碳纤维层合板弹体冲击仿真方法研究

为了研究碳纤维增强复合材料层合机匣对高速撞击碎片的包容能力,通过LS-DYNA对圆柱弹体撞击BMS8-212层合增强复合材料进行动态仿真计算。有限单元计算模型中,层板材料采用连续损伤材料本构模型,层间采用固连失效接触模式。通过与试验结果的比较,验证了数值仿真方法的可靠性。发现,纤维增强复合材料层合板在弹体的横向高速撞击下主要的失效形式为纤维剪切、纤维和基体挤压、分层破坏、拉伸失效。     

高速侵彻弹体表层侵蚀效应理论计算

高速侵彻混凝土过程中,弹体的侵蚀效应随着撞击速度的提高而愈发显著。基于弹体表层材料热塑性失效机理,分析确定了高速侵彻过程弹体与靶体间摩擦效应和弹体材料塑性应变效应引起的温升。结合弹靶间局部作用情况,根据热传导方程和塑性功转热公式,利用Johnson-Cook本构方程,计算了弹体表层内两种效应引起的温度分布情况。利用临界温度判据,通过差分迭代法,计算得到了弹体表层材料失效厚度,分析不同工况下弹体高速侵蚀侵彻过程,得到了弹体轮廓演化情况,并与已有试验结果进行对比,验证了该模型的正确性。     

刚性卵形头弹撞击角度对编织复合材料层合板侵彻特性的影响

利用一级气炮发射卵形头弹撞击2 mm厚度的编织复合材料层合板,撞击角度分别为0°、30°和45°,通过高速相机记录弹靶撞击过程,并获得弹体速度数据。基于拟合公式处理试验数据,计算获取弹道极限,分析撞击角度对弹道极限、靶板能量吸收率及其失效模式的影响规律及机制。结果表明：弹体撞击角度为45°时,靶板弹道极限最高,其次为0°,撞击角度为30°时最小。随着冲击角度增加,层合板损伤形状从菱形逐渐转变为椭球形,损伤面积随冲击速度增加而增大,且45°冲击时层合板损伤面积最大,0°和30°冲击时损伤面积近似相等。弹体初始撞击角度对靶体失效模式存在影响,弹体撞击角度为0°时,纤维断口主要是剪切应力导致的横截面。撞击角度为30°时,纤维断口主要是剪切应力和拉伸应力导致的斜截面。45°斜撞击时,纤维断口主要是拉伸应力导致的横截面。     

弹体冲击效应试验的数值模拟分析

为了对刚玉块石混凝土抗弹体冲击性能进行机理性研究,采用ANSYS/LS-DYNA软件,对弹体冲击混凝土和刚玉块石混凝土试验进行了数值模拟,形象展现了弹体冲击作用下,混凝土和刚玉块石混凝土靶体破碎、飞溅成坑和背面震塌等现象,真实再现了弹体在混凝土和刚玉块石混凝土中冲击、破坏的物理过程,计算结果与试验宏观破坏现象和高速录像数据吻合良好,说明材料模型和参数正确,模拟方法可行。     

单层A3钢薄靶在不同头型弹体斜撞击下的失效模式和防护性能研究

利用轻气炮设备对平头、卵形弹进行了以5种角度撞击2 mm单层A3钢薄靶的斜穿甲试验,得到了不同头型弹体在各个角度撞击单层靶的初始-剩余速度曲线及靶板的弹道极限,获得并对比分析了弹体头部形状、撞击角度对靶板的防护性能及失效模式的影响。结果发现,平头弹在各个撞击角度下较卵形弹更容易击穿靶板,撞击角度较大时卵形弹较平头弹更容易发生跳飞现象;靶板的防护性能与弹体造成的靶板损伤和失效模式紧密相关,随着斜撞击角度变大,平头弹造成的靶板局部穿孔毁伤模式逐步由剪切冲塞失效转向以拉伸撕裂失效为主,同时整体结构弯曲和膜变形减小,而薄板在卵形弹斜撞击下的失效模式则以局部斜形非对称花瓣开裂为主。     

弹体高速侵彻陶瓷复合厚靶的计算模型研究

针对平头弹高速撞击陶瓷复合厚靶的问题,以集中质量法为基础并考虑靶体的内摩擦效应对Fellows模型加以改进,建立侵彻过程的理论计算模型并利用Matlab编程求得不同撞击速度下弹体侵彻复合靶体的侵彻深度,模型得到了试验结果和数值计算结果的验证。参数分析的结果表明,陶瓷厚度的增加可提高复合靶体的抗侵彻能力,但随着初始撞击速度的提高,弹体的侵彻深度增长曲线趋于平缓。     

弹体侵彻刚玉块石混凝土的理论分析模型

根据弹体侵彻刚玉块石混凝土后破坏、变形特征,在Taylor理论的基础上,建立了变形弹体侵彻刚玉块石混凝土靶体的理论分析模型.通过Rang-Kutta法数值解,得到了弹丸侵彻刚玉块石混凝土靶体过程中弹体尾部的位移时程、速度时程和侵彻深度计算公式,计算结果与试验数据吻合良好.     

球形弹体打击作用下宽距水间隔铝板的动态响应特性

设计了水间隔靶板在球形弹体撞击下动态响应的实验装置,利用高速相机记录了整个过程,分析了不同阶段的复杂物理现象,讨论了弹体在水中运动时的位移变化和速度衰减规律,对比了背空靶板和背水靶板在相近速度弹体侵彻作用下的变形特点。得到以下主要结论:(1)球形弹体侵彻宽间距水间隔铝板的过程可以划分为3个阶段,弹体在水中运动的过程中,水中将产生巨大的空化气穴,弹体动能转变为水的动能和势能,且在弹体碰撞后板后,水中势能再次转化为水的动能施加在靶板上;(2)球形弹体在水中运动过程中,阻力系数近似为常数,约为0.38;(3)球形弹体侵彻时,靶板由于局部径缩产生花瓣开裂,背水靶板将比背空靶板产生更小的塑性变形,且背水靶板的花瓣开裂数更少。     

长杆弹超高速侵彻半无限靶理论模型的对比分析与讨论

分别基于六组典型长杆弹超高速侵彻金属靶体以及三组长杆弹侵蚀侵彻混凝土靶体的实验数据,对经典一维AT模型及其五个改进模型对弹体侵彻深度的预测能力进行了评估,并讨论了靶体等效强度(Rt)变化以及弹体的轴线速度变化。计算结果表明,对于长杆弹高速侵彻金属靶体的分析计算,应首选AW模型,其次为LW模型。而对于混凝土靶体,已有有限的实验数据表明,上述六个模型对于长杆弹侵蚀侵彻混凝土靶体侵彻深度预测均不适用,其主要原因在于Rt不能反映超高速侵彻下混凝土靶体的响应。最后基于分析结果,给出了长杆弹侵蚀侵彻混凝土靶体进一步的研究方向。     

半球头长杆弹高速侵彻半无限厚靶临界速度理论模型

高速/超高速侵彻问题一直是武器设计者和防护工程专家关注的焦点问题之一。随着撞击速度的提高,弹体由刚体侵彻转入变形、流体侵彻状态,进而导致侵彻深度不再随速度呈单一上升趋势。为预测大着速范围下弹体的侵彻状态,基于弹体质量守恒、动量守恒及弹体动态强度计算方法,建立了弹体侵彻过程中的动力学平衡方程,进而确定高速侵彻临界速度。在与已有实验结果对比验证的基础上,分析了不同弹靶参数对侵彻临界速度的影响规律。结果表明:随着弹体静态屈服强度增大,弹体的变形长度减小,弹体的临界侵彻速度增大;弹靶塑性波波速等参数对高速侵彻状态临界速度也有显著影响。     

纤维体积分数对W纤维/Zr基非晶合金复合材料压缩性能的影响

采用渗流铸造法制备了含不同体积分数W纤维的W_f/Zr基非晶合金复合材料,其中W_f体积分数分别为47%、66%、77%和86%。研究了W_f体积分数对Zr基非晶复合材料室温准静态压缩力学性能以及变形行为的影响。结果表明:随W_f体积分数的增加,W_f/Zr基非晶复合材料的屈服强度单调增大,塑性应变先增大后减小,W_f体积分数为66%时塑性应变最大,W_f/Zr基非晶复合材料塑性应变的变化主要取决于非晶基体和W_f相互作用的程度。随着应变量的增大,基体中剪切带的数量和密度也随之增大,主剪切带向大于45°方向偏转。由于压头的影响,W_f/Zr基非晶复合材料压缩过程中样品端部和中部的受力状态不同,导致两部分的剪切带方向也明显不同。随W_f体积分数的增大,W_f/Zr基非晶复合材料的断裂方式由剪切断裂向纵向劈裂转变,断裂行为符合摩尔库伦准则。     

Wear and mechanical properties of carbon fiber reinforced copper alloy composites

The mechanical properties and wear behavior of lead-free metal matrix composite, and carbon fiber reinforced copper alloy composites were studied, and compared with a common leaded copper (Cu-6wt.%Zn-6wt.%Sn-3 wt.%Pb) alloy. The effects of carbon fibers and alloy element Sn on these properties were investigated. Carbon fiber/Cu–Sn–Zn composites showed higher hardness and bending strength than the leaded copper alloy when carbon fibers content is less than 12 vol.%. Tribological tests were conducted with disks made from these materials, and tested against a steel counterface. The carbon fiber/Cu–Sn–Zn composites showed higher wear resistance than the leaded copper alloy under a constant load of 50 N. Observations on surface morphology were utilized in understanding the wear properties of these materials. The results show that the wear mechanism of the leaded copper alloy is adhesive wear, while it is mainly adhesive wear accompanied by oxidative wear for the 12 vol.% carbon fiber/Cu–Sn–Zn composites. The 12 vol.% carbon fiber/Cu–Sn–Zn composites are likely to provide optimum substitutes for the leaded copper alloy under the load of 50 N.     

后热处理对C_f/ZrC复合材料微观结构及性能的影响

以C/C复合材料为基材、Zr_2Cu合金为渗剂,采用低温反应熔渗工艺制备得到碳纤维增强碳化锆陶瓷基复合材料(Cf/ZrC),重点研究后热处理对Cf/ZrC复合材料微观结构及性能的影响。结果表明:经1400~2200℃热处理后,材料密度下降,开孔率增大;材料在后热处理过程中会发生残余富铜熔体的流失、ZrC基体体积分数的增加以及ZrC基体结构的破坏;后热处理造成材料力学性能下降,热处理温度达到2200℃时,材料的弯曲强度保留率仅为52.3%。     

Thermal expansion coefficient and thermal fatigue of discontinuous carbon fiber-reinforced copper and aluminum matrix composites without interfacial chemical bond

Fully dense carbon fiber-reinforced copper and aluminum matrix (Cu–CF and Al–CF) composites were fabricated by hot press without the need for an interfacial chemical compound. With 30 vol% carbon fiber, the thermal expansion coefficients (TECs) of pure Cu and Al were decreased to 13.5 × 10^?6 and 15.5 × 10^?6/K, respectively. These improved TECs of Cu–CF and Al–CF composites were maintained after 16 thermal cycles; moreover, the TEC of the 30 vol% Cu–CF composite was stable after 2500 thermal cycles between ?40 and 150 °C. The thermal strain caused by the TEC mismatch between the matrix and the carbon fiber enables mechanical enhancement at the matrix/carbon fiber interface and allows conservation of the improved TECs of Cu–CF and Al–CF composites after thermal cycles.     

碳纤维连续镀镍生产工艺及其屏蔽复合材料

为了提高碳纤维镀镍工艺的生产效率以及对填充复合型电磁屏蔽材料的开发,使用自行研发的碳纤维(CF)连续电镀镍生产设备生产镀镍碳纤维(Ni-CF),并制备了镀镍碳纤维增强丙烯腈-丁二烯-苯乙烯共聚物(ABS)复合材料(Ni-CF/ABS),研究了偶联剂对复合材料力学性能的影响,以及纤维金属化及纤维含量对复合材料电磁屏蔽性能的影响。结果表明,偶联剂使复合材料具有更好的力学性能,拉伸和弯曲强度分别达到41 MPa和61.4 MPa。纤维质量分数为12%时,复合材料达到最佳的电磁屏蔽效能。     

添加微量Ti 元素对Diamond/Cu复合材料组织及性能的影响

分别采用在Cu基体添加0. 1 wt%的Ti 元素形成Cu₂Ti合金和在Diamond 颗粒表面镀钛(DiamondTi) 的方法, 制备了含Diamond 体积分数为60 %的Diamond/Cu₂Ti 复合材料和DiamondTi/Cu 复合材料。对比分析了Ti 元素对复合材料微观组织、界面结合及性能的影响规律。结果表明: 添加0. 1 wt%Ti 元素能改善Diamond与Cu 的界面结合, 在界面处观察到明显的碳化物反应层; 且以Cu₂Ti合金的方式添加Ti 元素改善界面的效果优于在Diamond 颗粒表面镀Ti 的方式。所制备的Diamond/Cu₂Ti 复合材料的热导率为621 W(m·K) - 1, 而DiamondTi/Cu复合材料的热导率仅为403. 5 W(m·K) -1, 但均高于未添加Ti 制备的Diamond/Cu 复合材料。      

Formation of Al2Cu and AlCu intermetallics in Al(Cu) alloy matrix composites by reaction sintering

We report the fabrication and characterization of a series of Al(Cu) alloy-based matrix composites. The composites were produced by sintering and rapid quenching three powder mixtures of Al and Cu with hypoeutectic, eutectic, and hypereutectic compositions. The morphology of the reinforcements formed in the Al(Cu) matrices of these composites was found to be variable. A two-phase Al₂Cu–Al(Cu) nanoeutectic, with lamellar spacing of 200–300 nm, was found in the Al(Cu) matrix of the sample having hypoeutectic composition after it was oil-quenched from 1000 °C to room temperature. While oil quenching the sample with eutectic composition, produced single Al₂Cu crystals of 2–2.5 μm size, embedded in a lamellar nanoeutectic matrix. As for the hypereutectic alloy, the matrix of the oil-quenched sample consisted mainly of Al₂Cu intermetallic, and a secondary phase of AlCu dendrites with dendrite arms spacing of 1–1.5 μm.     

Fabrication and Microstructure of C/Cu Composites

C/Cu composites were prepared by a melting infiltration technique in vacuum. In order to improve the wettability between Cu and carbon fibers, Ti (8 wt.‐%) and Cr (1 wt.‐%) were added to the Cu alloy. Microstructures of the composites and interface between C and Cu were investigated by XRD, SEM, EDS and HRTEM. The results show that the Ti and Cr improved the wettability between Cu and C? C preform and the infiltration ability of Cu into C? C preform greatly. The prepared C/Cu composites are characterized as having good interface bonding and high density. In the process of infiltration, Ti and Cr concentrate on the boundary of carbon fiber. Formation of TiC results from the reaction of Ti and C between Cu and carbon fiber.     

Si_3N_4原位增强Cu基复合材料的制备

采用感应炉熔炼及水雾化工艺制得了Cu-Si合金粉末,经N2、H2混合气体选择氮化和真空放电等离子烧结(SPS)成型,制备得到了Si3N4原位增强Cu基复合材料(Si3N4/Cu),利用萃取法研究了选择性氮化产物及其晶体结构。结果表明:复合粉末中N含量随氮化温度的升高和氮化时间的延长而增大。在1 000℃下氮化,持续时间大于60h时,粉末中的N含量明显提高;Cu的衍射峰出现整体向大角度方向的明显偏移,同时晶格常数变小,表明Si从Cu基体中脱溶,与N反应生成Si3N4;Si3N4/Cu复合材料的增强体以β-Si3N4为主;随着氮化温度的升高和氮化时间的延长,Si3N4/Cu复合材料的电导率和硬度逐步提高。     

Interfacial microstructure and its effect on thermal conductivity of SiCp/Cu composites

Thermal conductivity of SiCp/Cu composites was usually far below the expectation, which is usually attributed to the low real thermal conductivity of matrix. In the present work, highly pure Cu matrix composites reinforced with acid washed SiC particles were prepared by the pressure infiltration method. The interfacial microstructure of SiCp/Cu composites was characterized by layered interfacial products, including un-reacted SiC particles, a Cu–Si layer, a polycrystalline C layer and Cu–Si matrix. However, no Cu₃Si was found in the present work, which is evidence for the hypothesis that the formation of Cu₃Si phase in SiC/Cu system might be related to the alloying elements in Cu matrix and residual Si in SiC particles. The thermal conductivity of SiCp/Cu composites was slightly increased with the particle size from 69.9 to 78.6 W/(m K). Due to high density defects, the real thermal conductivity of Cu matrix calculated by H–J model was only about 70 W/(m K). The significant decrease in thermal conductivity of Cu matrix is an important factor for the low thermal conductivity of SiCp/Cu composites. However, even considered the significant decrease of thermal conductivity of Cu matrix, theoretical values of SiCp/Cu composites calculated by H–J model were still higher than the experimental results. Therefore, an ideal particle was introduced in the present work to evaluate the effect of interfacial thermal resistance. The reverse-deduced effective thermal conductivities of ideal particles according to H–J model was about 80 W/(m K). Therefore, severe interfacial reaction in SiCp/Cu composites also leads to the low thermal conductivity of SiCp/Cu composites.