基于声发射和数字图像相关方法编织复合材料损伤破坏研究

发布时间：2018-10-17 14:17

【摘要】：碳纤维编织复合材料以其优异的性能如高强度、高模量和耐腐蚀等在航空航天,汽车和工业领域广泛应用,而其损伤破坏过程较为复杂,了解碳纤维编织复合材料的损伤演化过程有助于其安全运行和延长使用寿命。本文通过声发射(AE)技术和数字图像相关(DIC)方法对碳纤维编织复合材料、碳/玻混杂编织复合材料和碳纤维编织复合材料压痕试件的损伤过程进行实时监测。通过这种互补检测技术记录编织复合材料试件损伤过程中的产生声发射信号、位移场和应变场信息。另外,利用应变电测技术测量试件在拉伸过程中的宏观应变,借助扫描电镜(SEM)研究其断口特征,对试件的拉伸过程进行有限元分析(FEA)得到其应变场和位移场,并与实验结果对比。碳纤维编织复合材料损伤过程分为三个阶段,分别为初始阶段,损伤累积阶段和损伤破坏阶段。碳纤维编织复合材料的载荷-时间曲线和应力应变曲线呈线性关系;幅度为50-70dB,峰值频率为200-300kHz的声发射信号与基体损伤有关,而幅度为80-100dB,峰值频率为300-600kHz的声发射信号与纤维断裂有关。利用数字图像相关方法测得试件位移场和应变场信息,发现对于相同的载荷增量,位移呈逐渐减小的趋势,而最大拉伸应呈先增加然后减小趋势。通过有限元分析方法对试件拉伸过程进行数值模拟,其分析结果与应变电测量技术测得的应力-应变曲线和DIC方法测量的实验结果吻合良好。对于碳/玻混杂编织复合材料试件,其损伤分为两个阶段,分别为损伤累积阶段和破坏阶段。声发射信号幅度分布于碳纤维编织复合材料试件大致相同。通过数字图像相关方法测得碳/玻混杂斜纹编织复合材料在损伤过程中的位移场和应变场变化,在相同的载荷增量下,碳纤维方向的位移场和应变场变化与碳纤维编织复合材料试件相同,而玻璃纤维拉伸方向的位移场呈先减小后增加趋势。根据有限元分析结果得知,数值模拟得到的位移场与应变场分布与DIC测量结果和应力-应变曲线有良好的一致性。对于碳纤维编织复合材料压痕试件,压痕损伤过程分为两个阶段:损伤累积阶段和破坏阶段。在损伤累积阶段以50-70dB低幅度信号为主,在破坏阶段,80-100dB高幅度信号明显增多;通过数字图像相关方法对编织复合材料压痕试件的压缩过程监测。分析试件在损伤过程中的位移场和应变场变化,试件侧面位移场变化准确的表现出试件分层损伤过程,结合试件断裂图,发现随着试件压痕损伤程度增加,分层损伤越不明显。声发射技术、数字图像相关方法、扫描电镜技术和应变电测技术的组合是一种有效的补充检测技术,结合有限元分析可以有效的描述编织复合材料的变形,损伤演变从而分析失效机理。另外,声发射检测技术、数字图像相关方法、扫描电镜技术、有限元分析方法和电测技术相结合的检测方法不仅有助于碳纤维编织复合材料的结构健康监测,而且可以更好地发现结构健康监测系统中的早期损伤征兆和损伤演变。
[Abstract]:The carbon fiber woven composite material is widely applied in the fields of aerospace, automobile and industry due to its excellent properties, such as high strength, high modulus and corrosion resistance, It is understood that the damage evolution process of carbon fiber braided composites is helpful to its safe operation and extended service life. In this paper, the damage process of carbon fiber braided composites, carbon/ glass hybrid braided composites and carbon fiber braided composites by acoustic emission (AE) and digital image correlation (DIC) is monitored in real time. The acoustic emission signal, the displacement field and the strain field information in the damage process of the braided composite material are recorded by the complementary detection technique. In addition, the strain field and displacement field were obtained by finite element analysis (FEA), and the strain field and displacement field were obtained by finite element analysis (FEA). The damage process of carbon fiber braided composites is divided into three stages: initial stage, damage accumulation stage and damage destruction stage. The load-time curve and the stress-strain curve of the carbon fiber braided composites are linear. The amplitude is 50-70dB, the peak frequency is 200-300kHz, the acoustic emission signal is related to the matrix damage, and the amplitude is 80-100dB, and the acoustic emission signal with the peak frequency of 300-600kHz is related to the fiber fracture. Using digital image correlation method to test the displacement field and strain field information of the test piece, it is found that for the same load increment, the displacement is decreasing gradually, and the maximum stretching should increase first and then decrease the trend. Through the finite element analysis method, the tensile process of the test piece is simulated numerically, and the results of the analysis agree well with the experimental results measured by the stress-strain curve and the DIC method. For carbon/ glass hybrid braided composites, the damage is divided into two stages: damage accumulation stage and destruction stage. The amplitude distribution of acoustic emission signals is about the same as that of carbon fiber braided composites. The displacement field and the strain field change of the carbon/ glass hybrid twill woven composite material during the damage process are measured by the digital image correlation method, and the displacement field and the strain field change in the direction of the carbon fiber are the same as the carbon fiber braided composite material under the same load increment, and the displacement field of the glass fiber stretching direction is firstly reduced and then the trend is increased. According to the results of finite element analysis, the displacement field and strain field distribution obtained by numerical simulation have good agreement with the result of DIC measurement and stress-strain curve. For carbon fiber braided composites indentation test pieces, the process of indentation damage is divided into two stages: damage accumulation stage and destruction stage. At the stage of damage accumulation, the signal of low amplitude is 50-70dB, and in the destruction stage, 80-100dB high amplitude signal is obviously increased, and the compression process of the woven composite material indentation test piece is monitored by digital image correlation method. The displacement field and strain field change of the test piece during the damage process are analyzed, the change of the displacement field of the lateral displacement field of the test piece shows the delamination damage process of the test piece accurately, and the fracture diagram of the test piece is combined, and the delamination damage is not obvious as the indentation damage degree of the test piece is increased. The combination of acoustic emission technology, digital image correlation method, scanning electron microscope (SEM) and strain electrical measurement technology is an effective supplementary detection technique. Combined with the finite element analysis, the deformation and damage evolution of braided composites can be effectively described and the failure mechanism is analyzed. In addition, the detection method of the acoustic emission detection technology, the digital image correlation method, the scanning electron microscope technology, the finite element analysis method and the electrical measurement technology not only contributes to the structural health monitoring of the carbon fiber braided composite material, Moreover, early damage signs and damage evolution in the structural health monitoring system can be better found.
【学位授予单位】：河北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB332

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