Experimental Analysis of Low-Velocity Impact Behaviors of Carbon Fiber Composite Laminates

Manufacture processing of composite laminates often leads to unequal thickness of lamina and different impact responses. However, almost all existing works neglected this problem because they considered equal thickness for each lamina. This paper aims to study the influence of unequal thickness of each lamina on the impact behaviors of composite laminates by experiments. Effects of the layup patterns and impact energy are mainly studied. Results in terms of the impact experiments of carbon fiber composite laminates show that subtle difference for the thickness of the total laminate leads to relatively large errors for the impact responses, especially for the impact force-deflection curves. Also, the ratio of absorbed energy to the impact energy increases with the specimen thickness. Therefore, the practical design of composite laminates should be taken into account this difference fully due to manufacturing.     

Effects of Fiber Architectures on the Impact Resistance of Composite Laminates Under Low-Velocity Impact

Applied Composite Materials - This present work focuses on evaluating the impact resistance of five marine superstructure laminated structures according to the engineering application requirements,...     

A Progressive Damage Model for Predicting Permanent Indentation and Impact Damage in Composite Laminates

In this paper, a progressive damage model was established on the basis of ABAQUS software for predicting permanent indentation and impact damage in composite laminates. Intralaminar and interlaminar damage was modelled based on the continuum damage mechanics (CDM) in the finite element model. For the verification of the model, low-velocity impact tests of quasi-isotropic laminates with material system of T300/5228A were conducted. Permanent indentation and impact damage of the laminates were simulated and the numerical results agree well with the experiments. It can be concluded that an obvious knee point can be identified on the curve of the indentation depth versus impact energy. Matrix cracking and delamination develops rapidly with the increasing impact energy, while considerable amount of fiber breakage only occurs when the impact energy exceeds the energy corresponding to the knee point. Predicted indentation depth after the knee point is very sensitive to the parameter μ which is proposed in this paper, and the acceptable value of this parameter is in range from 0.9 to 1.0.     

Finite Element Simulation of Low Velocity Impact Damage on an Aeronautical Carbon Composite Structure

Low velocity barely visible impact damage (BVID) in laminated carbon composite structures has a major importance for aeronautical industries. This contribution leads with the development of finite element models to simulate the initiation and the propagation of internal damage inside a carbon composite structure due by a low velocity impact. Composite plates made from liquid resin infusion process (LRI) have been subjected to low energy impacts (around 25 J) using a drop weight machine. In the experimental procedure, the internal damage is evaluated using an infrared thermographic camera while the indentation depth of the face is measured by optical measurement technique. In a first time we developed a robust model using homogenised shells based on degenerated tri-dimensional brick elements and in a second time we decided to modelize the whole stacking sequence of homogeneous layers and cohesive interlaminar interfaces in order to compare and validate the obtained results. Both layer and interface damage initiation and propagation models based on the Hashin and the Benzeggagh-Kenane criteria have been used for the numerical simulations. Comparison of numerical results and experiments has shown the accuracy of the proposed models.     

缝合泡沫夹层复合材料低速冲击数值模拟及实验

在ABAQUS分析平台中建立了缝合泡沫夹层复合材料在低速冲击下的动力学有限元模型,采用杆单元模拟缝线树脂柱的作用,基于Hashin破坏准则模拟层板面内损伤,通过各向同性硬化本构模型利用等效塑性变形模拟泡沫夹芯损伤演化。针对相同铺层的缝合和未缝合泡沫夹层结构,模拟了相同冲击能量下的低速冲击响应过程及面板、泡沫的损伤情况,数值结果与实验结果吻合较好,证明了该方法的有效性和准确性。研究结果表明,在低速冲击下,泡沫夹层结构引入缝线后虽然降低了泡沫缓冲吸能的作用,使得面板表面受到较大的冲击破坏,但增强了整体刚度,增大了面板抵抗弯曲变形的能力,减小了内部面板的损伤,使其在改善复合材料面板易分层缺陷的同时还依然拥有优良的面内性能。     

Impact Damage to Composite Laminates: Effect of Impact Location

Accidental impact loading of Composite laminates during manufacture and in-service can occur in different locations including near the edge or on the edge of a composite structure. This paper describes investigation of the effect of impact to composite laminates and compares the damage arising from central, near edge and on edge impact events. The damage tolerance of impact damaged laminates using both compression and tension tests has been measured. These results reveal the different damage mechanisms arising from different locations of impact. These different damage mechanisms have been investigated using X-Ray computed tomography. Impact on the edge of composite laminates is found to lead to smaller damage area, but more fibre failure; the severity of this damage is not revealed in standard compression after impact tests.     

复合材料斜削结构试验和损伤模拟研究

本文对复合材料斜削结构进行拉伸试验和相应的有限元模拟分析,编制损伤子程序模拟结构内部的损伤.通过对试验数据和数值结果进行对比,数值模拟和试验结果吻合较好.试验和模拟结果显示,由于削层的存在,使得结构更复杂,尤其在过渡段内,各截面的性能不同.通过损伤模拟,预测了三种损伤形式的萌生位置和扩展方向,得出结构首先发生基体损伤,然后是纤维-基体剪切和纤维断裂损伤,基体开裂损伤对斜削结构的影响很小,而纤维-基体剪切和纤维断裂损伤对结构是灾难性的.     

表面织构与复合板联合轧制成形的数值模拟研究

目的研究结合界面带微织构的复合板的轧制成形过程。方法基于Deform软件,以CDA-377铜和1100铝复合板为研究对象,模拟铜板表面微织构加工过程以及带微沟槽的铜板与铝板的轧制复合过程,分析整个轧制复合过程中轧制力的变化规律,然后在复合板稳定轧制过程中对板料金属单元进行样点追踪以及应力分析,最后以铝板温度、压下率为变量,分析铝板温度、压下率对稳定轧制阶段轧制力的影响。结果通过改变铝板温度和压下率进行多次模拟,发现铝板温度为200℃,压下率为25%时,在整个复合轧制过程中,咬入阶段轧制力先上升到最大值608 N,随后下降并稳定在366 N左右,并进入稳定轧制阶段;在稳定轧制过程中,铝板基层和凹陷层的应力变化规律基本一致,应变主要集中在铝板一侧;随着铝板温度升高、压下率降低,稳定轧制阶段的轧制力呈下降趋势。结论微织构复合板轧制过程中轧制力的变化规律、稳定轧制状态下的轧制力受温度和压下率影响的机理与普通复合板基本一致,而稳定轧制状态下结合界面的应力变化规律与微织构相关。     

Simulation of Low Velocity Impact Induced Inter- and Intra-Laminar Damage of Composite Beams Based on XFEM

In this paper, the Inter-Fiber Fracture (IFF) criterion of Puck failure theory based on the eXtended Finite Element Method (XFEM) was implemented in ABAQUS code to predict the intra-laminar crack initiation of unidirectional (UD) composite laminate. The transverse crack path in the matrix can be simulated accurately by the presented method. After the crack initiation, the propagation of the crack is simulated by Cohesive Zoom Model (CZM), in which the displacement discontinuities and stress concentration caused by matrix crack is introduced into the finite element (FE) model. Combined with the usage of the enriched element interface, which can be used to simulate the inter-laminar delamination crack, the Low Velocity Impact (LVI) induced damage of UD composite laminate beam with a typical stacking of composite laminates [0₅/90₃]_S is studied. A complete crack initiation and propagation process was simulated and the numerical results obtained by the XFEM are consistent with the experimental results.     

Modeling Lightning Impact Thermo-Mechanical Damage on Composite Materials

Carbon fiber-reinforced polymers, used in primary structures for aircraft due to an excellent strength-to-weight ratio when compared with conventional aluminium alloy counterparts, may nowadays be considered as mature structural materials. Their use has been extended in recent decades, with several aircraft manufacturers delivering fuselages entirely manufactured with carbon composites and using advanced processing technologies. However, one of the main drawbacks of using such composites entails their poor electrical conductivity when compared with aluminium alloy competitors that leads to lightning strikes being considered a significant threat during the service life of the aircraft. Traditionally, this problem was overcome with the use of a protective copper/bronze mesh that added additional weight and reduced the effectiveness of use of the material. Moreover, this traditional sizing method is based on vast experimental campaigns carried out by subjecting composite panels to simulated lightning strike events. While this method has proven its validity, and is necessary for certification of the structure, it may be optimized with the aid provided by physically based numerical models. This paper presents a model based on the finite element method that includes the sources of damage observed in a lightning strike, such as thermal damage caused by Joule overheating and electromagnetic/acoustic pressures induced by the arc around the attachment points. The results of the model are compared with lightning strike experiments carried out in a carbon woven composite.     

轨道交通动态客流对轮轨力特征影响研究

为了研究轨道交通动态客流对轮轨力特征的影响,通过对列车实际线路进行试验分析动态客流对列车轮轨力、脱轨系数及频谱特征参数的影响。在线路曲线段位置钢轨上粘贴应变片,获得列车在不同客流工况下通过该区间段时的轮轨力大小,分析比较客流高峰期、客流非高峰期典型工况下轮轨力幅值大小、幅值变化趋势、脱轨系数大小及主频范围与频率变化规律。结果表明：动态客流对轮轨力幅值影响较大,随着客流增大轮轨垂向力幅值增大12.9 %,轮轨横向力幅值增大7.5 %。列车正常运营状态下脱轨系数在0.12～0.16 之间变化,动态客流对脱轨系数影响较小,均在安全行车范围内。动态客流引起轮轨力主频幅值大小变化,钢轨内轨横向力共振频率由175 Hz偏移到155Hz,共振频率出现了偏移,但轮轨力频谱特征趋势基本保持一致。     

A Progressive Damage Model for unidirectional Fibre Reinforced Composites with Application to Impact and Penetration Simulation

The computationally efficient simulation of the progressive damage behaviour of continuous fibre reinforced plastics is still a challenging task with currently available computer aided engineering methods. This paper presents an original approach for an energy based continuum damage model which accounts for stress-/strain nonlinearities, transverse and shear stress interaction phenomena, quasi-plastic shear strain components, strain rate effects, regularised damage evolution and consideration of load reversal effects. The physically based modelling approach enables experimental determination of all parameters on ply level to avoid expensive inverse analysis procedures. The modelling strategy, implementation and verification of this model using commercially available explicit finite element software are detailed. The model is then applied to simulate the impact and penetration of carbon fibre reinforced cross-ply specimens with variation of the impact speed. The simulation results show that the presented approach enables a good representation of the force-/displacement curves and especially well agreement with the experimentally observed fracture patterns. In addition, the mesh dependency of the results were assessed for one impact case showing only very little change of the simulation results which emphasises the general applicability of the presented method.     

平面编织复合材料层压板低速冲击后的压缩失效

采用超声C扫描检测、断口分析、有限元分析等方法研究低速冲击损伤对G803/5224与G827/5224两种平面编织复合材料层压板失效行为的影响。结果表明,低速冲击后压缩载荷作用下,G803/5224层压板最终为剪切分层失效,G827/5224层压板最终为剪切屈曲失效,两种层压板低速冲击后压缩的失效模式与未受损伤层压板基本相同。建立了平面编织复合材料层压板的损伤扩展与失效模型,该模型的计算结果与试验结果吻合较好,可用于平面编织复合材料层压板的失效仿真。     

边界条件对纤维增强复合材料层板高速冲击损伤影响的数值模拟

根据复合材料三维粘弹性本构关系,建立纤维增强复合材料层板高速冲击损伤的有限元分析模型。模型中引入界面单元模拟层间分层,结合三维Hashin失效准则进行单层板面内损伤判断。对数值结果进行分析,得到如下结论:边界四面不带应力层板的损伤面积最大,两个对面带应力层板的损伤面积次之,一面和三面带应力层板的损伤面积最小;边界应力增大而冲击速度不变时,剩余速度基本不变,损伤面积先增大后减小;冲击速度增大而边界应力不变时,剩余速度线性增大,损伤面积先增大后减小。     

Simulation of High Velocity Impact on Composite Structures - Model Implementation and Validation

High velocity impact on composite aircraft structures leads to the formation of flexural waves that can cause severe damage to the structure. Damage and failure can occur within the plies and/or in the resin rich interface layers between adjacent plies. In the present paper a modelling methodology is documented that captures intra- and inter-laminar damage and their interrelations by use of shell element layers representing sub-laminates that are connected with cohesive interface layers to simulate delamination. This approach allows the simulation of large structures while still capturing the governing damage mechanisms and their interactions. The paper describes numerical algorithms for the implementation of a Ladevèze continuum damage model for the ply and methods to derive input parameters for the cohesive zone model. By comparison with experimental results from gas gun impact tests the potential and limitations of the modelling approach are discussed.     

Damage Tolerance of Pre-Stressed Composite Panels Under Impact Loads

An experimental test campaign studied the structural integrity of carbon fibre/epoxy panels preloaded in tension or compression then subjected to gas gun impact tests causing significant damage. The test programme used representative composite aircraft fuselage panels composed of aerospace carbon fibre toughened epoxy prepreg laminates. Preload levels in tension were representative of design limit loads for fuselage panels of this size, and maximum compression preloads were in the post-buckle region. Two main impact scenarios were considered: notch damage from a 12 mm steel cube projectile, at velocities in the range 93–136 m/s; blunt impact damage from 25 mm diameter glass balls, at velocities 64–86 m/s. The combined influence of preload and impact damage on panel residual strengths was measured and results analysed in the context of damage tolerance requirements for composite aircraft panels. The tests showed structural integrity well above design limit loads for composite panels preloaded in tension and compression with visible notch impact damage from hard body impact tests. However, blunt impact tests on buckled compression loaded panels caused large delamination damage regions which lowered plate bending stiffness and reduced significantly compression strengths in buckling.     

表面带金属层的复合材料层合板低速冲击数值模拟

使用Abaqus/Explicit建立表面带金属层的复合材料层合板和复合材料裸板低速冲击有限元模型,与已有文献对比验证结果的可靠性,研究结果对复合抗弹结构有很好的借鉴和参考价值.采用Johnson-Cook本构关系模拟铝合金和钛合金层的力学行为,选用Hashin准则对复合材料层内损伤进行失效判断,用二次应力准则来模拟粘结层Cohesive单元的层间失效.结果表明,相同铺层与冲击能量下,表面带铝合金层合板对内部纤维的保护性能优于表面带钛合金层合板,表面带钛合金层合板的抗冲击性能优于复合材料裸板;[§/0°/90°/0°/90°/0°]s铺层层合板的抗冲击性能优于[§/-45°/90°/0°/45°/-45°]s铺层层合板的抗冲击性能;在子弹刚冲破层合板与子弹完全离开层合板阶段,表面带铝合金层合板对子弹动能吸收率最大.     

微谐振式低速气体流速传感器的有限元模拟

提出一种基于昆虫风速接受器的微谐振式仿生传感器,用以测量低速气体流动.由于设计的复杂性,使用有限元模拟对其进行评估.基于有限元模拟得到流体雷诺数与其绕流无限长梁的粘滞系数的数值关系,从而有助于确定该传感器的线性工作范围.使用有限元模拟进行流体结构耦合分析,得到气体流速与固有频率偏移的数值关系.有限元模拟结果证实当雷诺数小于1时,传感器的输入与输出呈现线性关系,其灵敏度为1.6 Hz/(cm·s-1).     

A Plane-Stress Damage Model for Vectran Laminated Composite

Applied Composite Materials - The aim of this paper is to present a plane-stress damage model based on the Classical Lamination Theory (CLT), developed for polymer fibre-based composite. The...