Quick questions on Composite materials in aircraft: HSC Engineering Studies Aeronautical Engineering

CFRP combines high-strength carbon fibres (typically 7 micron diameter) in an epoxy resin matrix. Fibres carry the tensile and compressive load; the matrix transmits load between fibres and protects them from environment. The fibres are oriented based on the load direction at each point in the structure (laminated layups with plies at 0°, 90°, +45° and -45° to give multi-directional strength).

Modern aerospace CFRP is made by pre-preg autoclave processing:

Specific strength: CFRP is roughly twice as strong per unit mass as aerospace aluminium. The factor doubles in fatigue-limited applications because CFRP has a much higher fatigue threshold.

The Boeing 787 uses composites for:

CFRP wins on mass, fatigue and corrosion but loses on cost, repairability and impact tolerance. Specific issues:

Qantas Airlines operates the Boeing 787-9 on routes including Perth-London (14{,}500 km, 17 hours) and Sydney-San Francisco. Project Sunrise (formally announced in 2022, first flights expected 2026-2027) will use the Airbus A350-1000 for Sydney-London non-stop. Both aircraft rely on the CFRP airframe for the fuel economy and cabin environment that make ultra-long-haul economically viable.

CFRP wins on engineering but costs 10 times more per kg than aluminium. The economic case rests on the lifetime fuel saving, not capital cost alone.

Composites suffer barely-visible damage from ground impact (tug hits, hail). Inspection programmes are different from those for aluminium.

Aerospace pre-preg autoclave cure produces void-free, fibre-volume-fraction 60 percent parts. Automotive RTM produces lower-fibre-volume parts at higher production rate. Different processes.