FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1970
1970 - 0647.PDF
FLIGHT" Internotr'onol, 9 April 1970 595 CARBON FIBRES AT BAC By MOLLY NEAL BSC, DIC, CEm, AFRA.S H IGH-STRENGTH lightweight carbon fibres of great stiffness, developed by the Royal Aircraft Establishment, Farn-borough, have been hailed as the first real materials breakthrough for 20 years, with the potential for revolution ising aircraft and missile structures. But before the structural revolution can take place, industry has to learn how to handle a completely new type of material, whether it has any vices or incompatibilities, how to design components to take full advantage of its capabilities and avoid its shortcomings, how to achieve consistent quality in manufacture, how to carry out inspection and repair. RAE has developed two types of carbon fibres, Type 1, of exceptionally high stiffness, and Type 2, less stiff but with a higher tensile strength. In fact, gradations of properties between the two types are possible, and may well be specified by the user industries. Specific properties compared with other reinforcing filaments are shown in Fig 1. For practical use, parallel tows of carbon fibres are embedded in a load-distributing and stabilising plastics matrix (usually an epoxy resin). The composite carbon-fibre- reinforced plastic (CFRP) is extremely strong and stiff in the direction of the fibres: Fig 2 shows how attractively these materials compare with conventional structural alloys. When loaded at an angle to the fibre direction, however, strength and stiffness fall off rapidly. Hence CFRP is most efficiently used under unidirectional loads acting parallel to the fibre direction. Under more complex two-dimensional loading, CFRP can, with adequate knowledge, be tailored effectively to carry the stress in a cross-plied laminated construction. The general practice growing up in Britain is to use, as raw material, pre-impregnated tape or sheet with continuous carbon-fibre reinforcement parallel to the length. Several specialist processors are supplying "pre-pregs" to user's specifi cation. These can be cut to size and laid up to form unidirec tional or cross-plied laminates. Fundamental difficulties in using CFRP arise from several intrinsic characteristics: in a structure that depends on con tinuity for strength, how to introduce concentrated loads, and how to join it; from its stiffness, which allows no latitude for manoeuvre in assembly; from the unorthodox thermal
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
