基于应变监测的CFRP层合板钻孔分层缺陷机理研究
发布时间：2018-10-23 11:18
【摘要】：复合材料因其质轻高强、比强度和比刚度高的优良性能,使其在航空、军事和汽车等领域的应用广受欢迎。但其脆硬性和可设计叠加层压的制造工艺,却成为钻孔缺陷的诱因。针对纤维增强复合材料(Fiber Reinforced Plastics,FRP)的钻孔缺陷问题,以FRP层合板为研究对象,采用有限元仿真分析钻削加工过程中层合板的应变响应;根据材料失效准则,对分层区域加以评价,并与实验结果对比分析,进而阐释FRP钻孔分层缺陷的产生机理。论文主要内容包括以下方面:首先,基于大量文献,梳理FRP层合板出现的钻孔缺陷,对各缺陷出现的已有主要原因进行分析总结,并在此基础上选取最易出现的分层缺陷加以研究。其次,采用ABAQUS有限元软件,建立FRP层合板的二维冲击和三维钻孔有限元仿真模型;基于HASHIN和PUCK两种材料失效准则,分析钻削分层缺陷出现的条件,编制相应的VUMAT用户材料子程序,结合界面粘结单元(cohesive element)技术,对碳纤维增强复合材料(Carbon Reinforced Plastics Fiber,CFRP)进行三维钻削仿真,给出钻孔过程的CFRP层合板钻孔周围的应力应变分布,并对应变的大小和所在的位置的关系加以分析。第三,基于仿真结果,制定传感器布设方案,对玻璃纤维/环氧树脂复合材料层合板(Glass-Fiber-Reinforced Plastic,GFRP),分别进行入口侧、出口侧的单侧及双侧应变响应测试;分析复合材料层合板缺陷产生和分布特点,优化CFRP层合板钻孔实验方案。第四,搭建CFRP层合板钻孔应变响应监测实验平台,采用双钻尖顶角的改良麻花钻,分别对有、无垫板两种支撑装夹条件下的CFRP层合板进行钻孔实验。结果表明:垫板支撑有利于抑制分层缺陷的出现;钻孔周边沿纤维方向更容易出现分层,同时伴有撕裂和毛边缺陷;出口侧的缺陷较入口侧更为严重。对实验结果与仿真结果进行对比分析,二者在出现缺陷的形式及位置上基本吻合;同时,利用最大直径比的方法对分层缺陷进行评价,其分层因子仅相差5.8%,仿真模型的有效性可在一定程度上对CFRP层合板钻孔缺陷进行预测。
[Abstract]:Composite materials are widely used in aviation, military and automobile fields because of their excellent properties such as light and high strength, high specific strength and specific stiffness. However, its brittleness and design superimposed lamination process are the inducement of drilling defects. Aiming at the drilling defects of fiber reinforced composites (Fiber Reinforced Plastics,FRP), the strain response of middle laminates in drilling process was analyzed by finite element simulation, and the delamination region was evaluated according to the failure criterion of the material, taking the FRP laminated plate as the research object, and the finite element simulation was used to analyze the strain response of the middle laminates during drilling. Compared with the experimental results, the mechanism of FRP borehole delamination defects is explained. The main contents of this paper are as follows: firstly, based on a large number of literatures, the paper combs the hole defects in FRP laminates, and analyzes and summarizes the main causes of the defects. On the basis of this, the most easily occurring delamination defects are selected to be studied. Secondly, ABAQUS finite element software is used to establish the 2D impact and 3D drilling finite element simulation models of FRP laminated plates, and based on the failure criteria of HASHIN and PUCK, the conditions of delamination defects in drilling are analyzed. The corresponding VUMAT user material subprogram is compiled, and the three-dimensional drilling simulation of carbon fiber reinforced composite material (Carbon Reinforced Plastics Fiber,CFRP) is carried out by combining with the interface bonding unit (cohesive element) technology. The stress and strain distribution around the CFRP laminate borehole during the drilling process is given. The relationship between strain size and location is analyzed. Thirdly, based on the simulation results, the sensor placement scheme was developed, and the strain response of the glass fiber / epoxy composite laminated plate (Glass-Fiber-Reinforced Plastic,GFRP) was measured on one side and two sides of the inlet side, the outlet side and the side of the glass fiber / epoxy composite laminate (Glass-Fiber-Reinforced Plastic,GFRP), respectively. The characteristics of defect generation and distribution of composite laminated plate were analyzed and the drilling experiment scheme of CFRP laminated plate was optimized. Fourthly, an experimental platform for monitoring the borehole strain response of CFRP laminates is built. The modified twist drill with double drill tip angle is used to drill the CFRP laminated plates under two kinds of supporting clamping conditions. The results show that the pad bracing is helpful to restrain the appearance of delamination defects; the edge of the borehole is more prone to delamination along the fiber direction with tear and edge defects; the defect on the outlet side is more serious than that on the inlet side. The comparison between the experimental results and the simulation results shows that the defect forms and positions are basically consistent with each other. At the same time, the maximum diameter ratio is used to evaluate the delamination defects. The difference of the stratification factor is only 5.8. The validity of the simulation model can be used to predict the drilling defects of CFRP laminated plates to some extent.
【学位授予单位】：广州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB33
本文编号：2289069
[Abstract]:Composite materials are widely used in aviation, military and automobile fields because of their excellent properties such as light and high strength, high specific strength and specific stiffness. However, its brittleness and design superimposed lamination process are the inducement of drilling defects. Aiming at the drilling defects of fiber reinforced composites (Fiber Reinforced Plastics,FRP), the strain response of middle laminates in drilling process was analyzed by finite element simulation, and the delamination region was evaluated according to the failure criterion of the material, taking the FRP laminated plate as the research object, and the finite element simulation was used to analyze the strain response of the middle laminates during drilling. Compared with the experimental results, the mechanism of FRP borehole delamination defects is explained. The main contents of this paper are as follows: firstly, based on a large number of literatures, the paper combs the hole defects in FRP laminates, and analyzes and summarizes the main causes of the defects. On the basis of this, the most easily occurring delamination defects are selected to be studied. Secondly, ABAQUS finite element software is used to establish the 2D impact and 3D drilling finite element simulation models of FRP laminated plates, and based on the failure criteria of HASHIN and PUCK, the conditions of delamination defects in drilling are analyzed. The corresponding VUMAT user material subprogram is compiled, and the three-dimensional drilling simulation of carbon fiber reinforced composite material (Carbon Reinforced Plastics Fiber,CFRP) is carried out by combining with the interface bonding unit (cohesive element) technology. The stress and strain distribution around the CFRP laminate borehole during the drilling process is given. The relationship between strain size and location is analyzed. Thirdly, based on the simulation results, the sensor placement scheme was developed, and the strain response of the glass fiber / epoxy composite laminated plate (Glass-Fiber-Reinforced Plastic,GFRP) was measured on one side and two sides of the inlet side, the outlet side and the side of the glass fiber / epoxy composite laminate (Glass-Fiber-Reinforced Plastic,GFRP), respectively. The characteristics of defect generation and distribution of composite laminated plate were analyzed and the drilling experiment scheme of CFRP laminated plate was optimized. Fourthly, an experimental platform for monitoring the borehole strain response of CFRP laminates is built. The modified twist drill with double drill tip angle is used to drill the CFRP laminated plates under two kinds of supporting clamping conditions. The results show that the pad bracing is helpful to restrain the appearance of delamination defects; the edge of the borehole is more prone to delamination along the fiber direction with tear and edge defects; the defect on the outlet side is more serious than that on the inlet side. The comparison between the experimental results and the simulation results shows that the defect forms and positions are basically consistent with each other. At the same time, the maximum diameter ratio is used to evaluate the delamination defects. The difference of the stratification factor is only 5.8. The validity of the simulation model can be used to predict the drilling defects of CFRP laminated plates to some extent.
【学位授予单位】：广州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB33
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