Helicopter rotor blade

R. L. Pinckney, Helicopter Rotor Blades, in Applications of Composite Materials, Michael J. Salkind and Geoffry S. Hollister (Editors), ASTM STP 524, American Society for Testing and Materials, 1973, pp. 108-133 (reprinted with permission). 

Carbon fibres are manufactured from rayon and polyacrylonitrile. Carbon fibres can be heated up to 1500°C and contains up to 95% of elemental carbon. Graphite fibres can be heated above 2500 C with 99% carbon. The formation of carbon fibres from polyacrylonitrile is outlined in Fig. 1 -34. Carbon fibres are used in the aerospace industry, in compressor blade to jet engines, helicopter rotor- blades, aircraft fuselage structures, golf-club shafts, cross-bows for archery and in high speed reciprocating parts in loom. 

Limited at first to the inspection of metallic components, it was later demonstrated that high-frequency magnetic fields causing eddy current production could be applied to the testing of composites containing conductive fibers, or a certain amount of graphite [108.109], Eddy current testing has been successfully applied in the detection and characterization of defects in carbon fiber reinforced plastics (CFRP) panels, helicopter rotor blades, truck tires, and more [110-112]. 

A lack ol reproducibility, of ultrasounds for the detection of disbonds on helicopter rotor blades made of glass fiber reinforeed titanium or carbon fibers, made eddy current inspection an alternative technique with high reproducibility [119]. A longer life-cycle is achieved with composite rotor blades, and certain blades have demonstrated a service life... 

Figure 9 Disbonds on a helicopter rotor blade detected by eddy currents (view from above).

Figure 18 CT radiograph of a section of carbon fiber helicopter rotor blade with light delamination.

Nylon epoxy adhesives were developed in the early 1960s. These extremely tough adhesives were used to laminate helicopter rotor blades and in honeycomb core-to-skin bonding [9, p. 157]. 

Applications for Kevlar include aircraft interiors, ducting, helicopter rotor blades, radomes and avionics. 

Helicopter rotor blades, with 1000 hour design life, develop cracks after... 

Computer Control. The Army s desire to test an all-purpose, multiaxis tape placement machine led to the next step forward, an automatic machine built in 1974 for helicopter rotor blades for the Army Aviation Systems Command (AVSCOM) (19). This was the first 6-axis minicomputer-controlled tape-laying... 

This machine was an excellent tool for developing the techniques of spar making, skin lay-ups, and attachment of helicopter rotor blades it pointed the way to specialty production machinery (see Figs. 28 and 29). 

Fig. 32. CNC Viper fiber-placement system lays individual tows on a mandrel, shown here making a helicopter rotor blade spar at Bell Helicopter Textron (Fort Worth, Tex.). Courtesy of Cincinnati Machine and Bell Helicopter.

Solid-state actuation signifies the use of the induced-strain effect present in active materials to achieve actuation without any moving parts, i.e., in a solid-state manner. Already, solid-state actuation has found niche application in the aerospace industry. The aero-servo-elastic control of vibrations and flutter with solid-state actuated flaps, tabs, vanes, etc. for helicopter rotor blades and aircraft wings is currently being experimented on. 

Konstanzer, P. Decentralized Vibration Control for Active Helicopter Rotor Blades. Doctoral thesis Univ. Stuttgart, VDI Fortschrittsberichte, Reihe 8, Nr. 923, VDI-Verlag Diisseldorf/Germany (2001)... 

---