平纹编织复合材料层压板低速冲击后剩余强度分析
发布时间：2018-08-08 19:01
【摘要】：平纹编织型复合材料由于具有比强度高、质量轻和稳定性能好等特性,在航空等结构中的应用越来越广泛。但平纹编织复合材料抗冲击性能差,受冲击作用后结构内部容易出现纤维断裂、基体裂纹及分层等现象,严重损害结构的承载能力,从而引发安全事故。为了评估结构的损伤容限,因此对复合材料受冲击后的压缩性能开展研究具有重要的意义。本文基于ASTM D7136标准对三种铺层层压板进行低速冲击试验,研究了其冲击损伤特性;采用Abaqus有限元分析软件进行了低速冲击过程的动态模拟,揭示其损伤规律。为分析层压板冲击后剩余强度,进行压缩试验,得到冲击能量与剩余强度的关系;并将有限元模拟中的冲击损伤后末状态作为压缩的数值模拟的起始状态来实现层压板冲击及冲击后压缩的衔接。最后,进行了湿热环境下含冲击损伤层压板的压缩试验。(1)对三种铺层层压板进行了不同能量的冲击试验,发现三条凹坑深度-冲击能量曲线都会出现拐点;通过超声C扫描得出,在拐点前层压板内部主要出现分层损伤,拐点后冲击背面伴随有纤维断裂及基体开裂现象。建立层压板冲击模型,采用Hashin失效准则对面内损伤进行预判,引入cohesive单元模拟层间损伤,并采用Quads准则作为界面初始损伤判据。计算结果显示层压板分层损伤面积类似花生状、椭圆形等,分层损伤面积也与试验值接近。三种层压板的分层损伤都是由冲击背面向正面扩展的,模拟结果也可以发现少量的纤维断裂损伤及基体开裂损伤。(2)含冲击损伤层压板压缩过程中出现局部屈曲以及分层扩展等现象,最终发生剪切分层失效。并且剩余强度会受冲击能量的影响,冲击能量越大,剩余强度就下降的越多;相比于无损层压板,其剩余强度都不同程度的下降了30%到62.5%。在含损伤层压板数值模拟后处理中发现:压缩损伤会在冲击损伤区域逐渐向周围扩展,并且90度铺层方向扩展的最快,45度和-45度次之,0度方向最慢;模拟的压缩破坏载荷较试验值比较吻合。(3)相比常温下含冲击损伤层压板,吸湿后的层压板破坏载荷下降超过10%,说明湿热效应会使层压板结构压缩性能降低。
[Abstract]:Plain braided composites are widely used in aeronautical structures because of their high specific strength, light weight and good stability. However, the impact resistance of plain braided composites is poor, and fiber fracture, matrix cracks and delamination are easy to appear in the structure after the impact, which seriously damages the bearing capacity of the structure and causes safety accidents. In order to evaluate the damage tolerance of structures, it is of great significance to study the compressive properties of composites after impact. In this paper, three kinds of laminated laminates are subjected to low speed impact tests based on ASTM D7136 standard, and their impact damage characteristics are studied, and the dynamic simulation of low speed impact process is carried out by using Abaqus finite element analysis software to reveal the damage law. In order to analyze the residual strength of laminates after impact, the relation between impact energy and residual strength was obtained by compression test. The final state of impact damage in finite element simulation is taken as the initial state of compression numerical simulation to realize the connection of laminated plate impact and post-impact compression. Finally, the compression tests of laminates with impact damage were carried out in humid and hot environment. (1) three kinds of laminated laminates with different energy were tested with different energy, and it was found that the inflection points appeared in the three crater depth-impact energy curves; The ultrasonic C scan shows that the laminated laminates are mainly delaminated at the inflexion point, and there is fiber fracture and matrix cracking on the back of the impact after the inflection point. A laminated plate impact model was established, and the Hashin failure criterion was used to predict the internal damage. The cohesive element was introduced to simulate the interlaminar damage, and the Quads criterion was used as the initial damage criterion of the interface. The results show that the delamination damage area of laminate is similar to that of peanut, ellipse and so on, and the delamination damage area is close to the experimental value. The delamination damage of all three laminates extends from the back of the impact to the front. The simulation results also show a small amount of fiber fracture damage and matrix cracking damage. (2) Local buckling and delamination propagation occur during compression of laminates with impact damage and finally shear delamination failure occurs. And the residual strength will be affected by the impact energy, the larger the impact energy, the more the residual strength will decrease, and compared with the non-destructive laminates, the residual strength of the laminates will be reduced by 30% to 62.5% in varying degrees. In the post-processing of numerical simulation of laminates with damage, it is found that compression damage will gradually expand around the impact damage area, and the fastest spreading direction in the direction of 90 degrees layer is 45 degrees and -45 degrees followed by zero degrees. The simulated compressive failure load is in good agreement with the experimental value. (3) compared with the laminated plate with impact damage at room temperature, the damage load of the hygroscopic laminate decreases by more than 10%, which indicates that the hygrothermal effect will reduce the compressibility of laminate structure.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33
[Abstract]:Plain braided composites are widely used in aeronautical structures because of their high specific strength, light weight and good stability. However, the impact resistance of plain braided composites is poor, and fiber fracture, matrix cracks and delamination are easy to appear in the structure after the impact, which seriously damages the bearing capacity of the structure and causes safety accidents. In order to evaluate the damage tolerance of structures, it is of great significance to study the compressive properties of composites after impact. In this paper, three kinds of laminated laminates are subjected to low speed impact tests based on ASTM D7136 standard, and their impact damage characteristics are studied, and the dynamic simulation of low speed impact process is carried out by using Abaqus finite element analysis software to reveal the damage law. In order to analyze the residual strength of laminates after impact, the relation between impact energy and residual strength was obtained by compression test. The final state of impact damage in finite element simulation is taken as the initial state of compression numerical simulation to realize the connection of laminated plate impact and post-impact compression. Finally, the compression tests of laminates with impact damage were carried out in humid and hot environment. (1) three kinds of laminated laminates with different energy were tested with different energy, and it was found that the inflection points appeared in the three crater depth-impact energy curves; The ultrasonic C scan shows that the laminated laminates are mainly delaminated at the inflexion point, and there is fiber fracture and matrix cracking on the back of the impact after the inflection point. A laminated plate impact model was established, and the Hashin failure criterion was used to predict the internal damage. The cohesive element was introduced to simulate the interlaminar damage, and the Quads criterion was used as the initial damage criterion of the interface. The results show that the delamination damage area of laminate is similar to that of peanut, ellipse and so on, and the delamination damage area is close to the experimental value. The delamination damage of all three laminates extends from the back of the impact to the front. The simulation results also show a small amount of fiber fracture damage and matrix cracking damage. (2) Local buckling and delamination propagation occur during compression of laminates with impact damage and finally shear delamination failure occurs. And the residual strength will be affected by the impact energy, the larger the impact energy, the more the residual strength will decrease, and compared with the non-destructive laminates, the residual strength of the laminates will be reduced by 30% to 62.5% in varying degrees. In the post-processing of numerical simulation of laminates with damage, it is found that compression damage will gradually expand around the impact damage area, and the fastest spreading direction in the direction of 90 degrees layer is 45 degrees and -45 degrees followed by zero degrees. The simulated compressive failure load is in good agreement with the experimental value. (3) compared with the laminated plate with impact damage at room temperature, the damage load of the hygroscopic laminate decreases by more than 10%, which indicates that the hygrothermal effect will reduce the compressibility of laminate structure.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33
【参考文献】
相关期刊论文 前10条
1 饶辉;许希武;朱炜W，
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