Method for determining allowable defects of helicopter composite main rotor blade

Abstract

The invention relates to a method for determining allowable defects of a helicopter composite main rotor blade and belongs to the technical field of structural fatigue design of helicopters. The method comprises the following steps: determining forms and easily occurring areas of a defect according to the function and structure of each area of a main rotor blade and process control and other conditions in the manufacturing process; predicting the maximum allowable size of the defect based on the principles such as detection simplicity, statistics and process controllability, and prefabricating on a full-sized test piece; determining the rationality of defect parameters by adopting a test of simulating fatigue and residual strength in a real load environment, determining the defect types in critical prevention and control of the composite main rotor blade, and establishing the defect allowable standard. According to the method, a technical basis can be provided for treatment of the various defects in the production, usage and maintenance processes.

Description

technical field [0001] The invention belongs to the technical field of fatigue design of helicopter structures, and in particular relates to a method for determining allowable defects of main blades of composite materials of helicopters. Background technique [0002] Defect tolerance was first proposed by FAA (Federal Aviation Administration) in 1989 in response to several civil aviation accidents caused by defects. The FAA believes that various defects will inevitably appear in the aircraft structure during production and use, and it is not reasonable to carry out fatigue design based on the ideal state of no damage to the structure. After 2000, structural long-life design gradually became the mainstream. For example, the fatigue design life of the key structure of a civil helicopter reached 6,000-20,000 flight hours. It is more likely that defects will evolve into hazards in a long life cycle. Therefore, the defect tolerance performance verification of structures has grad...

AI Technical Summary

Problems solved by technology

However, the manufacture of composite main blades needs to go through multiple complex processes such as placing support ribs, foam linings, winding, cross-laying, gluing, high-temperature molding, etc., and it is difficult to completely avoid internal defects in this process. Existence, such as delamination, misalignment, wrinkles, inclusions, etc.; and the working mode of the high-speed rotation of the main blade during use is easily affected by impact damage caused by foreign objects such as flying sand and stones.

[0004] When the helicopter performs flight missions, the main blades are always in a complex stress environment, which not only bears the load cycle caused by ground-air-ground flight, but also bears the periodic aerodynamic force, elastic force, and inertial force. Shimmy bending moment, torque and centrifugal force, once the structure has initial defects or accidental damage during use, the harsh load environment can easily lead to a decrease in structural strength or stiffness, affecting the safety of use

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