In order to study the dynamic behavior of stiffened cylindrical shells with composite material sandwiched by co-cured damping films under the clamped boundary condition,the specimens of stiffened cylindrical shell with composite material sandwiched by co-cured damping films were prepared,and the dynamic modal test platform was set up.The fundamental frequency,damping ratio and modal shapes of stiffened cylindrical shell specimens were solved,and the accuracy of finite element model was verified.The influence of geometric parameters on structural vibration characteristics was further discussed by the numerical simulation method.The results show that,the fundamental frequency,damping ratio and modal shape of the structure will change abruptly when the height of stiffeners changes,and there is a suitable height value before the abrupt change to make the whole structure consider both damping and stiffness requirements;when the thickness of composite materials is constant,the fundamental frequency of the whole structure decreases gradually and the damping ratio increases gradually with the increase of the damping thickness or damping layer number of single layer;for the stiffened cylindrical shell of single layer damping composite materials,the closer the damping layer is to the inner skin,the higher the stiffness is,and vice versa,the damping capacity is better.

Damped sandwich composite structures are increasingly used in the aerospace, automotive and energy sectors due to their high damping and lightweight properties. Here, a novel porous fiber-reinforced sandwich composite structure is proposed, by punching holes in fiber cloth with impregnated damping solution, and resin flows through the holes during the formation of the composite structure, connecting the upper and lower prepreg layers. This paper focuses on the theoretical study of the free vibration behavior of simply supported composite porous multilayer fiber-reinforced sandwich composite structures with arbitrary delamination angles. The vibrational differential equation including the orientation angle was established and solved using Rayleigh-Ritz method and Navier method. Subsequently, the Abaqus finite element method and modal test analysis were used to evaluate the dynamic performance of the structure with different orientation angles, verify the proposed theoretical model and solution strategy, and perform structural optimization based on a genetic algorithm. The results show that the panel with the area ratio of the damping layer of 94.854% and a fiber orientation angle of multiples of 45 degrees has excellent dynamic performance. This model has significant advantages in improving structural stiffness and provides a theoretical basis for practical engineering applications.Highlights A dynamic model of porous multilayer damping plate is established. The effect of different fiber orientation angle on porous plate is studied. An experimental platform is constructed to corroborate the theoretical accuracy. Structural optimization of porous plate is conducted using a genetic algorithm. The influence of structural parameters on the porous plate is analyzed.

The finite element model of a 7.62 mm armor-piercing incendiary bomb penetrating lightweight composite target is established. The structure of the target plate is composed of boron carbide ceramic/carbon fiber laminate/aramid fiber laminate/damping material. The reasonable distribution position of damping material is explored by designing the material structure and geometric parameters. Genetic algorithm is used to optimize the structure of the lightweight composite target plate, and the feasibility of the optimization results is verified through experiments. The results show that under the same surface density, the energy absorption value of the target plate with a certain thickness of back layer damping is 1.36% higher than that of the target plate without damping. And the damping material on the back layer can act as a buffer layer to reduce blunt trauma caused by bullets to the human body. The surface density of the optimized lightweight composite target plate is reduced by 21.6% under the same protection capability. This work provides a theoretical foundation for the impact resistance design and optimization of lightweight composite target plates.Highlights Impact resistance performance of lightweight composite target plate is investigated. The impacting analytical model of the structure is established. The validity of the optimized impacting analytical model is verified by numerical simulation. Impact failure deformation contour plots of target plate and bullet. image

In the present study, a discrete layer model was established to explore the vibration performance of Functionally Graded Carbon Nanotube-Reinforced Composite (FG-CNTRC) open cylindrical shells with damping film embedded based on the first-order shell theory. There are four configurations of stacking arrangements considered for FG-CNTRC open cylindrical shells with damping film embedded. The equivalent structural parameters of the top and bottom FG-CNTRC panels are generated by implementing the extended mixing rule. Governing equations are derived based on the Hamilton principle and solved with the Naiver solution. Subsequently, after verifying the validity of this paper's solution by comparing it with the published literature, a parametric elaborated investigation discloses the variation patterns of vibration performance of four FG-CNTRC open cylindrical shells with damping film embedded. The conclusions of the study can be used as a useful guide about open cylindrical composite shell structures with the design of high strength and damping.Highlights Discrete layer vibration model was bulit based on first-order shell theory. Vbration performance of FG-CNTRC open sandwich shells was studied. Variation patterns of frequency and loss factor was disclosed. Vibration analysis of FG-CNTRC open sandwich shells. image

Abstract In order to conduct the vibration performance of laminated composite structures, the relationship between the vibration frequency and the parameters such as aspect ratio, width-thickness ratio, elastic modulus ratio and lay-up angle of the plate structure under different boundary conditions was investigated and the variation law of its vibration characteristics was obtained. The conclusions are as follows: 1. The vibration frequency tends to be smaller and smaller as the value of length increases. 2. The vibration frequency tends to be larger and larger as the value of thickness increases. 3. The vibration frequency increases with the increase of the value of elastic modulus.4. The symmetrical lay-up structure with the lay-up angle of the middle ply at 45 degrees has the lowest vibration frequency.

This paper investigates the effective elastic constants of the perforated fibre-reinforcement damping membrane, taking into account the variations in perforation array and ply orientation angle using the homogenization method and the off-axis stress-strain relation. The equations for the free vibration of the composite beam with multi-layer perforated fibre-reinforcement damping membranes are derived using the first-order shear deformation theory and the Hamilton principle. These equations are then solved using the Navier method. The novelty of this paper lies in the achievement of an effective elastic constants model and vibration analysis for the multi-layer composite beam under simply supported boundary conditions. The calculated results are then compared with experimental values and finite element results to validate the theoretical model and method. Furthermore, the paper explores the graphical variation of mechanical performance with system parameters, providing a theoretical foundation for future researchers in the composite field.

The high temperature co-curing damping composite was investigated by co-curing technology to improve the mechanical property and damping performance of the traditional fiber reinforced resin matrix composite. Fluororubber with stable chemical properties and high-temperature resistance was used as the core layer of novel carbon fiber reinforced bismaleimide resin matrix High-temperature Co-curing Damping Sandwich Composites (HCDSC). The curing temperature and curing time of fluororubber were consistent with that of bismaleimide resin by adjusting the formula. The viscoelastic damping properties and thermal stability of zinc methacrylate reinforced fluororubber were investigated in detail. Static mechanical tests, modal tests and interfacial shear tests prove that HCDSC display excellent mechanical and damping properties. The interfacial microscopic analysis reveals that viscoelastic sandwich materials are closely bonded with the composites. The dynamic characteristics of damping sandwich composite plate with fixed support on four sides is analyzed theoretically, and the vibration equilibrium equation of composite plate is derived by combining first-order shear deformation theory, variational principle, and Hamilton principle. The damping performance of the composite plate are discussed through modal tests to verify the accuracy of theoretical derivation. This research is of great significance to solve the problem of structural dynamics, and provides a new idea for the design of structural and functional composite materials. Highlights A viscoelastic damping material with large damping and high strength was prepared. The dynamic performance of co-curing sandwich composite structures was studied. The free vibration of composite structures was explored via experiment and theory.

The interfacial properties of carbon fibre (CF) reinforced epoxy resin composites are the key factors affecting the mechanical properties of the materials. To improve the interfacial adhesion between CF and epoxy resin, an effective CF surface modification method is proposed in this paper. The surface of graphene oxide (GO) was functionalised with 3-aminopropyltriethoxysilane (APTES), and then the functionalised graphene oxide (FGO) was grafted on the surface of CF. The surface roughness of modified CF was significantly improved by the SEM experiment. The effectiveness of grafting was verified by FTIR and XPS, and the chemical functional groups on the surface of modified CF were increased. The microstructure of the failure interface of the composites was observed, the modification did not reduce the tensile strength of CF, and the interlaminar shear strength (ILSS) of modified CF/ epoxy resin composite was increased by 39.91%. It was found that the CF modified by FGO was beneficial to the improvement of the interface properties of CF/epoxy resin composite. This has positive academic significance for improving the interfacial and mechanical properties of CF composites.

针对嵌银丝包覆药柱整形过程中的盲孔加工质量和安全要求,提出了一种包覆药柱盲孔自动安全加工及检测技术.首先,通过已标定的工业相机采集药柱端面图像,并进行数字化图像处理,获取银丝坐标数据后进行自动对位钻孔;然后,利用基于压缩空气吹吸原理的多余物清理组件清理盲孔内多余物,并用识别算法对孔内残留药屑进行检测并量化评分;最后,通过红外温度传感器对加工温度进行监测,并通过温度仿真和工艺试验分析了不同加工参数对钻削温度影响.结果表明,盲孔端面银丝识别率超过99％,钻孔位置精度满足不大于?0.25 mm的要求;盲孔内多余物被高效吹净,且检测算法适用性好;加工温度有效控制在50℃安全阈值内.综上,该技术可有效保障嵌银丝包覆药柱盲孔成型质量和安全性,可满足批量生产应用.

提出了一种由阻尼材料、碳纤维层合板、UHMWPE纤维层合板构成的复合防弹结构.应用LS-DYNA软件进行有限元分析,研究该结构抗7.62 mm子弹侵彻性能;通过改变结构几何参数,研究其对冲击结果的影响规律,进一步探究阻尼层的最佳涂刷位置和最优厚度.结果表明:涂刷面层阻尼对靶板抗侵彻性能提升最为显著,涂刷芯层阻尼会降低靶板抗冲击性能;同等面密度条件下,与增加碳纤维层合板或UHMWPE纤维层合板的厚度相比,添加面层阻尼材料时,靶板抗子弹侵彻能力最高.可为阻尼材料在抗高速冲击领域的应用提供依据.

使用硅烷偶联剂对芳纶纤维平织布进行表面接枝改性,研究表面改性对芳纶纤维橡胶基复合材料的层间结合性能和抗冲击性能的影响.对改性后的芳纶纤维表面进行FT-IR分析,研究改性原理,并利用SEM对改性前后纤维表面进行微观结构分析.通过对改性前后芳纶纤维制成的橡胶基复合材料板进行层间结合力测试和落锤式低速抗冲击测试,得出纤维表面改性后复合材料层间结合力和冲击峰值载荷分别提高42％和33.06％.研究表明,纤维表面的改善对于抗低速冲击性能有积极影响,为芳纶纤维橡胶基复合材料抗冲击性能的提高提供了新的思路,对复合材料复杂环境下的应用有重要意义.

To improve the interface strength between aramid fiber (PPTA) and NI-IR composites, the silane coupling agent (A172) and graphene oxide (GO) were used to have the graft modification treatment to the aramid fiber surface and analyze the chemical construction, surface topography and H -pull test of aramid fiber before and after treatment. The microstructure of the pull out fiber surface and section of the rubber-based aramid fiber reinforced polymer(AFRP) was analyzed by SEM. The results show that the oxygen -containing groups on the fiber surface are increased and the chemical activity is improved after the secondary surface modification to the aramid fiber is conducted with the silane coupling agent and GO. The obvious attachments can be found on the surface after treatment. The fiber structure has no obvious damage and its surface roughness is improved substantially. The H -pull test after treatment increases with an optimal effect of aramid fiber H -pull test after the secondary modification with GO (improved to 48.748 MPa from 18.192 MPa). The interface bonding strength between the aramid fiber and NI-IR is improved dramatically, thus confirming the effectiveness of the silane coupling agent and GO in the secondary modification to the aramid fiber, which provides reference for the study of the performance of the rubber-based AFRP.

本文采用球磨的方式将氧化铝纤维粉末均匀分散在氧化铝陶瓷浆料中,利用喷雾造粒塔造粒、干压成型后进行常压烧结.探究氧化铝纤维粉末的添加量对氧化铝纤维/氧化铝陶瓷复合材料的性能及微观结构的影响规律,以及陶瓷材料制作的工艺过程中造粒粉粒径的大小、干压成型过程中压力的大小和保压时间对复合材料性能的影响规律.结果表明:当纤维含量为10％时,材料的抗弯强度、断裂韧性和硬度达到最大值,相较于纤维含量为0％时的纯氧化铝陶瓷,抗弯强度提高了17.15％,断裂韧性提高了30.33％,但材料致密度在纤维含量为5％时达到最大值.在干压成型过程中,模压的压力越大,材料的抗弯强度越大,保压时间为8 min时,材料性能最佳,再延长保压时间对材料性能基本没有提高.

为了研究复合材料阻尼结构的抗冲击性能,利用ANSYS/LS-DYNA有限元软件模拟了12.7 mm的穿甲燃烧弹弹芯侵彻氧化铝/阻尼层/超高分子量聚乙烯(UHMWPE)复合装甲的过程,分别计算了钨合金弹芯以不同角度及不同速度侵彻靶板时的吸收能量情况,并探究了不同位置阻尼层厚度对复合装甲吸能效果的影响.计算结果表明,随着复合装甲靶板斜置角度的增加,靶板吸收的能量逐渐增加.通过模拟不同速度的钨合金弹弹芯斜侵彻复合装甲的过程,发现在700 m/s～850 m/s速度范围内复合装甲展现出最佳的吸能效果,且在复合装甲中不同位置的阻尼层达到最佳吸能效果的厚度不同.本工作可为后续研究阻尼复合结构的抗中高速冲击性能提供参考.

提出一种由碳化硼陶瓷、UHMWPE层合板、阻尼材料构成的复合靶板.应用LS-DYNA动力学软件进行数值仿真分析,研究该靶板在12.7 mm穿甲爆炸燃烧弹高速冲击下的性能,并通过实验对数值模拟进行可行性验证.进一步研究靶板抗侵彻性能随结构几何参数变化的关系,探究阻尼材料的最佳分布位置和最佳厚度.结果表明:随着陶瓷厚度增大,靶板吸收子弹动能和弹道性能指数呈线性增加;在UHMWPE层合板厚度较大时,增加其厚度对靶板抗侵彻性能的提升更明显;同等面密度条件下,与提高陶瓷或者UHMWPE层合板的厚度相比,涂刷1 mm背层阻尼材料时,复合靶板弹道性能指数最高,抗高速侵彻性能最好,为阻尼材料作为减震层在抗高速冲击领域的广泛应用奠定了基础.

针对火箭发动机氧化剂装填翻转设备跟随装填位置精度较差的问题,提出了一种装填设备协同运动方法.对氧化剂料桶倒料口位置建立矢量模型,求出倒料口位置运动方程,根据外部测控手段设定目标运动轨迹,运用五次多项式轨迹规划方法,对各自由度驱动电机进行轨迹规划,实现对氧化剂料筒位置的精确控制.通过软件仿真,将仿真结果与目标轨迹对比,结果表明:机构运动的最大速度为0.18 m/s,角速度为6 rad/s,最大加速度为0.06 m/s2,最大角加速度0.58 rad/s2,实际轨迹与目标轨迹的最大误差值为4.23 mm;该方法可保证氧化剂原料落点位置处于不同接料目标区域内,实现对氧化剂原料倒料过程的柔顺及精准控制.