Flexural Properties of Grooved Perforation Sandwich Composites

Selecting H-60 PVC foam, four-axis E-glass non-woven fabric and vinyl resin, a type of innovative reinforced sandwich composite as grooved perforation sandwich （GPS） were fabricated by VIMP. The interfacial structure between the face and core of the sandwich is innovative because of the acuminate grooves in both sides of foam core and the holes perforated along core’s height. The fabrication results show that VIMP is a high-speed and cost-effective manufacturing method. The mechanical properties of the reinforced foam core were tested. The typical flexural failure modes of sandwich specimens were observed. The flexural stiffness and ultimate bearing capacity of sandwich were studied by ordinary sandwich beam theory and finite element method.

A Mathematical Model and a Method for the Calculation of the Downhole Pressure in Composite-Perforation Technological Processes

Using the conservation equations for mass,momentum and energy,a model is elaborated to describe the dynamics of high-energy gases in composite-perforation technological processes.The model includes a precise representation of the gunpowder combustion and related killing fluid displacement.Through numerical solution of such equations,the pressure distribution of the high-energy gas in fractures is obtained,and used to determine crack propagation.The accuracy of the model is verified by comparing the simulation results with actual measurements.

Damping and Mechanical Properties of Cocured Composite Laminates with Embedded Perforate Viscoelastic Layer

The composite laminates with embedded acrylonitrile butadiene rubber （NBR） layer were fabricated by cocuring process. The embedded layers were perforated with a series of small holes to allow resin to flow through the damping layer and completely couple the structure to improve bending stiffness and interlaminar shearing strength of these cocured composite laminates. The damping, bending stiffness and shearing strength of these composite laminates with different perforation diameters were investigated. The experimental results show that increasing the perforation diameter leads to significant decreases in damping and significant increase in bending stiffness up to an area ratio of 7.065%. The area ratio here is defined as the ratio of perforation area to the total damping area. Beyond the area ratio of 7.065%, increasing the diameter to an area ratio of 50.24% results in only a slight variation in damping and bending stiffness. Moreover, increasing the perforation diameter does not always increase the shearing strength of the embedded viscoelastic layer. The shearing strength of embedded viscoelastic layer increases only when the area ratio is greater than 19.625%; instead, it will decrease.

Can composite performance measures predict survival of patients with colorectal cancer?

AIM: To assess the relationship between long-term colorectal patient survival and methods of calculating composite performance scores.

Prediction of Final Velocity of Aramid Fabric-Resin Composite Laminates Subjected to Ballistic Impact

The strain rate effects of aramid fiber material, quasi-static and ballistic impact perforation of composite laminates made of aramid fabric and phenolic resin/PVB are investigated respectively by means of MTS, split Hopkinson tension bars and ballistic impact apparatus. The tensile impact experiments on aramid fiber material are performed in strain rate range from 0.01/s to 1000/s. Experimental results show that the mechanical properties of aramid fiber material are insensitive to strain rate in the range from 0. 01/s to 1 000/s. An energy model to predict final velocity of composite laminates subjected to ballistic impact is proposed on the basis of experimental data of quasi-static perforation through the targets. The predicted final velocities show good agreement with the experimental final velocity.

Multi-pulse orbits dynamics of composite laminated piezoelectric rectangular plate

The multi-pulse orbits and chaotic dynamics of a simply supported laminated composite piezoelectric rectangular plate under combined parametric excitation and transverse excitation are studied in detail. It is assumed that different layers are perfectly bonded to each other with piezoelectric actuator patches embedded. The nonlinear equations of motion for the laminated composite piezoelectric rectangular plate are derived from von Karman-type equation and third-order shear deformation plate theory of Reddy. The two-degree-of-freedom dimensionless equations of motion are obtained by using the Galerkin approach to the partial differential governing equation of motion for the laminated composite piezoelectric rectangular plate. The four-dimensional averaged equation in the case of primary parametric resonance and 1:3 internal resonances is obtained by using the method of multiple scales. From the averaged equation, the theory of normal form is used to find the explicit formulas of normal form. Based on the normal form obtained, the energy phase method is utilized to analyze the multi-pulse global bifurcations and chaotic dynamics for the laminated composite piezoelectric rectangular plate. The analysis of the global dynamics indicates that there exist multi-pulse jumping orbits in the perturbed phase space of the averaged equation. Based on the averaged equation obtained, the chaotic motions and the Shilnikov type multi-pulse orbits of the laminated composite piezoelectric rectangular plate are also found by numerical simulation. The results obtained above mean the existence of the chaos in the Smale horseshoe sense for the simply supported laminated composite piezoelectric rectangular plate.

MULTI-PULSE ORBITS AND CHAOTIC DYNAMICS OF A COMPOSITE LAMINATED RECTANGULAR PLATE

This paper presents an analysis on the nonlinear dynamics and multi-pulse chaotic motions of a simply-supported symmetric cross-ply composite laminated rectangular thin plate with the parametric and forcing excitations. Firstly, based on the Reddy＇s third-order shear deformation plate theory and the model of the yon Karman type geometric nonlinearity, the nonlinear governing partial differential equations of motion for the composite laminated rectangular thin plate are derived by using the Hamilton＇s principle. Then, using the second-order Galerkin dis- cretization, the partial differential governing equations of motion are transformed to nonlinear ordinary differential equations. The case of the primary parametric resonance and 1：1 internal resonance is considered. Four-dimensional averaged equation is obtained by using the method of multiple scales. From the averaged equation obtained here, the theory of normal form is used to give the explicit expressions of normal form. Based on normal form, the energy phase method is utilized to analyze the global bifurcations and multi-pulse chaotic dynamics of the composite laminated rectangular thin plate. The theoretic results obtained above illustrate the existence of the chaos for the Smale horseshoe sense in a parametrical and forcing excited composite laminated thin plate. The chaotic motions of the composite laminated rectangular thin plate are also found by using numerical simulation, which also indicate that there exist different shapes of the multi-pulse chaotic motions for the composite laminated rectangular thin plate.

带胫骨的胫后动脉逆行岛状皮瓣修复足部复合组织缺损

目的探讨带胫骨的胫后动脉穿支嵌合皮瓣逆行转移修复足部复合组织缺损的临床效果。方法2013年6月-2020年3月,采用带胫骨的胫后动脉穿支嵌合皮瓣逆行转移修复足部复合组织缺损创面10例,术后对皮瓣外形满意度,痛觉、触觉、温度觉、两点分辨觉及患肢功能行AOFAS评分。结果术后10例皮瓣全部成活,供区植皮成活良好,伤口一期愈合,胫前供区外形重塑良好。8例获得1~2年的随访,2例因是外地患者失访。皮瓣具有较好的外形,伤口一期愈合,移植骨与受区骨质愈合良好,供区胫骨外形重塑良好,皮瓣无瘢痕增生,无骨髓炎发生,患者对皮瓣外形及足部功能均表示满意,术后1年皮瓣两点分辨觉平均为(10.2±2.1)mm,感觉评级为S3+,根据美国踝-足部AOFAS评分平均为90.8分。结论带胫骨的胫后动脉穿支嵌合皮瓣手术操作简单、血供可靠、供区影响小足部功能恢复好、外形满意,是修复足部复合组织缺损一种可供选择的方法。

细菌纤维素基CNFs/ZnO吸波材料的制备及性能

随着电子信息技术的不断发展,电磁污染问题日益严重,高效吸波材料的研究受到越来越多的关注。该文以生物多孔材料细菌纤维素为碳源,采用碳化改性和水热法两步制备了细菌纤维素基CNFs/ZnO复合材料,研究了二水合醋酸锌的浓度对CNFs/ZnO复合材料吸波性能的影响。通过X射线衍射仪(XRD)、冷场发射扫描电子显微镜(FESEM)、矢量网络分析仪(VNA)对复合材料的结构、形貌和吸波性能进行表征。结果表明:CNFs/ZnO复合材料被成功制备,其中碳纳米纤维(CNFs)没有明显的衍射峰,呈无定形状态;碳化和改性CNFs均保持了细菌纤维素三维网络多孔架构的精细纳米纤维微观形貌,但是CNFs变得卷曲且直径明显减小;CNFs/ZnO复合材料中,ZnO被紧密吸引在CNFs表面或随机插入CNFs的空隙中。通过改变二水合醋酸锌的浓度可以控制ZnO在复合材料中的含量,进而调控复合材料的电磁参数,获得良好的阻抗匹配。当二水合醋酸锌的浓度为0.25 mol/L时,ZnO在CNFs上分散得最为均匀,此时CNFs和ZnO的电阻损耗、介电损耗和界面极化等协同作用于三维多孔网络结构上,增加了复合材料对电磁波的多次反射、散射和长程耗散作用。该条件下制备的CNFs/ZnO复合材料,在涂层厚度为2.8 mm、频率为15.1 GHz附近时,其最佳反射损耗为−57.5 dB,有效吸收带宽为7.1 GHz,是一种可靠的复合吸波材料。

装配式槽钢组合梁中开孔钢板连接件力学性能

为研究新型装配式双拼槽钢-混凝土组合梁中开孔钢板剪力连接件(PSP剪力连接件)的力学性能,设计7组标准试件并开展推出试验,对比分析不同参数PSP剪力连接件的受剪承载力和破坏模式。利用ABAQUS非线性有限元模型对PSP剪力连接件的破坏模式和受力机制进行数值模拟,并与试验结果对比验证计算结果的可靠性。在此基础上,进一步分析开孔钢板厚度、开孔直径、混凝土强度、穿孔钢筋及连接件间距对PSP剪力连接件力学性能的影响。结果表明:除10 mm厚度的PSP剪力连接件外,所有4 mm与6 mm厚度的PSP剪力连接件均发生明显弯曲变形,试件破坏时连接件周围混凝土均出现斜向裂缝;开孔直径和穿孔钢筋对受剪承载力和抗剪刚度影响较小,而增加开孔钢板厚度、混凝土强度能提高剪力连接件受剪承载力和抗剪刚度;对于双排PSP剪力连接件,增大连接件间距能够显著提高单排PSP剪力连接件平均承载力,当间距为250 mm时,单排平均承载力达到单个PSP剪力连接件的91.2%。根据试验及有限元荷载滑移曲线提出装配式双拼槽钢-混凝土组合梁中单个PSP连接件荷载滑移曲线计算公式,为装配式双拼槽钢混组合梁的设计提供参考。

压缩天然气用环缠绕复合气瓶泄漏原因分析

针对某压缩天然气缠绕复合气瓶在使用不久后发生泄漏,采用化学成分分析、力学性能检验、金相检验、电镜观察等手段,分析了泄漏原因。结果表明:气瓶泄漏的原因是在充装使用过程中混入了水分,天然气中混有的H_(2)S、CO_(2)和氯化物溶于水滴后形成酸性溶液与瓶壁金属发生了电化学腐蚀,形成局部点状腐蚀,加上腐蚀和应力损伤持续进行,最终导致气瓶内壁穿孔失效,引起泄漏。

道路声屏障组合吸声结构设计与评估

声屏障在道路交通噪声污染防治中得到了广泛应用,但同时面临材料吸声性能有限、轻量化程度有待提升等问题。为了更好地提升道路声屏障的降噪效果,需要研究组合吸声结构的声学性能及其影响因素。建立了二维阻抗管有限元模型,与实验数据进行对比验证了其可靠性。基于有限元仿真构建了微穿孔板-双层多孔吸声材料-空腔组合吸声结构,研究了几何参数对组合结构的吸声性能的影响,并在实际道路场景中进行了仿真分析。结果表明,微穿孔板的孔径和厚度减小,组合结构在中高频段的吸声效果提升;穿孔率减小,组合结构在低频段的吸声性能提升,但是中高频吸声性能显著降低;多孔吸声材料厚度的增加能提升组合结构中高频吸声系数。在多孔吸声材料背后合理设置空腔并不会降低组合结构的声学性能。穿孔率3%,孔径0.4 mm,板厚1 mm的微穿孔板与3 cm聚酯纤维+3 cm三聚氰胺+2 cm空腔的组合吸声结构降噪效果较好,将其作为吸声型声屏障的材料。吸声型和隔声型声屏障插入损失的规律基本一致,采用组合吸声结构的吸声型声屏障较隔声型声屏障插入损失提升1~2 dB,能够较好地控制中低频交通噪声,具有实际工程价值。

亥姆霍兹共振腔复合结构的吸声特性

针对由亥姆霍兹共振腔构成的声学结构,研究了在结构尺寸不变的约束下,有效提升吸声性能的方法。首先,基于声电类比,设计了单腔亥姆霍兹共振器;然后,对单腔进行非均匀分割,形成具有不同腔深的多个亥姆霍兹共振腔,构造多腔并联结构,并建立计算吸声系数的数学模型;接着,在多腔并联结构中添加多孔吸声材料,研究材料厚度对吸声性能的影响;最后,用微穿孔板替代多孔材料,构造亥姆霍兹共振腔微穿孔板复合结构,结合微穿孔板理论,研究结构的吸声性能。结果表明,通过对单腔进行非均匀分割,构造多腔并联结构,能显著提高吸声性能,但随着腔体个数的增加,低频截止频率有向高频偏移的趋势;在多腔并联结构底部添加多孔吸声材料,对吸声性能的提升效果十分有限;在多腔并联结构中布置微穿孔板,能显著拓宽有效吸声带宽,并提高整体吸声系数;结合多腔并联结构的设计和布置微穿孔板,能实现结构吸声性能的大幅提高,且随着并联腔数的增加,吸声性能提升效果更明显,吸声系数曲线更平滑。

在线激光打孔脉冲持续时间对中支卷烟理化指标及其稳定性的影响研究

【目的】为中支卷烟在线激光打孔参数设计提供参考。【方法】分别采用显微镜和3D显微镜表征中支卷烟接装纸在线打孔的孔形态特征,考察在线打孔脉冲持续时间对中支卷烟理化指标及其稳定性的影响。【结果】①脉冲持续时间过短(≤47µs),出现孔未打透的情况,脉冲持续时间过长(≥90µs),出现椭圆孔的情况。②脉冲持续时间与孔直径、孔面积均呈线性正相关关系。③在线打孔脉冲持续时间与卷烟吸阻、滤嘴通风率和总通风率呈二次函数关系,且决定系数R2均在0.99以上;在线打孔脉冲持续时间与卷烟各项化学指标呈线性函数关系,且决定系数R2主要在0.96以上;卷烟水分释放量与打孔持续时间呈二次函数关系,决定系数为0.9767。④随着孔面积的升高及打孔个数的减小,卷烟的吸阻变化较小,均能保持相对稳定,卷烟总粒相物、烟碱、焦油、CO等释放量的标准偏差在脉冲持续时间适中(50~60μs)时比较小。

基于低频吸声超构材料的复合消声器

针对管道内低频噪声难以抑制的问题,基于亥姆霍兹共振腔阵列吸声板和穿孔管消声器组合,设计了一种复合式宽带消声器。首先利用有限元法仿真分析传统穿孔管消声器,发现中低频消声能力较差,通过嵌入亥姆霍兹共振腔阵列吸声板吸收中低频噪声。采用仿真与实验的方式研究吸声板的声学性能:在400∼1000 Hz频段内的平均吸声系数达到了0.88。然后对复合式消声器进行数值模拟及3D打印阻抗管实验测试对比:复合式消声器在400∼1718 Hz频率范围内的平均传递损失为18.15 dB。最终实现了管道内全频带噪声有效控制。

连续纤维增强热塑性复合材料嵌件注射成型研究进展

连续纤维增强热塑性复合材料的嵌件注射成型工艺通过结合连续和非连续纤维增强热塑性复合材料的优势,提升了产品的力学性能和生产效率,广泛应用于航空航天和新能源汽车领域。介绍了连续纤维增强热塑性复合材料嵌件注射成型工艺特点及应用,综述了材料体系、界面改性、工艺参数对嵌件注射成型制件界面结合性能和力学性能的影响。最后总结了嵌件注射成型复合材料目前研究存在的问题以及提升界面性能的方法,并对未来发展趋势进行了展望。

Temperature Adjustment Mechanism of Composite Embankment with Perforated Ventilation Pipe and Blocky Stone

Based on the advantages of perforated ventilation characteristic of perforated ventilation pipe embankment and large porosity of blocky stone embankment, composite embankment with ventilation pipe and blocky stone is more efficient to protect the underlying permafrost. The temperature fields and cooling effect of composite embankment with air doors are simulated by examining the effects of holes＇ position drilled in the pipe, diameter in pipe and density of holes. It is shown that the underlying permafrost temperature obviously reduces by composite methods, the location of 0℃ isotherm raises significantly, especially permafrost temperature under the center and shoulder of embankment reduces more quickly, the composite embankment with holes drilled in the lower side of pipe is the most efficient, the increase of diameter has a slight influence on the 0℃ isotherm＇s raising, and the density of holes slightly influences the raising of 0℃ isotherm.

Crack nucleation and propagation simulation in brittle two-phase perforated/particulate composites by a phase field model

Fracture is a very common failure mode of the composite materials,which seriously affects the reliability and service-life of composite materials.Therefore,the study of the fracture behavior of the composite materials is of great significance and necessity,which demands an accurate and efficient numerical tool in general cases because of the complexity of the arising boundary-value or initial-boundary value problems.In this paper,a phase field model is adopted and applied for the numerical simulation of the crack nucleation and propagation in brittle linear elastic two-phase perforated/particulate composites under a quasi-static tensile loading.The phase field model can well describe the initiation,propagation and coalescence of the cracks without assuming the existence and the geometry of the initial cracks in advance.Its numerical implementation is realized within the framework of the finite element method(FEM).The accuracy and the efficiency of the present phase field model are verified by the available reference results in literature.In the numerical examples,we first study and discuss the influences of the hole/particle size on the crack propagation trajectory and the force-displacement curve.Then,the effects of the hole/particle shape on the crack initiation and propagation are investigated.Furthermore,numerical examples are presented and discussed to show the influences of the hole/particle location on the crack initiation and propagation characteristics.It will be demonstrated that the present phase field model is an efficient tool for the numerical simulation of the crack initiation and propagation problems in brittle two-phase composite materials,and the corresponding results may play an important role in predicting and preventing possible hazardous crack initiation and propagation in engineering applications.

开孔钢箱-混凝土组合梁浇筑前后正截面受弯承载力研究

外包钢组合构件承载力高,但钢与混凝土容易滑移发生破坏.为有效防止钢与混凝土之间剥离,充分发挥材料强度,提出一种开孔钢箱-混凝土组合梁方案.首先研究开孔钢箱-混凝土组合梁浇筑前后的受弯性能,对共计四根试件进行四点弯曲试验,分析剪跨比对开孔钢箱-混凝土组合梁受弯承载力的影响,并建立ABAQUS模型进行有限元分析.研究结果表明:开孔钢箱梁受弯承载力与挠度均满足施工要求;随着剪跨比减小,受弯承载力增大;开孔钢箱-混凝土组合梁达到极限荷载时,界面未出现滑移,底部钢板屈服;所有试件均为受弯破坏,荷载-挠度曲线呈现弹性与弹塑性两个工作阶段,具有较好延性;ABAQUS有限元模型与实验数据吻合较好,可为试件在实际工程中的应用提供参考.

耐高温密级配AC型沥青混合料技术研究

为探究提升密级配AC型沥青混合料耐高温性能的方法,从基质沥青的复合改性及沥青混合料矿料空间结构的优化方面进行试验研究。研究得出,采用SBS改性剂和抗车辙剂对沥青复合改性能有效提升沥青耐高温性能。改性剂最优掺量为2%SBS改性剂加6%抗车辙剂。在规范允许级配范围内,将AC型沥青混合料矿料的空间结构从悬浮密实往骨架密实结构靠拢,能有效提升沥青混合料的耐高温性能,其中需重点控制4.75mm骨架分界筛孔通过率。