Abstract
Unlike metal structure, composite structures don’t give any clue till the fatal final collapse. The problem is more complicated when applied load on the structure is aeroelastic in nature. Under such loading, composite laminate experiences stresses. The first layer failure happens when stresses in the weakest ply exceed the allowable strength of the laminate. This initial layer-based failure changes overall material characteristics. It is important now to degrade the composite laminate characteristics for the subsequent failure prediction. The constitutive relations are required to be updated by the reduction in stiffness. The rest of the undamaged laminates continue to take the load till the updated strength is reached. In the present work, layer wise progressive failure analysis under aeroelastic loading has been performed by the inclusion of different failure criteria which allow for the identification of the location of the failure. ANSYS APDL environment has been used to model geometry of helicopter rotor. Under the loading conditions, stresses are calculated in the blade. Using stress tensor and failure criteria, failure location and modes have been predicted. It has been found that failure starts at higher speeds and failure starts from the root chord and tend towards the tip chord.
Highlights
Composite materials have shown distinct characteristics in term of strength and weight in such a way that all industries in general and aerospace industry in particular are drifting towards modifying their manufacturing processes and using composite materials in their product development
An APDL code has been developed in ANSYS environment putting finite element structural model, lift, gravity, centrifugal forces and the composite failure criteria at one place making the code attractive for the solution of any practical problem
Helicopter rotor blade is subjected to complex aerodynamic loading and its structural design is of utmost importance
Summary
Composite materials have shown distinct characteristics in term of strength and weight in such a way that all industries in general and aerospace industry in particular are drifting towards modifying their manufacturing processes and using composite materials in their product development. A composite helicopter rotor blade separate damage modes as discussed above, few research- (Pawar & Ganguli, 2006) using shell and solid elements ers have modeled the progressive damage accumulation has been used. (Helicopter blade in all plies and in a multi-directional laminate and may is rotating and its vibration modes will be differlead to laminate failure by de-lamination or fiber break- ent with that at wind off conditions this effect has been age Such a model was proposed by Shahid and Chang accounted by axial loading of the blade and calculating (1995) for predicting the accumulated damage and stud- pre-stressed modes). Two different versions of finite strip method have been used by Ovesy et al (2006) to predict geometrically nonlinear behavior of composite laminate under progressive end-shortening and to pressure loading. Centrifugal force has been applied using the parameter of rotation speed, ω
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