| The three-dimensional fabric reinforced composites have the enhanced structure in thickness direction with good interlaminar properties,shear resistance,structural stability and designability.Generally,three-dimensional fabric structure includes orthogonal three-dimensional structure,2.5D similar satin structure,three-dimensional weaving structure and strengthen warp and weft direction structure,these structures are widely used in various types of composite materials.The 2.5D similar satin structure is a new three-dimensional fabric structure with long float yarn and less intertwined points,so it has good torsion deformation capacity,suitable for stengthening bending,twisting and curve surface structure Composite materials,typical applications such as blade-reinforced fabric structure and radome-reinforced fabric structure.In order to ensure the safe use of 2.5D similar satin fabric reinforced composites in fatigue environment,it is necessary to study the tensile properties and tensile-fatigue properties.According to the characteristics of the 2.5D similar satin weave structure,we designed the fabric opening process and an open auxiliary tooling to realize the continuous weaving of the fabric on the three-dimensional loom.After compositing,we got the 2.5D similar satin fabric composite,called as FC(Fabric Composite)?The inside structure of the composites was studied by cutting the specimens.The meso-scale model of warp and weft yarns was established,and calculated the 2.5D satin fabric Geometric parameters.At the same time,production the satin laminated composite materials,called as LC(Laminates Composite),for comparative study.Based on the DIC full-field strain system,the tensile and stress-strain relationships of the FC and LC specimens were tested in the in-plane of the warp direction,and the effects of the structures on the tensile properties of the two composites were investigated.The tensile and tensile fatigue properties of FC and LC specimens also were investigated.The fatigue strength,modulus and fatigue damage modes of the two composites under high-cycle fatigue were analyzed as meso-level.In the warp direction tensile test,FC specimens is 5%less tensile strength,9%higher tensile modulus and 5%bigger elongation at break,compaerd to LC specimens.The difference is small mainly because the strength structure in-plane and the fiber volume fraction are similar.But the Poisson ratio is 93%larger than that of the LC specimen,mainly because the 2.5D similar satin weave fabric has a good deformation capability in weft.In the fatigue test,the fatigue life of the FC specimen reaches 100 million cycles at the 70%fatigue stress level,while LC specimen is 52.5%when the fatigue cycle touch one million,indicating that the fatigue resistance of FC specimen is stronger than that of LC specimen.FC and LC specimens have three stages of development in tensile fatigue test.The regularity modulus declining trend and the plastic deformation growth trend of FC specimens are obviously weaker than LC specimens,which indicates that FC anti-fatigue performance is superior to LC specimen.After fatigue,the strength loss of FC specimen is 31.2%,the tensile modulus is decreased by 22.6%,the elongation at break is decreased by 27.8%and the Poisson's ratio is decreased by 2.5%.Post-fatigue strength loss of LC specimen is 51.7%,the tensile modulus decreases by 4.2%Elongation decreased by 50.9%,and Poisson's ratio was 123%.All the performance changes were related to the degree of fatigue damage.The results of fatigue fracture and Non-destructive testing post-fatigue show that there were obvious damage in the warp and weft interweave and weft direction in the FC specimen,and developed along the interweave direction and weft direction.The LC specimen had obvious damage between the layers,along the direction of force diffusion.Compared with two sets of tensile test results,the results showed that 2.5D similar satin weave fabric composite had superior anti-fatigue performance compare with satin fabric laminates composite specimens.The research based on the pratical application,studying the application feasibility of 2.5D satin fabric as reinforcement structure for high cycle fatigue composites.The experimental data and design basis were provided for its application and improvement of fatigue resistance. |
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