Failure Analysis Of Fiber Reinforced Composite Shaft Structure Based On Interface Mechanics

During the design of a new generation of high thrust-weight ratio turbofan engines,failure mode analysis of composite shaft structures is an important part of the structural integrity of low-pressure turbine shaft.In this paper,according to the failure mode composite shaft structure,The mechanical properties analysis of the composite shaft structure,the calculation and analysis of the stress concentration coefficient under the transverse tensile load and the failure calculation of composite materials with interface were carried out in three aspects:Based on the macroscopic mechanics theory of composite materials,the macroscopic mechanical analysis model of composite shaft structure was constructed,the macroscopic mechanical properties of shaft structures under different loading and layering schemes were calculated.The analysis shows that under different temperature loads,The composite shaft structure with a layering Angle of 45° and a layering number of 5 layers has a good torsional load bearing capacity.The composite shaft structure with a layering Angle of 90° and a layering number of 5 layers has a good tensile loading capacity.For the problem of stress concentration in the matrix of unidirectional fiber reinforced composite with uniform arranged fiber under transverse tensile load,A method to characterize the stress concentration coefficient of matrix under transverse tensile load was presented,the stress concentration coefficient of matrix under single and biaxial transverse tensile load was calculated,the validity of the computational model was verified by Si C/TC4 composite tensile test.The effect of fiber volume fraction,material composition and temperature on the stress concentration coefficient of transverse tensile stress of matrix was analyzed by using the model.Based on the micromechanics theory of composite materials,the representative volume element model with interface layer was established,the interface damage process was calculated and analyzed based on cohesion model.The closed composite micromechanical failure envelope was obtained.Combined with the macroscopic mechanical analysis of composite axial structure,the failure strength of composite shaft structure was calculated.In this paper,the failure analysis of composite shaft structure is completed,the research is of important reference value to the study of structural integrity of low pressure turbine shaft of fiber-reinforced metal based aero-engine,and provides a basis for the application of composite low pressure turbine shaft in aero-engine.