CaCl1和多巴胺处理对芳纶纤维表面结构与性能的影响

采用氯化钙(CaCl2)乙醇溶液和多巴胺水溶液浸渍法对芳纶纤维表面进行改性处理,对改性后芳纶纤维表面的化学结构、微观形貌、表面粗糙度、单丝拉伸强度和芳纶纤维/环氧树脂复合材料的界面性能等进行了测试分析.结果表明,采用CaCl2乙醇溶液处理芳纶纤维后,芳纶纤维表面有刻蚀出的沟槽,表面粗糙度增大,芳纶纤维/环氧树脂复合材料的层间剪切强度明显提高,同时由于纤维结构受到破坏,单丝拉伸强度下降了11.12％;采用多巴胺水溶液处理时,芳纶纤维表面沉积了聚多巴胺涂层,表面粗糙度增大,芳纶纤维/环氧树脂复合材料的层间剪切强度进一步提高,纤维结构几乎不受影响,单丝拉伸强度降幅较小;采用CaCl2乙醇溶液和多巴胺水溶液先后处理芳纶纤维后,纤维表面的聚多巴胺涂层更致密,复合材料的层间剪切强度达到最大值,同时改性后的纤维具有一定的抗紫外性能,此方法改性效果最优.     

CaCl_2和多巴胺处理对芳纶纤维表面结构与性能的影响

采用氯化钙(CaCl_2)乙醇溶液和多巴胺水溶液浸渍法对芳纶纤维表面进行改性处理,对改性后芳纶纤维表面的化学结构、微观形貌、表面粗糙度、单丝拉伸强度和芳纶纤维/环氧树脂复合材料的界面性能等进行了测试分析。结果表明,采用CaCl_2乙醇溶液处理芳纶纤维后,芳纶纤维表面有刻蚀出的沟槽,表面粗糙度增大,芳纶纤维/环氧树脂复合材料的层间剪切强度明显提高,同时由于纤维结构受到破坏,单丝拉伸强度下降了11.12%;采用多巴胺水溶液处理时,芳纶纤维表面沉积了聚多巴胺涂层,表面粗糙度增大,芳纶纤维/环氧树脂复合材料的层间剪切强度进一步提高,纤维结构几乎不受影响,单丝拉伸强度降幅较小;采用CaCl_2乙醇溶液和多巴胺水溶液先后处理芳纶纤维后,纤维表面的聚多巴胺涂层更致密,复合材料的层间剪切强度达到最大值,同时改性后的纤维具有一定的抗紫外性能,此方法改性效果最优。     

基于声发射技术的单丝复合材料界面性能研究

为了克服传统单丝断裂实验局限于透明及高应变树脂的缺点,进一步拓展其应用范围,将声发射技术与传统单丝断裂实验相结合以评估单丝复合材料界面性能.通过声发射技术监测了单丝复合材料的断裂过程,采用参数分析、波形分析以及聚类分析对单丝复合材料拉伸过程中的声发射信号特征进行研究,并与显微镜观察法测得的纤维断裂模式和界面剪切强度相对比。实验结果表明:声发射技术可以对单丝复合材料断裂过程中的断裂模式和界面性能进行高效评估,采用该方法分析得到的界面剪切强度与传统单丝断裂实验中的光弹花样观察分析结果一致。声发射技术可以拓展单丝断裂实验的研究对象,为单丝界面剪切强度的计算提供一种高效、通用的评价方法。     

LiCl处理对芳纶纤维表面结构与性能的影响

为提高芳纶纤维与复合材料基体间的界面强度,首先,使用LiCl乙醇溶液处理芳纶纤维一定时间;然后,对LiCl处理芳纶纤维表面的化学组成、微观形貌、单丝拉伸强度及芳纶纤维/环氧树脂复合材料的界面性能等进行了测试分析。结果表明:使用LiCl乙醇溶液处理芳纶纤维后,芳纶纤维表面的含氮官能团含量增加;处理后,芳纶纤维表面有刻蚀出的沟槽,表面粗糙度增大,进而改善了芳纶纤维与环氧树脂基体的界面粘接性能,使芳纶纤维/环氧树脂复合材料的层间剪切强度由处理前的21.75 MPa提升到37.98 MPa;最佳处理时间为3~4 h,而处理时间过长会导致芳纶纤维的单丝拉伸强度及复合材料的层间剪切强度下降。所得结论证实使用LiCl处理芳纶纤维是一种有效的表面改性方法。      

C/C复合材料的界面演化规律

研究了单丝界面和纤维束界面结构在细编穿刺C/C复合材料制备过程中的演化规律以及两种界面剪切强度随着生产周期增加的不同变化趋势.在C/C的制备过程中单丝界面和纤维束界面的形成速度不同,单丝界面优先得到完善,经过四个周期界面剪切强度既可达到最高水平;而束界面剪切强度在六个周期后才达到较高水平.     

单丝断裂双树脂法研究碳纤维/环氧树脂界面粘结性能

建立了单丝断裂双树脂体系法, 利用外层树脂的韧性使包埋于内层脆性树脂中的纤维单丝断裂达到饱和, 解决了断裂伸长率较低的树脂基体采用传统的单丝断裂法无法测得界面剪切强度的问题。分别采用界面剪切强度和界面断裂能作为表征参量, 考察了干态及湿热条件下两种T300级和两种T800级碳纤维/环氧树脂的界面性能, 并与单丝断裂单树脂体系的界面性能进行比较。结果表明: 单丝断裂双树脂体系与单树脂体系在表征碳纤维/环氧树脂的界面性能上定性规律一致; 双树脂体系界面断裂能和界面剪切强度均可评价界面的耐湿热性能, 且二者得到的变化规律一致; 湿热处理后界面粘结性能均呈下降趋势, 国外碳纤维体系的界面耐湿热性能明显优于国产碳纤维体系。     

电热作用对碳纤维/树脂复合材料界面应力的影响电热作用对碳纤维/树脂复合材料界面应力的影响

碳纤维/树脂复合材料广泛应用于民用航空器结构中,在服役期间会受到复杂环境（湿热、腐蚀、复杂应力和电热作用等）的作用,低强度电流对碳纤维/树脂复合材料的影响受到的关注较少。以碳纤维/树脂复合材料为研究对象,根据碳纤维的温敏效应和通电时的电阻变化规律,计算出碳纤维单丝/环氧树脂复合试样的界面温度范围,之后采用拉曼光谱测试和单丝断裂实验研究了低强度电流对单丝复合体系界面应力和界面剪切强度的影响。结果表明:随着电流强度的提高,单丝复合体系的界面温度随之升高,电流为8 mA时,界面温度高达约200℃。随着电流强度的增大,单丝复合体系的界面压缩应力表现为先增大后减小的趋势,电流高于7 mA后,界面处树脂出现烧蚀降解破坏;单丝断裂实验结果表明随着电流强度增大,单丝复合体系的界面剪切强度呈现先升后降的趋势,在6 mA时界面剪切强度达到最大值62.39 MPa,而8 mA时界面剪切强度仅为34.95 MPa。      

含碳纳米管上浆剂的制备及对碳纤维/环氧树脂复合材料界面的影响

首先采用"Friedel-Crafts"酰化反应制备羧基化多壁碳纳米管(MWCNTs)并将其与环氧树脂、丙酮混合制成含MWCNTs的上浆剂,然后用该上浆剂浸渍碳纤维制备碳纳米管/碳纤维多尺度增强纤维。采用扫描电镜研究了上浆处理对碳纤维表面形貌的影响,采用短臂梁剪切测试方法研究了含碳纳米管的上浆剂对碳纤维/环氧树脂复合材料层间剪切强度(ILSS)的影响。结果表明,碳纳米管在上浆剂中的分散状态直接影响纤维表面碳纳米管分布的均匀性;与未浸渍的碳纤维相比,含碳纳米管上浆剂浸渍后的碳纤维/环氧树脂复合材料的ILSS提高了34.33%。通过上浆剂红外光谱表征、纤维束表面浸润性测试及ILSS试样端口形貌的观察,分析了层间增韧机理。研究表明,碳纤维束表面浸润性的提高以及碳纤维/环氧树脂界面处化学键合作用增强,是ILSS提高的主要原因。     

单丝断裂双树脂法研究碳纤维/环氧树脂界面粘结性能

建立了单丝断裂双树脂体系法,利用外层树脂的韧性使包埋于内层脆性树脂中的纤维单丝断裂达到饱和,解决了断裂伸长率较低的树脂基体采用传统的单丝断裂法无法测得界面剪切强度的问题.分别采用界面剪切强度和界面断裂能作为表征参量,考察了干态及湿热条件下两种T300级和两种T800级碳纤维/环氧树脂的界面性能,并与单丝断裂单树脂体系的界面性能进行比较.结果表明:单丝断裂双树脂体系与单树脂体系在表征碳纤维/环氧树脂的界面性能上定性规律一致;双树脂体系界面断裂能和界面剪切强度均可评价界面的耐湿热性能,且二者得到的变化规律一致;湿热处理后界面粘结性能均呈下降趋势,国外碳纤维体系的界面耐湿热性能明显优于国产碳纤维体系.     

芳纶纤维的磷酸表面处理及其树脂基复合材料界面性能

采取不同浓度的磷酸水溶液对芳纶纤维进行表面处理, 并对不同处理条件下芳纶纤维的单丝强度、表面性质及其环氧树脂复合材料的界面性能进行了分析和测试。结果表明: 20 wt %磷酸溶液处理的芳纶纤维, 纤维表面含氧官能团含量最高; 继续提高磷酸溶液的浓度, 含氧官能团含量下降, 纤维表面趋于平整, 单丝强度上升。用20 wt %磷酸溶液处理芳纶纤维, 纤维/ 环氧树脂基复合材料的层间剪切强度达到62 MPa , 界面剪切强度提高18 % , 是一种简单有效的表面处理方法。纤维表面粗糙度和纤维表面含氧官能团的数量是影响芳纶纤维/ 环氧树脂复合材料界面结合性能的关键因素。      

Effects of emulsion sizing with nano-SiO<Subscript>2</Subscript> on interfacial properties of carbon fibers/epoxy composites

Nano-SiO₂ particles were used to modify epoxy emulsion sizing of carbon fibers to improve the interfacial properties of carbon fibers reinforced epoxy composites. The mechanical interfacial strength between fibers and matrix was investigated by the single fiber fragmentation test and the 3-point short beam shear test, respectively. Dynamic contact angle analysis (DCAA), X-ray photoelectron spectrometry (XPS) and atomic force microscopy (AFM) were performed on the carbon fibers with unmodified sizing and nano-SiO₂ modified sizing. The results indicated that modified sizing with nano-SiO₂ slightly increased the surface energy, the hydroxyl functional group and the surface roughness of carbon fibers compared to unmodified sizing, so that the interfacial shear strength (IFSS) of the single fiber composites and the interlaminar shear strength (ILSS) of composites were enhanced. SEM images of fracture sections of composites proved powerfully that the interfacial adhesion between fibers and matrix was improved after nano-SiO₂ modified emulsion sizing treatment.     

Role of a gradient interface layer in interfacial enhancement of carbon fiber/epoxy hierarchical composites

To improve the interfacial properties of carbon fibers/epoxy composites, we introduced a gradient interphase reinforced by graphene sheets between carbon fibers and matrix with a liquid phase deposition strategy. Interlaminar shear strength and flexural strength of the composites are both improved. The interfacial reinforcing mechanisms are explored by analyzing the structure of interfacial phase with linear scanning system of scanning electron microscope and atomic force microscope. Results indicate that carbon element shows a graded dispersion in the interface region and a gradient interface layer with the modulus decreasing from fibers and matrix is found to be built. To verify the effect of gradient interphase on the interfacial properties of composites, the mixture of carbon fiber/graphene/epoxy is sonicated before curing to disperse graphene sheets in matrix homogeneously. As a result, gradient interphase structures are disappeared and interfacial performance of composites is found to be weakened. The role of gradient interface layers in enhancing interfacial performances is further proved from a different angle.     

Application of continuously-monitored single fiber fragmentation tests to carbon nanotube/carbon microfiber hybrid composites

To assess the effect of carbon nanotube (CNT) grafting on interfacial stress transfer in fiber composites, CNTs were grown upon individual carbon T-300 fibers by chemical vapor deposition. Continuously-monitored single fiber composite (SFC) fragmentation tests were performed on both pristine and CNT-decorated fibers embedded in epoxy. The critical fragment length, fiber tensile strength at critical length, and interfacial shear strength were evaluated. Despite the fiber strength degradation resulting from the harsh CNT growth conditions, the CNT-modified fibers lead to a twofold increase in interfacial shear strength which correlates with the nearly threefold increase in apparent fiber diameter resulting from CNT grafting. These observations corroborate recently published studies with other CNT-grafted fibers. An analysis of the relative contributions to the interfacial strength of the fiber diameter and strength due to surface treatment is presented. It is concluded that the common view whereby an experimentally observed shorter average fragment length leads to a stronger interfacial adhesion is not necessarily correct, if the treatment has changed the fiber tensile strength or its diameter.     

单丝断裂能量法研究温度对碳纤维/环氧界面性能的影响

针对两种不同上浆剂碳纤维/高温固化环氧树脂体系, 采用基于WND(Wagner-Nairn-Detassis)能量模型的单丝断裂法, 测试分析了从室温到130 ℃范围内单丝复合体系界面断裂能的变化规律, 研究了碳纤维上浆剂对界面耐热性能的影响, 并结合复合材料层板的短梁剪切性能, 分析了微观和宏观界面性能的关联性。结果表明: 在测试温度范围内, 碳纤维/环氧体系的界面断裂能随温度升高呈先下降而后基本不变的趋势, 去除上浆剂后界面断裂能及其随温度的变化程度与未去除上浆剂的情况存在差异, 说明上浆剂对界面耐热性有重要作用。碳纤维/环氧树脂层板层间剪切强度随温度升高线性下降, 与界面断裂能的变化规律不一致, 这与两种测试方法的原理及界面破坏位置的不同有关。      

Evaluation of water degradation of vinylester and epoxy matrix composites by single fiber and composite tests

Degradation of the mechanical properties of vinylester and epoxy matrix composites exposed to water has been approached by monitoring the strengths of glass and carbon fibers and resins. In addition, the fiber/matrix (F/M) interface strengths and debond lengths of single-fiber composites were determined and test results were compared to test results of macroscopic composite specimens. The single-fiber tensile test results indicate a substantial loss of the tensile strength of glass fibers and the fragmentation tests reveal loss of F/M shear strength and substantial debonding for both glass and carbon fiber composites after water exposure. The transverse strengths of the composites are also degraded to large extents. The tests results identify water degradation of the F/M interface as a major strength limiting mechanism.     

Effect of carbon nanotubes on the interfacial shear strength of T650 carbon fiber in an epoxy matrix

The interfacial shear strength of carbon nanotube coated carbon fibers in epoxy was studied using the single-fiber composite fragmentation test. The carbon fibers were coated with carbon nanotubes (CNT) on the fiber surface using thermal chemical vapor deposition (CVD). The CVD process was adjusted to produce two CNT morphologies for the study: radially aligned and randomly oriented. The purpose of the CNT coating was to potentially produce a multifunctional structural composite. Results of the single-fiber fragmentation tests indicate an improvement in interfacial shear strength with the addition of a nanotube coating. This improvement can most likely be attributed to an increase in the interphase yield strength as well as an improvement in interfacial adhesion due to the presence of the nanotubes.     

高性能有机纤维单丝复合体系界面粘结性能实验研究

采用单丝复合体系多次断裂法,通过对纤维单丝断点数的统计及其断点形貌的分析,考察了PBO纤维、芳纶Twaron纤维、超高分子量聚乙烯纤维(UHMWPE)3种高性能有机纤维与韧性环氧基体的界面剪切强度;并对比考察了界面剪切强度与对应复合材料单向板层间剪切强度之间的关系;结合XPS、SEM等手段分析了有机纤维表面物理化学特性对界面剪切强度的影响。结果表明,Twaron/环氧的界面剪切强度高于PBO/环氧,UHMWPE/环氧的界面粘结弱,该方法不能测试;上述体系界面剪切强度与对应的复合材料单向板层间剪切强度变化趋势是一致的;表面化学活性高的纤维对应的界面剪切强度高。     

纤维／聚合物基体界面性能的原位表征

建立了复合材料界面强度原位测试系统，研制出界面剪切强度有限元分析软件并探讨了影响界面剪应力分析的因素，提出了改进的微观力学模型；利用该系统，研究了表面经不同改性处理的ＣＦ增强ＰＭＲ—１５聚酰亚胺复合材料界面的微观力学性能，结果表明：有效的表面处理可使ＣＦ／ＰＭＲ—１５界面剪切强度明显提高，并与其宏观性能具有较好的对应趋势。本文还初步探讨了界面破坏的过程。