As early as the 1950s, glass fiber reinforced composite materials were used in non-load-bearing components of helicopter fuselage structures, such as fairings and inspection hatches, but their application was very limited.
The breakthrough application of composite materials in helicopters occurred in the 1960s. While the service life of metal rotor blades is generally no more than 2000 hours, composite blades can reach over 6000 hours, or even have unlimited life, and can be maintained "on-demand." This not only improves helicopter safety but also significantly reduces the total lifespan cost of the blades, resulting in considerable economic benefits. The simple and easy-to-operate molding and curing process of composite materials, along with the customizable design of strength and stiffness (including damping characteristics), allows for more effective aerodynamic shape improvement and optimization of rotor blades, as well as optimization of rotor structure dynamics. Starting in the 1970s, research into new airfoils led to a series of high-performance helicopter rotor blade airfoils. These new airfoils are characterized by a shift from symmetrical to fully curved and asymmetrical airfoils, significantly increasing the maximum lift coefficient and critical Mach number, reducing the drag coefficient, and maintaining a relatively stable moment coefficient. Improvements to the rotor tip shape, from rectangular to swept, tapered tips, parabolic swept downward-facing tips to advanced thin swept BRP tips, have greatly improved the aerodynamic load distribution, vortex interference, vibration and noise characteristics of the blades, and increased rotor efficiency.
Furthermore, the designers conducted multidisciplinary integrated optimization design of rotor blade aerodynamics and structural dynamics, combining composite material optimization design with rotor optimization design, achieving the optimization design goals of blade performance, vibration reduction, and noise reduction. As a result, in the late 1970s, almost all newly developed helicopters adopted composite material blades, while older models of metal blades were replaced and upgraded with composite material blades, achieving very significant results.
The main considerations for using composite materials in helicopter airframe structures are: helicopters have complex curved surfaces, but the structural load is not very large, making them suitable for composite material processing and forming to improve structural damage tolerance and ensure safe and reliable use; both transport helicopters and attack helicopters require the use of composite materials for airframe structure weight reduction; and there is a need for crash-resistant energy-absorbing structures and stealth structure design.
Composite materials are initially used in fuselage structures such as the tail boom, vertical tail, and horizontal tail, primarily for weight reduction and because complex curved surfaces like ducted vertical tails are easier to mold using composite materials. Composite materials are also used in crash-resistant and energy-absorbing structures to achieve weight reduction. However, for lightweight helicopters with simple structures, low loads, and thin walls, using composite materials may not necessarily be economical.
