Multicontinuum Failure Analysis of Composite Structural Laminates

Damage in a composite typically begins at the constituent level and may, in fact, be limited to only one constituent in some situations. Accurate predictions of constituent damage at points in a laminate provide a genesis for progressively analyzing failure of a composite structure from start to finish. In this article we develop an efficient constituent-based failure analysis for composite structural laminates. Continuum-based (phase-averaged) constituent stress and strain fields are computed in a finite-element environment without a computational time penalty. Constituent stress-based failure criteria are developed and used to construct a progressive failure algorithm in which one constituent is allowed to fail while the other constituent remains intact, e.g., matrix cracking. The proposed failure algorithm was used to predict failure of a variety of laminates under uniaxial and biaxial loads. The results were shown to be superior to comparable single-continuum failure analyses and in good agreement with experimentally determined failure loads.     

平面编织复合材料层压板的冲击失效行为

对复合材料层压板进行不同能量的落锤冲击试验,根据凹坑深度将冲击损伤分为无损伤、目视不可检、目视可检与穿透损伤4个等级。通过C-扫描检测、热揭层、损伤截面观察等方法,研究了不同等级损伤的失效特征、失效模式与失效过程。结果表明,不同等级损伤的失效模式不同,目视不可检损伤主要为分层失效,目视可检损伤主要为分层与基体开裂,穿透损伤主要为纤维断裂。损伤达到穿透前后的失效过程也存在差异。     

Simulating Initial and Progressive Failure of Open-Hole Composite Laminates under Tension

A finite element (FE) model is developed for the progressive failure analysis of fiber reinforced polymer laminates. The failure criterion for fiber and matrix failure is implemented in the FE code Abaqus using user-defined material subroutine UMAT. The gradual degradation of the material properties is controlled by the individual fracture energies of fiber and matrix. The failure and damage in composite laminates containing a central hole subjected to uniaxial tension are simulated. The numerical results show that the damage model can be used to accurately predicte the progressive failure behaviour both qualitatively and quantitatively.     

Ultimate Failure of Defective Pipelines Reinforced with Composite Repair Systems

Journal of Failure Analysis and Prevention - This paper presents a numerical model describing a corrosion-defect-containing pipeline subjected to internal pressure, including the FRP layer, the...     

Damage Model and Progressive Failure Analyses for Filament Wound Composite Laminates

Recent improvements in manufacturing processes and materials properties associated with excellent mechanical characteristics and low weight have made composite materials very attractive for application on civil aircraft structures. However, even new designs are still very conservative, because the composite failure phenomenon is very complex. Several failure criteria and theories have been developed to describe the damage process and how it evolves, but the solution of the problem is still open. Moreover, modern filament winding techniques have been used to produce a wide variety of structural shapes not only cylindrical parts, but also “flat” laminates. Therefore, this work presents the development of a damage model and its application to simulate the progressive failure of flat composite laminates made using a filament winding process. The damage model was implemented as a UMAT (User Material Subroutine), in ABAQUS^TM Finite Element (FE) framework. Progressive failure analyses were carried out using FE simulation in order to simulate the failure of flat filament wound composite structures under different loading conditions. In addition, experimental tests were performed in order to identify parameters related to the material model, as well as to evaluate both the potential and the limitations of the model. The difference between numerical and the average experimental results in a four point bending set-up is only 1.6 % at maximum load amplitude. Another important issue is that the model parameters are not so complicated to be identified. This characteristic makes this model very attractive to be applied in an industrial environment.     

Failure Analysis of Bolted Joints in Cross-ply Composite Laminates Using Cohesive Zone Elements

A strength prediction method is presented for double-lap single fastener bolted joints of cross-ply carbon fibre reinforced plastic (CFRP) composite laminates using cohesive zone elements (CZEs). Three-dimensional finite element models were developed and CZEs were inserted into subcritical damage planes identified from X-ray radiographs. The method makes a compromise between the experimental correlation factors (dependant on lay-up, stacking sequence and joint geometry) and three material properties (fracture energy, interlaminar strength and nonlinear shear stress-strain response). Strength of the joints was determined from the predicted load-displacement curves considering sub-laminate and plylevel scaling effects. The predictions are in a reasonable agreement with the experimental data.     

复合材料层合板机械连接处失效过程的数值模拟

考虑了损伤累积、刚度退化和破坏准则,研究了带孔洞复合材料层合板受面内载荷作用的失效过程.应力分析建立在三维有限元模型基础上,借助有限元商业软件ANSYS中的参数化设计语言APDL,考虑材料损伤累积和刚度退化,采用迭代算法,实现了层合板机械连接处的破坏过程模拟.为验证三维有限元模型的有效性,将模拟计算得到的孔边应力分布与文献中的结果进行了比较,两者十分吻合.进一步计算了层合板的位移一挠度曲线,并与实验结果进行了比较,验证了数值模拟的正确性.     

Stress and Failure Analysis of Composite Laminates with an Inclusion under Multiaxial Compression-Tension Loading

The present paper investigates the failure of orthotropic laminates with a filled hole subjected to biaxial compression-tension loading. This is an idealised case that simulates a situation where the impact damaged laminate has been repaired by drilling a hole and then plugging the hole with a perfect-fit core made of a dissimilar material. The exact stress distribution in the laminate has been determined using the complex variable mapping method. These stresses are then employed in a fracture mechanics failure model to predict the failure load of a laminate with a filled hole under in-plane compression-dominated multi-axial loading. Failure strength predictions are compared to open hole results and experimental data.     

Acoustic Emission in Composite Laminates

The response of a laminated plate to internal acoustic emission events is examined in detail. The plate consists of four layers of a unidirectional fiber composite material arranged in a cross-ply configuration. The sources considered include a vertical line couple, a horizontal line couple and a line double couple without moment. The latter is produced by the combination of two equal and opposite line couples and may be associated with a shear dislocation in the plane of the laminate. The particular response presented here is that of the normal upper surface displacement. Four different orientations of the line sources relative to the core fiber direction are considered. The sources may be located at any depth within the plate and results are shown for three locations, namely, the upper interface, the midplane and the lower interface. The receiver is positioned on the upper surface at a known distance from the line of action of the source. When this distance is small relative to the depth of the plate, it is possible to associate some of the peaks and troughs present in the response with the arrival of individual rays. At larger distances, the disturbance arises from the propagating Rayleigh Lamb modes.     

织物-树脂复合材料层压板的准静态侵彻机理

本文利用MTS得到了芳纶和高强维纶织物复合材料层压板受尖头侵彻体穿孔的准静态侵彻曲线 ,比较和分析了不同类型纤维集合体与热固性树脂和热塑性树脂复合材料的破坏模式 ,并考察了芳纶织物复合材料层压板侵彻的逐步破坏过程 ,揭示了复合材料层压板的准静态侵彻机理。     

Identification of Elastic Properties of Composite Laminates

This article is focused on application of the response surface method (RSM) for solution of structural identification problems. The approximating functions are obtained from the data of deterministic numerical experiment. The numerical experiment is performed in the sample points of experiment design. A minimal mean squared distance Latin hypercube (MMSDLH) design is used in the present paper. For building the response surfaces, a local approximation method is employed. An example of application of the response surface method and experiment design for identification of elastic properties of laminated composite material is discussed. Elastic properties of carbon/epoxy laminate are determined employing the experimentally measured eigenfrequencies of composite plates. The identification functional represents differences between experimentally measured and numerically calculated frequencies, which are dependent on variables to be identified. The identification parameters are five elastic constants of material. The elastic constants identified from vibration test have been compared with the values obtained from independent static test. Good agreement of the results is observed.     

On the Viscoelastic Response of Composite Laminates

The present work deals with the determination of theviscoelastic properties of composite laminates based on the viscoelasticbehaviour of the single lamina. A viscoelastic lamination theory isdeveloped assuming that the lamina stiffness matrix is fully complex andfrequency dependent.For the measurement of the complete setof frequency dependent viscoelastic properties of the single lamina(i.e. complex moduli and Poisson's ratio) a new methodology has beenintroduced, based on the free and forced vibration of unidirectional and[45/–45] _ns composite laminates.Allmeasurements have been performed both in air and in vacuum. Since thevibration amplitude was very small, in order to fulfil linearityrequirements, the results do not show any significant difference due toair damping.The effects of experimental errors on theevaluation of the viscoelastic properties of the single lamina have alsobeen discussed.     

复合材料层板在疲劳下的剩余刚度衰退理论

本文根据实验规律,将复合材料层板的性能参数视成随机变量,提出了一个剩余刚度的衰退理论。建立了剩余刚度分布函数公式,给出了剩余刚度和剩余强度以及寿命的关系,并用试验进行了验证。     

复合材料层合矩形板非线性湿热振动

在考虑湿热影响的基础上，研究了复合材料层合矩形板的非线性湿热振动，并讨论分析了湿度、温度、长宽比对复合材料层合矩形板非经性固有振动周期的影响。     

仿生层状复合材料研究概况

从仿生的角度介绍了仿生复合材料尤其是层状复合材料的设计原理，制备方法，主要研究内容和现状。指出了仿生复合材料的应用前景和今后的发展方向。     

Characterization of Nonlinear Behavior in Woven Composite Laminates

Nonlinear stress–strain behavior in woven glass/epoxy laminates under off-axis tension has been investigated experimentally. The validity of an orthotropic plasticity model of such behavior, with three parameters, is discussed. The parameters have been determined from the experimental results. An attempt is also made to describe the nonlinear behavior of the woven composite as a cross-ply laminate using assumed unidirectional composite properties. The nonlinear behavior of the unidirectional laminate is assumed to be described by the one-parameter plasticity model. It is shown that there is a possibility that the one-parameter plasticity model can be used to predict the nonlinear behavior of woven composites.     

Design and Ballistic Performance of Hybrid Composite Laminates

This paper presents an initial design assessment of a series of novel, cost-effective, and hybrid composite materials for applications involving high velocity impacts. The proposed hybrid panels were designed in order to investigate various physical phenomenon occurring during high velocity impact on compliant laminates from a previous study on Dyneema® and Spectra®. In the first, screening phase of the study twenty different hybrid composite laminates were impacted with 20 mm Fragment Simulating Projectiles at 1 km/s striking velocity. The best performing concepts were put forward to phase II with other hybrid concepts involving shear thickening fluids, commonly used in low velocity impacts. The results indicated that it is possible to design hybrid laminates of similar ballistic performance as the reference Dyneema® laminate, but with lower material costs. The optimal hybrid concept involves a fibre reinforced Polypropylene front and a Dyneema® backing.     

一个适合于复合材料层合板分析的应力杂交单元

本文根据修正的余能变分原理构造了一个适合于复合材料层合板特点的三角形单元。此单元能够考虑横向剪切变形的影响和局部扭曲效应。三角形单元的三个顶点取为节点,每个节点具有5个自由度,三个位移自由度,二个转角自由度。文中用此单元计算了几种层合板的固有频率,并将结果与解析解进行了比较。计算表明,此单元计算精度较高,应用方便。