聚乙二醇/氧化锑锡纳米复合纤维结构及保温透气性能

功能户外防护材料中热能管理是一个重要的方面。对于功能织物开发而言，大都采用涂层后整理技术，但是其功能性和透气性的平衡是关键。本文以静电纺丝技术制备了聚乙二醇/氧化锑锡（PVA/ATO）纳米复合纤维膜，采用扫描电镜（SEM）、傅里叶红外光谱（FTIR）、X射线衍射（XRD）、热重（TG）对纳米复合纤维进行了表征，并对PVA/ATO/黏胶热轧复合材料的保温性能及透气性进行了测试。结果表明：PVA中ATO具有良好的分散性，部分ATO纳米颗粒镶嵌在纤维表面。PVA/ATO/黏胶热轧复合材料的保温率相对于基材黏胶热轧布提高了28.9%，达到37.1%，相应传热系数为12.62W/m²·℃，克罗值0.32。ATO纳米颗粒的加入可以直接改善PVA纳米纤维膜的堆积结构，使得PVA/ATO/黏胶热轧复合材料的透气性相对于PVA/黏胶热轧复合材料有明显提高，但趋势随纳米纤维层厚度的增加而降低。PVA/ATO纳米复合膜可以复合到多种基材上，从而为基于纳米纤维功能材料开发保温透气功能提供了思路。     

碳纤维增强聚氨酯密封胶强度分析

利用复合材料层合板理论对碳纤维增强聚氨酯(PU)密封胶在海水压力下的受力状况进行了简要的数学分析,并结合耐压试验结果,对碳纤维增强PU密封胶的老化及渗漏性能进行了分析。结果表明:应用层合板理论计算得到的复合材料环体的轴向压缩强度、环向拉伸强度、径向压缩强度及受力情况均满足设计要求;但是,上述计算均以碳纤维增强PU胶粘剂材料的静态力学性能为依据的,而复合材料环体在工作时呈动态力学状态,故应用层合板理论进行相关性能的计算还存在着一定的误差;目前采用碳纤维增强PU缠绕工艺、辅以表面处理剂和净水隔离剂后所制备的电缆密封胶,在7MPa压力作用下,环型管节没有泄漏,与计算结果预测一致。     

Determination of mechanical properties of glass‐epoxy composites in high temperatures

The objective of this study is to determine the tensile, compressive, and shear properties of unidirectional glass/epoxy composite plates under room (∼20°C) and high (40, 60, 80, and 100°C) temperatures. Mechanical properties were determined according to the ASTM standards. A hot lamination press was used for fabrication of composite plates. For curing process, laminated plates were retained at a constant pressure (250 kPa) and 120°C during 2 h. And then, composite plate is cooled to room temperature at the same pressure. The fiber volume fraction of laminated composite plate is measured as 65%. Experimental results show that the mechanical properties (except for the transverse tensile strength) of glass/epoxy composites are reduced by increasing temperature. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

轻质碳纤维复合材料帆船桅杆的设计与制备

碳纤维复合材料与金属相比,具有重量轻、可设计性强等优点.本文目的是设计并制备轻质碳纤维复合材料桅杆.基于等刚度准则,对具有等壁厚、异型截面的中空碳纤维复合材料桅杆进行设计,并运用数值模拟技术对结构铺层进行优化.采用纤维铺放和缠绕工艺制备出长度为16m的大尺寸碳纤维复合材料帆船桅杆,与铝合金桅杆相比减重43.4%.在设计工况下,桅杆变形试验值与数值模拟结果相近.     

A novel fiber–veneer-laminated composite based on tannin resin

Natural nonwoven fiber was impregnated with a tannin resin and laminated with wood veneer for preparation of laminated composites. The tannin resin used showed a good compatibility with the natural fiber, and was easy to assemble with the wood veneers. The tannin resin penetration into the wood veneer was observed by light microscopy. The laminated composite shows very good mechanical properties and water resistance. Shear force–displacement testing demonstrates that the laminated composite had a ductile behavior under wet testing conditions. The laminated composite was prepared using 100% natural biorenewable raw materials and had good properties compared to conventional plywood bonded with synthetic resin.     

Properties of unidirectional kenaf fiber–polyolefin laminates

The objective of this research was to evaluate the effect of kenaf fiber orientation and furnish formulation on the properties of laminated natural fiber–polymer composites (LNPC). The uniaxial fiber orientation provided property enhancement of the LNPC. The randomly oriented kenaf fibers, regardless of fiber contents in the laminates, provided an equal performance compared to the composites made of 25% fiber glass reinforced polyvinyl ester resin in the same laboratory processing conditions. Thermal properties of the laminates obtained from thermal gravimetry with differential scanning calorimetry (TG‐DSC) showed that the melting point (T_m) of the polypropylene (PP) film laminates decreased, and the crystallization peak increased as the kenaf fiber content in the laminates increased. The surface morphology results of the kenaf fiber and fractures of the laminates showed that some fibers pulled out from the matrix. The mechanical properties increased as the kenaf fiber content increased. The tensile stress of the laminated composites fabricated with unidirectional fiber orientation was about 2–4 times higher than those with the randomly oriented samples. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

修复对含分层损伤复合材料层合板振动特性的影响

本文工作是通过对含不同大小分层层合板结构分析,讨论拉伸和剪切修复刚度对含层间分层损伤复合材料层合板振动特性的影响.基于修补分层损伤结构变形特点,将含损层合板的基板、上子板和下子板采用Mindlin板单元离散,而损伤区修复效应以虚拟连接单元模拟,建立相应的有限元分析模型和计算方法.通过对含损层合板的振动分析,讨论并验证本文提出的修复分层损伤模拟连接单元模型的可能性和正确性,依据拉抻和剪切修复刚度对含损层合板固有频率的分别影响与综合影响,得到对分层损伤复合材料层合板修补的指导性原则.     

混杂FRP复合材料单轴拉伸性能研究

为制备优异综合性能的混杂FRP(Fiber Reinforced Plastic/Polymer)复合材料,本文试验研究了芳纶、玄武岩、玻璃纤维与碳纤维混杂复合材料的单轴拉伸力学性能,分析了纤维种类、碳纤维相对体积含量、铺层方式等混杂参数对混杂效应的影响。结果表明,HFRP(Hybrid FRP)复合材料的单轴拉伸弹性模量基本符合混合定律,层间混杂FRP复合材料均表现出良好的混杂效应。当碳纤维铺层在中间时,碳/芳纶/玻璃层间混杂复合材料的混杂效应系数为0.647,混杂效应最优。     

含缺陷复合材料加筋壁板承载能力的数值预测

碳纤维复合材料加筋壁板是飞机结构的典型部件,成型过程中的制造缺陷对其极限承载能力和失效行为具有显著影响,是结构完整性评估的重要内容。通过数值手段开展了3点弯曲载荷作用下含缺陷复合材料加筋壁板的数值分析,重点考虑了缺陷尺寸和位置对结构承载能力的影响。首先基于Abaqus/Standard建立了加筋壁板的三维有限元模型,引入双线性内聚力模型用于描述复合材料加筋壁板的层间失效行为,然后结合文献相关实验数据验证了该模型的有效性,最后基于该有限元模型研究了缺陷尺寸和位置对结构承载能力的影响。结果表明:建立的有限元模型计算结果与文献实验结果吻合;结构的承载能力随着缺陷尺寸的增大而降低,且对蒙皮/桁条界面中部缺陷较为敏感;缺陷的存在导致结构的破坏模式发生转变,但起始裂纹始终发生在界面附近的基体区域。     

风电叶片用真空灌注树脂体系的研究

本文研制了一种风电叶片用真空灌注环氧树脂体系。分别使用旋转粘度计、万能材料力学试验机、差示扫描量热仪对环氧树脂体系及其固化物的工艺性能、力学性能、热性能等进行了表征。通过叶片灌注模拟及层合板性能检测对该环氧树脂体系与玻璃纤维的匹配性进行了表征。结果表明,该环氧树脂体系具有粘度低、工艺操作性好、力学性能及热性能优异、纤维匹配性好等优点,可用于风力发电叶片的制备。     

An analytical method for prediction of the damping in symmetric balanced laminated composites

To obtain the effective damping of a laminated composite beam, two different analytical methods were compared. Also, we modified the basic loss factors on the basis of experimental data. In the first method, Ni and Adams's theory was used. In the second method, new energy approach was developed to determine the damping of laminated composite beams. Five typical laminated composites with [±Θ]s, [0/±Θ]s, [0/Θ]s, [0/±Θ/90]s and [90/±Θ/0]s stacking sequences were employed for this study. The present method was favorably compared with Ni and Adams's method. In this study, we found that damping was highly influenced by fiber volume fraction, fiber orientation and stacking sequence.     

Electromechanical characteristics of unidirectional glass fiber epoxy composites

Because crack detection for laminated composites in‐service is an effective method for improving structural reliability, various nondestructive methods have been studied to detect cracks in laminated composites. A recent study on the damage monitoring of composite materials using the piezoelectric method, which uses the piezoelectric characteristics of polymeric materials for the matrix of composite materials, concluded that the piezoelectric method can be a useful, nondestructive method for the damage monitoring of glass fiber epoxy composites. The dielectric and piezoelectric properties of composites are the basic properties used for the analysis of electromechanical coupling systems, along with the mechanical properties. In this research, therefore, the electromechanical characteristics of unidirectional glass fiber epoxy composites as well as their electric and mechanical characteristics were investigated. The dielectric, piezoelectric, and mechanical properties of unidirectional glass fiber epoxy composites were measured experimentally with respect to the fiber orientation, and the relationship between the piezoelectric and mechanical characteristics of unidirectional glass fiber epoxy composites was analyzed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Enhancement of fracture toughness of carbon fiber laminated composites using multi wall carbon nanotubes

In this paper, the effect of Multi Wall Carbon Nanotubes (MWNT) as a toughening agent of laminated composites is experimentally investigated. Carbon fiber laminates were manufactured by resin film infusion technique in which the resin flows in the through-the-thickness direction. The modified polymer systems showed 17% improvement in the stress intensity factor (K_Ic), whereas the laminated composites showed up to 48% improvement in Mode I and 143% improvement in Mode II fracture toughness. Scanning Electron Microscope (SEM) was then used to study the fractured surface and to explain the contrasting behavior of the MWNT-modified polymers when compared to the laminates.     

Optimal design of the cure cycle for consolidation of thick composite laminates

Autoclave cure of the prepreg lay-up has been an importance method for fabrication of advanced fiber reinforced composites in the aerospace industry. Quality of the autoclave cured composite is largely affected by the cure cycle. In this study, the genetic algorithm is applied to design a cure cycle for the consolidation of thick laminated composites. The objective of the design is to select a cure cycle that results in a shorter cycle time for the process while avoiding the thermal runaway inside the composites. The results show that the genetic algorithm is a feasible and robust search algorithm to determine the cure cycle for the consolidation process.     

不同工艺碳纤维增强复合材料构件的力学性能

针对碳纤维增强复合材料在电动汽车车身上的应用,分别采用手糊、真空袋压和模压三种成型工艺,设计制备了碳纤维增强复合材料层合板和双帽形管件两种实验样件。对样件进行了单向拉伸和三点弯曲试验,对构件的力学性能、表面质量、微观结构和破坏形式进行了比较,并分析了不同工艺性能存在差异的原因。研究表明:采用模压工艺成型的复合材料结构件气泡少,孔隙率小,表面质量最好;模压成型的层合板拉伸强度比手糊成型的提高了14.39%,管件弯曲强度比手糊成型管件提高了一倍,比真空袋压成型管件提高了47.58%。研究证实模压成型相对于手糊和真空袋压工艺,产品具有较优良的力学性能和一致性,较适合于电动汽车等轻量化结构的成型。     

Coating of Carbon Fibers—The Strength of the Fibers

The 6k carbon fiber Torayca T800H was coated with pyrolytic carbon by a CVD process. Fiber bundles were tested and evaluated. By this procedure, the whole distribution of the failure probability with respect to the fiber strength is obtained in a single experiment. The 50% strength of the fiber bundle, i.e., the strength at which 50% of the fibers in the bundle are broken, is inversely proportional to the square root of the thickness of the coating. By relating the strength to the defect size according to linear-elastic fracture mechanics (LEFM), the probability density function of the defects was derived. It is Weibull-shaped for the uncoated fiber and shows an increasing bimodal shape for the increasing coating thicknesses.     

Effect of imbibed moisture on monotonic and low-velocity impact behavior of injection over-molded short/continuous fiber reinforced polypropylene composites

Design of automotive components with over-molded short/continuous fiber reinforced thermoplastic composites necessitates understanding of their behavior under extreme outdoor conditions. The short, quasi-isotropic and over-molded short/continuous glass fiber reinforced polypropylene (PP) composite specimens were prepared as per standard and immersed in water until equilibration to study their relative moisture absorption characteristics and consequent mechanical behavior. As the absorbed moisture mostly occupied the interface between fiber and matrix in laminated composite inserts and moisture absorption of short fiber composite core is insignificant, the moisture absorption of over-molded composites is just above 50% of that of laminated composites. The flexural, interlaminar shear and impact behavior of equilibrated composites is primarily governed by the quantum of imbibed moisture of composite materials. Optical analysis of failed moisture equilibrated over-molded specimens showed a marginal delamination between plies of the inserts without any perceptible damage within the short fiber composite similar to dry as molded specimens.     

高强织物防穿刺作用特征与机制分析

高强织物广泛应用于防刺领域。为了研究高强织物防穿刺作用特征与机制,自行设计了可调重量与高度的自由落体式实验装置,选用单刃刀、三棱刀、锥对芳纶与超高分子量聚乙烯纤维织物进行刺入实验,考察了冲击能量、刀具截面形状、刺入角度对穿刺作用的影响,研究了织物纤维种类、结构、叠层密度与织物防穿刺作用的关系,分析了刀具对高强织物穿刺作用的机制。结果表明,穿刺效果主要由能量的大小决定,受其速度、质量的组成比例影响较小;刀具的截面形状决定其穿刺织物时的剪切破坏与排挤破坏的组成形式;防刺材料的结构是影响其防穿刺性能的关键因素,同种材料不同结构织物抗排挤能力越强。织物对锥和单刃刀的防穿刺能力越强。对三棱刀的防穿刺能力变化不明显。     

多层碳纤维布复合材料超声检测的有限元模拟

结合飞机复合材料无损检测需求,介绍了多层碳纤维布的材料工艺,分析了超声反射法的基本原理及其特点,并利用有限元方法对超声检测过程进行了数值模拟。通过实验波形和数值模拟的波形进行对比,可以看出有限元分析法对复合材料的超声检测提供了有力的理论依据,在一定程度和范围内可以对实验进行结果预测和评估。同时实验结果表明,超声波检测复合材料检测精度较高,检测效果较明显,可以准确的识别出是否存在缺陷以及判断出缺陷的位置。     

Rapid evaluation of thermal aging of a carbon fiber laminated epoxy composite

This study concentrated on the thermal aging mechanism and lifetime of a carbon fiber laminated epoxy composite. Samples of the laminated composite and the neat resin (as a contrast) were exposed in air circulating ovens set at 90, 120, and 150°C for various periods of time up to 13 days. The flexural properties combining with FTIR, weight loss, DSC, SEM, and surface morphology analyses were performed on the unaged and aged samples. The flexural strength of the composite deteriorated by a factor of 3 as a result of weight loss, microcrack formation, and chain scissions. The two‐way ANOVA results indicated that the aging time had significant effect on the flexural strength of the composite and the aging temperature had no significant effect on it. Two statistical models were established to predict the residual flexural strength and lifetime of this composite. POLYM. COMPOS., 35:975–984, 2014. © 2013 Society of Plastics Engineers