| Carbon fiber composite materials have the characteristics of light weight,high strength,corrosion resistance and so on.They are widely used in the Marine field.Corrosion and high pressure in Marine environment put forward strict requirements on corrosion resistance and fatigue performance of materials.In recent years,laminated composite materials have developed rapidly to overcome the weakness of traditional laminated composite materials with low interlaminar strength.In this paper,the fatigue properties of layered composite materials with different structures under salt spray environment are compared and analyzed,which provides technical support for their application in Marine environment.Firstly,based on the microstructure analysis,two kinds of layered woven composites were designed and prepared.The yarn shape in the cross section of laminated composite was observed by profilometer.Based on the observation results,the yarn section assumptions of each system were established,the yarn interlacing geometric relations were derived,and the mesoscopic model was established.Through comparative analysis,the material thickness and fiber volume content calculated by the mesoscopic model are close to the measured results of composite samples.On this basis,the technological parameters of plain weave and twill weave are designed,and the prefabricated pieces with two different structures are woven on the machine.The laminating composite material is prepared by RTM process,and the volume fraction of the fiber is controlled at about 53%.Secondly,the quasi-static three point bending properties of two kinds of composite materials with different structures under salt spray environment are compared and analyzed.The difference of the bending properties of the two kinds of composite materials without salt spray treatment was characterized through the macroscopic property test and the analysis of the damage morphology.The test results showed that the bending strength and bending modulus of the composite materials with twill lining and plain lining were 22.78% and 24.86% larger than those with plain lining and layered lining.After 0,4 and 8 days of salt spray aging treatment,the changes of fracture morphology,moisture absorption and weight gain rate and bending strength of twill lining laminated woven composites were compared and analyzed.The test results showed that salt spray reduced the interfacial bonding ability between fiber and resin.The hygroscopic law conforms to Fick law;After 8 days of salt spray aging,the bending strength of samples decreased by 4%.The bending strength of samples decreased by 11%after 8 days of salt spray treatment.Finally,the three point bending fatigue properties of two kinds of composite structures under salt spray condition were compared and analyzed.Through s-N curve,load-deflection curve,stiffness degradation rule and damage morphology observation,the fatigue performance of two kinds of structural composites without salt spray treatment was characterized.It was found that the fatigue life of twill lined laminated composite was better than plain lined laminated composite under the same stress.In the load-deflection curve,the spacing of hysteresis loops is related to the performance degradation.The sudden increase of spacing means the damage aggravation and the mechanical properties decrease rapidly.The law of stiffness degradation conforms to the characteristics of typical three stages.From the point of view of the law of degradation,except for the difference in the second stage,the law of degradation in the first and third stages is consistent.The three point bending fatigue test of the twill lining after salt spray aging treatment showed that under cyclic loading,salt spray aging treatment reduced the fiber/resin interface binding ability and the fatigue performance decreased significantly. |
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