【作者】 陈明；

【导师】 周储伟；

【作者基本信息】 南京航空航天大学 ， 工程力学， 2018， 硕士

【摘要】 低层间强度和脆性性能导致复合材料层合结构对低速冲击作用比较敏感,低速冲击作用后容易出现各种形式的损伤,这些损伤导致结构强度大大降低,为了能够有效的预测其损伤,选取凹坑深度作为低速冲击损伤和损伤阻抗的表征参数及剩余强度的评估标准,凹坑深度容易测量,数据分散性小,且其能与冲击能量较好地对应。因此研究永久凹坑的形成机理,实现准确的凹坑深度数值模拟,对评估复合材料结构性能及优化复合材料结构有十分重要的意义。本文主要内容如下:(1)研究了永久凹坑形成的机理,提出了一种复合材料基体横向压剪损伤的残余应变模型,发展了分层损伤的残余张(错)开模型,在低速冲击损伤分析的基础上研究了凹坑粘性回弹理论,构建了广义开尔文模型,对凹坑深度随时间的回弹进行数值分析计算。(2)提出了一种包含多铺层的块体单元模型,大量减少了有限元模型单元数目,有效节省了模型的分析时间,使用Python语言对有限元软件ABAQUS进行扩展,开发了复合材料层合板低速冲击损伤失效建模及后处理损伤查询的参数化模块,避免了重复建模及后处理的复杂过程。(3)对复合材料层合板进行了多种能量的低速冲击试验、凹坑深度的测量试验,并对冲击后的试验件进行损伤超声C扫,研究了凹坑深度、冲击能量和损伤之间的关系,测量了不同湿热环境下,几种能量冲击后复合材料层合板凹坑深度随时间的回弹量,并对正常环境条件下三种能量冲击后层合板的凹坑回弹进行了有限元分析。更多还原

【Abstract】 Low inter-laminar strength and brittle properties make the laminated composite structure more sensitive to low velocity impact.After low velocity impact,various forms of damage may occur easily,and these damages greatly reduce the strength of the composite structure.Meanwhile,because the dent depth is easy to measure,the data scatter is small,and it can correspond to the impact energy one by one,in order to predict the damage effectively,the pit depth is selected as the characterization parameter of low velocity impact damage,damage impedance and the evaluation standard of residual strength.Therefore,the research of the formation mechanism of permanent pit and the accurate numerical simulation of pit depth are of great significance to evaluate the structure property and optimize the composite structure.The main content of this paper are as follows.(1)Criteria for intra-laminar and delamination failures of composite laminate were developed in which transverse pressure shear residual strain and interfacial residual open(stagger)were modeled at the basis on taking the formation mechanism of the indentation into account.Meanwhile,the generalized kelvin model was constructed which was used to calculate the indent spring-back;(2)A multi-layer block unit model was presented,which effectively shortened the model calculation time by reducing the number of units.The software ABAQUS was used as platform,the parametric modeling module of the low-speed impact damage and the post-processing damage query of composite laminates was developed by using the scripting language Python,which avoided the tedious process of modeling and post-processing;(3)Low-velocity impact test,ultrasonic C scan test and the dent depth measurement test under different energy were carried out,which studied the relationship between the pits depth,impact energy and the damage.The dent rebound of composite laminates under different hydrothermal environments was measured after low velocity impact.Numerical analysis of the dent spring-back under three kinds of impact energy(35J,40 J,50J)in normal environment was carried out.更多还原