Study On The Structure And Tensile Properties Of 3-D Woven Fabric With Gradual Thickness Change In Unidirection

Three-dimensional woven fabric which are used in textile composite preform have excellent structural integrity and interlayer shear resistance,in the aerospace,automotive industry,sports and leisure areas have great room for development.Thickness gradient Three-dimensional fabric thickness has a thickness changes in the direction of thickness,apply to the components which's thickness need to change.Such as an engine fan blade,a wind turbine blade,an aircraft propeller,and so on.At present,the gradual thickness change of the composites mostly complete with the laminated process.However,the interlaminar shear of the laminated plate is poor and easy to peel,which has a great disadvantage compared with the three-dimensional weaving technology.If the 3-D fabric with gradual thickness change apply to composite reinforcement,it will greatly improve the comprehensive performance of composite.While the relationship between the weaving process and the structure and the tensile strength of the 3-D woven fabric with gradual thickness change is still in the immature stage.The invention solved the problem that the fabric can not be tightened in the beating-up and the fabric is not dimensional in the thickness direction,improved the weaving efficiency and the weaving property.In this paper,studied on the 3-D woven fabric with longitudinal thickness gradient,and according to the characteristics of the thickness gradient,two types of fabrics with cross-sectional shapes were designed:three-dimensional woven fabric with single-sided longitudinal thickness gradient(Section is a right-angled triangle)and three-dimensional woven fabric with double-sided longitudinal thickness(Section is isosceles triangle).Weaving is realized by gradually reducing the number of fabric layers and gradually reducing the number of weft yarns,and the three basic structures of layered orthogonal,layered angle interlock and multilayer joint are carried out.The microstructure and process parameters were design,and drew the organization chart,achieved the machine weaving.In the weaving process,the loom was partially modified,produced the"triangle reed" according to battening characteristics of weaving thick three-dimensional fabric.When woven single-sided longitudinal thickness gradient 3-D woven fabric,the fabric surface retained the loss of the yarn head,this affected the stability of the fabricstructure,so the yarn was designed three kinds of consolidation methods: Straight through,"S" and “inverted N ",designed the pulling-out experiment.The results show that the "S"consolidation mode has the least effect on the structural stability of the fabric,and the consolidation effect of the "S" consolidation mode in the multilayer joint is the least and the most solid.In the chapter on the relationship between fabric structure and thickness,the following conclusions are obtained:The one-sided thickness gradient fabric was the thickest and the thickness of multilayer structure fabric was the thinnest,and the thickness of three kinds of fabric were reduced evenly during the process of thickness changing.In the two kinds of cross-section shape of three-dimensional woven fabric,the change of the thickness of the single-sided longitudinal thickness fabric was bigger than the double-sided longitudinal thickness gradient fabric,which is determined by different ways of yarn reduction.Therefore,according feature of thickness changes of the single-sided thickness gradient fabric and double-sided thickness gradient fabric,the former can be used to achieve the thinner thickness of the components,the latter one can be used to weave the fabric which's thickness needs little change.In the testing of tensile properties of fabrics,the single-sided longitudinal thickness gradient of the three-dimensional woven fabric fractured in the thinnest layer of the fabric,multilayer structure of the fabric breaking strength was the biggest,orthogonal layered structure was the smallest,the relationship between the fabric's tensile strength and the thickness change of the woven fabric was non-linear relationship;In the tensile test of three-dimensional woven fabric with double-sided thickness gradation,the breaking strength of multilayer bonded fabric was the biggest,the layered angle interlock structure was the smallest,and the relationship between the fabric's tensile strength and the thickness of the woven fabric was linear.