【作者】 王志海；

【导师】 李永池；

【作者基本信息】 中国科学技术大学 ， 工程力学， 2008， 博士

【摘要】 纤维增强复合材料在防护领域有广泛的应用,其在冲击载荷作用下的动态力学行为、抗弹性能和破坏机理的研究已成国内外学者的研究热点。三向机织复合材料由于在厚度方向引入纤维增强,克服了层合板易分层,层间强度低等缺点,有效地改善了材料力学性能,但相关领域的研究工作,如多相结构以及应变率效应和损伤效应的各向异性、抗侵彻性能等的研究还相对薄弱。本文以Kevlar纤维/乙烯树脂三向正交机织复合材料（3DKW）为研究对象,采用实验、工程分析方法与数值计算相结合,围绕材料的动态力学性能、抗弹性能和破坏机理开展了较系统的研究。在材料本构关系的理论和本构算法的研究工作方面,对Misess类材料的“半径回归方法”给出了最一般性的严格理论证明,并由此提出了广义回归算法讨论了其适用性和局限性;以应力空间中的屈服函数和Drucker公设为基础,推导并建立了含有多应变率因子和多损伤的热粘塑性增量型本构关系的普适形式,即粘塑性流动的自洽增量算法,并提出了广义单参数应变率因子热粘塑性增量型本构关系的显式算法,从而可保证高效准确地描述材料应变率效应的各向异性;同时还分析了静水压在本构算法中的地位以及状态方程参数选取方法等。在3DKW复合材料动静态力学性能的研究方面,通过系列的MTS准静态实验和SHPB动态实验,对材料在不同加载方向的拉伸、压缩力学性能进行了相应的研究,得到了材料的基本力学参数,并进一步建立了由Hill-Tsai模型所表述的弹塑性屈服准则和本构关系。以实验结果为基础,对不同加载方向上材料强度的应变率效应进行了分析,并分析了材料在不同加载条件下的破坏模式。在3DKW复合材料抗弹性能的实验研究方面,采用球形弹和柱形弹分别对材料靶进行了系列的贯穿实验,弹速范围被控制在500-1100m/s,分析了弹型、靶厚、纤维粗细对靶板的抗侵彻性能的影响,进一步详细分析了不同弹速对靶板破坏模式的影响以及靶板的吸能机制。在高速贯穿实验结果基础上,首次提出了“超临界耗能”的概念,假定其为弹的初始动能的某种函数,并由此提出了一种以完全贯穿实验数据为基础预测靶材弹道极限V50的方法,由该法所预测的V50值比用传统面密度法和剩余能量法预测的V₅₀值更接近实测结果。在抗侵彻的工程分析方法研究方面,给出了一种基于球腔膨胀/柱腔贯穿相耦合的准一维工程分析方法,方法中靶板被视为横观各向同性材料,考虑了靶板强度的应变率效应和各向异性修正,并引入了波后锁应变的区域平均算法和柱腔贯穿对球腔膨胀的运动学修正。利用该方法对钢球侵彻贯穿靶板问题开展了系列分析计算,计算所得的剩余速度与实测剩余速度一致性很好。在抗侵彻的有限元计算方面,通过引入新的滑移面处理算法、新的破坏单元开关处理,引入粘塑性流动的自洽增量算法和适用于各向异性弹塑性的广义半径回归算法,改进和完善了已有的二维有限元程序HVP,并利用此软件对钢球贯穿3DKW靶板进行了2D的系列数值模拟,得到了侵彻贯穿图像、弹速衰减时程、剩余速度等结果,计算结果与实验结果吻合良好,较好地揭示了3DKW靶板抗侵彻/破坏的规律和机理。更多还原

【Abstract】 As fiber-reinforced composite is used extensively in defense engineering, study of the mechanical response, ballistic performance and failure mechanism of composite under impact loading being the hot-topic by the researchers in and out. Three-dimensional woven composite can overcome the defects of traditional laminates which are apt to delaminate and have low interstratified strength, because there are reinforced fibers along the thickness direction, which can improve the composite’s mechanical property, but the research works are still quite limited in this area, for example the multi-phase structure, anisotropic multi-strain.rate and damage modes, and the penetraion mechanism on it and so on. In this paper, systemic studies including experiments, engineering analyses methods and numerical simulations on the dynamic-static mechanical property and penetration property and failure mechanism of 3D Kevalr/vinyl orthogonal Woven composites（3DKW）.On the theory of constitutive relation and constitutive algorithm, a strictly theoritical testification of the radial-returan method on Misess material is given, based on the radial-return method ,a general return algorithm is deduced and its applicability is also discussed. On the modified Drucker’s postulate, the universal form of the thermo-visco-plastic incremental constitutive relations which is including multi strain rate and multi-damage mode, just is the self-consistent incremental algorithm of visco-plastic flow, then the universal single strain rate parameter constitutive relation is dedued; it can easily and fitly describe the anistropic strainrate material; More,the position of hydrostatic pressure in the constitutive relation is studied, and the determination of parameters on Equation Of States are also studied.The dynamic-static mechanical properties of 3DKW composites are studied by a series of MTS quasi-static experiments and SHPB dynamic experiments, the main parameters of basic mechanical are obtained, furthermore, the Hill-Tsai model is got, which is used to describe the mechanical of 3DKW composites. Based on the experiment results, the strain-rate of strength and the damage patterns under different load are analyzed.On the ballistic experiment of 3DKW, a series of penetration experiments are carried out by spherical and cylindrical projectiles within velocity from 500m/s to 1100m/s. Based on the experiment results, the effects of projectile shapes, target thickness and the coarse of fiber on penetration resistances are investigated, the failure modes and absorbed energy mechanism of target are analyzed within different initial velocity. Based on the high velocity penetration experimental results, the definition of "critical consumption energy" is proposed, which is assumed to be a function of the initial kinetic energy of bullet, and so a new engineering method to forecast the ballistic limit (V₅₀) is presented, compared with the traditional surface-density method and the residual energy method which is used to forecast the ballisti limit value are more simlar to the experimental V₅₀ value which is directly got by the direct measurement method.On the engineering analysis method of penetration, An engineering analysis method of computing the penetration of a metal ball into fibre-reinforced composite targets is presented, the modified model which the spherical cavity dilatation model is coupled with the cylindrical cavity penetration method is presented. In the simulation, the sphere is regarded as rigid body and the 3DKW composite target is assumed to a transversely isotropic elasto-plastic material, the strength of 3DKW targets’ strain-rate, the modification of anistropic behavior, the floating lock strain being calculated by a zone-average method and the kinematic modification are also considered. The simulation results are in good agreement with the results for the 3-D Kevlar Woven composite （3DKW） anti-penetration experiments.On the finite element method, A series of new numerical method are investigated, such as the new algorithm of the sliding interface in the penetration computations, and a new damage switch to control the element failure and so on, by introduce the self-consistent incremental algorithm of visco-plastic flow and the generalized radial-return method for anisotropic elasto-plastic material constitutive calculations, the original high velocity penetration （HVP）software is improved greatly;A series numerical simulations of 3DKW composite plate penetrated by a steel ball are carried out by the improved HVP. The numerical results of the penetration process, the history of bullet velocity and the residual velocity of the ball are fitted with the experimental results well, which indicates strongly that the numerical simulations and the new software we developed are rational and effective in the study of ballistics resistance of fiber-reinforced laminates. Finally, the physical mechanism of failure and anti-penetration of 3-DKW composites are also studied .更多还原