PLA/苎麻与PVA/苎麻复合材料的制备及其力学性能研究

采用碱-硅烷偶联剂表面复合改性处理,以苎麻织物作为增强材料,分别以聚乳酸(PLA)和聚乙烯醇(PVA)为基体,经过层合热压制备出环保的苎麻织物增强复合材料,对其进行拉伸、弯曲测试,并用SEM进行表征。结果表明,PLA/苎麻、PVA/苎麻复合材料拉伸强度、弯曲强度相比未经表面改性处理复合材料,其提高幅度分别为44.42%、31.45%、35.88%、18.47%。PLA/苎麻、PVA/苎麻增强复合材料纬向拉伸强度和弯曲强度大于经向;SEM结果表明:改性处理后,苎麻纤维表面干净、杂质少,复合材料的界面结合效果较好。PLA基体相较于PVA对苎麻的浸润效果较好。拉伸断裂方式均为韧性断裂,断口参差不齐。     

三维六向编织SiCf/SiC复合材料的力学行为及其损伤机制

为解决陶瓷基复合材料在服役过程中因拉伸和弯曲导致的失效问题,以三维六向编织SiC_f/SiC复合材料为研究对象,分析了受力过程中复合材料力学行为与纤维及结构的联系机制。采用微计算机断层扫描技术获得材料结构及孔隙的三维图像,对复合材料纵向和横向进行拉伸、弯曲性能测试,并阐明其损伤机制。结果表明:复合材料呈现明显的各向异性特性,纵向拉伸强度和弯曲强度分别是横向的10.37、5.06倍;复合材料不同方向受力的损伤模式不同,拉伸载荷下纵向试样裂纹沿着六向纱呈Z字形扩展,而横向试样裂纹沿着编织轴向扩展,最终导致拉伸破坏;弯曲载荷下裂纹沿着厚度方向扩展,并最终导致纵向及横向试样的韧性断裂,且纵向韧性优于横向。     

氧化对高强对位芳纶纤维复合材料力学性能的影响北大核心

对位芳纶(PPTA)纤维用H2O2溶液进行氧化改性,制备改性芳纶增强环氧树脂基复合材料。研究表明,低浓度的H2O2可以有效地在芳纶纤维上引入极性基团,刻蚀纤维表面,同时增加纤维的比表面积。20层0.3 mol/L双氧水改性PPTA增强环氧树脂基复合材料的弯曲性能最佳,达405.0 MPa。     

亚麻纤维增强聚乳酸复合材料的制备与性能表征

针对预成型件的铺层角度对复合材料力学性能产生影响的问题,以亚麻纤维为增强体,与聚乳酸纤维通过开松、混合、梳理工序制成预成型件后,采用模压成型工艺制备了亚麻纤维/聚乳酸复合材料。研究预成型件的各种铺层角度对复合材料拉伸、弯曲性能的影响,并通过扫描电镜讨论亚麻/聚乳酸复合材料的破坏机制以及拉伸断裂形貌。结果表明：铺层角度为90°时,复合材料横向拉伸、弯曲强度和模量最高;铺层角度为0°时,复合材料纵向拉伸、弯曲强度和模量最高。     

等离子体改性芳纶及其针织物复合材料制备

为了提高芳纶纤维在复合材料中与树脂基体的界面黏结性,本文采用等离子体技术对芳纶纤维进行改性。通过单因素试验和正交试验优化了等离子体改性工艺,将改性后的芳纶纤维织造成针织物后用于制备复合材料,并对复合材料的拉伸性能进行了测试。结果表明,等离子体处理最优工艺为处理功率为150 W、压强为60 Pa、时间为120 s,以改性后的芳纶纤维编织的针织物为增强体制备的复合材料,抗拉强度纵向提高49%,横向提高33%。     

化学处理对混凝土中聚丙烯纤维加固效果的影响

通过对聚丙烯(PP)纤维进行多孔化处理及聚醋酸乙烯酯(PVAC)涂层,按不同配比掺入水泥基砂浆制得复合材料,进而探究改性处理对纤维增强水泥基复合材料力学性能的影响。结果表明:当Br_2+H_2O体积浓度为5 mL/L、PVAC涂层处理5 s、纤维掺量为0.7 kg/m~3、PP纤维长度为9 mm时,用其制得的复合材料力学性能最好。     

碳纤维/环氧树脂基复合材料增韧改性研究进展

为改善碳纤维/环氧树脂基复合材料的脆性断裂问题,常通过树脂增韧和纤维改性等方式实现。本文从树脂改性、界面改性及结构设计3个方面综述了碳纤维增强环氧树脂基复合材料的研究进展。其中树脂改性主要有纳米材料改性、橡胶弹性体改性及热塑性树脂改性增韧等方式,通过增加填充粒子与树脂基体间键合来提高环氧树脂的韧性;界面改性主要是碳纤维表面改性,通过增加碳纤维表面活性官能团或多尺度进行表面改性,增强碳纤维和环氧树脂之间的界面结合性能,达到复合材料增韧的效果;复合材料结构设计主要是设计纤维铺层角度、厚度、结构,通过结构优化来增强复合材料的韧性。最后分析了3种改性方式存在的问题,并指出3种方式结合使用是未来复合材料改性的研究方向。     

铺层角度对苎麻纤维复合材料性能的影响

基于真空辅助成型工艺,研究铺层角度对苎麻织物增强环氧树脂复合材料力学性能的影响,并将该铺层设计应用在复合材料桥梁模型上。结果表明:当铺层方式为纬向铺层(90°)时,复合材料的拉伸强度最大,为73.5 MPa;经纬交叉铺层(0°/90°)时,为72.4 MPa。当铺层方式为经纬交叉铺层时,复合材料的拉伸模量、弯曲强度、弯曲模量和剪切强度皆为最大,分别为3.8 GPa、108.2 MPa、5.0 GPa和21.7 MPa。综合拉伸、弯曲、剪切性能,经纬交叉铺层复合材料力学性能最优。苎麻纤维复合材料桥梁的最大载荷为8.79 kN,载荷质量比为12.08。     

超高分子量聚乙烯纤维表面改性研究进展

超高分子量聚乙烯(UHMWPE)纤维因具有高强高模低密等优异性能而受到广泛关注,但由于纤维表面惰性大、缺乏极性基团,导致其与树脂基体的黏结力低,限制了其在复合材料领域中的应用,因而需通过表面改性来提高其界面性能。本文综述了UHMWPE纤维表面改性的最新进展,介绍了UHMWPE纤维增强复合材料的界面性质及增强机理;概述了等离子体改性、辐照接枝改性、氧化刻蚀以及电晕改性和涂层改性等方法,并分析了这些技术的优势和局限性;最后,提出对UHMWPE纤维未来研究方向的展望。     

氢氧化钠处理对GF/VER复合材料界面及力学性能的影响

为改善玻璃纤维(Glass fiber, GF)与乙烯基酯树脂(Epoxy vinyl ester resin, VER)间界面性能，使用氢氧化钠溶液对GF进行表面改性处理。借助扫描电镜、红外光谱仪、万能材料试验机、摆锤冲击试验机等，分析改性前后GF的表面形态与化学结构的变化。测试改性前后GF/VER复合材料的单丝和纤维束界面剪切强度、弯曲强度、抗冲击强度。研究氢氧化钠处理对GF/VER复合材料的界面性能和力学性能的影响。结果表明：经过氢氧化钠溶液处理后，GF浸润性得到改善，表面变得粗糙，表面活性基团增多。单丝和纤维束的界面剪切强度相比改性前分别提升了25.31%、27.48%。GF/VER复合材料的弯曲强度与抗冲击强度相比改性前分别提升了20.96%、25.40%。     

聚乙烯网格水刺复合材料的力学性能研究

测试了聚乙烯网格及其"三明治"式加筋水刺复合材料的力学性能,分析了加筋复合材料中纤维的缠结机理。实验结果显示,网格45°方向的断裂强力小于纵向或横向的断裂强力;纤维性能和水刺工艺对复合材料的力学性能有明显的影响;加入网格的加筋复合材料的强力有显著提高。     

FRP-水泥砂浆抗弯性能的研究

利用三点弯研究了水泥砂浆外贴碳纤维和芳纶纤维片材后的抗弯性能,并对2种纤维进行表面处理,探讨纤维的表面处理对FRP水泥砂浆体系抗弯性能的影响。结果表明,用等离子体分别对碳纤维和芳纶纤维进行表面处理,CFRP和AFRP水泥砂浆的最大断裂载荷都能显著提高,而且构件在受弯过程中没有发生剥离破坏,FRP被拉断,纤维高强的特点得到充分发挥。     

Analysis of flexural strength of preoxidized fiber-reinforced composites made by a nonwoven process and hot-pressing

Preoxidized fiber was used here as a reinforcement for the first time. Polypropylene fiber was used as resin matrix, and the preform with the two types of fiber was prepared by a nonwoven process. Then, hot-pressing was applied to make a treatment for the preform, and the thermoplastic composites reinforced with preoxidized fiber were prepared. The effects of the hot-pressing temperature, hot-pressing pressure, weight percentage of preoxidized fiber, and nonwoven process on bending failure strength along the machine direction (MD) and transverse direction (CD) were studied under a three-point bending load. It was concluded that the flexural strength of the composites along MD and CD decreases with increasing hot-pressing temperature and hot-pressing pressure, while an initial increase and then decrease was observed with the increase in the weight percentage of preoxidized fiber. However in both directions, flexural strength of the composites is influenced significantly by the nonwoven process. Finally, the bending failure mode of the composites generated micro-flaws, which can be observed on the center surface of the composites. The micro-flaws extend to the ends along the thickness direction of the composites, and plastic bending failure is observed due to partial delamination.     

黄蒿纤维增强复合材料的开发

为开发黄蒿纤维增强复合材料,首先测定了其纤维化学成分,测试并分析了纤维长度、宽度、强度以及长宽比等参数。结果表明黄蒿纤维化学成分与竹纤维相近,优化工艺制得的纤维性能优良,适合作为增强材料。以聚丙烯短纤为基体,与黄蒿工艺纤维经热压工艺制备黄蒿/PP复合材料板材。对板材拉伸及弯曲性能的测试与分析表明：黄蒿纤维在板材受力过程中起到承力作用;板材纵向力学性能优于横向;拉伸及弯曲性能随黄蒿纤维质量的增加而提高。     

Bending load capacity of carbon fiber reinforced concrete beams as a function of fiber performance index (FPI)

Over the past several decades, textile reinforced concrete (TRC) materials have been developed due to their superior mechanical properties, corrosion resistance, lightweight application, and high load-bearing capacity. In this study, the effect of three main factors on bending load capacity of carbon fiber reinforced concrete (CFRC) beams is investigated; the number of reinforcements (carbon-fiber rovings), penetration of the cement within the fibers, and the post-cracking factor. The second and third factors are defined as the fiber performance index (FPI) for evaluating bending load capacity of CFRC beams. The best FPI for a different number of reinforcements was estimated using empirical values of bending load capacity of CFRC beams. The results were indicative of the efficiency and accuracy of the proposed FPI for a wide range of roving numbers, namely 2–24 with 800 tex as the titer. The post-cracking factor was suggested as 2.67 for TRCs and CFRCs materials, which are reinforced by rovings. In order to improve the FPI, the roving was impregnated partially with epoxy, which increased the maximum load capacity and displacement of the beams up to 26.68 and 23.24%, respectively. In addition, the impacts of roving numbers, the first factor, on the failure mode, load-bearing capacity, ductility, and toughness of the CFRC beams were investigated.     

常压氩等离子体改善超高分子量聚乙烯纤维的界面性能

 改变低温常压氩等离子体处理条件,考察处理后超高分子量聚乙烯纤维束强度与环氧树脂层间剪切应力与各变化因子的关系曲线,通过比较性能的变化,研究氩等离子体处理条件对纤维界面性能的影响。观察处理后纤维束纵向的微观结构,测试用最优化工艺参数处理的纤维束制成的纤维增强复合材料的单向性能,进一步论述等离子体处理对纤维束黏合性能的影响。     

聚乙烯醇/磷虾蛋白纤维的氢键作用机制及其性能

为解决聚乙烯醇(PVA)难以热塑加工和功能单一的问题,以磷虾蛋白(AKP)和水为增塑剂,通过熔体纺丝制备了PVA/AKP纤维。通过红外光谱仪表征了PVA/AKP纤维中的氢键作用,并分析氢键作用机制。借助X射线衍射仪、扫描电子显微镜、差示扫描量热仪和单纤维强力仪等分析了PVA/AKP纤维的结晶性、形态结构、热性能和力学性能等。结果表明:随着AKP质量分数的增加,PVA/AKP纤维中分子内氢键含量和结晶度呈先增大后减小趋势,当AKP质量分数为2%时,PVA/AKP纤维中分子内氢键含量达到最大值(85.37%),结晶度也达到最大值(48%),该条件下纤维断裂强度达到最大值,为2.15 cN/dtex;AKP的加入有助于提高PVA纤维的表面光滑性,PVA/AKP纤维断面呈规则圆形;PVA/AKP纤维对碱溶液的响应性更强,在水中浸渍2 h后纤维吸水率恒定在36%。     

The effect of hydrophilic (polyvinyl alcohol) fiber content on the flexural behavior of engineered cementitious composites (ECC)

This paper investigates the effect of hydrophilic polyvinyl alcohol (PVA) fiber’s content (1.2–2.0% volume of composite) on the flexural behavior of engineered cementitious composites (ECC) materials. Different parameters of flexural behavior such as strength at first-cracking and post-cracking stages, deflection at ultimate load, toughness indices according to ASTM 1018, flexural modulus, and energy absorption were determined. Test results showed that the flexural strength and flexural modulus of composites significantly increases by increment in fiber content. However, flexural strength of composites varies from 8.5 to 14 MPa depending on amount of PVA fibers. The toughness indices, deflection at max load and energy absorption were decreased by further increase in the fiber content from 1.6 to 2%. It was indicated that there was an indirect relationship between flexural strength and ductility of composite in higher amount of fiber content.     

碱处理对涤纶/光敏树脂复合材料力学性能的影响

针对光敏树脂经3D打印成型后试样力学性能较差问题,采用涤纶长丝增强光敏树脂的方法,使用光固化3D打印设备将涤纶长丝和光敏树脂复合成型制备涤纶增强复合材料。为获得较好的增强效果,对涤纶进行碱处理,研究了碱处理各条件下涤纶的减量率与纤维形貌和力学性能的关系,以及其对复合材料力学性能的影响。结果表明:随着减量率的增加,涤纶的形貌及力学性能改变越明显;当涤纶减量率为16.2%时,纤维表面出现连续纵向沟壑,力学强度下降6%,纤维的增强效果最好;经过改性处理的涤纶增强复合材料的拉伸强度和弯曲强度分别达到78 MPa和471 MPa,相比于未处理的纤维增强复合材料分别提升了66%和336%。