盐雾环境中玻璃纤维/不饱和聚酯复合材料腐蚀深度对弯曲性能的影响

采用中性盐雾加速老化试验模拟海洋大气环境, 对玻璃纤维/不饱和聚酯复合材料在盐雾环境中的弯曲性能进行了研究。通过玻璃纤维/不饱和聚酯复合材料经盐雾加速老化后的吸湿率、玻璃化转变温度、巴氏硬度和弯曲性能的变化, 结合金相显微镜观测得到的腐蚀深度, 研究腐蚀深度对玻璃纤维/不饱和聚酯复合材料耐久性的影响。结果表明:老化初期玻璃纤维/不饱和聚酯复合材料的吸湿率随时间增长较快, 随后增长逐渐趋于稳定。玻璃纤维/不饱和聚酯复合材料的玻璃化转变温度呈现先增加后下降的趋势, 老化180 d后玻璃化转变温度增加了2.1%;老化180 d后玻璃纤维/不饱和聚酯复合材料的巴氏硬度与老化前相比降低了17.6%, 弯曲强度损失率为10%。基于金相显微镜分析得到老化后玻璃纤维/不饱和聚酯复合材料的腐蚀深度, 建立了腐蚀深度与弯曲强度之间的关系。      

碳纤维增强环氧树脂复合材料盐雾腐蚀行为及其老化分子机制

碳纤维增强环氧树脂复合材料(CFRP)综合性能优异,广泛用于国防军工、航空航天等领域。文中针对CFRP在海洋气候环境下的实际应用需求,研究了具有产品结构特征的NOL环及层压板试样在高温、高浓度盐雾（55℃,10%NaCl）条件下的盐雾腐蚀行为,并通过研究材料在老化过程中的吸湿行为、盐分扩散行为及树脂分子/交联网络结构及体系界面结构的演变,探究了其老化分子机理及界面损伤机制。其老化过程可分为3个阶段,在此期间水分子对树脂的溶胀与塑化作用、纤维-基体湿膨胀系数不匹配诱发的界面损伤作用及盐分/水分对树脂的腐蚀断链作用均可导致体系交联密度降低、界面脱粘及基体破碎,诱使材料力学及界面强度劣化。老化90 d后,NOL环及层压板试样的层间剪切强度（ILSS）保留率分别为73.75%及84.10%。     

碳纤维/碳纳米管-环氧树脂复合材料的耐老化性能

将环氧树脂基体与氨基化碳纳米管(MWNTs)复合,制备了碳纤维/氨基化碳纳米管-环氧树脂(CF/MWNTs-EP)复合材料。表征CF/MWNTs-EP三相复合材料的断面,并在标准条件下测试其冲击、拉伸等力学性能,研究了耐老化性能。结果表明:氨基化碳纳米管的加入明显提高了材料的耐盐雾性、耐热氧老化性和耐湿热性能。氨基化碳纳米管的加入改善了纤维与基体树脂间的界面性能,同时,促进了环氧树脂的固化,降低孔隙率,导致耐老化性能显著提高。当MWNTs-NH2的添加量(质量分数)为1.0%时,在72h和168h不同盐雾时间下,三相复合材料的耐盐雾老化性比CF/EP复合材料分别提高了61.8%和67.5%。在48h、96h和168h热氧老化时间下,三相复合材料的耐热氧老化性比CF/EP复合材料分别提高了43.5%、48.5%和41.7%。在72h和168h不同湿热时间下,三相复合材料的耐湿热老化性比CF/EP复合材料分别提高了52.8%和60.0%。     

环境性能试验对导电橡胶性能的影响

通过环境性能试验前后导电橡胶材料的体积电阻率及力学性能的变化,研究环境试验对导电橡胶性能的影响。采用扫描电镜观察了金属填料在橡胶体系中的分布。结果表明,热空气老化性能试验、耐盐雾性能试验和耐霉菌性能试验使材料外观发生了变化,体积电阻率增加,其中盐雾试验影响最明显;另外盐雾试验使材料力学性能下降,其他试验变化不明显。     

碳纤维增强树脂基复合材料模拟海洋环境长期老化及失效行为

选取两种先进轻质复合材料:碳纤维增强酚醛树脂复合材料(CF/S-157)与碳纤维增强环氧树脂复合材料(CF/TDE-85),开展模拟海洋环境实验室盐雾老化、湿热老化和盐水浸泡环境长达9600 h加速试验.基于各种力学性能(拉伸强度、弯曲强度、压缩强度及层间剪切强度)开展材料老化行为规律研究,利用傅立叶变换衰减全反射红外...     

土木工程应用中碳纤维/环氧树脂界面在环境影响下退化的分子模拟研究进展

在土木工程领域,碳纤维增强复合材料 (CFRP) 由于有着优异的力学性能而被越来越多地用在建筑结构中。碳纤维与环氧树脂之间粘结界面的性能对于 CFRP 内部应力的有效传递极为关键,并很大程度上决定了复合材料的长期耐久性能。然而,纤维/树脂粘结界面易受到湿热、盐雾及海水等恶劣环境的侵蚀,导致界面脱粘及最终的复材破坏。为了确保复材的长期耐久性能,需要全面认识界面在环境侵蚀下的退化行为。分子动力学模拟可以“自底向上”地描述界面在环境侵蚀下的行为,有利于探究界面的退化和失效机制。本文综述了不同环境因素影响下碳纤维/环氧树脂界面退化的分子模拟研究进展,包括界面模型的建立,界面在潮湿、盐雾等环境中结构、性能的退化及其背后的机制。最后,提出了未来界面退化的研究方向,例如纤维/树脂粘结界面模型的进一步完善。      

盐雾环境对玻璃纤维增强树脂基复合材料力学性能的影响

采用中性盐雾条件模拟海洋大气环境进行加速老化试验, 评价玻璃纤维增强环氧改性酚醛树脂基复合材料( GFRP) 在海洋气候中的耐久性。通过该复合材料经盐雾老化后的质量变化和纵向拉伸强度、横向拉伸强度、压缩强度、层间剪切强度的变化, 结合湿热老化机理, 研究其老化规律。结果表明, 随着老化时间的增加, 复合材料的吸湿量增加, 力学强度下降, 压缩和层间剪切曲线表现出塑性特征。吸湿最初阶段对力学性能影响最大, 纵向拉伸强度、横向拉伸强度、压缩强度、层间剪切强度分别下降到56. 1 %、54. 7 %、54. 0 %、61. 0 %。其中拉伸强度变化趋势最稳定, 更适用于评价该复合材料的老化程度。      

铸造铝合金真空浸渗针孔修复组织及性能研究

本文采用真空浸渗技术,对铸造铝合金(ZL101A)针孔缺陷进行修复,并研究其修复后的综合性能.修复前后的试样分别进行显微组织及能谱分析、摩擦磨损实验、盐雾腐蚀试验等性能测试.研究结果表明:真空浸渗工艺后的铸铝合金表面针孔有效得到填充;摩擦磨损曲线更加平滑,摩擦系数0.61小于未浸渗试样的摩擦系数0.73;盐雾实验测试防腐等级由3级升到6级,表明真空浸渗修复工艺较好地提高了铸造铝合金的力学性能与防腐蚀性能.     

纳米TiO2涂层耐蚀性及抗紫外老化性能研究

通过添加改性纳米TiO2获得纳米复合涂层.采用紫外线加速老化试验和盐雾试验考察纳米复合涂层的抗紫外老化腐蚀性能.利用电化学测试(EIS)监测老化过程涂层性能变化并研究了纳米TiO2材料在涂层老化过程中的作用.结果表明,纳米TiO2材料的加入能够同时提高彩涂板涂层的抗老化及耐腐蚀性能,纳米TiO2质量分数为1%左右时其抗老化及耐腐蚀性能最佳.     

热氧老化对碳纤维双马树脂基复合材料性能的影响

采用三点弯曲测试方法,研究热氧老化对碳纤维双马树脂基复合材料弯曲性能的影响,分析复合材料的失重行为以及不同老化时间下的弯曲性能、断口形貌、动态力学性能和红外谱图。结果表明:随着老化时间的增加,老化温度为100℃时的质量损失率逐渐趋于平稳,180℃时的质量损失率逐渐增加。老化温度为100℃时,只是物理老化,没有新物质的生成;而老化温度为180℃时,发生了化学老化,产生了热老化效应和氧化反应,引起了基体性能和界面性能的退化。热氧老化对复合材料弯曲强度的影响要大于对弯曲模量的影响。     

Salt-fog corrosion behavior of C/SiC and its effect on ablation resistance

Carbon fiber-reinforced silicon carbide(C/SiC) composites are significantly important candidates for thermal protection materials. The corrosion mechanism of C/SiC composite materials is the basis of their optimization and application. In this study, structural evolution of C/SiC composites fabricated by chemical vapor infiltration was investigated in the salt-fog storage environment. Furthermore, the effect of salt-fog on their ablation behaviors under oxyacetylene flame environment was studied. The ablation morphologies and corrosion mechanisms of C/SiC composites were analyzed and discussed. The results indicated that silica layer with size of c.a. 20 nm was formed on the surface of composite. The extent of corrosion in salt fog was limited, and it had little effect on the ablation behavior of the C/SiC composites,as well on the tensile strength and bending strength.     

Investigations on the fabrication and the characterization of glass/epoxy,carbon/epoxy and hybrid composites used in the reinforcement and the repair of aeronautic structures

This paper reports the fabrication and the characterization of glass/epoxy, carbon/epoxy and hybrid laminated composites used in the reinforcement and/or the repair of aeronautic structures. These composites were manufactured by the hand lay-up process. Their physical, thermal and mechanical behaviors are discussed in terms of moisture absorption, thermal stability, tensile strength, elastic modulus, flexural strength, flexural modulus and abrasive wear resistance. The impact of hygrothermal aging on the mechanical properties of each composite group has been also investigated.The main results indicated that after water immersion, all composites showed significant moisture absorption especially for glass/epoxy composite. Thermogravimetric analysis showed that the hybrid composite presented the best thermal stability behavior while the glass/epoxy composite the bad behavior. The mechanical properties of the carbon/epoxy composites, in the bulk material, were considerably higher than those of the glass/epoxy; the hybrid structure presented intermediate mechanical properties. The same trend was also observed in terms of wear properties. Finally, a deleterious effect on the strength of all composites due to hygrothermal exposure was established. However, carbon/epoxy composites seem to be less susceptible to aging damage after 90 days at 90 °C.     

Characterization of carbon/epoxy materials for structural repair of carbon/BMI structures

Characterization and compatibility of high-performance epoxy resins were investigated for on site repair of carbon/bismaleimide aircraft structures. First, processing of three bi-component resins was studied. Then, physical and mechanical characterizations were carried out on carbon fabric/repair resin composite laminates (materials A, B and C) before and after ageing and results are presented. One composite (material A) was chosen, according to industrial specifications, the main criterion being the glass transition temperature. The compatibility of this material with the carbon/BMI structures to be repaired was checked with lap shear tests. Compatibility between the selected repair material and carbon/epoxy composites, whose repair procedure is already known, was conducted and considered as reference point. The obtained results allowed to validate material A for on site step structural repair of the carbon/BMI structures of our industrial partner.     

抗菌剂用于牙科复合树脂的研究进展

龋病是常见的口腔疾病,填充修复是治疗的重要手段.复合树脂凭借色泽美观和理化性能优异等特点,广泛应用于牙科修复材料中.继发龋是临床应用中导致修复失败的主要原因之一.为了抑制继发龋、延长树脂使用寿命,研发具有长期抗菌功能的牙科复合树脂具有重要意义.目前,主要通过向复合树脂体系中添加抗菌型无机粒子或抗菌型有机单体赋予材料抗菌...     

蜂窝夹层修理结构的弯曲性能试验分析

采用四点弯加载方式研究分析了含损伤蜂窝夹层修理结构的弯曲性能,该夹层结构由碳纤维增强的聚合物面板和蜂窝芯子组成。进一步分析了挖补斜度、挖补方式、损伤程度、修理设备和修理材料对修理板弯曲性能的影响。研究表明,修理板的破坏模式可分为补片边缘折断、补片中面折断和胶层破坏三种,相同破坏模式修理板的名义弯曲强度相近,其中前两种破坏模式修理板的名义弯曲强度与完好板相近,而第三种破坏模式修理板的名义弯曲强度相对较低。所有修理板的名义弯曲强度恢复率基本处于95%以上,同时修理后抗弯刚度也满足修理准则。     

A scientific evaluation of the approximate 2D theories for composite repairs to cracked metallic components

In this paper, we show how the published literature reveals that the approximate two-dimensional solution for the stress intensity factor associated with cracked panel repaired using an externally bonded composite repair is inconsistent with experimental data, and that for short to mid-size cracks the fibre bridging effect is often a second-order effect. The result of this finding is that prediction of the effect of a composite repair on the structural integrity of cracked components repaired by an externally bonded composite repair is dramatically simplified. We also show why structures repaired using Glare patches have a fatigue performance that is superior to structures repaired using boron epoxy or carbon fibre patches.     

原位聚合碳纤维增强聚甲基丙烯酸甲酯基复合材料损伤与修复研究

基于热塑性复合材料易修复的特性,开展了碳纤维增强聚甲基丙烯酸甲酯(PMMA)基复合材料修复技术研究。研究了工艺温度、压力和时间对复合材料力学性能的影响规律。结果表明：在200℃、0.75 MPa压力下保持10 min可以获得优化的复合材料力学性能。引入低速冲击损伤,使用热压修复工艺修复碳纤维增强PMMA基复合材料的损伤。通过X射线断层扫描测试、超声波无损检测技术和断面摄像方法评估了此复合材料的损伤行为和修复效果。结果表明：低速冲击对碳纤维增强PMMA基复合材料的损伤分为低变形量区域的纵向开裂与分层和高变形量区域的纤维断裂与基体失效的混合模式。碳纤维增强PMMA基复合材料损伤试样经过热压修复后,损伤外形恢复良好,损伤区域大小显著减少,内部的开裂和分层等损伤恢复良好,复合材料压缩强度从140 MPa恢复至263 MPa,达到未损伤复合材料压缩性能(307 MPa)的85.7%。     

Low viscosity cyanate ester resin for the injection repair of hole-edge delaminations in bismaleimide/carbon fiber composites

The repair efficiency of bisphenol E cyanate ester (BECy) resin was investigated for the injection repair of high temperature polymer–matrix composites by ultrasonic C-scan mapping, fluorescent dye penetration, optical microscopy, hole plate shear (HPS), and post delamination compression tests. Bismaleimide/carbon fiber (BMI–cf) composites were chosen as a model substrate. A vacuum-based resin injection repair method was used for repairing the pre-damaged composite specimens. The effect of surface wettability on the repair efficiency of BECy on BMI–cf composite substrate was studied by temperature dependent contact angle measurements. C-scan, fluorescent dye penetration, and optical microscopy images of pristine, delaminated, and repaired specimens reveal efficient infiltration of resin in specimens repaired at elevated temperatures. The repair efficiency calculated from HPS and post delamination compression tests was observed to be 155% and 100%, respectively, illustrating the capability of BECy for repairing high temperature structural composites.     

Nonlinear analysis of bonded composite patch repair of cracked aluminum panels

Analyses of adhesively bonded composite patches to repair cracked structures have been the focus of many studies. Most of these studies investigated the damage tolerance of the repaired structure by using linear analysis. This study involves nonlinear analysis of the adhesively bonded composite patch to investigate its effects on the damage tolerance of the repaired structure. The nonlinear analysis utilizes the three-layer technique which includes geometric nonlinearity to account for large displacements of the repaired structure and also material nonlinearity of the adhesive. The three-layer technique uses two-dimensional finite element analysis with Mindlin plate elements to model the cracked plate, adhesive and composite patch. The effects of geometric nonlinearity on the damage tolerance of the cracked plate is investigated by computing the stress intensity factor and fatigue growth rate of the crack in the plate. The adhesive is modeled as a nonlinear material to characterize debond behavior. The elastic-plastic analysis of the adhesive utilizes the extended Drucker-Prager model. A detailed discussion on the effects of nonlinear analysis for a bonded composite patch repair of a cracked aluminum panel is presented in this paper.     

复合材料管状结构的能量吸收性能

复合材料结构作为防撞结构的能量吸收元件,已经逐步得到工程领域的广泛认同。复合材料结构的能量吸收能力是一种特殊要求的力学性能,它的研究目标和研究手段有其独特之处。综述了近年来复合材料管状结构能量吸收性能研究的最新进展,以及有待进一步研究的问题。