航空复合材料短柱加筋板压缩性能试验研究

开展了航空复合材料短柱加筋板的轴向压缩试验。试验件的破坏形式主要包括壁板的撕裂、筋条的断裂和端部的压溃现象,试验过程中,壁板及筋条没有出现明显的脱粘现象。在试验加载初期,载荷-应变曲线呈线性一致的增加趋势,位移测量点的离面位移值基本保持在0 mm附近;当压缩载荷超过临界屈曲载荷时,载荷-应变曲线出现了明显的分岔现象,且离面位移值快速增加。复合材料短柱加筋板失稳后仍然具有后屈曲承载能力,但是该承载能力较小,当短柱加筋板发生失稳后,随着压缩载荷的增加,试验件会很快发生破坏。有限元仿真结果与试验结果较一致,仿真结果表明短柱加筋板主要发生了壁板的局部失稳。     

基于FBG传感技术的复合材料T型加筋板低速冲击在线监测研究

将布拉格光纤光栅(Fiber Bragg Grating,简称"FBG")埋植在复合材料加筋板结构三角填充区,在线监测复合材料加筋板冲击过程及压缩过程的应变信号。研究了冲击点位置、冲击能量对FBG传感器应变监测性能的影响,分析了FBG传感器对复合材料T型加筋板冲击及压缩过程监测的精确性。结果表明:在相同冲击能量条件下,随着冲击点位置与FBG传感器距离的增加,FBG传感器测得的复合材料T型加筋板应变值呈下降趋势;当复合材料T型加筋板出现较为明显的损伤时,FBG传感器未发生断裂失效。将FBG传感器埋植于加筋板的三角填充区内,在压缩过程中,FBG传感器反射波谱保持单个波峰且形状未发生变化,初步实现了对复合材料T型加筋板冲击及冲击后压缩过程应变信号的在线监测。     

嵌入式共固化穿孔阻尼复合材料的制备与性能

为了提高复合材料的阻尼性能,促进阻尼复合材料的发展,本文探索一种新的嵌入式共固化穿孔阻尼复合材料。在T300碳纤维布上刷涂阻尼胶浆,晾干后制出规则分布的小孔,按真空导入成型工艺制备预成型体,将其放入温度试验箱进行固化,得到嵌入式共固化穿孔阻尼复合材料,并将复合材料按尺寸切割成试件。对试件进行模态试验、自由衰减试验和层间剪切试验。试件板的一阶模态阻尼达到3.65%,固有频率为12.88 Hz;试件梁的一阶模态阻尼达到2.02%,固有频率为34.25 Hz;试件梁的层间剪切力最大值为6488.452 N,剪切强度为5.19 MPa。结果表明这种嵌入式共固化穿孔阻尼复合材料具有较好的阻尼性能与层间力学性能。     

复合材料T型加筋壁板后屈曲承载能力研究

为了研究飞机复合材料T型加筋壁板结构在轴压载荷下的承载能力,对复合材料T型加筋壁板进行了轴压试验,并使用工程算法和有限元法仿真进行了分析,得到了加筋板的屈曲载荷及破坏载荷、载荷-位移曲线及损伤演化过程。对比两种分析方法与试验结果可以得到:当复合材料加筋壁板屈曲后,还有较强的后屈曲承载能力;相对于有限元分析方法,工程算法误差更大;准静态法可以有效地模拟出加筋板的屈曲及后屈曲行为,但是计算代价相对较大。     

复合材料帽形加筋板极限承载能力

本文研究了复合材料长加筋板在轴向压力作用下的纵向极限承载能力推导出复合材料梁柱的极限承载能力公式。并考虑了加筋板的初始几何缺陷,载荷偏心,蒙皮屈曲后的有效蒙皮宽度对复合材料长帽形加筋板的极限承载能力的影响。     

长玻纤填充尼龙6复合材料研究

采用熔体浸渍工艺制备长玻纤增强PA6复合材料。研究了玻纤种类、玻纤含量长度、界面改性等对复合材料力学性能及电性能的影响。试验结果表明：在玻纤含量35％时,切粒长度7mm,粒径3．5mm时,复合材料表现出优异的力学性能和电性能。     

硅橡胶热膨胀法制作复合材料加筋面板

本文研究了采用硅橡胶热膨胀法制作复合材料加筋面板的工艺方法,对该法的基本原理进行了简单阐述,探讨了关键参数工艺间隙值的设定方法,并分析了工艺间隙对制件质量的影响,最终制备了优良的复合材料加筋面板结构试验件.     

玻纤增强尼龙6的挤出工艺及力学性能

采用长玻纤连续添加和短切玻纤制备了玻纤增强尼龙6(PA6)复合材料。主要考察了玻纤含量、玻纤种类以及挤出工艺条件对复合材料力学性能的影响,并利用扫描电子显微镜对复合材料的冲击断面和拉伸断面及玻纤形态进行了观察。结果表明,采用短切玻纤加入时,玻纤含量对GF/PA6复合材料的力学性能影响很大。随玻纤含量的增加,复合材料的力学性能越来越高,断裂伸长率变低。加工工艺参数对复合材料的力学性能有影响。采用长玻纤连续添加时,玻纤的添加位置对复合材料的性能影响不大。在玻纤含量相同时,采用长玻纤连续添加得到的材料力学性能明显优于采用短切玻纤时的性能。玻纤能均匀地分散在PA6基体中,玻纤的保留长度和长度分布对复合材料的性能有直接影响。     

复合材料帽型加筋板界面应力与失效模拟

基于内聚力模型,采用界面单元模拟筋条和蒙皮之间的粘接界面,建立了复合材料帽型加筋板结构的有限元模型,探究了复合材料帽型加筋板在四点弯曲载荷作用下的界面应力和脱粘失效问题。结果表明,胶层脱粘是复合材料帽型加筋板的主要失效形式,脱粘失效主要受剪应力的影响,脱粘导致加筋板承载能力下降,加剧了整体结构的损伤。     

复合材料格栅板受弯性能试验研究与数值分析

以纤维增强复合材料格栅板为研究对象,包括不设蒙皮的纯格栅板、设单面蒙皮的格栅加筋板和设双面蒙皮的格栅夹层板。采用不饱和聚酯树脂作为基体材料,玻璃纤维作为增强材料,通过模塑工艺加工成型格栅板。针对该板的受弯性能开展试验研究与数值分析。对按不同方式设置蒙皮的格栅板进行了三点弯和四点弯加载试验,研究其受弯承载力、破坏形态等,结果表明:采用上蒙皮增强纯格栅板,可显著提高试件的抗弯承载力和刚度,并使结构具备良好的延性破坏特征。针对格栅板的受弯性能进行了数值分析,并对比试验结果,验证了有限元模拟的准确性;针对蒙皮厚度、格肋高度、格肋厚度和格肋间距等因素对格栅板受弯性能的影响规律进行了参数分析。     

CCF-1／5405复合材料“工”字型加筋的工艺质量控制

简介了CCF-1／5405复合材料的“工”字型加强筋结构件的制造流程,重点研究了制备过程中的工艺控制方案及其尺寸精度控制途径,总结出影响成型质量及尺寸精度的因素。结果表明,采用预吸胶、定位预压后二次胶接共固化技术制备出“工”字型加筋结构件,通过上缘条尺寸及填充料芯子定量、上缘条压条分段及压条厚度控制等工艺措施能有效控制...     

Energo-Mechanical Evaluation of Damage Growth and Fracture Initiation in Aviation Composite Structures

The aim of the present paper is to (1) highlight the results of laboratory damage detection and monitoring in the aviation composite materials, during a mechanical testing constituted of multiple loadings, and (2) obtain a detailed understanding of damage evolution of composite specimens with regard to impact energy. Woven 12-ply glass fiber and 16-ply carbon fiber–reinforced epoxy composites (GFRP 92 125/L285/287 and CFRP 98 131/L285/287) were used as less studied subjects in research. This study explored the resistance to cracking and delamination of glass and carbon fiber laminates with the same resin system under low-load conditions.     

Fracture and acoustic emission characteristics of glass fiber reinforced plastics panels for hot water

This study deals with the fracture process and acoustic emission (AE) characteristics of a randomly oriented E-glass fiber mat reinforcement with a crosslinked polyester. These panels were evaluated after they were immersed in hot water. The fiber volume content of the panel was 19%. Glass fiber reinforced plastics (GFRP) panels wer immersed in water at 81°C. Bending and AE monitoring tests were Performed and after bending, the cross-section of the specimen was observed by an optical microscope and SEM. The influence of degradation, due to water immersion, on the changes of fracture process of GFRP is discussed. The dominant fracture mode of the virgin specimen was matrix cracks, whereas that of the immersed specimen was debondings at the fiber bundle/matrix and fiber/matrix interfaces. This change was caused by reduction of the bonding strength at the interface. The scale of fracture can be estimated by both AE amplitude and AE energy and this estimation method was used to estimate the fracture mode changes of GFRP panels immersed in hot water.     

碳纤维增强桉杨复合胶合板的制备及性能研究

为开发碳纤维/木基复合材,设计了全桉木、全杨木、杨桉交错、桉杨交错四种结构用桉杨复合胶合板,采用碳纤维(CF)进行表面增强,研究增强前后桉杨复合胶合板的物理力学性能以及保温性能,探讨老化前后四种结构之间的性能变化。结果表明:经碳纤维表面增强后,桉杨交错结构吸水厚度膨胀率为2.6%,下降幅度为44.7%,吸水率下降幅度为46.5%;四种结构浸渍剥离性能均满足标准,最好为桉杨交错结构;桉杨交错结构老化前纵向静曲强度为98.5 MPa,提高率为107.4%,纵向弹性模量为15810 MPa,提高率为129.8%,老化后杨桉交错结构纵向弹性模量为10150 MPa,提高率为176.3%,且杨桉交错结构胶合强度可达1.74 MPa,但对于横向静曲强度、弹性模量和胶合强度提高均较小。综合而言,碳纤维增强后物理力学性能较好的结构为杨桉交错和桉杨交错,总体反映了桉杨复合胶合板结构上纵横强度比差异较大,在实际应用中根据需求调整纵横强度设计比例;经碳纤维表面增强后桉杨复合胶合板导热系数均值为0.44 W/(m·℃),导热系数值接近保温材料,碳纤维表面增强后对其保温性能影响不明显。     

Improved strain sensing performance of glass fiber polymer composites with embedded pre-stretched polyvinyl alcohol–carbon nanotube fibers

Polyvinyl alcohol–carbon nanotube (PVA–CNT) fibers differing on their pre-stretching condition were embedded in glass fiber reinforced plastic (GFRP) composites and used as strain sensors for damage monitoring of the composite. Strain sensing of the composite was made by the in situ measurement of the embedded fiber’s electrical resistance change during the mechanical tests. Four glass fiber composite plates were manufactured; each one had embedded a different type of produced PVA–CNT fibers. The multi-functional materials were tested in monotonic tensile tests as well as in progressive damage accumulation tests. The electrical resistance readings of the PVA–CNT fibers were correlated with axial strain values, taking into account the induced damage of the composite. It has been demonstrated that increasing the fiber’s pre-stretching ratio, its electrical resistance response increases due to higher degree of the CNTs alignment in the PVA matrix. Higher fiber pre-stretching degree enables the better strain monitoring of the composite due to higher measured electrical resistance change values noticed for the same applied axial strain values. To this end, it enables for the better monitoring of the progressive damage accumulation inside the composite.     

Durability of glass‐fiber‐reinforced polymer nanocomposites in an alkaline environment

This study was conducted to determine the effect of clay content in GFRP (glass‐fiber‐reinforced polymer) composite samples as they were aged in an alkaline solution. Two kinds of GFRP composite samples were prepared. One was E‐glass‐fiber‐reinforced vinyl ester polymer, and the other was nano‐GFRP composites prepared with the addition of 1 and 2 wt% of montmorillonite clay to the polymer matrix. These samples were aged in alkaline solution of pH 13.2 with and without sustained load. The load was 1335 N or 18.7% of the tensile strength of the composite samples. The aging was evaluated by measuring the reduction in tensile strength after 6 months. Also, absorption of alkaline solution into the plain and nano‐GFRP samples was investigated so as to elucidate the diffusion behaviors. It was found that for a short exposure time (e.g. 1 month) and without sustained load, dispersing 2 wt% of the nanoclay in the polymer matrix of the GFRP samples reduces the diffusivity by 39%. However, with the application of sustained load, the glass fiber composite samples deteriorate more with increasing clay content. The reduction in tensile strength was 7.1%, 12.1%, and 18.1% for the samples containing 0, 1, and 2 wt% of clay, respectively. J. VINYL. ADDIT. TECHNOL., 12:25–32, 2006. © 2006 Society of Plastics Engineers     

Influence of multiwalled carbon nanotubes on the processing behavior of epoxy powder compositions and on the mechanical properties of their fiber reinforced composites

This study reports the preparation of advanced carbon fiber composites with a nanocomposite matrix prepared by dispersing multiwall carbon nanotubes (CNTs) in a powder type epoxy oligomer with two different processing techniques (1) master batch dilution technique and (2) direct mixing (with the help of twin‐screw extruder in both cases). The master batch technique shows a better efficiency for the dispersion of the CNTs aggregates. The rheological results demonstrate that the incorporation of the CNTs into the epoxy oligomer leads, as expected, to a marked increase in the viscosity and of the presence of a yield stress point that also depends on the processing technique adopted. Carbon fiber (CFRP) and glass fiber (GFRP) composite materials were produced by electrostatic spraying of the epoxy matrix formulations on the carbon and glass fabric, respectively, followed by calendering and mold pressing. The mechanical properties of the obtained epoxy/CNT‐matrix composite materials, such as interlaminar fracture toughness, flexural strength, shear storage and loss moduli are discussed in terms of the processing techniques and fabric material. The incorporation of 1 wt% CNTs in the epoxy matrix results in a relevant increase of the fracture toughness, flexural strength and modulus of both CFRP and GFRP. POLYM. COMPOS., 37:2377–2383, 2016. © 2015 Society of Plastics Engineers     

Structural improvement of strengthened deck panels with externally bonded plates

Concrete bridge decks require eventual replacement and rehabilitation due to decreasing load-carrying capacity. This paper compares different strengthening design procedures that improve the usability and structural performance of bridge decks. The failure characteristics of bridge decks strengthened with various materials such as carbon fiber sheet, glass fiber sheet, steel plate, and grid CFRP and GFRP are analyzed, and the theoretical load-carrying capacities are evaluated using traditional beam and yield line theory, and punching shear analysis. The strengthening materials increase the punching shear strength of the deck and change the failure mode of the strengthened panel.     

Damage characterization of repeatedly impacted glass fiber reinforced polyester‐armor steel composites with cone beam computed tomography technique

This article utilizes the characterization of single and repeated low velocity impact damage behavior of glass fiber reinforced polyester (GFRP) armor steel composite. Cone beam computed tomography technique (CBCT) was used for damage assessment. Impact energies, maximum loads and the permanent deflection of GFRP, armor steel composites are determined with instrumented drop weight impact test machine. The repeated impact performance and damage resistance were evaluated. On the other hand, preliminary single impact loading tests also performed in order to find the energy levels, which were ranged fully elastic energy level to perforation energy level for GFRP, armor steel composites. Additionally, CBCT was used to provide a novel, multiscale approach for assessing impact damage. Deformation areas of both single and repeatedly impacted GFRP, armor steel composites were assessed three‐dimensionally by CBCT. An innovative approach was used to visualize the internal damages. POLYM. COMPOS., 37:583–593, 2016. © 2014 Society of Plastics Engineers     

碳纤维复合材料压力容器的透声性能研究

以环氧树脂为基体材料,分别以S2高强玻璃纤维和T700碳纤维为增强材料,采用缠绕成型工艺,制备了玻璃纤维复合材料（GFRP）透声试件和碳纤维复合材料（CFRP）透声试件;测试了试件的透声性能,为成功研制碳纤维复合材料透声压力容器提供依据。结果表明：CFRP的透声性能和力学性能远远优于GFRP;内衬层对容器的透声性能影响不大;研制的碳纤维透声压力容器达到了满意的透声效果。