【作者】 张璐；

【导师】 王荣国；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2012， 博士

【摘要】 纤维增强复合材料层合板由于其优异的力学性能已成为现代飞机工业中最重要的结构材料之一。但是在其制造过程中，常由于诸多不确定因素，使结构发生分层损伤，降低结构件承载能力及使用寿命，对于复合材料层合板结构而言分层损伤是一个不容忽视的安全隐患。本文以飞机实际构件中的典型分层缺陷为研究对象，针对飞机工业中应用较为广泛的碳纤维/环氧树脂材料体系，开展分层缺陷的理论分析、数值模拟及试验研究，旨在预报分层在压缩载荷及疲劳载荷作用下的扩展情况，定量分析分层缺陷对复合材料结构的影响，为工程应用提供评估理论及试验依据。针对飞机用复合材料在制造过程中产生的真实分层缺陷，通过统计与分析分层的特征参数，确立了具有工程实际研究价值的典型分层。并以典型分层为研究对象，在ABAQUS平台上以内聚力理论为基础，建立有限元计算模型，对压缩载荷作用下含分层缺陷复合材料层合板的分层屈曲及扩展行为进行预测。并且，通过开展层间力学性能试验及分层屈曲试验，验证了数值模型的有效性。并利用数值分析的方法，对试样长宽比、分层尺寸和分层厚度位置等分层参素对分层行为的影响进行定量分析，形成了分层参数敏感性的评价标准。此外，层合板结构的实际制备过程中，常由于不均匀的固化温度场及其固化残余应力以及树脂的不均匀分布，使一定范围的层合板区域内出现若干个分层，其分层间存在的作用关系尚无资料可寻。因此，在单一分层扩展行为研究的基础上，针对层合板制造过程中形成的多分层缺陷，以建立多分层许用容限为目的，在前述的内聚力模型基础上，从数值模拟的角度，首次开展了厚度位置和平面位置上双分层的扩展行为研究。确定了双分层的屈曲模式和分层间存在耦合作用，建立了分层间作用范围的三阶段理论，并从数值模拟的角度，详细讨论了影响分层间耦合作用及分层扩展行为的分层尺寸及厚度位置等因素。结构件在经历长期疲劳作用时，由于损伤的累积作用而导致的分层扩展给结构的使用安全带来巨大隐患。针对此问题，在所开展的静载荷基础上，开展了压缩疲劳试验，研究复合材料层合板的分层疲劳扩展特性，包括分层扩展速率和分层稳定长度。并采用有限元方法，计算了分层前缘的应变能释放率，并充分地考虑了各分量的作用，定量地分析载荷水平、分层尺寸和厚度位置等参数对分层疲劳扩展行为的影响。并采用扫描电镜对分层扩展路径的微观形貌进行表征，分析分层扩展行为的微观机制。同时，以分层疲劳扩展试验为基础，提出了一种简化的疲劳分层计算模型；通过试验数据的曲线拟合，确定了数值分析所需要的半经验参数。对贯穿分层的疲劳扩展行为进行数值模拟，利用前述试验验证了该简化模型定性预测分层疲劳扩展行为的有效性。此外，基于国际尚无针对复杂工况及实际分层的疲劳扩展计算案例，本文利用该简化模型成功地完成了压缩疲劳作用下的中心分层扩展特性预测，充分证明了该模型所具有的数值计算的可实现性和解决工程问题的实用性。更多还原

【Abstract】 Fiber reinforced composite laminates have become one of the most importantstructural materials in modern airplane industry because of the excellent mechanicalproperties. However, during the manufacture process, the delamination in laminatedcomposites is unavoidable, which will lower the loading capacity and the fatigue life.Therefore, the delamination existed in laminated composites is a key factor to thestructure security and must be payed full attention. In this paper, aimed at the typicaldelamination existed in actual structures in airplane, theoretical analysis, numericalresearch and experimental study have been put forward to predict the delaminationstatus of carbon fiber reinforced resin composite laminate under both compressiveload and compressive fatigue load, in order to investigate the effect of delaminationon the mechanical property of the composite structure quantificationally and providethe evaluation theory and the experiment foundation ulteriorly.Through collecting statistics of the actual delamination existed in compositesduring the airplane manufacturing, we establish the typical delamination parameters,based on which the investigation has practical value in engineering application.Furthermore, we build the numerical model based on the cohesive element theoryand the delamination buckling and growth behavior in laminated composites hasbeen predicted. And by implementing experiments of interfacial mechanicalproperties and delamination buckling, the validation of numerical model has beenproofed. Besides, the effect of specimen length-width ratio, delamination size anddepth position on the delamination behavior has been investigated quantificationallyin order to build evaluation standard of the sensitivity parameters on delaminations.Otherwise, during the fabrication of laminated structures, the uneventemperature field and the corresponding residual stress and the uneven distributingresin are always unavoidable which results in several delaminations appearing thesame time in a certain scope of the laminated composites. At present, there is noreference introducing the coupling behavior between those coexisting delaminations.Therefore, based on the research of single delamination, chapter three focuses on themultiple delaminations and the corresponding delamination growth behavior, in orderto build the allowance for multi-delaminations. For the first time, we investigate thedelamination behavior of double delaminations both in depth position and in plane.Using the cohesive element method, we ascertain the buckling mode and thecoupling behavior between the existing delaminations; we put forward a three stagetheory of the coupling scope; and we investigate the effect of delamination size anddepth position on the coupling behavior between coexisting delaminations in detail.As the delaminated plate undergoes repeated buckling and unloading, aprogressive accumulation of damage at the delamination front occurs. As a consequence, an existing delamination may grow, even if the static growth criterionis not satisfied. Therefore, in chapter four we implement the compressive fatigueexperiments based on the static experiment and study the delamination fatiguegrowth behavior including the delamination growth rate and the delaminationstabilized length. Otherwise, the components of energy release rate have beencomputed and fully considered by finite element method using VCCT technology.The effect of loading level, delamination size and depth position on delaminationfatigue growth behavior has been analyzed quantificationally. And a SEMfractographic analysis has been performed to investigate the micro mechanics ofdelamination growth behavior.In chapter five, we put forward a simplified model on delamination fatigue.Based on the compressive fatigue experiment, the empirical parameters for numericalanalysis have been obtained by curve fit of experimental data, and there exists highsimilarity between numerical results and experimental results proving the validationof this numerical model. Otherwise, using this simplified model we haveaccomplished the prediction of fatigue delamination growth for central delaminationsuccessfully, proofing that the mentioned model is highly computable and applicable.更多还原