【作者】 许蔚；

【导师】 金观昌；

【作者基本信息】 清华大学 ， 固体力学， 2003， 硕士

【摘要】 纤维增强复合材料作为一种新型的高科技材料,具有很高的比强度、比模量、层间剪切强度、断裂韧性和抗冲击性等优异的性能,在航空航天等现代高新技术发展中已引起极大的关注和开发研究与应用,但是它的力学性能存在着许多悬而未决、尚待研究的问题。特别是纤维复合材料的动态损伤及冲击性能评估,目前是力学与材料科学等交叉学科领域的前沿课题。论文利用高速摄影技术与焦散线技术相结合,对层状复合材料的冲击性能进行动态实验研究。主要包括冲击下载荷作用局部区域的动态应力集中问题和I型裂纹尖端的动态应力集中问题。主要成果是:[1]推导两种情况下复合材料应力奇异性的焦散线方程,并进行了数值模拟和定性分析;[2]对两种不同层状纤维复合材料在冲击作用下的动态局部应力集中问题进行了动态实验研究,记录一系列动态焦散斑图,提取了反映材料局部应力问题的力学参数:应力强度因子和材料实际承受的载荷;[3]对两种复合材料的抗冲击性能进行了比较,结果表明理论分析与实验研究相符合。这些研究工作对于复合材料冲击性能评估具有指导意义。更多还原

【Abstract】 The widely application of fiber-reinforced composites in the field of the aerospace and automotive industries is due to the fact that these materials have a very high stiffness to weight ration, high strength to weight ratio, and impact resistance. But there are many unsolved mechanical problems about composites that must be researched on the instant. Especially, the study of dynamic deformation and impact behavior of composites subjected to concentrated load is an important subject.In this paper high speed photography and optical caustic method is introduced to study impact behavior of laminated Composite. The research includes two aspects: dynamic stress concentration of region of loading and crack tip of Mode I. First, the parametric equations of the caustic and its initial curve surrounding the stress concentration zone are derived by the theoretical closed-form elastic solutions and the principle of reflective caustics. Theoretical caustics and initial curves for laminate orthotropic composites are simulated and analysed. Second, experimental study of two kinds of materials by means of multi-spark high-speed camera is performed to investigate the dynamic evolution of local stress singularities in laminated composites subjected to impact-concentrated loading. Using relation between the local concentrated load or the stress intensity factor and the geometric characteristic size of caustic curve, the local concentrated load and the stress intensity factor is obtained. Finally, the impact behavior of two kinds of materials is compared. These results account with theoretical analysis and can help to evaluate strength and predicte service life for composite structures.更多还原