纤维拔出时Coulomb摩擦界面应力传递

假设纤维/基体界面分离区域内的摩擦剪切应力遵循Coulomb摩擦律，包括泊松效应的影响，建立了纤维拔出时的摩擦界面应力传递模型，获得了包含摩擦滑移和由纤维/基体热失配引起的法向残余热应力效应的纤维轴向应力和界面剪切应力的表达式.对纤维增强复合材料SCS-6/Ti-6Al-4V作参数化的数值计算，且和有限元结果进行比较.结果表明，随纤维轴向位置的增加，纤维轴向应力和界面剪切应力均减小；法向残余热应力、高纤维体积分数和短纤维延缓纤维失效.     

Ballistic Performance and Damage Characteristics of Chemical Vapor Infiltration Quasi 3D-Cf/SiC Composites

To investigate the ballistic performance and damage characteristics of quasi threedimensional(3D) needle-punched Cf/SiC composites prepared by chemical vapor infiltration(CVI),penetration experiments were conducted by using 7.62 mm armor piercing incendiary(API).Macro and micro fracture morphologies were then observed on recycled targets.The results show that the protection coefficient of 3D Cf/SiC composites is 2.54.High porosity and many micro thermal stress cracks may directly lead to the lower ballistic performance.Flat fracture morphology was observed on the crater surface.The low dynamic fracture strength along layer direction may be attributed to the voids and microcracks caused by residual thermal stress.The damage characteristics of Cf/Si C composites include matrix cracking,fiber bundle cracking,interfacial debonding,fiber fracture,and fiber bundle pull-out.And interfacial debonding and fiber fracture may play major roles in energy absorption.     

加铺碳纤维桥面板与桥面铺装结构层间剪切试验研究

为了评价加铺碳纤维的桥面板与桥面铺装结构层间的抗剪强度是否满足要求,利用剪力试验机进行了试件层间剪切试验,研究了加铺碳纤维桥面板的表面特性,分析了温度对层间抗剪强度的影响,探索了结构层间施工工艺。结果表明:碳纤维表面的AECR树脂胶能够增强层间粘结层的粘结性能;在加铺碳纤维的桥面板上撒布机械砂3.0 kg/m2,涂层改性沥青1.3 kg/m2,主涂胶涂抹8 h后撒布机械砂,施工工艺最合理,界面抗剪强度最高。     

Modification of interfacial performance of Fiber Bragg grating embedded in the composite materials

The interfacial performance of the Fiber Bragg grating (FGB) embedded in the composite was studied and the influence of interface modification on the final profile of the spectra of the FBG sensor was examined. A type of polyamine (Pentaethylenehexamine, PEHA) was proposed to modify the coating of PI on FBG, and the interfacial performance was evaluated by a pull-out test. Sharp improvements of the interfacial shear strength (77%) were obtained by 40 min treatment of PEHA. Compared with untreated specimen, FGB spectra of treated specimen in the tensile tests show improved linearity within the test regime, which proves that the enhanced interface is beneficial for the sensing performance.     

Effect of sizing on the interfacial shear strength of carbon fiber/epoxy resin monofilament composite

The single fiber fragmentation test （SFFT） was used to measure the interracial shear strength （IFSS） of sized and unsized CF800/epoxy resin monofilament composite in order to evaluate the effect of sizing respectively. Besides, the interfacial reinforcing mechanism was explored by analyzing the surface morphology of the carbon fibers, the wettability between the carbon fibers and the epoxy resin, and the chemical characteristics of the fiber surface. Moreover, the effect of sizing on heat and humidity resistance of interface was investigated by aging test. The results show that sizing improves IFSS of CF800/epoxy resin monofilament composite by 59% through increasing the functional groups containing oxygen and through enhancing wettability, while after sizing the heat and humidity resistance of interface is decreased.     

硅烷涂层提升钢纤维-砂浆界面性能的试验研究

为了提升钢纤维-砂浆界面的黏结性能,采用9种基于硅烷的表面处理剂对钢纤维进行浸渍处理并高温固化成膜;埋置于水泥砂浆圆柱体试块中,开展单根纤维拉拔试验,获得拉拔荷载-位移曲线. 试验结果表明,采用不同的硅烷涂层对钢纤维进行表面改性,可以不同程度地改善钢纤维-砂浆界面的黏结性能;拉拔峰值荷载最高增加5.75倍,拉拔能耗最多增加2.48倍. 硅烷Z6011和Z6020及复合涂层能够较大幅度地提升界面黏结强度,主要增加钢纤维与砂浆界面的化学黏结力;硅烷Z6030和Z6040及复合涂层对界面黏结强度的提升幅度相对较小,主要增加界面滑移摩擦力. 采用扫描电子显微镜（SEM）研究界面黏结性能的提升机理,发现硅烷涂层使得界面过渡区的微观结构更致密,显著提升了钢纤维-砂浆之间的黏结性能.     

木梁-夯土界面粘结滑移性能及其计算方法

福建土楼中夯土与木梁的界面性能是二者能够共同工作的基础,而木梁与夯土界面的粘结滑移关系是其界面性能的综合反映.为探讨木梁夯土界面的粘结滑移性能,进行了8个木梁-夯土节点试件的拉拔模型试验,考虑竖向压力、木梁伸入长度和木梁表面粗糙度对其粘结力组成、极限荷载等的影响,对木梁-夯土界面进行有限元建模分析,并提出粘结力的计算方...     

新旧混凝土界面结合状态研究

研究了在不同的界面干湿状态下，几种常见的修补材料和界面剂对新旧混凝土界面结合强度的影响。运用拉拔强度评价新旧混凝土界面结合状态，并借助显微硬度仪测量界面处的显微硬度值对试验结果进行了验证和分析。结果表明，在界面处于不同的干湿状态时，提高新混凝土的强度可使结合强度略有增大。在修补材料中掺入纤维会明显提高界面结合强度，且聚丙烯纤维要优于碳纤维．使用界面剂后界面干湿程度对界面结合强度影响减小。     

Effect of nano-silica modification on the tensile property of SMA/GF/CF/epoxy super hybrid woven fabric composites

Tensile properties of epoxy casts together with shape memory alloy (SMA), glass (GF) and carbon (CF) woven fabric reinforced epoxy matrix super hybrid composites were investigated, respectively. In order to enhance the mechanical strength of this advanced material, two categories of modifications including matrix blending and fiber surface coating by nano-silica were studied. Scanning electron microscopy (SEM) and fiber pull-out tests were adopted to complement the experimental results, respectively. Experimental results reveal that the toughness of epoxy matrix is enhanced significantly by adding 2wt% nano-silica. The failure mechanism of SMA reinforced hybrid composites is different from that of GF/CF/epoxy composites. Compared with the matrix modification, the fibers modified by coating nano-silica on the surface have better tensile performances. Moreover, the fiber pull-out test results also indicate that composites with fiber surface modification have better interfacial performances. The modification method used in this paper can help to enhance the tensile performance of the mentioned composite materials in real engineering fields.     

纤维-基体早龄期界面性能的影响因素

通过自行改造的测试系统,实现了对早龄期纤维增强水泥基复合材料体系中纤维–基体界面性能的测定,考察了龄期、基体组成、埋入深度、纤维表面特征等因素对界面性能的影响规律.结果表明:随着龄期的增加,界面的黏结强度逐渐增加,相对密实的基体组成有利于提高界面性能;随着埋入深度的增加,纤维–基体的界面黏结强度降低;而三角形截面及化学沉积改性的纤维与基体之间具有更高的界面黏结强度.     

Nature of the Pull-out System of Carbon Nanorope/Polyethylene Composite and Twisting Effect on Interfacial Behavior

The nature of the pull-out system of carbon nanorope/polyethylene(CNRP/PE) composite is studied by using molecular dynamics approach. The deformation of the CNRP/PE composites in pull-out process is exhibited. The influence of twisting deformation on the interfacial interaction of the composites is investigated. The results show that the energy of the pull-out system is conserved; and the interfacial bonding is weak resulting in a sliding failure of the CNRP inside PE matrix.     

软基上吸力式沉箱抗拔承载力的改进极限平衡法

为了计算软土地基上吸力式沉箱的抗拔承载力,在简化极限分析方法的基础上,进一步考虑沉箱侧壁与土之间的界面摩擦效应,提出了一种改进的极限平衡分析方法.通过与相应的三维有限元数值计算以及离心模型试验结果的比较,验证了所提出的改进极限平衡分析方法的合理性.采用该方法探讨了结构长径比、软基的不排水抗剪强度、荷载作用点位置等因素对于沉箱承载力的影响.结果表明,沉箱与土之间的界面摩擦系数对于其抗拔承载力具有一定影响;沉箱的最优系缆点位置一般位于筒顶以下0.55～0.7倍的筒高之间.     

端部锚固对温度作用下CFRP-混凝土界面黏结行为影响

为了明确端部锚固措施对碳纤维复合材料(CFRP)-混凝土界面黏结行为的影响,采用解析理论手段建立了温度作用下端锚CFRP-混凝土界面剥离全过程理论模型。结合常温界面黏结理论,引入双线性黏结-滑移本构,推导了界面滑移、界面剪应力以及CFRP正应力分布表达式,给出了界面荷载-滑移响应及界面剥离承载力模型,通过与试验和数值结果对比验证了解析模型的正确性,并在此基础上进行了参数化分析。分析结果表明:相比于纯外贴的CFRP-混凝土黏结界面,端部锚固可提高温度作用下的界面剥离承载力,能有效限制温度变化引起的黏结界面端部的界面滑移和剪应力,提高CFRP在温度作用下所承担的正应力,即提高CFRP的强度利用效率;对于端部锚固CFRP-混凝土黏结界面,在温度达到胶黏剂玻璃化温度前,温升会提高界面的承载性能,而温降会导致加载端界面提前剥离,降低加固界面的剥离承载力;CFRP黏结厚度和弹模的增加会使温度变化对界面黏结行为的影响更加显著。     

纤维增强复合材料的界面分离准则

考虑泊松效应和分离界面上摩擦应力的作用，建立了描述界面弹性应力传递的摩擦桥联理论模型，获得了纤维和基体的所有应力解.基于界面分离过程的能量平衡，获得了分离能释放率的表达式.通过引入一个界面分离准则，给出了求解临界分离长度的方法，获得了临界分离应力和桥联本构关系的表达式.对纤维增强复合材料SiC/Ti-6Al-4V作数值计算，结果表明建立的模型比剪滞模型更准确.     

Meso-mechanical interfacial behavior of elbow steel fiber reinforced concrete

The strain distributions near the interface when the elbow steel fiber is pulled out from the half-mould concrete matrix are directly measured using a combined method of single fiber pull-out test and digital image correlation. Meanwhile, the real-time processes of the bonding, debonding and sliding at the interface are observed. The micro-mechanism of the strain localization in the failure process of interface when debonding occurs and the strengthening mechanism at the imbedded fiber are discussed. The experimental results show that the meso-scale strain localization gives rise to the localization of shear damage near the fiber interface. This strain localization characterized by the debonding process near the interface occurs, develops and moves gradually at an apparently regular interval. At the elbow part of the imbedded fiber, the peak value of the shearing stress occurs. But the primary debonding does not occur at this place because the strength of the shear damage is increased at the local area of the elbow part in the concrete, displaying an apparent reinforced effect at the end of the fiber.     

改善新老混凝土界面粘结性能的措施研究

通过16组共48个100mm×100mm×100mm四种纤维混凝土与既有混凝土粘结的立方体试件劈拉试验,研究了新混凝土中纤维种类、纤维掺量对粘结试件劈拉性能的影响。结果表明各种纤维的加入总体上均有利于新老混凝土粘结性能的提高。效果最佳的是碳纳米管,其次是聚丙烯腈纤维,然后是玄武岩纤维和钢纤维。然后通过64组共192个100mm×100mm×100mm纤维增强聚合物改性混凝土与既有混凝土粘结的立方体试件劈拉试验,研究了新混凝土中纤维种类、纤维与聚合物掺量组合对粘结试件劈拉性能的影响。苯丙乳液的复合掺入总体上可进一步提高新老混凝土的粘结劈拉强度。各种纤维与苯丙乳液复掺时,均存在一个苯丙乳液掺量的最佳值。     

秸秆纤维水泥基复合材料性能的研究

对秸秆纤维水泥复合材料的基体相、界面相、复合效果、秸秆纤维水泥基复合材料性能，以及界面剂对其性能的影响等方面进行了研究，结果表明，在界面剂的作用下，秸秆植物纤维和水泥之间取得了良好的界面效果。     

非直钢纤维拔出过程的数值模拟

对纤维与基体的相互作用进行了力学分析，完成了纤维拉拔荷载与拉拔位移全过程的数值计算。针对非直钢纤维末端锚固长度大的平直段，给出了纤维压力分布的解析解答，并考虑了纤维与基体摩擦渐进硬化与衰减效应，在锚固段通过纤维平直通道时计入了残余弯矩作用，最后得到了与试验较为一致的纤维拉拔曲线。     

形状记忆合金增强复合材料界面剪应力研究

为研究形状记忆合金长纤维增强复合材料界面剪应力的分布情况,基于单纤维双圆柱拔出模型,推导了脱粘区和粘结区界面剪应力表达式.基于复合材料内部温度分布均匀,马氏体体积分数只与纤维内部轴向应力和温度相关等假设,分别讨论了恒定外应力荷载条件下温度(303、323、343 K)、预应变水平(0％、2％、4％、6％)及固定脱粘长度对界面剪应力分布的影响.数值模拟结果表明,通过控制外界温度和预应变水平,可以改变模型最大界面剪应力的值,进而控制界面脱粘现象的发生.对进一步研究SMA长纤维增强复合材料界面力学行为提供了一定的理论参考.     

UHTCC与钢材界面的剪切型断裂试验研究

为了将超高韧性水泥基复合材料(UHTCC)应用于大跨径钢箱梁桥,研究双材料界面的力学性能. 采用无切口单边对称加载复合试件,研究UHTCC与钢材界面剪切型裂缝扩展过程. 利用数字图像相关法(DIC),验证该方法用于定量测定双材料界面剪切型断裂韧度的可行性,探究不同界面处理方式对复合试件界面剪切型断裂韧度的影响. 试验结果表明,采用UHTCC-钢材无切口单边对称加载复合试件,结合DIC技术可以实现界面纯剪切型断裂韧度的定量测试;不同界面处理方式对UHTCC与钢材界面剪切型断裂韧度的影响均较小;UHTCC与钢材界面具有较高的剪切断裂韧度,抗剪切性能良好.