Dynamic Impact Compressive Behavior Investigation of Sisal Fiber-reinforced Coral Seawater Concrete

Split Hopkinson pressure bar(SHPB)was used to investigate the dynamic compressive properties of sisal fiber reinforced coral aggregate concrete(SFCAC).The results showed that,with the increase of strain rate,the dynamic compressive strength,peak strain and toughness index of SFCAC are all greater than its static properties,indicating that SFCAC is a kind of rate-sensitive material.When the sisal fiber was blended,the failure mode showed obvious ductility.At high strain rates,the SFCAC without sisal fiber specimen was comminuted,and the SFCAC showed a"cracked without breaking"state.The results indicated that the sisal fiber played a significant role in reinforcing and strengthening the properties of concrete.The finite element software LS-DYNA was used to simulate two working conditions with strain rates of 78 and 101 s-1.The stressstrain curves and failure patterns obtained were in good agreement with the experimental results.

Effects of Strain Rate and Fiber Content on the Dynamic Mechanical Properties of Sisal Fiber Cement-Based Composites

In this paper,a split Hopkinson pressure bar(SHPB)was used to investigate the dynamic impact mechanical behavior of sisal fiber-reinforced cement-based composites(SFRCCs),and the microscopic damage evolution of the composites was analyzed by scanning electron microscopy(SEM)and energy-dispersive X-ray spectrome-try(EDS).The results show that the addition of sisal fibers improves the impact resistance of cement-based composite materials.Compared with ordinary cement-based composites(OCCs),the SFRCCs demonstrate higher post-peak strength,ductility,and energy absorption capacity with higher fiber content.Moreover,the SFRCCs are strain rate sensitive materials,and their peak stress,ultimate strain,and energy integrals all increase with increasing strain rate.From the perspective of fracture failure characteristics,the failure of OCCs is dominated by the brittle failure of crystal cleavage.In contrast,the failure mode of the SFRCCs changes to microscale matrix cracks,multi-scale pull-out interface debonding of fibers(fine filaments and bundles),and mechanical interlock.This research provides an experimental basis for the engineering application of high-performance and green cement-based composites.

Analysis on degradation behaviors of sisal fibers at various pH conditions

The degradation behaviors(mass loss,tensile strength,crystallinity index,and microstructure)of sisal fibers immersed in sodium hydroxide solution with pH of 13.6,12.9,and 11.9 were investigated via X-ray diffraction and scanning electron microscopy.A three-stage degradation process of natural fibers in an alkaline environment was proposed.The results showed that the sisal fibers exhibited a sharp mass loss over the first 7 d of degradation under all pH conditions,attributable to the rapid hydrolysis of lignin and hemicellulose at the fiber surface.The sisal fibers degraded at pH 12.9 and 13.6 over 1 month exhibited significantly lower tensile strengths(181 and 195 MPa,respectively)than the original fibers(234 MPa)because of the loosely bound structure of the component microfibrils caused by the hydrolysis of the linking lignin and hemicellulose.After 6-month degradation,stripped microfibrils occurred in the fibers,resulting in substantial degradation in tensile strength.The sisal fibers degraded at pH 11.9 largely maintained their integrity and tensile strength,even after 6 months,indicating that reducing the environment pH can effectively mitigate the degradation.

Mechanical Analysis of Sisal Fibers to Use as a Reinforced Material in Wood Beams

Natural fibers have recently raised attention for presenting adequate mechanical characteristics for reinforcement of structural elements. The use of both natural fibers, in especial Sisal fibers, in wood laminated beams and also wood from reforestation, is in accordance with the current economic interest and ecological appeal. Specifically, the strengthening of wood laminated beams with Sisal fibers is more effective for structures that require an increase in their structural capacity without a significant increase in height of the cross section. Furthermore, it is recommended that this type of reinforcement is used in wood structural elements where the elastic modulus is at least equal to the Sisal fibers. The composition of Sisal fibers is basically of cellulose, lignin and hemicelluloses. In particular, the amount of cellulose and the angle that the micro-fibers with the axis of the fiber characterize the failure strength and the modulus of elasticity. The average mechanical characteristics of the Sisal fiber are： tensile strength 347 to 378 （MPa） and elastic modulus 15.2 （GPa） whereas these properties are lower for strips of Sisal fibers. In this context, this paper deals with the analysis and the viability of the use of Sisal fibers in wood structures as a reinforced material.

Elements of Structural Masonry Reinforced with Sisal Fibers

There is great interest in the use of natural fibers as reinforcement to obtain new construction materials due to its low cost, high availability and reduced energy consumption for its production. This paper evaluates the incorporation of sisal fibers of 20 mm and 40 mm in length and volume fraction of 0.5% and 1% for concrete masonry structural blocks, and determines the use of these units to build prisms and mini-walls. Laboratory tests were carried out to characterize the physical of blocks and mortar, in addition to the axial compression tests of the units, prisms, and mini-walls. The sisal had low apparent density and high water absorption, which is a common feature of such material due to the high incidence of permeable pores. The physical properties of the blocks with and without addition complied with the standard requirements established to validate their use. The obtained results showed that the fiber-reinforced mini-walls obtained values very close to or even higher than those obtained for the mini-walls without fibers, demonstrating better performance than the blocks and prisms.

Analysis of Production and Sales Situation of Sisal Fiber and Its Products in China

Based on results of previous studies,through investigations,the status quo,main advantages and disadvantages of using small hand-power scutchers and large-scale automatic sisal production lines to process sisal fiber were summarized and analyzed; the traditional uses and latest products of sisal fiber were studied,especially the comprehensive utilization of byproducts produced during sisal fiber processing as well as the broad prospects of new sisal products.

剑麻纤维加筋水泥土力学性能试验

目的 研究纤维掺量、纤维长度及养护龄期对剑麻纤维加筋水泥土无侧限抗压强度及巴西劈裂抗拉强度的影响规律。方法 设置纤维掺量为0~0.8%,加筋长度为7~19 mm,养护龄期为7 d、28 d及90 d,对不同影响因素下剑麻纤维加筋水泥土进行无侧限抗压强度试验及巴西劈裂试验。结果 剑麻纤维的掺入提升了水泥土的无侧限抗压强度及巴西劈裂抗拉强度,随着纤维掺量及加筋长度的增加呈现出先增大后减小的规律;当加筋长度为11 mm、纤维掺量为0.4%时,加筋效果最显著,无侧限抗压强度提高幅度达30.2%;剑麻纤维加筋水泥土的抗拉强度、拉压比与纤维掺量呈线性关系。结论 剑麻纤维的掺入改善了水泥土的脆性,提高了水泥土的破坏韧性;采用幂函数对试验数据进行拟合,得到了养护龄期与纤维掺量共同作用下剑麻纤维加筋水泥土无侧限抗压强度的预测模型,可以为实际工程提供参考。

改性植物纤维材质对人体慢跑过程下肢影响研究

为进一步提升植物纤维材质运动鞋的综合性能,以剑麻纤维制备纳米纤维粉代替运动鞋鞋底加工所需的白炭黑并制作了一种慢跑鞋。邀请若干位具有一定慢跑经验的男性运动员进行慢跑测试并记录穿着该运动鞋时的下肢生物力学参数。结果表明:与传统运动鞋和未改性植物纤维材质运动鞋相比,该改性植物纤维材质运动鞋对人体下肢生物力学的影响更为积极,人体在慢跑状态下的髋关节、膝关节、踝关节活动幅度更小,可以有效降低人体慢跑时的运动损伤风险。

剑麻纤维-聚丙烯酰胺改良客土干缩开裂试验研究

裸露岩质边坡的数量随着基础设施建设规模和数量的不断增大,客土喷播技术作为一种有效的边坡护坡绿化技术可以改善岩质边坡的表层稳定性,但多种因素造成表层土体失水开裂,影响客土喷播的修复效果。针对此问题,采用剑麻纤维和聚丙烯酰胺(PAM)对客土进行改良,开展了不同土层厚度、剑麻纤维和聚丙烯酰胺(PAM)含量条件下干缩开裂试验,研究了不同条件对土体干燥失水、表面裂隙发育的影响,采用微观扫描技术(SEM)对改良后客土的内在结构变化进行了测试。结果表明:随土层厚度增大,改良土蒸发稳定时间有所延长,且土层厚度增大能有效抑制试样表面裂隙的发育。剑麻纤维和PAM的掺入有效延长了黏土蒸发的路径,且随着纤维和PAM含量增加土体蒸发速率逐渐降低,抑制了土体表层裂隙发育。PAM的强吸水性能够降低土体的蒸发速率,纤维的“桥接作用”可以抑制裂隙的扩展,提高土体的整体性。

龄期对剑麻纤维风积沙改性土工程特性的影响

为了研究养护龄期对剑麻纤维风积沙改性土的物理和力学特性的影响,改善水泥固化风积沙改性土脆性开裂特性,选取通辽—新民北高铁所经的科尔沁沙地的实际高速铁路路堤风积沙改性土(95%风积沙+5%水泥),分别添加0%、0.1%、0.2%和0.4%的剑麻纤维,开展不同养护龄期(7,14,21及28 d)条件下的电阻率测试、纵波波速测试和无侧限抗压试验。试验结果表明:风积沙改性土的电阻率和纵波波速会随着养护龄期的增加而上升,前期增长显著而后期趋于平缓;在标准养护条件下,随着养护龄期的增加(从7~28 d),各组剑麻纤维掺量风积沙改性土的割线模量呈现对数函数形式增加,各组剑麻纤维掺量风积沙改性土的泊松比均呈小幅度下降趋势,其中不掺加剑麻纤维风积沙改性土的泊松比降幅较大(0.315~0.336,降幅6.63%),另外3组掺加剑麻纤维风积沙改性土的泊松比降幅较小(0.300~0.308,降幅2.60%),说明剑麻纤维的掺入对于改善风积沙改性土抵抗侧向变形的能力有限。风积沙改性土的无侧限抗压强度也会随着养护龄期和纤维含量的增加呈现抛物线形式上升,说明养护龄期的增加和剑麻纤维的掺入能有效提高风积沙改性土的抗压强度和延性特征,减轻风积沙改性土的脆性破坏。研究结果对沙漠地区风积沙改性土的工程应用与理论研究具有一定的参考价值。

剑麻纤维改良MgO-GGBS碳化粉质黏土物理力学性质与微观机制

为解决传统固化剂——水泥的能耗高和环境污染大等问题,本研究采用MgO-粒化高炉矿渣(GGBS)碳化加固粉质黏土,采用剑麻纤维改善固化土的抗裂性,探讨了纤维掺量和纤维长度对碳化改良土物理和力学性质的影响。结果表明:在相同纤维长度下,随纤维掺量增加,MgO-GGBS碳化固化土样的体积增长率、含水率和内摩擦角增加,而黏聚力先增加后减小,无侧限抗压强度先增大后减小最终趋于稳定,黏聚力和强度的峰值出现在0.4%纤维掺量处。在相同纤维掺量下,随纤维长度增大,MgO-GGBS碳化固化土样的体积增长率先减小后增大,在长度10 mm时达到最小;含水率几乎不变;强度先增加后趋于稳定,在长度5~10 mm时提升显著;破坏应变增加,但几乎不受纤维掺量影响;碳化含纤维土样的黏聚力与内摩擦角先增加后减小,并在长度10 mm时达到最大。基于试验结果,提出了剑麻纤维改良MgO-GGBS碳化土加固的机理概念图,揭示了碳化土体基于纤维交织作用、固定作用和填充作用的改良机制。用MgO-GGBS-剑麻纤维等低碳材料代替水泥能显著提高碳化固化粉质黏土体的处理效果和抗裂性能。研究成果将对促进工业固废GGBS和农业废弃纤维在加固软弱地基土中的应用提供理论指导,对岩土工程“双碳”目标实现具有重要意义。

Compressive and tensile strength of polymer-based fiber composite sand

Traditional soil additives like Portland cement and lime are prone to cause the brittle fracture behavior of soil,and possibly,environmental impacts.This study explores the potential use of polyurethane organic polymer and sisal fiber in improving the mechanical performance of sand.The effects of polymer content,fiber content,and dry density on the unconfined compressive strength(UCS)and direct tensile strength(DTS)of the polymer-fiber-sand composite were evaluated.The results showed significant increase in UCS and DTS of the reinforced sand with the increase of polymer content,fiber content,and dry density.At high dry density condition,a single peaked stress−strain curve is often observed.Higher polymer content is beneficial to increasing the peak stress,while higher fiber content contributes more to the post-peak stress.The combined use of polymers and fibers in soil reinforcement effectively prevents the propagation and development of cracks under the stress.Scanning electron microscopy(SEM)test was also performed to investigate the micro-structural changes and inter-particle relations.It was found through SEM images that the surface coating,bonding,and filling effects conferred by polymer matrix greatly enhance the interfacial interactions,and hence provide a cohesive environment where the strength of fibers could be readily mobilized.

Experimental Investigation on the Mechanical Properties of Natural Fiber Reinforced Concrete

Recently,addition of various natural fibers to high strength concrete has aroused great interest in the field of building materials.This is because natural fibers are much cheaper and locally available,as compare to synthetic fibers.Keeping in view,this current research conducted mainly focuses on the static properties of hybridized(sisal/coir),sisal and coir fiber-reinforced concrete.Two types of natural fibers sisal and coir were used in the experiment with different lengths of 10,20 and 30 mm and various natural fiber concentrations of 0.5%,1.0%,and 1.5%by mass of cement,to investigate the static properties of sisal fiber reinforced concrete(SFRC),coir fiber reinforced concrete(CFRC)and hybrid fiber reinforced concrete(HFRC).The results indicate that HFRC has increased the compressive strength up to 35.98%with the length of 20 mm and with 0.5%concentration,while the CFRC and SFRC with the length of 10 mm and with 1%concentration have increased the compressive strength up to 33.94%and 24.86%,respectively.On another hand,the split tensile strength was increased by HFRC with the length of 20 mm and with 1%concentration,CFRC with the length of 10 mm and with 1.5%concentration,and SFRC with the length of 30 mm and with 1%concentration have increased up to 25.48%,24.56%and 11.80%,respectively,while the HFRC with the length of 20 mm and with 0.5%concentration has increased the compressive strength of concrete but has decreased the split tensile strength up to 2.28%compared to PC.Overall,using the HFRC with the length of 20 mm and with 1%concentration provide the maximum output in terms of split tensile strength.

一种麦秸纤维替代木粉制备的景观用复材特性研究

为提高园林景观建筑材料的环保性、强度和耐水性等,试验以麦秸纤维代替传统木粉,并加入剑麻纤维,制备了一种木塑复合材料(WPC),并对其性能进行研究。试验结果表明,麦秸纤维可以代替木粉制备WPC,制备出的WPC力学性能相差不大;剑麻纤维的掺入,可以提升WPC的力学性能和耐水性;当掺20 phr麦秸纤维、5 phr长度5 mm的剑麻纤维时,试验制备的WPC材料弯曲、拉伸强度分别达到53.6、16.8 MPa,弯曲弹性模量为4200 MPa,吸水率低于7%,材料具备较好的强度性能,韧性和耐水性良好。试验制备的木塑复合材料综合性能良好,可以作为园林景观建筑材料实际应用。

纤维增强冻结充填材料强度与变形性能研究

为探索纤维增强冻结充填的应用潜力,设计正交试验测试冷冻固结法来完全或部分替代胶凝材料提供材料强度,同时采用纤维提高强度和变形性能,试验了剑麻、玄武岩和纤维素纤维等三种纤维对冻结充填材料力学性能的影响。试验结果表明剑麻和玄武岩纤维对冻结充填材料抗压强度增强效果明显。冻结充填材料强度远高于水泥胶凝和纤维增强效果,且纤维增强冻结充填材料表现出高弹模性、韧性变形。

关于两广地区剑麻纤维的物理性能比较

随机抽取20个试样,对广东、广西剑麻纤维长度、含杂率、回潮率以及束纤维断裂强力等核心物理性能指标进行分析,探讨物理性能指标差异的成因。结果显示,在纤维长度上,广西地区稍有优势;含杂率方面,两广地区差别细微;回潮率上,广西地区略高;束纤维断裂强力上,广东地区表现更为出色。此结论为两广地区剑麻纤维产业化发展提供科学依据。

剑麻-耐碱玻璃纤维对混凝土的性能影响

剑麻纤维作为一种绿色环保植物纤维,具有成本低廉、韧性和弹性模量高、抗拉抗腐蚀性好等诸多优点,混凝土中掺入剑麻纤维在一定程度上能够提高其劈裂抗拉强度和弹性模量,从而提高混凝土结构的耐久性,延长混凝土的使用寿命。耐碱玻璃纤维具有抗拉强度高、流动性好、与混凝土浆料的包裹黏结性好等特点。该纤维的掺入对于混凝土的抗折和抗拉强度有着明显提高,并且已经成功应用在了隧道工程当中,取得了较为成功的结果。这两种纤维所组成的双掺混合纤维不仅能够保留两者优点,而且能够加强其力学性能。文章主要探讨了两者混合所构成的混合纤维混凝土的特点及其对混凝土力学性能改善的效果。

剑麻纤维复合基材土岩界面剪切性能试验

为揭示剑麻纤维掺量与界面粗糙度对土-岩界面剪切力学性能的影响规律,采用表面起伏的混凝土模块作为岩面相似材料,进行了一系列的改进室内直剪试验,并结合扫描电镜试验进一步分析了剑麻纤维参与强化界面剪切性能的机理。结果表明:剑麻纤维通过提高黏聚力提高土-混凝土界面间的剪切力学性能;纤维添加量为0.8%的土-混凝土界面黏聚力提高80%~500%,内摩擦角提高10%~20%;界面粗糙度主要通过提高黏聚力增强界面剪切力学性能,6.5 mm粗糙度的界面黏聚力增量为7~15.5.kPa,提高20%~300%;对于素土界面和掺纤维界面,粗糙度对土-混凝土界面间剪切力学性能的强化表现为2种模式,加入纤维的界面黏聚力关于粗糙度的增长关系上,粗糙度的最优值出现在较小区间(0~2.5 mm)。

钢-剑麻混杂纤维再生混凝土断裂性能研究

为改善再生混凝土(RAC)的断裂性能,通过三点弯曲断裂试验,研究了钢纤维、剑麻纤维及钢-剑麻混杂纤维对RAC试件断裂性能的影响。同时,采用数字图像相关(DIC)技术测得RAC试件的裂缝扩展全过程。结果表明:未掺纤维的RAC试件断裂性能较差,而掺入纤维后的RAC试件断裂性能明显提升;单掺钢纤维时,试件的起裂韧度与纤维掺量无关;单掺剑麻纤维时,最佳体积掺量为0.15%,其试件的起裂荷载较未掺纤维RAC试件提高了67%。单掺纤维和混掺纤维均可提高失稳韧度和断裂能,但混掺纤维效果更佳。当体积掺量为1.0%的钢纤维和体积掺量为0.30%的剑麻纤维混杂时,其起裂韧度、失稳韧度和断裂能较未掺纤维的RAC试件分别提高了83.92%、575.86%和1244.05%。

剑麻纤维打浆特性及其成纸性能研究

采用剑麻纤维为原材料,通过槽式打浆机制备出不同打浆程度的剑麻纤维浆料,通过湿法抄纸制备了剑麻纤维纸,研究了不同打浆程度剑麻纤维的纤维特性及成纸性能。研究结果表明:剑麻纤维在机械力的作用下,纤维结构的变化是以其表层发生分丝帚化及主体纤维切断为主;随着打浆程度增加,剑麻纤维平均长度和弯曲度均降低,帚化度不断提升;随着打浆程度增加,剑麻纤维纸张的紧度、抗张强度以及电气强度均逐渐上升,透气度和吸液高度均逐渐降低。