钢-BFRP复合筋混凝土柱试验与骨架曲线模型研究

为了研究钢-玄武岩纤维(basalt fiber reinforced polymer,简称BFRP)复合筋混凝土柱的抗震性能,以复合筋的纤维含量(等效配筋率)为主要参数,开展了4个钢筋与复合筋混凝土柱的抗震性能试验。试验结果表明,随着复合筋二次刚度比的提高,构件承载力也有明显提高,构件具有较为显著的屈服后刚度。在试验基础上提出了钢-BFRP复合筋混凝土柱骨架曲线理论模型,建立了骨架曲线特征点参数与结构特性之间的解析关系,该表达式能够综合考虑矩形构件截面尺寸、轴压比和复合筋本构关系及配筋情况等参数影响。该模型与试验结果吻合较好,对普通钢筋混凝土柱也具有较好的预测性,说明该理论模型具有一定的实用性和精确性,可实现利用杆系模型开展结构层次的建模,供混凝土框架结构非线性分析参考。     

预应力CFRP/GFRP纤维加固梁的延性性能研究

碳纤维具有高强度、高弹性模量和延性较差的特点,玻璃纤维相对于碳纤维可起到互补作用,采用预应力碳纤维/玻璃纤维(CFRP/GFRP)加固混凝土梁是一项新的加固技术。基于分层单元理论,建立了加固混凝土梁的计算模型,分析了加固后混凝土梁在荷载作用下三分点加载全过程数据,对比分析了加固梁的屈服荷载、极限荷载、变形和延性性能开展情况,研究了不同混杂纤维配比等对加固梁延性性能的影响。结果表明,将CFRP与GFRP混杂后能充分发挥各自的优势,且能提高预应力纤维加固梁的特征荷载。     

基于运动学及力热分析的CFRP超声振动辅助螺旋铣孔质量影响机制

碳纤维增强复合材料(Carbon fiber reinforced polymer/plastic,CFRP)因其较高的比强度、耐腐蚀性、耐疲劳性等优异性能,被广泛应用于航空航天领域,但作为各向异性的难加工材料,制孔过程易产生损伤.针对CFRP超声振动辅助螺旋铣孔质量为研究内容,首先建立了轴向超声辅助螺旋铣孔的运动学方...     

钛合金/CFRP叠层构件螺旋铣孔界面切削热研究

随着钛合金和复合材料(Carbon fiber reinforced plastic, CFRP)在航空航天制造业的应用比例逐渐增多,其叠层构件切削加工也成为研究热点。由于切削温度不仅影响刀具的磨损和耐用度,同时也会直接影响工件的加工精度和表面质量,本文在分析螺旋铣孔特点的基础上,对钛合金/CFRP叠层构件界面热传递机理进行了研究,建立了钛合金/CFRP叠层构件界面热传递模型,通过有限差分法对模型进行数值仿真求解;结合钛合金/CFRP螺旋铣孔实验,修正了刀具与工件的热传递系数以及工件界面温度传导率,通过钛合金/CFRP叠层构件螺旋铣孔切削热理论模型与试验结果对比,发现本文提出的理论模型分析结果和实验测量结果具有较高的一致性,能为钛合金/CFRP叠层螺旋铣孔加工工艺优化提供理论依据。     

玻璃纤维筋断裂强度的理论和实验研究

玻璃纤维筋(glass fiber reinforced polymer rebar,GFRP筋)是一种具有较好的抗拉、耐腐蚀和抗电、磁等性能的纤维复合材料,在特殊环境下可以用来代替普通钢筋.文中通过自行设计的实验装置,测试GFRP筋的破坏强度和弹性模量,并利用载荷距离加权局部分配法则和破坏柱元的概念,用统计破坏理论分析计算纤维筋棒的断裂强度,与试验结果对比基本一致.     

铺层结构对CFRP准各向同性板损伤破坏的影响

研究铺层结构对CFRP(Carbon fiber reinforced plastics)准各向同性板损伤破坏和最终失效强度的影响，对几种不同的CFRP层合板进行拉伸试验，观察其损伤形态，并测定最终抗拉强度。利用有限元程序对完整结构以及带裂纹结构进行数值分析，讨论铺层结构、应力的数值分析结果以及损伤破坏之间的对应关系。     

预应力CFRP／GFRP混杂纤维布加固混凝土梁的预应力损失试验研究

层内混杂CFRP／GFRP纤维布是一种用土木工程加固的新材料。CFRP具有高强度、高弹性模量的特点,但延性较差,GFRP相对于CFRP可起到互补作用。预应力CFRP／GFRP混杂纤维布加固混凝土梁,纤维布施加预应力后出现应力松弛,产生预应力损失。试验表明,在纤维布张拉结束后的3h内预应力损失较为明显,其后预应力损失变化缓慢而逐渐趋于平稳。张拉结束约9h后,预应力损失基本不再继续增大,最终的预应力损失占到张拉预应力约22％,损失程度在正常范围之内;张拉结束后3h的预应力损失占到总共预应力损失约87％,预应力损失主要在张拉结束后的3h内完成。     

L形碳纤维增强复合材料/铝合金胶接复合构件剥离应力建模与分析

针对承受剥离载荷的L形碳纤维增强复合材料(Carbon fiber reinforced plastic/polymer,CFRP)/铝合金胶接复合构件,以微元受力平衡方程为基础,建立胶层平均剥离应力的二维分布方程。在方程中引入基材的弯曲刚度系数,描述背材与基材均为刚性材料的情况下胶层剥离应力的分布规律。其应力分布曲线为拉压应力交替作用的阻尼调和函数,周期与峰值由胶接件构型尺寸与材料性能参数决定。通过CFRP/铝合金剥离试验及三维有限元模拟对理论模型进行对比验证,结果的总体趋势与数值吻合程度较好,并分析不同方法获得的剥离应力分布状态之间的差异及其产生的原因。基于胶接复合构件的理论模型与三维有限元模型,研究基材厚度改变对剥离应力分布的影响,发现伴随着CFRP板厚度的增加,剥离应力的峰值明显下降,在剥离前沿的应力集中现象得到改善。     

基于三维多相有限元的CFRP细观切削机理研究

为深入揭示碳纤维增强树脂基复合材料(Carbon fiber reinforced plastic/polymer,CFRP)切削机理,针对目前宏观单相有限元方法无法直观体现纤维和基体的失效形式、切屑类型等问题,借助数值仿真方法建立了CFRP直角切削的三维多相有限元模型。测量刀具刀尖形貌,根据刀具和CFRP设计数据提取CFRP纤维、基体细观几何信息,建立直角切削细观几何模型;基于定义材料本构用户子程序(User subroutine to define material behavior,VUMAT)分别定义纤维和基体的材料本构(弹塑性、失效准则、损伤演化方式),对不同纤维方向角的三维多相CFRP直角切削模型进行仿真分析;设计直角切削试验对仿真结果进行对比验证。仿真结果直观地展示了基体和纤维的失效形式、切屑形成过程、不同情况下切削亚表面损伤深度,通过各种情况下切削力数据的分析,揭示了切削力随纤维方向角的变化规律,并通过试验验证了该有限元建模仿真方法的有效性。     

碳纤维复合材料超声辅助钻削加工孔质量研究

碳纤维增强复合材料(carbon fiber reinforced plastics,CFRP)因其是编织材料,具有各向异性、强度高等特点,其加工难度大,加工质量较差.针对这一现状,采用电镀金刚石套料钻,对CFRP开展了超声辅助钻削与普通钻削对比实验,通过出入口质量、内壁形貌分析,研究了超声振动作用对孔出入口、内壁质量...     

基于摩擦和胶接机理的混合锚固技术的研究

纤维增强复合材料加固的一般施工方法是利用树脂类胶结材料将FRP片材粘贴于混凝土表面,从而达到对结构构件补强加固及改善结构受力性能的目的。但是此种方法在利用FRP加固结构时,容易发生FRP-混凝土界面的早期剥离破坏,从而导致其加固效果受到限制,无法充分利用FRP的高强材料特点。为了解决上述破坏问题,本文研究一种新型的FRP片材粘结锚固技术,即基于摩擦和胶接机理的混合锚固技术(简称FAHB)。本文利用ANSYS软件对FAHB进行了非线性有限元分析,并与常规单粘结锚固技术进行对比。结果表明,FAHB粘结锚固技术可以有效避免整体粘结失效,从而显著提高构件的极限承载力,较单粘结锚固技术具有明显优势。     

预应力混杂FRP布加固混凝土梁的抗弯性能试验及裂缝发展模拟研究

预应力混杂FRP布加固混凝土梁是一项新的加固技术,对该加固混凝土梁的抗弯性能进行了试验研究,分析了加固后混凝土梁在荷载作用下三分点加载全过程及破坏形态,对比分析了加固混凝土梁的屈服荷载、极限荷载、变形、裂缝分布及扩展情况,研究了有效预应力、混杂纤维配比对加固混凝土粱抗弯性能的影响。基于分层单元理论建立了加固混凝土梁的计算模型,并对典型加载的混凝土裂缝分布及扩展进行了模拟,实现了裂缝可视化分析,研究结果为实际工程提供了参考。     

层压金属复合材料/纤维层合板静载作用下的强度优化设计

分别以静载作用下纤维层合板（FRP）和层压金属复合材料（FML）的强度为目标,对层合板中纤维层的铺层角度进行了优化设计,依据得到的优化结果对两种层合板在不同载荷下的强度性能进行了比较。采用有限元对层合板进行结构分析,结合Tsai-Wu准则和VonMises准则得到层合板的强度失效因子,然后将粒子群优化算法和有限元结合起来实现优化过程。优化结果表明,FML由于Al层的加入使其横方向承载能力加强,相比FRP,FML具备更好的抵抗面内双向拉伸载荷的能力;在受面外集中载荷作用时,FML在4种不同边界条件下的强度性能都优于FRP,并且FML的强度性能更为稳定。     

Experimental studies on performance of reinforced concrete beam strengthened with CFRP under cyclic loading using FBG array

Investigations are increasingly being carried out in the area of utilizing Fiber Reinforced Plastic (FRP) materials for retrofitting and repairing existing damaged concrete structures due to their excellent properties. Favorable mechanical and material characteristics of FRP composites make them attractive for strengthening applications, whereas relatively higher material costs, insufficient knowledge in mechanics of their behavior, long-term durability and lack of related design codes are the issues that need to be addressed for mainstream application of these materials. Although there has been growing interest and field applications of strengthening concrete structures using Carbon Fiber Reinforced Plastic (CFRP) sheet/plate, very little information exists regarding the flexural fatigue behavior of reinforced concrete beams strengthened with CFRP. A common cause of failure in such strengthened members is associated with the debonding of CFRP substrate from the concrete in an abrupt manner. In order to understand the mechanism of debonding in strengthened concrete structures, embedment of strain sensors (Fiber Bragg Grating (FBG) array) between the concrete and CFRP is proposed in this paper. Due to the compatibility with CFRP material and being small in size, fiber optic sensor is a good choice for embedding at the interface to measure interfacial strain. This paper presents the experimental studies carried out on CFRP strengthened concrete members subjected to cyclic loading. A special emphasis has been placed on understanding the failure pattern using the embedded FBG sensors. Based on the studies it is concluded that the strain at the interface of CFRP strengthened concrete members can be measured.     

预应力混凝土旧吊车梁疲劳及承载性能评估

某机械制造厂有预应力混凝土旧吊车梁数十根.为检验这批旧吊车梁能否继续使用,对两根锈蚀程度较严重的吊车梁进行疲劳强度试验和静力荷载试验.试验结果表明:在2×106次疲劳荷载下,旧吊车梁仍处于弹性工作阶段;在静力荷载作用下,旧吊车梁承载力满足正常工作要求且具有良好的延性,达到破坏荷载时端部的预应力锚具状态完好.     

Terahertz spectroscopy approach of the fiber orientation influence on CFRP composite solid laminates

Terahertz ray (T-ray) imaging applications have provided one of the most promising new powerful nondestructive evaluation techniques, and new application systems are under process development for area applications. Detecting flaws and defects in fiber reinforced plastic (FRP) composite laminates due to flaws in FRP composite laminate that affect laminate properties, including stiffness, strength, and thermal behavior, is very important. In this study, a new time-domain spectroscopy system was utilized for detecting and evaluating the flaws in FRP solid composite laminates. Extensive experimental measurements in reflection mode were made to map out T-ray images. In particular, electromagnetic properties, such as refractive index, were estimated in this characterization procedure. The estimates of properties were in good agreement with known data. Using these characteristic material properties, we successfully demonstrated the characteristics of the T-ray behavior propagating through FRP composites. Furthermore, layup effect and flaws of FRP composite laminates were observed in reflection mode, and limitations were discussed in the T-ray processing.     

3D Progressive Damage Based Macro-Mechanical FE Simulation of Machining Unidirectional FRP Composite

Finite element(FE) simulation is a powerful tool for investigating the mechanism of machining fiber?reinforced polymer composite(FRP). However in existing FE machining simulation works,the two?dimensional(2 D) progressive damage models only describe material behavior in plane stress,while the three?dimensional(3 D) damage models always assume an instantaneous sti ness reduction pattern. So the chip formation mechanism of FRP under machin?ing is not fully analyzed in general stress state. A 3 D macro?mechanical based FE simulation model was developed for the machining of unidirectional glass fiber reinforced plastic. An energy based 3 D progressive damage model was proposed for damage evolution and continuous sti ness degradation. The damage model was implemented for the Hashin?type criterion and Maximum stress criterion. The influences of the failure criterion and fracture energy dissipa?tion on the simulation results were studied. The simulated chip shapes,cutting forces and sub?surface damages were verified by those obtained in the reference experiment. The simulation results also show consistency with previous 2 D FE models in the reference. The proposed research provides a model for simulating FRP material behavior and the machining process in 3 D stress state.     

The Evalution Of Elastic Modulus for Steel Fiber Reinforced Concrete

Since the addition of steel fibers to concrete has been shown to increase both the ductility and the fatigue strength of reinforced concrete. A series of uniaxial compression tests were conducted on 15×30L cm cylindrical specimens to evaluate the complete stress-strain behavior and elastic modulus for steel fiber reinforced concrete.     

Low velocity impact and axial loading response of hybrid fibre aluminium laminates

Journal of Mechanical Science and Technology - Fibre metal laminates (FMLs) are layered materials based on stacking arrangements of metals and fibre reinforced plastic (FRP) composite laminates....     

Drilling-induced damage in uni-directional glass fiber reinforced plastic (UD-GFRP) composite laminates

Uni-directional glass fiber reinforced plastic (UD-FRP) composite materials are a feasible alternative to structural members that bear loads in only one direction. FRP composite materials have excellent properties in the direction of the fibers. Drilling- induced damage acts as an inhibitor to their application, as the holes act as stress concentration sites for failure under loading. The present study is an attempt to study the influence of drilling-induced damage on the residual tensile strength of uni-directional composite laminates and to propose a mathematical model correlating the residual strength with the drilling parameters. A finite element model (FEM) is also developed to study the drilling-induced damage in composite laminates.