【作者】 王灿；

【导师】 陈浩然；

【作者基本信息】 大连理工大学 ， 工程力学， 2012， 博士

【摘要】 界面是泡沫夹复合材料的一个重要组成部分,它决定着面板和芯体是否能够有效地协同承载。在实践应用中存在大量界面首先发生破坏并危及整体结构的现,结构的整体承载能力往往不是取决于面板和芯体材料的强度,而是取决于界面的强度和韧性。本文采用实验研究与数值模拟相结合的方法,对泡沫夹芯复合材料界面破坏模式、界面增韧、界面蠕变断裂行为以及界面裂纹曲折扩展路径开展了较为系统的研究。本文的研究工作是973计划课题(2006CB601205)和国家自然科学基金课题(10672027、90816025)中相关子课题研究内容的重要组成部分。本文研究工作主要内容包括：1.设计了泡沫夹芯复合材料梁界面断裂破坏双悬臂梁(DCB)试验方案,采用真空辅助树脂注射技术制备了含初始裂纹损伤的DCB试件,进而考察了准静态加载下具有不同芯体密度和弹性模量的DCB试件的界面断裂破坏模式,得到了界面裂纹沿界面破坏模式和曲折破坏模式的破坏特征。对不同的界面破坏模式进行了力学机理分析,指出面板／芯体弹性模量比是出现不同界面破坏模式的支配因素。2.基于单根短切纤维细观增韧机理分析,将复合材料层合板层间短切纤维增韧技术拓展到了泡沫夹芯复合材料界面增韧中。制备了短切纤维界面增韧的泡沫夹芯复合材料DCB试件,并对增韧和未增韧试件的界面承载能力和界面断裂韧性进行了测试和评价,结果显示增韧试件的界面断裂韧性和界面承载能力都得到了显著提高。此外,通过对具有不同芯体厚度的DCB试件界面断裂韧性测试结果的比较,探讨了界面断裂韧性随着芯体厚度变化的规律及其力学机理。3.基于数字图像相关法设计了一套精密的界面裂纹蠕变位移场测量系统,对恒定载荷作用下泡沫夹芯复合材料DCB试件界面裂纹尖端附近的蠕变位移场进行了测量,并从蠕变位移场中得到了界面裂纹断裂参数的蠕变响应及其特征。最后,比较了不同树脂体系对界面蠕变断裂行为的影响。4.基于可视准则推导了包含裂纹的物质点算法,通过算例验证了该方法在断裂参数计算以及裂纹扩展模拟问题中的有效性和精确性。利用本文提出的包含裂纹的物质点算法,对具有不同芯体密度的泡沫夹芯复合材料梁界面裂纹曲折破坏特征和完整的曲折扩展破坏路径进行了数值模拟,数值模拟得到的界面裂纹曲折破坏角、扩展路径以及扩展形貌与试验结果具有很好的一致性。本文研究方法和研究成果将为泡沫夹芯复合材料界面增韧工艺设计、界面止裂设计以及界面安全评估提供有益的参考。更多还原

【Abstract】 The face/core interface plays an important role in structural performance of foam core sandwich composites. The overall load capacity of sandwich composites is often limited not by the strength of face material but by the strength and toughness of face/core interface. In this paper, the interfacial failure modes, interfacial toughness enhancement, interfacial creep fracture behavior as well as the interfacial crack kinking path in foam core sandwich composites are investigated experimenally and numerically under the framework of973Project (No.2006CB601205) and National Science Foundation in China (No.10672027, No.90816025).Related studies of this paper are summarized as follows:1. A double cantilever beam (DCB) test scheme is designed to investigate interfacial frature behavior of foam core sandwich composites. DCB specimens with artificial interfacial crack are manufactured using the vacuum assisted resin injection (VARI) process, and interfacial failure modes of DCB specimens with various foam core are experimentally examined. Two different failure modes of interfacial crack are observed during the test, and their characteristics are also obtained. Analysis is conducted on the mechanism of interfacial failure modes, and the result indicates that interfacial failure modes are mainly dominated by face/core modulus ratio of DCB specimens.2. According to the analysis results of meso-mechanism in chopped fiber toughening and the meso characteristics of foam core surface, an interfacial toughness enhancement method using relatively long chopped glass fibers is proposed. DCB specimens with and without interfacial enhancement are manufactured using VARI process. The interfacial load capacity and interfacial fracture toughness of specimens with and without interfacial enhancement are tested, and the results indicate that the interfacial toughness enhancement technique proposed by this paper can significantly promote the interfacial toughness as well as the interfacial load capacity of the foam core sandwich composites. In addition, the interfacial fracture toughness of specimens with various core thickness is also tested. It is found that the interfacial fracture toughness decreases with increasing core thickness, however, when core thickness is larger than20mm, the interfacial fracture toughness becomes a constant value. The mechanism of this phenomenon is discussed subsequently. 3. Based on digital image correlation (DIC) technique, a precise measurement system is designed to investigate the interfacial creep fracture behavior of foam core sandwich composites. Creep displacement fields near interfacial crack tip of DCB specimens are measured by this system, and creep responses of interfacial fracture parameters are extracted from the creep displacement fields. The creep test results show that creep responses of interfacial fracture parameters present the characteristics of standard solid creep model.’At last, the influences of resin materials on interfacial creep fracture behavior are discussed in detail.4. For the sake of handling cracks in numerical simulation, material point method (MPM) algorithm with cracks is developed in which discontinuity was introduced into MPM by visibility rule. The methodology is validated by typical examples, and the results demonstrate the accuracy and efficiency of the algorithm. After that, the MPM algorithm with cracks proposed in this paper is employed to simulate interfacial crack kinking angles and crack kinking paths in DCB specimens with various foam core, and good accordance is found between numerical results and experimental observations.The method and conclusions presented in this paper would benefit the interface design and interface safety assessment of foam core sandwich composites.更多还原