内压复合材料圆柱壳损伤容限研究
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摘要
复合材料圆柱壳在纤维缠绕成型、加工、使用等环节会产生一定的初始缺陷和使用缺陷,必将给材料性能带来相应的影响,为保证复合材料性能能够最大化利用的同时,还能保证其安全性,在结构设计中必须进行损伤容限研究,这是复合材料结构设计中需要考虑的重要问题之一。本文对复合材料圆柱壳的初始缺陷和在内压载荷下的使用缺陷进行了深入研究,首先确定了初始缺陷的检测方法,得到复合材料圆柱壳初始损伤类型主要为孔隙,并且大部分集中在圆柱壳的螺旋层,同时建立了孔隙率对复合材料性能影响的指数衰减模型,定性分析了孔隙率对复合材料性能的影响,得到孔隙率每增加1%,纵向拉伸强度降低3. 3%,纵向拉伸模量降低1. 8%的结果。然后通过理论结合试验的方法确定了圆柱壳在内压载荷下的使用损伤,损伤类型为螺旋层基体开裂,并研究了其对复合材料圆柱壳的影响。最后综合考虑初始损伤和使用损伤,采用"损伤无扩展"的设计方法对复合材料圆柱壳的剩余强度进行了评估,确定了合理损伤容限设计要求,得到影响剩余强度的主要因素是孔隙率大小,在孔隙率小于3%的情况下,圆柱壳的强度安全性能很高。本项研究为全碳纤维复合材料圆柱壳在压力容器中的合理应用奠定了理论基础。
Some initial defects and service defects may occur in composite cylindrical shell during fiber winding forming,processing and application,which will bring the corresponding influence to the material performance.In order to ensure the maximum utilization of composite materials' properties and ensure their safety,damage tolerance should be studied in structural design,and it's one of the important problems to be considered in the structural design of composite materials. This paper studies the initial defects of composite materials' cylindrical shell and the service defects under internal pressure load in depth. Firstly,the detection method of initial defect is determined,and the initial damage type of composite cylindrical shell is mainly porosity. In the meanwhile,most of the damage is concentrated in the spiral layer of cylindrical shell,and an exponential decay model of the influence for composite properties by porosity is established,and the effect of porosity on the properties of composites are analyzed qualitatively. The result is that the longitudinal tensile strength reduces every 3. 3% and the longitudinal tensile modulus reduce every 1. 8% with every 1% increase of porosity. Then,the service damage under internal pressure of the cylindrical shell is determined by combining theory with experiment,and the damage type is the crack of spiral matrix and its effect on the composite cylindrical shell is studied. Finally,considering synthetically the initial damage and service damage,the residual strength of the composite cylindrical shell is evaluated by using the design method of "no damage extension",and the reasonable design requirements of damage tolerance are determined. The result is that the main factor affecting residual strength is porosity,and the safety of the strength of cylindrical shell is very high under the condition that the porosity is less than 3%. This study lays a theoretical foundation for the rational application of all-carbon fiber composite cylindrical shells in pressure vessels.
Some initial defects and service defects may occur in composite cylindrical shell during fiber winding forming,processing and application,which will bring the corresponding influence to the material performance.In order to ensure the maximum utilization of composite materials' properties and ensure their safety,damage tolerance should be studied in structural design,and it's one of the important problems to be considered in the structural design of composite materials. This paper studies the initial defects of composite materials' cylindrical shell and the service defects under internal pressure load in depth. Firstly,the detection method of initial defect is determined,and the initial damage type of composite cylindrical shell is mainly porosity. In the meanwhile,most of the damage is concentrated in the spiral layer of cylindrical shell,and an exponential decay model of the influence for composite properties by porosity is established,and the effect of porosity on the properties of composites are analyzed qualitatively. The result is that the longitudinal tensile strength reduces every 3. 3% and the longitudinal tensile modulus reduce every 1. 8% with every 1% increase of porosity. Then,the service damage under internal pressure of the cylindrical shell is determined by combining theory with experiment,and the damage type is the crack of spiral matrix and its effect on the composite cylindrical shell is studied. Finally,considering synthetically the initial damage and service damage,the residual strength of the composite cylindrical shell is evaluated by using the design method of "no damage extension",and the reasonable design requirements of damage tolerance are determined. The result is that the main factor affecting residual strength is porosity,and the safety of the strength of cylindrical shell is very high under the condition that the porosity is less than 3%. This study lays a theoretical foundation for the rational application of all-carbon fiber composite cylindrical shells in pressure vessels.
引文
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[3]沈真.复合材料飞机结构损伤容限特性[J].沈阳飞机设计研究所.2004.
[4]王荣秋.孔隙及其对复合材料力学性能的影响评述[J].航空制造技术,2009(15).
[5]朱洪艳.孔隙对碳/环氧复合材料层压板性能的影响与评价研究[D].哈尔滨工业大学.2010.
[6]Z.GURDAL,A.P.TOMASINO,S.B.BIGGERS.Effects of Processing Induced Defects on Laminate Response:Interlaminar Tensile Strength[J].SAMPE Journal,1991,27(4):39~49.
[7]吴富强,姚卫星.纤维增强复合材料剩余强度衰减模型[J].南京航空航天大学学报,2008(8).
[8]唐啸东,沈真,陈普会,等.带损伤复合材料层压板剩余强度估算方法研究[J].飞机强度研究所技术报告Q/623S-9503-25,1995.