Influence of perforation damage size and direction on composite blade vibration characteristics

The finite element model of the whole rotor blade was established to study the effect of perforation damage size and direction on vibration performance.For the rectangular section of blade root at z=50mm and the leading edge section of its midst at z=835mm, the relation between vibration performance and size of perforation damage was obtained by simulating different holes of perforation damage in the leading edge, wing box and trailing edge respectively.And the relation between vibration performance and perforation damage direction was also obtained by means of changing perforation damage direction of the leading edge.It shows that the damage cannot induce the change of vibration modality but affects vibration frequency.As the perforation hole is increased, the vibration frequencies go down wholly.When the damage arose in the leading and trailing edge, lag frequencies go down great, and lowing twist frequency mostly occurred in the wing box area.The effect of perforation on vibration frequency is concerned with not only the perforation location and structure, but also with the geometry of perforation section.When the perforation direction is at the angle with 75° and 105° to the blade chordwise in the root rectangular section, lag frequency is influenced maximum.While in the midst airfoil section, as the angle approaching to 0°(180°), twist frequency is effected greatest.