| The possible delamination of the traditional laminated composites is avoided by2.5D fabric due to that the yarn layers are connected into a whole structure by the crimp warp in the thickness direction;Changing the interweaving law can form a variety of derivative structures with strong designability;The near net shape of preform can be realized by the change of the yarn fineness and the number of yarn layers,so it is one of the reinforcements in the field of aerospace,and also the ideal reinforcement for composite blade that has complex structure and high performance requirements;The in-plane shear and torsional properties of 2.5D carbon fiber fabric used in blade were studied theoretically and experimentally in order to provide experimental data and theory for blade preform preparation;At the same time,the preparation of typical carbon fiber blade preform and composite was completed.(1)The in-plane shear of 2.5D woven fabric with varying thickness was studied by bias-tensile test.Element size and element number to realize 2.5D fabric thickness change were compared and analyzed.The results show that the change of element size leads to the asymmetry of the deformation of the fabric and the thinner yarns is easily pull out from the fabric;The in-plane shear deformation property of the fabric with the change of the number of surface elements is better than that of the fabric with the change of the number of interior elements.The meso-structures of 2.5D fabric was measured by Micro-CT technology,then the fabric geometry model was established;The bias-tensile properties of unbalanced fabrics were investigated by numerical method.The numerical and experimental results provide data support for the profile design of blade preforms.(2)Based on the study of in-plane shear deformation of 2.5D fabric,the torsional deformation of 2.5D fabric for blades was studied.First of all,the torsion model of cylindrical helix was established.Secondly,the concepts of ultimate elongation torsion angle and failure mode of ultimate elongation were proposed.When the yarn length reaches the maximum elongation,the torsion angle is called the elongation ultimate torsion angle.This failure mode is called the elongation ultimate failure.The torsion angle of shear locking is called ultimate shear torsion angle,and this failure mode is called ultimate shear failure.Thirdly,the mathematical model of the axial yarns length is deduced,and the elongation ultimate torsion angle is predicted.Finally,the theoretical results were verified by torsion test.The results show that the theoretical results are basically consistent with the experimental value.The model provides theoretical guidance for the profile design of 2.5D structural blade preform.(3)Based on the research of 2.5D fabric deformation properties,the profile design of 2.5D structural blade preform was carried out.First of all,the thickness of the blade body was disassembled,and a set of analysis methods for different structuresare blade was established.On these grounds,the weaving technology of blade preform is designed;Secondly,finite element software was used to simulate the formability of the blade body and the weaving process was optimized;Finally,the2.5D blade preform was designed and prepared.(4)The formability of the blade preform was verified by the self-designed mold.The results show that the preform has good formability.RTM has a good mold filling process.The surface of blade is smooth and it has no glue deficiency and dry spot. |
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