纤维铺层角度对复合材料薄壁圆管轴向压溃吸能特性影响研究

研究T700/3234复合材料薄壁圆管轴向压溃吸能特性受纤维铺层角度变化的影响规律。开展复合材料力学性能试验和薄壁圆管轴向准静态压溃试验。通过对比圆管轴向压溃峰值载荷及比吸能等指标的试验结果,验证建立的复合材料圆管有限元模型和分析方法。基于验证的有限元分析方法,探讨了复合材料纤维铺层角度的变化对薄壁圆管轴向压溃吸能特性的影响规律。结果表明,在准静态轴向压缩载荷下,随着纤维铺层角度的增大,比吸能先增大后减小;纤维角度为±45°时,初始峰值载荷最低,载荷效率最高,圆管易于进入渐进破坏吸能阶段。研究结果可为复合材料纤维铺层角度设计及复合材料薄壁结构有限元建模提供参考。     

典型螺栓连接CFRP薄壁C型柱轴压失效行为:试验及数值模拟

为了研究典型螺栓连接碳纤维增强树脂复合材料(CFRP)薄壁C型柱的轴压失效模式及吸能特性,进行了5组不同铺层方式C型柱的准静态轴压试验,即[0/90]_4s、[±45]_4s、[±45/90₂/0₄]_s、[±45/90/0₂/90/0₂]_s、[90/±45/0]_2s,获得其失效形貌及载荷-位移曲线。采用Lavadèze单层壳单元模型、Puck-Yamada失效准则、层间胶粘单元及螺栓模型,建立C型柱层合壳模型进行轴压仿真,并与试验失效形貌、载荷-位移曲线及吸能特性评估指标进行对比分析。结果表明:0°、±45°、90°纤维可以显著影响C型柱轴压失效模式及吸能特性。在轴压载荷下,±45°纤维铺设C型柱发生局部屈曲失效模式,吸能特性差。±45°纤维铺设在外部,0°和90°纤维交替铺设在内部的C型柱,其轴压失效过程平稳,吸能特性好。与C型柱轴压试验结果相比,层合壳模型获得的整体变形和局部失效形貌吻合较好,载荷-位移曲线变化趋势和吸能特性评价指标基本一致。研究结果对CFRP薄壁C型柱吸能设计具有一定的指导意义。      

铺层顺序对复合材料薄壁圆管轴向压溃吸能特性的影响研究

采用仿真和试验相结合的方法探讨复合材料薄壁圆管在准静态轴向压缩载荷下的失效吸能特性和吸能机理。首先,建立复合材料薄壁圆管"层合壳"有限元模型,通过显式动力学方法求解其在准静态轴向载荷下的压溃失效力学行为。仿真与试验结果在圆管轴向压溃变形过程、初始峰值载荷、平均压溃载荷及比吸能等主要吸能参数上具有很好的一致性,验证了"层合壳"复合材料圆管有限元模型和建模方法的有效性。其次,采用解析模型与仿真分析方法分别对[0/90]_3s、[0/90/0₂/90₂]_s、[0₃/90₃]_s三种不同铺层顺序的复合材料圆管的屈曲载荷与吸能特性进行了对比,进一步分析了铺层顺序对圆管失效吸能特性的影响。研究表明,0°与90°铺层交替程度对复合材料圆管的吸能特性影响较大,保证纤维失效方式在结构宏观失效中占主导地位能够提高材料失效吸收能量。     

复合材料/铝复合管轴向准静态及冲击压溃的吸能特性

用数值模拟方法,研究了方形和圆形截面的复合材料/铝复合管在轴向准静态及冲击压溃下的吸能特性,计算得到压溃力-位移曲线。通过将一组方形截面复合管在准静态压溃条件下的计算结果与文献的实验数据进行对比,以验证有限元模型和参数设置的正确性。在铝管的管厚、管长以及截面外周长相同,缠绕不同厚度的复合材料情况下,对比分析了方形和圆形截面复合管在准静态及冲击压溃条件下的轴向压溃吸能特性。结果表明,复合管的截面构型对其吸能效果影响很大,在轴向准静态压溃条件下,圆形截面复合管吸能能力要强于方形截面复合管;冲击压溃吸能量不但与结构自身吸能力有关,还受到外界冲击大小的影响。在设计复合材料层厚度时,需要控制复合管的刚度,避免回弹造成吸能量的降低。     

复合材料吸能圆管在半圆凹槽触发机制下的斜向压溃失效行为

有效的触发机制能诱导并改善复合材料吸能结构的轴向渐进压溃行为,但仍无法解决汽车吸能结构在斜向冲击载荷下的失稳问题。为了提出新的设计来改善失稳行为,对复合材料吸能圆管在半圆凹槽触发机制下的斜向压溃行为和失效机制进行研究。建立引入半圆凹槽触发机制的圆管有限元模型,采用界面和层内非线性损伤演化模型来模拟其真实的压溃失效模式。通过对比模拟和实验对应的轴向压溃载荷、吸能和失效模式来验证圆管的准静态压溃模型。进而,预测斜向压溃角度(10°～50°)对圆管在半圆凹槽触发机制下压溃行为的影响,并详细揭示其轴向和斜向压溃失效机制及其区别。结果表明,压溃载荷、吸能及失效面积随角度增大而明显减小,不稳定的压溃过程使材料失效耗能不充分。圆管在轴向压溃下表现为渐进破坏,而在斜向压溃下以“渐进破坏”向“失稳破坏”过渡为特征,导致斜向压溃载荷与吸能曲线均存在一个过渡。本研究加深了对圆管在外部触发机制下斜向压溃失效机制的理解,为改善斜向压溃失稳行为提供了一定的设计依据。     

玻璃-环氧圆柱壳吸能特性的试验研究

主要研究[±H]5 玻璃-环氧圆柱壳在轴向压缩载荷作用下的吸能特性。通过试验研究, 分析了纤维缠绕角度对能量吸收性能的影响; 比较了不同纤维缠绕角度的圆柱壳在不同加载条件下的压缩过程、压碎破坏模式及吸能能力。      

复合材料层合板端部压溃试验研究EI北大核心CSCD

通过对T800复合材料层合板进行一系列的端部压溃试验,重点研究了长度、厚度、铺层顺序、触发角以及胶结压力等因素对复合材料层合板破坏模式和力学性能的影响。分析复合材料板在端部压溃过程中的载荷-位移曲线和观察试验样件端部破坏形貌,揭示其破坏机理。结果表明:复合材料平板的端部压溃过程为非稳态脆性断裂模式,而含45°触发角的复合材料层合板的端部压溃过程为层束弯曲破坏模式;在端部压溃试验中复合材料平板压缩强度随着厚度的增加逐渐上升,而长度的增加会减少其压缩强度,同时[45°/0°/-45°/0°]_(3s)铺层比[45°/90°/-45°/0°]_(3s)铺层拥有更好的抗轴向承载能力;触发角的加入会改变试件在压溃过程中的破坏模式并极大降低试件压溃时的压缩强度,是影响复合材料结构吸能能力的关键因素;研究还发现不同胶结压力下,复合材料层板的力学性能随着胶结压力的增加逐渐提高,但达到一定胶结压力值后,继续增加胶结压力力学性能反而下降。     

复合材料结构的能量吸收

针对缠绕成型的 [± 75 ]n玻璃纤维 /聚酯和 [0 /± 75 ]n玻璃纤维 /环氧树脂圆柱管的轴向与非轴向压缩失效行为及能量吸收特性进行了研究 (轴压的倾斜角度变化范围 0～ 2 5°) ,分析了复合材料圆柱管的宏观破坏模式和能量吸收机理 ,比较了轴向与非轴向载荷下能量吸收的特点 .研究表明 :复合材料圆柱管在偏轴角度下其压缩损伤过程可分为 3个阶段 ,即初始引发阶段、稳态渐进阶段以及压实或失稳阶段 ;圆柱管的压缩行为和吸能能力主要取决于偏轴压缩角度和载荷位移历程     

复合材料层合结构破坏机理及压溃吸能特性分析

针对纤维增强复合材料层合试验样件,对[90]_(16)和[0]_(16)试验样件分别进行拉伸、压缩试验,对[±45]_(4s)试验样件进行剪切试验,分析其破坏模式,通过SEM扫描电镜观察试验样件断口微观形貌,揭示其细观破坏机理。针对纤维增强复合材料层合薄壁结构,对[±45/0/0/90/0]_s圆管、[0/90]_(3s)圆管、[0/90]_(3s)方管和[±45]_(3s)方管进行准静态轴向压溃试验,分析其宏观破坏模式及吸能特性。结果表明:宏观破坏模式是多种细观破坏机理共同作用的结果,包含纤维断裂、基体变形与开裂、层间与层内裂纹扩展等;[±45/0/0/90/0]s圆管为横向剪切破坏模式,比吸能最大;[0/90]_(3s)圆管为层束弯曲失效模式,比吸能次之;[0/90]_(3s)方管为层束弯曲失效模式,比吸能第三大;[±45]_(3s)方管为局部屈曲失效模式,比吸能最小。不同铺层方式复合材料层合薄壁圆管和方管压溃破坏失效模式差异较大,比吸能差距也较大,通过合理设计可以改变复合材料层合薄壁结构破坏模式,改进其吸能特性。     

新型碳纤维增强复合材料-钢复合管海水海砂混凝土圆柱轴压试验

为研究原状海水海砂混凝土在复合管混凝土中的应用可行性,提出一种新型由内外壁纤维增强复合材料(FRP)和夹心钢管复合的碳纤维增强复合材料(CFRP)-钢复合管海水海砂混凝土柱结构。对12个新型CFRP-钢复合管海水海砂混凝土圆柱试件进行了轴压试验,研究了CFRP层数和核心混凝土强度等级变化对其轴压性能的影响。试验结果表明,内外壁CFRP的包裹能够有效地提高结构承载力和变形能力;CFRP-钢复合管海水海砂普通混凝土圆柱破坏形态为混凝土压溃,而CFRP-钢复合管海水海砂高强混凝土圆柱破坏形态为剪切破坏;结构的极限应力与CFRP层数、混凝土强度呈正相关,而极限应变随着CFRP层数增加而提高,却随着混凝土强度提高而减小;核心混凝土和钢管对极限应力的贡献随着CFRP层数增加基本不变,且当包裹两层及以上CFRP时,CFRP对试件极限应力的贡献占主导地位。      

Numerical Study on Hybrid Tubes Subjected to Static and Dynamic Loading

The commercial finite element program LS-DYNA was employed to evaluate the response and energy absorbing capacity of cylindrical metal tubes that are externally wrapped with composite. The numerical simulation elucidated the crushing behaviors of these tubes under both quasi-static compression and axial dynamic impact loading. The effects of composite wall thickness, loading conditions and fiber ply orientation were examined. The stress–strain curves under different strain rates were used to determine the dynamic impact of strain rate effects on the metal. The results were compared with those of a simplified analytical model and the mean crushing force thus predicted agreed closely with the numerical simulations. The numerical results demonstrate that a wrapped composite can be utilized effectively to enhance the crushing characteristics and energy absorbing capacity of the tubes. Increasing the thickness of the composite increases the mean force and the specific energy absorption under both static and dynamic crushing. The ply pattern affects the energy absorption capacity and the failure mode of the metal tube and the composite material property is also significant in determining energy absorption efficiency.     

碳纤维-玻璃纤维混杂增强环氧树脂三维编织复合材料薄壁圆管压溃吸能特性与损伤机制

基于三维编织成型及真空辅助树脂传递成型技术,制备了编织纱和轴纱不同混杂方式(编织纱/轴纱:碳纤维-碳纤维(CF-CF)、碳纤维-玻璃纤维(CF-GF);玻璃纤维-碳纤维(GF-CF))增强环氧树脂(EP)的三类三维编织复合材料薄壁圆管,通过准静态轴向压溃及详细的破坏断面观察,研究了纤维混杂方式对薄壁圆管的能量吸收性能和破坏模式的影响。研究发现:CF-CF/EP样品的比能量吸收值分别比GF-CF/EP大36%,比CF-GF/EP大12%。编织纱为碳纤维时(CF-CF/EP及CF-GF/EP),圆管的破坏模式均为折叠破坏模式,编织纱采用碳纤维能有效地遏制中央裂纹的轴向扩展,折叠变形的三维结构内部发生了较多细小的微观破坏。而编织纱为玻璃纤维的GF-CF/EP,破坏模式则为开花内外弯曲式,中央裂纹产生,三维结构呈现分层并向圆管内外弯曲。      

Finite element modelling of the progressive crushing of braided composite tubes under axial impact

Composite tubular structures are of interest as viable energy absorbing components in vehicular front rail structures to improve crashworthiness. Desirable tools in designing such structures are models capable of simulating damage growth in composite materials. Our model (CODAM for COmposite DAMage), which is a continuum damage mechanics based model for composite materials with physically based inputs, has shown promise in predicting damage evolution and failure in composites. In this study, the model is used to simulate the damage propagation, failure morphology and energy absorption in triaxially braided composite tubes under axial compression. The model parameters are based on results from standard and specialized material testing and a crack band scaling law is used to minimize mesh sensitivity (or lack of objectivity) of the numerical results. Axial crushing of two-ply and four-ply square tubes with and without the presence of an external plug initiator are simulated in LS-DYNA. Refinements over previous attempts by the authors include the addition of a pre-defined debris wedge, a distinguishing feature in tubes displaying a splaying mode of failure, and representation of delamination using a tiebreak contact interface that allows energy absorption through the un-tying process. It is shown that the model adequately predicts the failure characteristics and energy absorption of the crushing events. Using numerical simulations, the process of damage progression is investigated in detail and energy absorptions in different damage mechanisms are presented quantitatively.     

玻璃/环氧圆柱管能量吸收细观机理

研究了玻璃纤维增强环氧圆柱管轴向撞击和准静态压缩下的能量吸收特性。总结了稳态压缩的三种宏观破坏模式,即层束弯曲、局部屈曲和横向剪切。从细观角度出发,详细研究了不同宏观破坏模式的复合材料圆柱管的能量耗散机理,并比较了吸能能力。随着铺设角度增大,能量吸收机理由基体控制向纤维与基体共同控制转化,因此能量吸收逐渐增大。本文还比较了撞击和准静态下能量吸收的特点。     

Effect of fiber orientation on energy absorption characteristics of glass cloth/epoxy composite tubes under axial quasi-static and impact crushing condition

The collapse characteristics and energy absorption capability of composite tubes made of 759/5224 woven glass cloth/epoxy with different fiber orientations were studied in the present article under axial quasi-static and impact crushing condition. The effects of fiber orientation and loading condition on the crushing modes and energy absorption capability were discussed in detail. The fiber orientation could be found to have significant influences on energy absorption performance. Based on results, the energy absorption capability could be improved by selecting proper fiber orientation. The energy absorption capability in impact crushing tests could be found to be slightly lower than that in quasi-static crushing tests.     

圆-方异形截面复合材料管件物能量吸收机制

圆形截面复合材料管件物的能量吸收性能比方形截面管件物更加优越,但具有平整表面的方形管件物更容易与其他部件相装配,即方管在实际运用中更具优势。结合圆形与方形管件物的各自优势,以碳纤维为增强体,环氧树脂为基体,利用编织成型方法以及真空辅助树脂传递成型技术制备出编织角度为15°和60°的3类复合材料圆-方形管件物,编号为T15-15、T15-60及T60-60。通过准静态压缩实验研究了3类管件物的能量吸收性能,发现通过合理的编织角设计,可以利用周向纤维限制轴向中央裂纹的扩展,使复合材料内部更多的纤维发生断裂,从而提高纤维增强复合材料管件物的能量吸收性能。最终制备了集高能量吸收性能与易装配性于一身的圆-方异形截面复合材料管件物。     

Composite sandwich structures with nested inserts for energy absorption application

Polymer composite sandwich structures are promising candidate structures for reducing vehicle mass, thereby improving the fuel economics. Nonetheless, to fully explore this material as the primary structure and energy absorber in vehicles, it is important to understand the energy absorption capability of this material. Hence, in the present work, comprehensive experimental investigation on the response of composite sandwich structures to quasi-static compression has been carried out. The crashworthiness parameters, namely the peak force, absorbed crash energy, specific absorbed energy, average crushing force and crush force efficiency of various types of composite sandwich structures were investigated in a series of edgewise axial compression tests. The tested composite sandwich specimens were fabricated from glass and carbon fiber with epoxy resin. Four distinct modes of failure were observed and recorded. The primary mode of failure observed was progressive crushing with high energy absorption capability. The optimized design in this study had a specific energy absorption capability of 47.1 kJ/kg with a good crush force efficiency of 0.77, higher than conventional metals.     

复合材料波纹梁冲击试验与数值模拟

为了探究复合材料波纹梁的吸能性能,针对铺层形式分别为[(±45)3/(0,90)/(±45)3]、[(±45)8]和[(±45)7]的3种复合材料波纹梁元件,进行了动态冲击试验,得到了吸能载荷-位移曲线,并对其损伤破坏形貌进行了分析。以连续损伤力学为基础,结合改进的Hashin损伤判定准则以及损伤演化规律,提出了针对波纹梁耐撞性损伤分析的刚度退化模型,并基于有限元软件平台开发了适用于波纹梁渐进损伤分析的子程序。对3种不同结构形式的波纹梁进行了渐进失效数值分析,模拟得到了能量评估参数比吸能(SEA)和平均载荷值,并将模拟结果与试验结果进行了对比分析。比较分析了不同薄弱环节复合材料波纹梁的吸能能力。结果表明:波纹梁在冲击载荷作用下发生了渐进压溃失效;平均压溃载荷的相对误差不超过12%,能够满足工程应用要求;薄弱环节的设置需综合考虑复合材料性能和铺层方式等因素。     

Experimental investigation into dynamic axial impact responses of double hat shaped CFRP tubes

This paper aims to explore the dynamic responses and crashing characteristics of double hat shaped tubes made of weave carbon fiber reinforced plastic (CFRP). Experimental investigations were carried out into three different thicknesses and lengths of the composite tubes fabricated by the bladder molding process. Three distinct failure modes, classified as progressive end crushing, mid-length collapse and overlap opening, were observed in the dynamic crushing tests. Unlike continuous splaying fronds observed in the quasi-static tests, dynamic tests exhibited a number of fragment segments in the progressive end crushing mode. It is shown that the ply number was a critical parameter affecting the failure mode and energy absorption capability. The increase in ply number led to increases in the peak load and specific energy absorption (SEA); whereas the tubal length seemed insensitive to energy absorption capability. Compared to the quasi-static cases, the dynamic impact tests resulted in the higher peak load (increased from 46 % to 125 %) and lower SEA (reduced from 21 % to 33 %) for the tested tubes.