Aircraft Composite and Non-Metallic Materials

Vocabulary flashcards covering aircraft composite materials, fabric orientations, core types, plastics, and sealing processes based on lecture notes.

Composite

A combination of two or more materials that forms a much stronger structure than either material by itself.

Delamination

A type of material failure in composites where layers separate, often difficult to detect during inspection.

Boeing 787 Composite Composition

The aircraft uses composites for $50 \%$ of its weight and $80 \%$ of its volume.

Reinforcing Fibre

The primary load-carrying element of a composite material, such as fibreglass, aramid, or carbon fibre.

E-glass

A type of fibreglass named for 'Electric' used for electrical applications due to its high resistance to current flow.

S-glass

A type of fibreglass named for 'Strength' used when high tensile strength or modulus is required.

Aramid (Kevlar)

An aromatic polyamide polymer with low density ($1.45\,g/cm^3$) and high heat resistance up to $260\,^\circ\text{C}$, often used in impact-prone areas.

Carbon Fibre (Black Graphite)

A very strong and rigid material used for primary structures like ribs and beams, but it can cause galvanic corrosion when bonded to aluminium.

Boron Fibres

Fibres made by applying vaporised boron onto a thin tungsten or carbon wire core, primarily used to repair cracked aluminium parts in military aircraft.

Ceramic Fibres

Composites used for high-temperature applications that retain strength up to $1200\,^\circ\text{C}$, such as space shuttle tiles and aircraft firewalls.

Warp

Threads that run along the length of the fabric as it comes off the roll, designated as $0^\circ$.

Weft (Fill)

Fibres that run perpendicular to the warp fibres in a fabric weave.

Bias

The fibre orientation that runs at a $45^\circ$ angle to the warp threads, allowing the fabric to be stretched for contoured shapes.

Selvage Edge

The edge of a fabric woven to prevent unravelling, which must be removed before the material is utilized.

Quasi-isotropic Lay-up

A stack of plies in specific sequences (like $0^\circ, -45^\circ, 45^\circ, 90^\circ$) that provides constant strength and stiffness in all directions.

Mats

Chopped fibres compressed together, typically used in the marine industry but not commonly used in aircraft repair due to lower strength.

Plain Weave

The simplest and most stable form of weave, though it has the lowest mechanical properties and is difficult to cover complex shapes.

Twill Weave

A weave that provides superior wet-out and mechanical properties because of reduced crimp compared to plain weave.

Satin Weave

A flat weave style with fewer intersections that covers well and is often used for aircraft repairs.

Resin Matrix

A bonding material that surrounds and strengthens fibres; in modern aircraft, this is typically an epoxy resin.

Thermoplastic

A category of plastic that can be softened by heat and hardened by cooling multiple times without changing its chemical composition.

Thermosetting

A category of plastic that, once moulded and cured by heat, cannot be reshaped or remoulded.

Pre-pregs

Fabrics already saturated with the correct amount of resin by the manufacturer, often requiring cold storage to prevent premature curing.

Sandwich Composite

A construction consisting of a core material bonded between two thin face sheets, offering an extremely high strength-to-weight ratio.

Honeycomb Core

A structural core material with a cross-section resembling bee cells, often made from aramid paper, used for high stiffness and low weight.

PEEK (Polyetheretherketone)

A semi-crystalline organic polymer with an operating temperature up to $232\,^\circ\text{C}$, used for valve seats and pump gears.

Torlon (PAI)

A high-strength polyamide-imide plastic used in thrust reverser assemblies that retains strength up to $260\,^\circ\text{C}$.

Teflon (PTFE)

A fluorocarbon polymer that acts as an electrical insulator and is used for insulating wires and cables in aircraft.

Monolithic Plastic

Transparent plastic manufactured in single, solid, uniform sheets.

Application Time

The time in hours after thawing during which a two-part sealant can be extruded from a sealant gun.

Squeeze-Out Life

The time in hours after thawing during which a faying surface sealant can still be squeezed out of a joint during fastener installation.

Anaerobic Adhesives

Adhesives used for thread locking and sealing that cure in the absence of oxygen and the presence of metal ions.