定向钢纤维增强水泥基复合材料断裂特性模拟分析

利用钢纤维随机生成算法建立了钢纤维增强水泥基复合材料有限元模型,基于粘聚裂纹模型模拟了定向钢纤维水泥砂浆三点弯曲断裂全过程.将数值模拟得到的荷载-绕度曲线与已有试验结果进行对比,验证了数值模型的可靠性.研究了砂浆基体不同粘聚律对定向钢纤维水泥砂浆断裂全过程的影响.计算分析了不同尺寸试件模型的断裂全过程,研究了试件尺寸对定向钢纤维水泥砂浆断裂特性的影响.结果表明:本文建立的定向钢纤维水泥砂浆有限元模型的数值结果与试验结果对比较好,粘聚律的变化对断裂全曲线影响较小;随着试件尺寸的增大,定向钢纤维水泥砂浆的名义强度存在一定的尺寸效应,本文建立的细观模型可有效研究钢纤维增强水泥基复合材料的细观断裂机理.     

断裂韧度对PVA纤维水泥基材料弯曲性能的影响

对加入超强吸水性能SAP颗粒形成的聚乙烯醇(PVA)纤维增强水泥基材料,通过楔劈拉伸试验研究了材料的断裂韧度,三点弯曲试验研究了材料的弯曲性能,同时基于微观力学机理分析了断裂韧度对PVA纤维水泥基材料延性的影响.断裂试验结果表明:水泥基体断裂韧度随SAP颗粒掺量增大而减小;弯曲试验结果表明:开裂强度与弯曲强度随SAP颗粒掺量增大而降低,但弯曲韧度随SAP颗粒掺量增大而提高;依据能量准则与强度准则发现:掺入SAP颗粒后的PVA纤维水泥基材料的延性提高与高的E值与S值相关.     

碳纤维增强聚乙烯复合材料切削加工性能分析

在各碳纤维方向下的碳纤维增强聚乙烯(CFRP)会表现出力学与热性能的较大差异,通过控制不同切削实验参数,利用控温直角切削测试系统测试了各纤维方向CFRP在设定温度下的切削特性。研究结果表明:在刀具对工件最初切入时,主切削力快速增大,达到一个稳定的阶段之后大幅减小。纤维和刀具形成垂直切削角的情况下,切削力随温度上升而显著减小,到达高温状态时切削力相对于低温状态只有10%。在90°切削角条件下,在切削面下产生了更明显的开裂损伤;在135°的切削角条件下,刀具跟CFRP材料尤其是纤维形成更大的接触面积,降低了接触力;形成180°的切削角后,纤维和刀具的切削刃保持相互平行的状态。本文研究为设计新的CFRP切削条件与后续新工艺的开发创造了基础。     

竹原纤维增强复合材料的研究

竹原纤维与低熔点聚酯纤维及聚丙烯纤维的混合纤维集合体加工成非织造物,再经热压成型后,制成竹原纤维增强聚酯、聚丙烯热塑性树脂复合材料板材,并与竹原/亚麻纤维增强聚酯、聚丙烯热塑性树脂复合材料进行性能对比,进一步探讨这种复合材料板材的最佳制作工艺。鉴于这种材料可以被用于汽车和建筑等领域,通过对材料力学性能测试结果的模糊综合评判,选出性能最优的复合材料为竹原纤维/LMPET(40/60),在模压温度、时间、压力分别为165℃,30min和30MPa的条件下,所压制复合材料的纵向拉伸强度为136MPa,横向为87·58MPa;纵向弯曲强度为534MPa,横向为470MPa。     

E-Glass Fiber Reinforced Composites in Dental Applications

Fiber reinforced composites (FRCs) are more and more widely applied in dentistry to substitute for metallic restorations: periodontal splints, fixed partial dentures, endodontic posts, orthodontic appliances, and some other indirect restorations. In general in FRCs, the fiber reinforcement provides the composite structure with better biomechanical performance due to their superior properties in tension and flexure. Nowadays, the E-glass fiber is most frequently used because of its chemical resistance and relatively low cost. Growing interest is being paid to enhance its clinical performance. Moreover, various techniques are utilized to reinforce the adhesion between the fiber and the matrix. Oral conditions set special requirements and challenges for the clinical applications of FRCs. The biomechanical properties of dental materials are of high importance in dentistry, and given this, there is on-going scientific interest to develop E-glass fiber reinforced composite systems. FRCs are generally biocompatible and their toxicity is not a concern.     

Thermal Aging Properties of Graphite Fiber Reinforced Peek and Graphite Fiber Reinforced Bmi Composites

Graphite fiber reinforced poly(ether ether ketone) (PEEK) and graphite fiber reinforced bismaleimide (BMI) composite materials are two kinds of advanced fiber-reinforced polymer matrix composites with good thermal stability and excellent mechanical properties at high temperature. They are currently receiving considerable attention. the main limitation on their application is the lack of knowledge regarding their behaviors during extended use at high temperature. Thermal aging properties are the main parameters for new polymer matrix composites that will be used in advanced spacecraft structural components. From the results of thermal aging effects on the properties—including interlaminar shear strength, drop-weight impact strength, and impact energy—of graphite/PEEK and graphite/BMI composites, it is found that unidirectional graphite fiber reinforced composites retain higher strength compared to multidirectional, and that multidirectional graphite/PEEK composites keep higher property retentions than multidirectional graphite/BMI composites after thermal aging at 190°C. From scanning electron photomicrographs, it is also found that graphite/PEEK composites have better fiber/resin adhesion, intraply adhesion, and microcrack resistance compared to graphite/BMI composites after thermal aging.     

Regeneration of Interfacial Adhesion in Fiber Reinforced Composites

Our studies of the regeneration of interfacial adhesion in micro-composites have shown that fiber/thermoplastic (aramid/polycarbonate) bonds can be completely regenerated, the degree of regeneration depending on both time and temperature of heating. Complete regeneration requires high temperatures, suggesting that mechanical interlocking resulting from flow of heat-softened resin into fiber surface crevices may be the primary mechanism of bond strength regeneration. Only partial regeneration of fiber/thermosetting resin (epoxy with aramid and carbon fibers) bond strength has been achieved, and this appears to be independent of fiber and reheating time. Apparently, the viscoelastic behavior of the resin is a critical factor in bond strength regeneration.     

碳纤维增强液晶高聚物复合材料的研究

研究了碳纤维(CF)增强热致性液晶聚合物(TLCP)制备高性能复合材料;探讨了不同纤维含量、不同纤维类型对复合材料力学性能、微观结构的影响;扫描电镜(SEM)结果证实了液晶聚合物在加工过程中自取向,形成了微纤结构,具有自增强作用,使复合材料表现出非常高的力学性能。     

连续纤维增强聚芳醚砜酮复合材料的性能

采用高性能工程塑料二氮杂萘联苯型聚芳醚砜酮(PPESK)为树脂基体，分别用连续碳纤维和芳纶纤维为增强材料，通过溶液浸渍、模压成型制备单向增强复合材料。对树脂基体和复合材料的力学性能进行测试、分析，研究纤维含量和复合材料力学性能的关系，并通过扫描电镜对复合材料的微观形貌进行观察研究。     

连续纤维增强热塑性树脂基复合材料制备过程中纤维束分散分析

熔融浸渍工艺制备连续纤维增强热塑性树脂基复合材料,要求纤维束必须预分散以提高纤维的浸渍度。本文利用柱状分散装置使纤维分散,通过受力分析及数值崐计算,发现纤维束在柱状分散辊中的包覆角接近３００°时,可被较好地分散,但过高的包覆角容易损伤纤维。实验结果与理论分析基本一致。利用聚丙烯对上述纤维束进崐行熔融浸渍,获得了浸渍状态良好的复合材料。     

苎麻纤维增强复合材料的光老化性能

制备了苎麻织物增强不饱和聚酯复合材料,放置于荧光紫外灯下和氙弧灯下加速老化.测试老化后的弯曲性能,通过弯曲性能的退化规律推断复合材料的老化规律,并通过其他分析手段,研究苎麻织物增强不饱和聚酯复合材料的老化机理.测试结果表明,在荧光紫外灯照射的600 h内,复合材料的力学性能下降约30％;在氙弧灯照射的1200 h内,复...     

短纤维补强氯丁橡胶的性能研究

研究短纤维种类和用量对短纤维/氯丁橡胶(CR)复合材料中短纤维取向和分散以及复合材料粘合性能和溶胀性能的影响.结果表明:随着短纤维用量的增大,短纤维/CR复合材料的相对交联密度和短纤维取向度均增大,抗溶胀性能提高,取向度大小顺序为芳纶短纤维、聚酯短纤维、锦纶66短纤维和短切棉纤维;聚酯纤维与CR基体的粘合性能最差,短切棉纤维在CR中分散性最差;短纤维/CR复合材料的性能呈现出明显的各向异性.     

纤维及其复合材料老化机理研究进展

对于纤维及其复合材料而言,潮湿、遇热、光照等环境条件对其力学性能的影响明显,会导致其强度和刚度下降。本文阐述了国内外纤维及其复合材料的人工气候老化、热氧老化、光氧老化、湿热老化、臭氧老化等方面研究现状,提出了纤维及其复合材料老化的一些主要机理。在探讨了一些新研究手段的发展和取得的成果的基础上,进而展望了纤维及其复合材料老化研究存在的不足,并提出纤维及其复合材料老化研究的趋势。     

长纤维增强热塑性复合材料的研究进展

本文论述了热塑性树脂基复合材料的发展特点。除介绍了最具发展潜力的长纤维增强热塑性复合材料的浸渍工艺和成型工艺外，还着重介绍了新型长纤维增强热塑性复合材料和其应用前景。     

玻璃纤维增强热塑性复合材料的研究进展

综述了LFT和GMT加工工艺的进展，介绍了最新的两种GMT材料，提出了玻璃纤维增强热塑性复合材料的发展方向，并对未来趋势作出预测。     

Progress Report on Natural Fiber Reinforced Composites

This century has witnessed remarkable achievements in green technology in material science through the development of natural fiber reinforced composites. The development of high‐performance engineering products made from natural resources is increasing worldwide day by day. There is increasing interest in materials demonstrating efficient use of renewable resources. Nowadays, more than ever, companies are faced with opportunities and choices in material innovations. Due to the challenges of petroleum‐based products and the need to find renewable solutions, more and more companies are looking at natural fiber composite materials. The primary driving forces for new bio‐composite materials are the cost of natural fibers (currently priced at one‐third of the cost of glass fiber or less), weight reduction (these fibers are half the weight of glass fiber), recycling (natural fiber composites are easier to recycle) and the desire for green products. This Review provides an overview of natural fiber reinfocred composites focusing on natural fiber types and sources, processing methods, modification of fibers, matrices (petrochemical and renewable), and their mechanical performance. It also focuses on future research, recent developments and applications and concludes with key issues that need to be resolved. This article critically summarizes the essential findings of the mostly readily utilized reinforced natural fibers in polymeric composite materials and their performance from 2000 to 2013.     

竹纤维增强聚双环戊二烯复合材料的研究

将竹纤维(BF)和聚双环戊二烯(PDCPD)通过反应注塑成型制备竹纤维增强PDCPD复合材料。采用干燥法、碱处理法、硅烷偶联剂处理法分别对竹纤维进行表面改性,结合力学性能、红外光谱、扫描电镜(SEM)等分析检测手段,确定最佳竹纤维处理方法和最佳竹纤维用量。结果表明:采用硅烷偶联剂处理后的竹纤维用量为2%时,PDCPD/BF复合材料的拉伸强度、弯曲强度、冲击强度分别为49.824 MPa、99.903 MPa和94.34 J/m~2,比改性前分别提高了104.7%、61.82%和624.6%;改性后PDCPD/BF复合材料的热变形温度(HDT)达到108.2℃,比改性前提高了53.2%。     

长纤维增强PP复合材料的制备与性能研究

通过开炼–模压成型工艺方法,制备了长玻璃纤维(LGF)增强聚丙烯(PP)复合材料,首先研究了β成核剂对纯PP力学性能和结晶性能的影响,在此基础上研究了LGF对PP/LGF复合材料力学、结晶性能及热稳定性的影响,最后探讨了增容剂马来酸酐接枝三元乙丙橡胶(EPDM-g-MAH)对复合材料力学性能的影响。结果表明,β成核剂可以改善PP的冲击韧性,但降低了PP的拉伸和弯曲强度,当β成核剂质量分数为0.2%时,PP的综合性能最好;随LGF含量增加,PP/LGF复合材料的拉伸、弯曲和冲击强度及结晶度总体上呈先增大后减小的趋势,不同LGF含量下的复合材料起始热分解温度均在390℃以上,当LGF质量分数为20%时,复合材料的综合性能最好;少量的EPDM-g-MAH能改善LGF与PP基体的界面相容性,大幅增强了复合材料的韧性,其最适宜的质量分数为10%。     

GF增强PPS复合材料的制备及性能

采用熔融共混工艺和熔融浸渍分别制备了短玻璃纤维增强聚苯硫醚复合材料（PPS/SGF）和长玻璃纤维增强聚苯硫醚（PPS/LGF）复合材料,并对复合材料的力学性能和耐热性能进行了对比分析。研究结果表明,在玻璃纤维质量分数为30%时,PPS/SGF和PPS/LGF复合材料的拉伸强度分别为110 MPa和122 MPa;弯曲强度分别为175 MPa和208 MPa;弯曲弹性模量分别为8 GPa和9 GPa;缺口冲击强度和无缺口冲击强度分别为7.7,11.9 kJ/m²和31,37 kJ/m²。PPS/LGF复合材料的拉伸强度、弯曲强度、弯曲弹性模量、缺口冲击强度和无缺口冲击强度相较于PPS/SGF复合材料分别提高了11.0%,18.9%,11.3%,54.5%和19.4%。PPS/SGF和PPS/LGF复合材料的热变形温度分别达到250℃和275℃,PPS/LGF复合材料的热变形温度高于PPS/SGF复合材料热变形温度10%。     

玻璃纤维增强复合材料在建筑材料中的应用

讨论了玻璃纤维增强复合材料的性能、特点及其在建筑材料中的应用,并指出了今后的发展方向。