The main problem of using fiber reinforced composite plastic for gear housing is low thermal conductivity and low hardness of the composite material. Because of the low hardness, the composite gear housing necessarily has numerous metal inserts laminated into the composite exterior or installed with adhesive in the prefabricated composite housing. High strength epoxy adhesives are used in fabrication of carbon fiber composite drive shafts for cars.
The metal inserts provide support for bearings, shafts, gears and other metal components of the gearbox. The composite gear housing does not remove heat as efficiently as an aluminum or magnesium housing. Composite gear housings require more expensive and reliable cooling systems. However, composite plastic material is widely used on low-power applications such as gear motors for electromechanical actuators. Die Casting Lightly loaded rotary gear actuators can be completely made of composite plastic material. Such electromechanical rotary actuators are installed, for example, on power windows of automobiles. Higher loaded actuators can contain metallic gears inside plastic composite housing for reduction of cost and corrosion resistance.
Some modern industrial robots incorporate electromechanical rotary gear actuators installed inside carbon fiber composite housing – robotic arm. Using carbon fiber material for robotic arm allows to reduce inertia of the arm and as a result makes robot operate faster. Gear Mechanic Co. uses composite gear housing for making a light weight and low inertia hypoid gear case for a racing car drive axles. Lower inertia allows faster acceleration and faster stopping which results in significant advantage on NASCAR racing and FORMULA ONE racing. In a modern airplane one can find numerous mechanical systems with gears, power drive units, drive shafts, actuators, hoists and other mechanical parts. People used to call helicopters "flying transmissions". Today an average airplane has more transmission components than a helicopter. The common transmission mechanical components of an airplane are: high lift system, bay door actuation system, cargo door actuation system, landing gears, hoists, cargo door actuation systems and sometimes primary flight control system. The overall cost and weight of the mechanical system of an airplane can be similar to the cost and weight of the helicopter transmission. Reduction of weight and cost of mechanical systems is important for reduction of the overall operating cost of the airplane.