Experimental and Numerical Investigation on Impact Performance of Carbon Reinforced Aluminum Laminates

It is known that fiber metal laminates (FML) as one of hybrid materials with thin metal sheets and fiber/epoxy layers have the characteristics of the excellent damage tolerance, fatigue and impact properties with a relatively low density. Therefore, the mechanical components using FML can contribute the enhanced safety level of the sound construction toward the whole body. In this study, the impact performance of carbon reinforced aluminum laminates (CARAL) is investigated by experiments and numerical simulations. Drop weight tests are carried out with the weight of 4.7 kg at the speed of 1 and 2 m/s, respectively. Dynamic non-linear transient analyses are also accomplished using a finite element analysis software, ABAQUS. The experiment results and numerical results are compared with impact load-time histories. Also, energy-time histories are applied to investigate the impact performance of CARAL.     

Influence of Temperature on the Fatigue Behaviour of Glass Fibre Reinforced Polypropylene

Abstract: The behaviour of a composite with a polymeric matrix subjected to fatigue was analysed. The study was conducted at ambient temperature, as well as at 50 and 100 °C. The material was observed to behave differently at each temperature. Furthermore, a statistical analysis was performed using Castillo’s model. Although certain similarities in behaviour were observed at ambient temperature and 50 °C, the material behaved differently at 100 °C. Structural modifications were found in the thermal analysis that justify these differences.     

钢管钢纤维高强混凝土抗冲击压缩性能的试验研究与数值模拟

遮弹层的建成及优化对防护工程的发展尤为重要。钢管钢纤维高强混凝土蜂窝遮弹层是一种具有高强抗力的新型遮弹层,文章对其组成构件钢管钢纤维高强混凝土进行霍普金森压杆(SHPB)动态力学性能试验,并借助动力有限元分析软件LSDYNA进行数值模拟。冲击压缩试验中,试件的钢纤维掺量分别为0%、0.5%、1.0%、1.5%,钢管壁厚分别为2mm、3mm。结果表明钢管钢纤维高强混凝土具有应变率强化效应,应变率越高,试件的动态抗压强度越大。当气压为1.0 MPa时,壁厚3mm、钢纤维掺量1.5%的试件强度达258.3 MPa。与钢纤维高强混凝土相比,钢管钢纤维高强混凝土的抗冲击压缩性能更好,动态抗压强度最大增幅达35.4%,且具备承受多次冲击压缩作用的能力。数值模拟与试验结果吻合度高,表明数值模拟方法具有可行性。     

高强玻纤复合材料静态力学性能实验研究

利用电子万能试验机和静态应变仪测定了高强2号玻纤复合板的静态拉伸、静态压缩和剪切性能,得到了较为完整的静态力学性能数据,并对复合材料的拉伸破坏现象进行了分析.结果表明,高强玻纤复合材料具有良好的力学性能,是一种性价比较高的结构材料.     

子弹药落地冲击响应的数值模拟及实验验证

采用数值模方法开展了子弹药以不同落角和攻角撞击混凝土介质的冲击响应的研究,对一定质量、速度的子弹撞击混凝土介质进行仿真计算和实验验证。获得了子弹在落速15m/s、落角60~90°和攻角不大于5°范围内撞击混凝土介质冲击峰值过载和碰撞作用时间的影响规律。数值模拟结果与实验结果吻合较好,研究结果对子弹落地冲击响应理论模型的建立及子弹结构部件的结构强度设计具有参考价值。     

玻璃/苎麻纤维混杂复合材料力学性能研究

混杂纤维增强复合材料由于可以综合利用各种纤维的优点,极大的提高了复合材料的性能,拓展了复合材料的适用范围。本文采用玻璃纤维和苎麻纤维混杂酚醛树脂制备复合材料,研究了复合材料混杂比和铺层顺序对混杂纤维复合材料力学性能的影响。从结果可以看出,玻璃纤维和苎麻纤维的不同比例对混杂复合材料的力学性能有着显著的影响,而采用玻璃纤维作为芯层的时候可以获得较好的拉伸性能,采用苎麻纤维作为芯层的时候可以获得较好的弯曲和剪切性能。     

Experimental Study and Numerical Modelling of Low Velocity Impact on Laminated Composite Reinforced with Thin Film Made of Carbon Nanotubes

In this work, polymer laminated composites based on Epon 862 Epoxy resin, T300 6 k carbon fibers and carbon nanotubes (CNTs) were tested with the aim to elucidate the effect of CNTs on impact properties including impact force and capacity to absorb impact energy. The polymer matrix was reinforced by a random distribution of CNTs with fraction ranging from 0.5 to 4.wt%. Composite panels were manufactured by using the infusion process. Taylor impact test was used to obtain the impact response of specimens. Projectile manufactured from a high strength and hardened steel with a diameter of 20 mm and 1.5 kg of mass was launched by a compressed gas gun within the velocity of 3 m/s. Impact force histories and absorbed energy of specimens were recorded. A numerical model was employed to simulate the impact performance. This model has been accomplished by forming a user established subroutine (VUMAT) and executing it in ABAQUS software. Finally, the effect of CNTs amount on dynamic properties of laminated composites was discussed.     

Fatigue Behaviour of Glass Fibre Reinforced Composites for Ocean Energy Conversion Systems

The development of ocean energy conversion systems places more severe requirements on materials than similar land-based structures such as wind turbines. Intervention and maintenance at sea are very costly, so for ocean energy supply to become economically viable long term durability must be guaranteed. Cyclic loading is a common feature of most energy conversion devices and composites are widely used, but few data are available concerning the fatigue behaviour in sea water of composite materials. This paper presents the results from an experimental study to fill this gap. The fatigue behavior of composite materials reinforced with different types of glass fibre is characterized in air and in sea water; the influence of testing in sea water rather than air is shown to be small. However, sea water ageing is shown to reduce the fatigue lifetime significantly and strongly depends on matrix formulation.     

玻纤增强尼龙6的断裂研究

通过对不同玻纤含量的玻纤增强尼龙复合材料(GFPA)的性能及断口形貌的研究,得出GFPA的宏观力学性能的变化可由断面形貌特征来定量表征。拉伸强度随拉伸断口断面平坦区面积与断面总面积之比AP/A0的变小而提高,Izod缺口冲击强度随GFPA的断面粗糙度参数RS的提高而线性提高。断面形貌的变化与玻纤在基体树脂中的应力集中作用及对裂纹扩展的阻碍作用有关。     

玻璃纤维/玻璃微珠混杂增强聚氨酯泡沫铝压缩性能研究

通过实验制备了泡沫铝、聚氨酯泡沫铝(PUF泡沫铝)和增强PUF泡沫铝试件,并对它们的压缩性能进行了研究。结果表明,增强PUF泡沫铝尤其是混杂增强PUF泡沫铝的压缩性能优于纯泡沫铝和PUF泡沫铝,且当玻璃纤维含量为4.5%(质量分数)、玻璃微珠含量为1.5%(质量分数)时,混杂增强PUF泡沫铝复合材料的增强效果最好,可作为一种缓冲性能很好的防护材料。     

玻纤含量对玻纤增强聚丙烯拉伸性能的影响

采用不同玻纤含量的标准拉伸试样,应用试验方法,通过玻纤含量对玻纤增强PP复合材料的拉伸性能进行比较,找出了实现最佳抗拉强度的玻纤含量。     

空化水射流冲击微成形数值模拟与实验研究

利用空化水射流中空泡溃灭产生的高压冲击波使TA2箔材产生微塑性变形,分析水射流主要工艺参数对微成形质量的影响规律。采用ANSYS/LS-DYNA数值模拟和实验研究对比的方法,通过不同冲击压力和持续时间对成形深度、成形件厚度减薄率影响的数值模拟,并进行成形工件形貌的实验验证。结果显示,对于不同冲击压力峰值和冲击压力持续时间下的板料成形,随冲击压力峰值和持续时间的增加,其成形深度、成形件厚度减薄率呈正比增加;当数值模拟冲击压力峰值Pmax=2.2 GPa、冲击压力持续时间t=40 ns时,与实验入射压力P=20 MPa、冲击时间t=1 min时的试样截面轮廓成形曲线和截面厚度减薄结果比较一致。TA2箔材微成形件圆孔阵列特征在空化冲击区内表面质量良好,具有较大的成形深度及其较好的成形深度一致性。     

Numerical and Experimental Analysis of Welding Deformation in Thin Plates

The use of welding to permanently join plates is common in industry due to its high efficiency. But welding creates thermal stresses, which can lead to residual stresses and physical distortion. This phenomenon directly influences the buckling stiffness of the welded structure. The welding distortion not only makes difficult the erection of the project, but also influences the final quality and cost of production. In this research, the thermo-elastic-plastic conditions were simulated by a three-dimensional (3D) finite element model (FE). Mechanical and thermal properties of the material were applied to the model, leading to eigenvalue analysis of the thermal and longitudinal stress distribution, buckling during welding and global. The research was performed on thin plates welded by butt joints and T-joints. A birth and death method depending on time was also used to model the molten pool. Since welding is a thermo-mechanical process, a coupling method was used to obtain results for nonlinear transient thermal analysis and introduce them in the structure analysis in order to investigate the buckling phenomenon. A comparison of our numerical results with those obtained from our experiments showed that the models can help predict when and where local buckling can occur. This method can also help predict the heat distribution and deformation during and after welding.     

Preliminary Investigation of the Wear Behaviour of Self-lubricating Carbon Fibre Reinforced Glass Matrix Composites in Vacuum

The self-lubricating wear behaviour of a C-fibre reinforced borosilicate glass matrix composite was investigated using a vane-stator configuration resembling a rotating vacuum pump. The vanes were made of the composite material and the stator was of cast iron. Tests were carried out under varying loads in the range 3.8 to 5.8 N. Rotational velocities varied between 5.5 and 7.8 m/s. Fibre fracture and glass matrix particle detachment were the damage mechanisms observed by scanning electron microscopy. Composite wear was accompanied by material transfer onto the stator surface. The formation of isle-type and continuous graphitic films on the counter-body surface was observed. These films provide adequate lubrication during friction, leading to a relatively low wear of the composite under the conditions investigated.     

多层SGP夹层玻璃受刚体冲击作用的实验研究

多层SentryGlas®Plus (SGP)夹层玻璃在建筑行业被广泛作为承重材料, 玻璃在动态冲击下的脆性失效易导致夹层玻璃的承重性能大幅降低, 而目前对多层SGP夹层玻璃抗冲击性能的研究数据较少。本研究基于平均最小破坏速度(MMBV)测试方法, 对三层SGP夹层玻璃面板展开刚体冲击实验。首先采用高速相机追踪裂纹产生和扩展情况, 将夹层玻璃的开裂顺序分成三类, 并通过分析其冲击响应, 研究开裂顺序、支撑条件和玻璃面板构成对SGP夹层玻璃抗冲击性能的影响。实验结果显示, 边缘夹固式夹层玻璃需要更高的平均最小破坏速度来触发玻璃破损, 且与驳接点支式试样相比, 其碎裂前刚度提高了44%。相比于钢化玻璃, 半钢化玻璃碎片在受压状态下可产生更强的锁合机制, 从而明显提高试样刚度, 平均最小破坏速度则稍有增加。研究还显示动态刚度在破坏后阶段将会显著降低。最后, 结合高速相片分析了两类动态脱层特征。     

对接试板焊接残余应力实测与数值模拟

使用压痕法对两副对接试板进行了表面焊接残余应力测试,并通过焊接有限元仿真获得了对接试板焊接残余应力分布规律,对比分析了表面残余应力实测和数值模拟结果。分析结果表明,焊接残余应力数值仿真结果和压痕法实测结果趋势一致,数值相差不大,残余拉应力峰值实测为599 MPa,仿真结果为597 MPa,表明数值模拟方法可预测焊接残余应力;焊缝及热影响区最大纵向残余应力属于拉应力,而最大横向残余应力为压应力,横向残余应力峰值低于纵向残余应力峰值;等效应力(Mises应力)峰值792 MPa,高于试板材料在常温下的初始屈服强度,表明该材料具有明显的加工硬化现象。     

Inverse Analysis of Impact Test Data: Experimental Study on Polymeric Materials Displaying Brittle Behaviour

This paper deals with the influence of the testing equipment on impact load measurements. A previously developed method of analysis and processing of the experimental data based on a refined analogical model of the impact event and inverse problem techniques is used. This method makes it possible to obtain the mechanical response of the material, notwithstanding the disturbance of the dynamic effects associated to the test. Results from tests carried out both on falling weight and swing pendulum instrumented testing machines are compared. It is shown that this method can give an accurate estimation of the actual bending force in impact testing independent of the testing equipment.