酰胺链硅烷界面结合剂对尼龙66/玻纤复合材料性能的影响

采用熔融挤出共混制备了尼龙66(PA66)/玻璃纤维(GF)复合材料,比较了常用硅烷偶联剂KH550与不同有机酸封端的酰胺链硅烷界面结合剂(ASI)对复合材料的力学性能、动态力学性能及界面层结构的影响,探究了复合材料中界面层形成的机理。结果表明,ASI与玻纤表面反应发生了化学反应,ASI添加量为1.5%时,对PA66/GF复合材料的力学性能改善效果最明显,其中,以对苯二甲酸封端,相对分子质量为2000左右的PTA-ASI使PA66/GF复合材料的界面能力提升最高,拉伸强度提高了54.8%,复合材料的综合性能提高最为显著。     

尼龙66及其复合材料的热分解动力学

使用热重分析仪测定尼龙66(PA66)和两种不同玻纤增强尼龙66复合材料(GF/PA)的热分解曲线,用Kissinger法和Crane法研究了PA66和GF/PA的热分解动力学。结果表明:PA66、GF/PA-1和GF/PA-2的热分解反应级数分别为0.949、0.912和0.921,表明均为一阶热分解过程;热分解活化能分别为218.65 kJ/mol、121.81 kJ/mol和132.23 kJ/mol,表明玻纤的加入显著降低了PA66的热分解活化能。在加热速率相同的条件下两种GF/PA达到最大热分解速率的温度都比PA66的低,表明玻纤虽然改善了PA66的性能,但是加快了PA66的热分解过程,说明存在着“灯芯效应”。     

The dispersion of SWCNTs treated by dispersing agents in glass fiber reinforced polymer composites

It is an obstacle issue for carbon nanotubes (CNTs) particularly for single-wall carbon nanotubes (SWCNTs) with nano-level dispersion in fiber reinforced polymer matrix composites. In this paper, the dispersing agents such as Volan and BYK-9076 were employed to treat SWCNTs to improve their dispersion in the glass fiber/epoxy (GF/EP) composites. The dispersing results of SWCNTs in composites were observed by scanning electron microscopy (SEM). Then the glass transition temperature (T_g) of these kinds of composites with treated and untreated SWCNTs were obtained by dynamic mechanical thermal analysis (DMTA). Moreover, the flexural tests were performed on these composites. Based on the experiment results, the dispersion of SWCNTs was improved and the flexural property of SWCNTs/GF/EP composite was enhanced too.     

多单体接枝聚丙烯对干态和湿态玻纤增强尼龙6性能的影响

通过熔融共混法,加入自制的多单体接枝聚丙烯(PP-g-MAH-EP)制备尼龙6(PA6)/玻璃纤维(GF)/PP-g-MAH-EP复合材料。研究了PP-g-MAH-EP对复合材料吸水前后静态和动态力学性能的影响,并通过扫描电镜与原子力显微镜分析试样断面微观形貌及微观力学性质的变化。结果表明,PA6/GF/PP-g-MAH-EP复合材料的吸水率随着PP-g-MAH-EP含量的增加逐渐降低,即PP-g-MAH-EP的加入能有效抑制PA6/GF复合材料的吸水率;在干态及相同吸水条件下,PA6/GF/PP-g-MAH-EP复合材料的力学性能明显优于PA6/GF。与PA6/GF相比,当PP-g-MAH-EP加入20 phr时,复合材料综合力学性能最好。PP-g-MAH-EP的加入,有效改善了纤维与尼龙6基体界面的粘接,吸水后的基体树脂在探针作用下的形变量明显降低。     

接头尺寸对玻璃纤维/热塑性树脂复合材料机械连接性能的影响接头尺寸对玻璃纤维/热塑性树脂复合材料机械连接性能的影响

对玻璃纤维/聚酰胺（GF/PA）、玻璃纤维/聚甲醛（GF/POM）、玻璃纤维/聚丙烯（GF/PP）这三种玻璃纤维增强热塑性树脂基复合材料进行机械连接试样的常规拉伸试验,以及低周疲劳拉伸试验,并对疲劳前后的试样断裂面进行SEM观察,研究了接头尺寸（宽径比w/d （试样宽度/开孔直径）和端径比e/d （试样端距/开孔直径））对机械连接件破坏载荷和破坏模式的影响。实验结果表明:玻璃纤维增强纤热塑性树脂复合材料机械连接件的承载能力在一定的宽径比时会随着e/d的增加而增加,当w/d≥3、e/d≥2时趋于稳定;破坏模式以拉伸破坏为主;低周疲劳拉伸对GF/POM和GF/PA机械连接试样拉伸强度产生一定的影响,而对GF/PP的拉伸强度无明显影响,低周疲劳拉伸对玻璃纤维增强热塑性树脂复合材料机械连接试样的破坏模式没有影响。SEM观察显示,随着疲劳载荷水平的增加,GF/POM和GF/PA的断裂面上被抽拔纤维数量增加,而GF/PP断裂面纤维与基体的存在状态无明显变化。      

The effects of Clay on fire performance and thermal mechanical properties of woven glass fibre reinforced polyamide 6 nanocomposites

The effects of small amount of organically modified Clay (Clay) in polyamide 6 (PA6) on fire performance and thermal mechanical properties of Clay/PA6/woven glass fibres (GF) laminates are investigated by cone calorimeter test, dynamic mechanical thermal analysis (DMTA), and heat distort temperature (HDT) measurement. The mechanical properties, such as tensile and flexural properties of Clay/PA6 composites and Clay/PA6/GF laminates were also measured. Up to 3 wt.% Clay in a Clay/PA6/GF laminate with fibre volume fraction of 30 vol.% delayed the ignition time and peak heat release rate (PHRR) time by 55% and 118%, respectively, even though the value of the PHRR or the HDT was not significantly affected. 2 wt.% Clay increased flexural modulus and strength of the Clay/PA6/GF laminate by 10% and 16%, respectively, but more Clay did not increase the mechanical properties accordingly. Small amount of Clay does not affect glass fibre dominated properties, such as HDT, but do affect matrix dominated properties, and significantly affect the fire performance in terms of delaying ignition time and PHRR time. Optimization of laminate making process could benefit from additions of more Clay, therefore further improve fire performance and enhance mechanical properties.     

Effect of phenoxy-based coating resin for reinforcing pitch carbon fibers on the interlaminar shear strength of PA6 composites

Carbon fiber-reinforced thermoplastic composites have not been considered as constituent materials for structural parts due to the poor interfacial adhesion between the fiber and the thermoplastic matrix. In this work, polyamide 6 (PA6) composites with pitch carbon fibers (pCF) were fabricated by alternatively stacking PA6 films and pCF fabrics followed by being pressed. In order to improve the interfacial adhesion, phenoxy resin-based materials were coated on the surface of the fiber. The surface analyses of the fiber were carried out by XPS, TGA and dynamic contact angle method. Interlaminar shear strength (ILSS) of the composites was measured to evaluate the effect of the coating materials. The results showed that the composites with the coated pCF had higher ILSS than that with neat pCF by more than 20%. This indicated that a proper coating material can improve mechanical properties of the PA6 composites, which can be applied to the structural parts.     

Compressive response and failure of fiber reinforced unidirectional composites

The compressive response of polymer matrix fiber reinforced unidirectional composites (PMC's) is investigated via a combination of experiment and analysis. The study accounts for the nonlinear constitutive response of the polymer matrix material and examines the effect of fiber geometric imperfections, fiber mechanical properties and fiber volume fraction on the measured compressive strength and compressive failure mechanism.Glass and carbon fiber reinforced unidirectional composite specimens are manufactured in-house with fiber volume fractions ranging over 1060 percent. Compression test results with these specimens show that carbon fiber composites have lower compressive strengths than glass fiber composites. Glass fiber composites demonstrate a splitting failure mode for a range of low fiber volume fractions and a simultaneous splitting/kink banding failure mode for high fiber volume fractions. Carbon fiber composites show kink banding throughout the range of fiber volume fractions examined. Nonlinear material properties of the matrix, orthotropic material properties of the carbon fiber, initial geometric fiber imperfections and nonuniform fiber volume fraction are all included in an appropriate finite element analysis to explain some of the observed experimental results. A new analytical model predictionof the splitting failure mode shows that this failure mode is favorable for glass fiber composites, which is in agreement with test results. Furthermore, this modelis able to show the influence of fiber mechanical properties, fiber volume fraction and fiber geometry on the splitting failure mode.     

Experimental study on the tension fatigue behavior and failure mechanism of 3D multi-axial warp knitted composites

An experimental study is described in this paper dealing with the tension–tension fatigue and failure mechanism of 3D MWK composites with different fiber architectures and material sizes. Macroscopic fracture morphology and SEM micrographs are examined to understand the fatigue damage and failure mechanism. The results show the fatigue properties and failure mechanism of composites can be affected significantly by the fiber architecture and material size. The fatigue life of material A(0°/0°/0°/0°) with small fiber orientation angle is significantly longer than that of material B(+45°/−45°/+45°/−45°). For material A, the fatigue properties of the long composite are better than that of the short one. It is 0° fiber bundles fracture under fatigue stress which cause the material failure and the long composite provides more space for the formation and propagation of local fatigue micro-cracks. However, for material B, the short composites have better fatigue properties. Moreover, the materials show typical ±45° zigzag fatigue fracture and obvious shear behavior. The fatigue cracks for the long composite can be spread more quickly along the fiber/matrix interface due to the fiber bundles realignment.     

湿热老化对玻璃纤维/环氧树脂复合材料性能的影响

为研究玻璃纤维(GF)/环氧树脂复合材料湿热老化机制, 首先, 利用称重法、动态热机械分析仪(DMA)、SEM和矢量网络介电分析仪研究了湿热老化对GF/环氧树脂608(EP608)复合材料性能的影响;然后, 分析了复合材料的吸湿率、力学性能、介电性能与老化时间的关系, 并对其老化机制进行了探讨。结果表明:随老化时间延长, GF/EP608复合材料的力学性能和介电性能均有不同程度的下降;湿热老化对GF/EP608复合材料吸湿率的影响符合Fickian扩散定律;树脂基体的塑化、水解和基体-纤维界面的破坏是造成GF/EP608复合材料力学性能和介电性能下降的主要因素。所得结论可为GF增强环氧树脂基复合材料的应用提供科学依据。      

短切碳纤维增强尼龙66复合材料注塑成型工艺模拟

采用毛细管流变仪和自制小型模具,对不同质量分数的短切碳纤维增强尼龙66(CF/PA66)复合材料颗粒进行了熔体流动性能分析和注塑成型工艺模拟,实现少量原料快速模拟CF/PA66的注塑成型工艺参数。研究表明:短切CF/PA66复合材料的熔体属于幂律流体,熔体黏度随温度、压力和CF质量分数变化显著,当温度和压力升高到临界值后熔体流变特性从假塑性区进入牛顿区;随着CF质量分数的增加,CF/PA66复合材料适宜成型温度提高。实验中PA66、CF质量分数为10wt%和20wt%的CF/PA66三种颗粒的适宜成型温度分别为278~285℃、280~287℃、290~298℃,通过对熔体进行Bagley压力校正,三种颗粒适宜成型的最小注塑压力分别为24.3MPa、29.4MPa、35.1MPa;将流变仪模拟所得参数应用于注塑成型工艺,所得样品的拉伸强度与流变仪制备的试样非常接近,进一步说明了毛细管流变仪模拟CF/PA66注塑成型过程的可行性和有效性,为其注塑成型工艺条件提供了理论依据。     

Polypropylene/glass fibre 3D-textile reinforced composites for automotive applications

Textile-reinforced thermoplastic composites offer huge application potentials for a rapid manufacturing of components with versatile possibilities of integrating functions. However, an application of these new materials requires the knowledge of the directional dependent material properties. In this study, results are presented concerning selected relevant load cases for industrial applications. For the new group of multi-layered flat bed weft-knitted glass fibre/polypropylene composites (MKF-GF/PP), tensile tests under different temperatures and test velocities have been carried out as well as Charpy impact tests, open hole tension tests and dynamic-mechanical analysis. The mechanical properties of MKF-GF/PP and unidirectional GF/PP composites with tailored fibre surface and interphase, respectively, have been compared to those of woven GF/PP composites and GF/PP composites made of non-crimp fabrics (NCF) as a benchmark.     

电子束辐射对玻纤/尼龙6复合材料性能的影响

利用电子束对30wt%玻璃纤维(GF)/尼龙6(PA6)复合材料进行辐射交联改性,研究了敏化剂的用量、辐射剂量等对GF/PA6复合材料的结构、力学性能、吸水性能以及热稳定性的影响,并通过SEM对复合材料的交联结构及燃烧后形成的炭层进行了观察。结果表明:当三烯丙基异氰脲酸酯(TAIC)含量为1wt%、辐照剂量为50kGy时,GF/PA6的拉伸强度、弯曲强度、常温及低温冲击强度分别提高了15.7%、43.2%、18.7%和17.3%;随着辐照剂量的增加,GF/PA6复合材料的交联密度不断增大;GF/PA6复合材料燃烧后会形成致密炭层,可以有效地减缓乃至消除尼龙6燃烧时形成的熔滴。     

玻纤增强聚丙烯复合材料的应变率敏感特性

采用层合热压实验法将玻璃纤维基毡与聚丙烯薄膜复合制成不同玻纤含量的玻纤增强聚丙烯(GF/PP)复合板材,在不同的加载速率下进行拉伸测试,研究GF/PP复合材料的应变率敏感特性,分析Burgers模型对该材料本构关系拟合预测的可行性。结果表明:GF/PP复合材料在低应变率范围内对应变率是敏感的,随应变率的增加,其断裂应力和抗拉强度增大;随玻璃纤维含量的增加,其所对应的应变率效应反而有所下降。同时,Burgers模型能够有效地拟合预测出该材料的拉伸应力-应变曲线,与实验曲线相比,进一步验证了GF/PP复合材料的应变率敏感特性及其变化趋势。     

New glass fiber/bismaleimide composites with significantly improved flame retardancy,higher mechanical strength and lower dielectric loss

Novel glass fiber (GF)/bismaleimide composites with significantly improved flame retardancy, higher mechanical strength and lower dielectric loss were developed, of which the resin matrix is a new flame retarding resin system (BDDP) based on 4,4′-bismaleimidodiphenyl methane (BDM), 2,2′-diallyl bisphenol A (DBA) and [(6-oxido-6H-dibenz [c,e] [1,2] oxaphosphorin-6-yl)-methyl]-butanedioic acid (DDP). The influence of the loading of DDP in the matrix on the integrated performances of composites was intensively studied. Results show that GF/BDDP composites not only have significantly improved mechanical and dielectric properties, but also possess excellent flame retardancy. The main flame retarding mechanism of GF/BDDP composites is the condensed phase mechanism. The introduction of DDP significantly strengthens the interfacial adhesion between GF and the resin matrix, this is responsible for the attractive performances of GF/BDDP composites.     

玻璃纤维表面纳米SiO_2改性对GF/PCBT复合材料力学性能的影响

为研究玻璃纤维(GF)表面纳米SiO2改性对GF增强树脂基复合材料力学性能的影响,利用真空辅助模压(VAMP)工艺制备了不同含量的纳米SiO2表面改性GF增强聚环状对苯二甲酸丁二醇酯(PCBT)复合材料。分析了GF表面改性对GF/PCBT复合材料力学性能的影响,研究了纤维表面改性对GF/PCBT复合材料抗湿热老化性能的影响规律。纤维拔出试验结果表明:经表面处理的GF/PCBT复合材料的界面剪切强度提高了1.16倍;采用含量为0.5wt%和2wt%(与树脂质量比)的纳米SiO2处理GF表面后,复合材料的三点弯曲强度分别提高1.5倍和1.67倍,弯曲模量分别提高1.03倍和1.17倍。SEM结果显示:当纳米SiO2用量为2wt%时,破坏后的纤维表面被树脂完全覆盖,树脂与纤维粘结良好。在湿热条件下,由于纳米SiO2颗粒的存在,水分子很难通过界面相扩散到改性后的材料内部,其抗湿热性能提高。     

Modeling the response,strength and degradation of 3D woven composites subjected to high rate loading

Experimental results which were obtained using a split Hopkinson pressure bar (SHPB) apparatus to determine rate dependent effects, and reported by the authors in [1] are used as the basis to perform dynamic simulations of 3D woven composites (3DWCs) using representative unit cells (RUCs). The input material properties for the RUC simulations were determined from the concentric cylinder model (CCM) in conjunction with the geometry of the textile architecture, mechanical properties of pure epoxy samples and fiber mechanical properties. The RUC model incorporates rate dependent plasticity. Additionally, linear-eigen perturbations that correspond to buckling modes are used to seed imperfections in the RUC model to capture buckling and subsequent failure that was observed in experiments. The RUC model results showed good agreement with experiment and correctly captured the observed modes of failure while pointing to transitions in failure modes.     

Effect of fiber surface modification on water absorption and hydrothermal aging behaviors of GF/pCBT composites

Water absorption and aging behaviors of fiber reinforced polymerized poly (cyclic butylene terephthalate) (GF/pCBT) composites are investigated. We coated nano-silica on glass fiber surface by physical vapor deposition (PVD) method. Subsequently, we immersed pCBT composites reinforced with nano-treated/untreated fibers in 25 °C and 60 °C distilled water until their saturated moisture. We also exposed some specimens in various hydrothermal aging environments. We tested the mechanical performance of these test specimens and found that the mechanical performance of both pCBT cast and GF/pCBT composites reduces obviously after water absorption and hydrothermal aging. However, nano-silica modified fiber reinforced composites have higher remaining strength than GF/pCBT. Scanning electron microscope (SEM) is used to study the microscopic phase and nanoparticle modified mechanism, and better interface characteristic between fibers and matrix is observed.     

对位芳纶/尼龙66的加工工艺对其力学性能的影响研究

由不同的加工工艺来研究对位芳纶/尼龙66(PPTA/PA66)复合材料的力学性能,结果表明:①随着PPTA纤维含量的增多,使用黏度较大的PA66基体进行复合时,PPTA/PA66复合材料的拉伸强度、弯曲强度都随之变大;对于冲击强度来说,PPTA纤维的加入,增加了其脆性,造成PPTA/PA66复合材料冲击强度不如原基体的冲击强度;②PPTA纤维含量在5%的情况下,当挤出机转速达到300r/min时材料的拉伸强度、冲击强度和弯曲强度出现极大值,此时的混合效果最理想;③较高的挤出温度有助于提高复合材料的拉伸强度和弯曲强度,对于冲击强度来说,PPTA/PA66复合材料冲击强度同样不如原基体的冲击强度;④PPTA纤维的长径比集中在65左右,芳纶纤维起到了增强效果。     

Compressive damage mechanism of GFRP composites under off-axis loading: Experimental and numerical investigations

Experimental and computational studies of the microscale mechanisms of damage formation and evolution in unidirectional glass fiber reinforced polymer composites (GFRP) under axial and off-axis compressive loading are carried out. A series of compressive testing of the composites with different angles between the loading vector and fiber direction were carried out under scanning electron microscopy (SEM) in situ observation. The damage mechanisms as well as stress strain curves were obtained in the experiments. It was shown that the compressive strength of composites drastically reduces when the angle between the fiber direction and the loading vector goes from 0° to 45° (by 2.3–2.6 times), and then slightly increases (when the angle approaches 80–90°). At the low angles between the fiber and the loading vector, fiber buckling and kinking are the main mechanisms of fiber failure. With increasing the angle between the fiber and applied loading, failure of glass fibers is mainly controlled by shear cracking. For the computational analysis of the damage mechanisms, 3D multifiber unit cell models of GFRP composites and X-FEM approach to the fracture modeling were used. The computational results correspond well to the experimental observations.