temperature resistance, incombustibility, low dilatation and thermal conductivity, good dielectric properties.

High modulus
Reinforcement made with two layers of supperposed yarns, without any crossing of those yarns. The cohesion between the two layers is made by a warp and a weft with thin yarns, that are not taking part to the mecanical properties of the reinforcement. Yarns layer are not deformed, so they are very resistant.

Honeycomb
A unique, lightweight, cellular structure made from either metallic sheet materials or non-metallic materials (e.g., resin-impregnated paper or woven fabric) and formed into hexagonal nested cells, similar in appearance to a cross-section of beehive.

Inlet Ducts
Intake passages or tubes that confine and conduct air. They are usually located at the upstream end of an airplane engine on the engine cowling and aid in propulsion and engine cooling.

Interiors
Finished internal aircraft components, such as overhead stowage compartments, lavatories, sidewalls, floor panels and ceilings.

Intermediar modulus
Said about a carbon fiber with a flexion modulus of 300 GPa.

Kevlar™
An aramid fiber from DuPont. Woven Kevlar(tm) fabrics are used in both ballistic and composite materials applications.

Layer
Yarns juxtaposition, most of the time linked by a reticulated or not matrix, or by some weft yarns.

Mat
Cut verrane yarns (mainly compatible with polyester resin).

Modulus of Elasticity
The physical measurement of stiffness in a material. A high modulus indicates a stiff material.

Monomer
Said about a usually very simple molecule, able to polimerize to get a polymer.

Multiaxial
Superposition combination of unidirectional layers, each layer orientated in a different way. The layers are linked together by a yarn.

Multi-Layer Laminate
An electrical laminate that uses three or more layers of circuitry. These laminates are used in complex, high density circuit designs.

Nacelle
The protective shell of a jet engine housed within the cowling, usually made from honeycomb. Provides noise absorption, insulation, structural support and can aid heat dissipation.

Nomex™
DuPont’s registered trade name for its high temperature resistant aramid papers, pressboard, staple fibers and filament yarns. Nomex(tm) aramid paper is used in the manufacture of honeycomb.

PAN (Polyacrylonitrile)
A polymer which when spun into fiber is used as a precursor material in the manufacture of certain carbon fibers.

Phenolic
Said about thermosetting matrix, prepared from phenols. Resistant to fire and temperature, quick polymerization.

Plain
Weaving method. Yarns of warp and weft are crossing each others alternatively. It is the most simple weave. This weaving methode usually offers the best flatness and the best stability, but it is less deformable.

Polyaddition
Polymerization reaction during which monomers are linking together with addition reactions between functional elements, without any elimination.

Polycondensation
Polymerization reaction during which monomers are linking together with a condensation reaction, usually with elimination of a water molecule.

Polyester
Generic name given to copolymers obtained by policondensation between glycols and carboxylic diacids. Good grip to glass fiber, possibility of translucency, easy implementation, good chemical behavior.

Polyethylene (fiber)
Good resistance to impact.

Polymer
Generic name given to macromolecules caracterized by a repetitive combination of smaller moleculary units, called monomers, from which the polymer is synthetised.

Polymerization
Said for chemical reactions when products are polymers.

Pot-life
From the moment where two components of a resin are mixed, and chemical reaction has started, you only have a small time period to use this resin between complete hardening. This period is called pot-life.

Precursor
The PAN, rayon or pitch fibers from which carbon or graphite fibers are derived.

Prepreg (Pre-impregnated)
A composite material made from combining high performance reinforcement fibers or fabrics with a thermoset or thermoplastic resin matrix, for an easier implementation. When cured under high temperature and pressure, exceptional structural properties are achieved.

Printed Circuit Board
An electronic platform containing etched copper circuitry and multiple layers of interconnected circuitry, and assembled with microprocessors, passive devices and other electronic components.

Primary Structure
A critical load-bearing structure on an aircraft. If this structure is severely damaged, the aircraft cannot fly.

Prototyping
Prototypes conception.

Radome
The housing which protects the aircraft radar system from the elements while allowing transmission of radar signals. Often the radome is in the nose of an aircraft but can be found at other locations on the aircraft, as well.

Reinforcement
A strong material which when combined with a resin matrix forms a composite material. Reinforcements are usually continuous fibers, which may be woven. Fiberglass, aramid and carbon fibers are typical reinforcements.

Reinforcement Fabrics
Woven fiberglass, carbon or aramid fabrics used in production of prepregs and honeycomb.

Repair and Retrofit
The reinforcement or repair of existing structures to strengthen them or increase their ability to withstand an earthquake or other forces. Until recently, repair and retrofit was done with traditional materials like steel. Now it can also be done with composite materials which are lighter weight and cost competitive with traditional materials.

Resin
Solid or liquid organic component, from artificial origin.

Resin Matrix
In reinforced fiber composites, a formulated polymeric substrate.

Reticulation
Irreversible chemical reaction during which a tridimensional network is constituted.

RIM (reaction injection molding)
Resin and hardener are injected separately in a two pieces mold : the mixing and the polymerization reaction take place in the mold. Short fibers are sometimes injected with one of the components (which is named R-RIM).

Rigid Laminate
A one or two sided copper clad standard electrical laminate used in low cost applications. Usually uses eight plies of 7628 fiberglass fabric.

Roving
Parallele fibers without any distortion, usually with plastic sising.

Sandwich Panels
A stiff and lightweight panel consisting of thin sheets such as aluminum or cured prepreg laminate bonded to a low density, rigid core material (e.g., foam or honeycomb).

Satin
Weaving method. A warp yarn above several weft yarns. E.g. in a 8 satin, one warp yarn crosses over 7 weft yarns. This weave is the most deformable. This weaving method allows the limitation of crossing points, and deformation of yarns at those points, offering better performances in flexion and traction, and less cutting effects.

Seismic Retrofit
The reinforcement of existing structures to increase their ability to withstand an earthquake. Until recently, the reinforcement was done with steel, but now it can also be done with composite materials.

Silicone
Generic name given to semi-organic polymers containing silicium, and named polysiloxanes, which general formule is —R1R2Si-O-.

Special Process Honeycomb
The forming, shaping, machining or bonding of sheets or blocks of honeycomb into profiled and complex shapes for use as semi-finished components in the fabrication of composite parts and structures.

Spectra™
A high strength polyolefin fiber from Allied Signal. Woven Spectra(tm) fabrics are very strong and lightweight and are used in both ballistic and composite materials applications.

Structures
Finished components for aircraft and industrial applications. For aircraft, these may be for primary or secondary external structures. Truck applications include chassis fairings and floors.

Twill
Weaving method. One yarn above two others, in both directions (warp and weft). This weaving is used when higher yarn density is wanted, but when the fabric needs to keep flexibility.

Unidirectionnal
Said about a reinforcement which all fibers are orientated in the same direction. Those fibers are only linked together by very thin yarns, which only aim is to maintain the cohesion of the piece.

Urethane
Generic name given to synthetic polymers obtained by diisocyanates (organic components containing two isocyanates groups N=C=O) reaction with other monomers having two fonctionnal groups. Urethane are used for rigid or flexible foams manufacturing, elastomers (textile fibers), plastics, and they are part of paint components, varnish, etc.

Verrane
Discontinuous fibers (good resistance to delaminating).