Material Property Degradation Method Research Articles

Failure analysis of Fiber Metal Laminate channel section column under axial compressive pulse loading

The study aims to analyse the dynamic buckling phenomenon and assess the role of the stress tensor components in the failure process of a short Fiber Metal Laminate column under axial compressive dynamic loading. The investigation is focused on a channel-section profile composed of three aluminium layers and two doubled composite plies [Al/0/90/Al/90/0/Al]. The numerical analysis was performed on the finite element model, which was validated by experimental static buckling tests. Employing a progressive failure algorithm, this analysis incorporated the material property degradation method and Hashin’s criterion as the damage initiation criterion. Failure initiation in metal layers was based on the HuberMises-Hencky failure criterion. Based on the conducted analyses, it was concluded that the dominant forms of destruction in the FML structure are yielding in the metal layers due to excessive compressive stresses and the failure of the matrix in composite plies as a result of compressive and shear stresses. Through a thorough examination of the stress tensor components, critical stresses contributing to aluminum plastic deformation and laminate failure mechanisms were identified.

Stress state failure analysis of thin-walled GLARE composite members subjected to axial loading in the post-buckling range

The paper investigated the load-carrying capacity and the participation of stress components in the failure analysis of top-hat-shaped composite columns subjected to uniform compression. GLARE members were axially compressed in laboratory tests employing a static testing unit. Failure tests were monitored in the full load range using the digital image correlation (DIC) system, which enabled visualization of full-field displacements and strains. Simultaneously, FEM numerical simulations were carried out to estimate the load-carrying capacity of the top-hat-shaped sections based on the nominal stress state in both the non-degraded and degraded composite models. In the latter, the material property degradation method (MPDG) allowed a progressive lowering of the material stiffness based on the presumed damage variables. Failure initiation in composite plies was monitored in FE simulations based on Hashin and Puck failure criteria. Stress state analysis was performed to investigate the participation of stress tensor components in the failure function of selected failure criteria. This enabled the identification of critical stresses contributing to aluminum plastic deformation and intra-laminar failure mechanisms that led to the composite fracture. The results of the numerical simulations were found to be in high agreement with the experimental evidence.

Optimization of open-hole variable stiffness composite plates under tensile loading using curved continuous fibers

This paper describes optimization of variable stiffness composite plates (VSCPs) with open-holes under tensile loading. Curved continuous fibers are used to optimize distributions of fiber orientation and the fiber volume fraction during the optimization for the VSCPs. The modeling of VSCPs is performed by means of fiber trajectories, which are aligned in the direction of maximum principal stress. The progressive failure of the VSCPs is modeled by a material property degradation method, taking into account the variable distributions of material properties to predict the ultimate load. It is demonstrated that the ultimate load for the composite plates is increased using the change in a reinforcement structure and a transition from unidirectional to curvilinear reinforcement of fibers. Thus, application of VSCPs with curved fibers compared with unidirectional composites results in more effective use of composite materials in various fields of industry.

Numerical and experimental post-buckling analysis of slender thin-walled GLARE members subjected to compressive loading

This study deals with a post-buckling analysis of thin-walled GLARE members subjected to axial compressive loading. Considered slender GLARE samples are a hybrid composite that consists of alternating thin layers of aluminium alloy sheets and unidirectional glass fibrereinforced prepregs. Comparative study was performed for different thin-walled, open cross–section members that included channel, Z-shape and top-hat-shaped slender sections. This study is mainly focused on assessing the performance of top-hat-shaped sections which provided the highest strength when subjected to the compressive test. Various layer arrangements of GLARE samples were investigated based on the fibres alignment in the composite layer. GLARE laminates were manufactured by autoclaving technique which provided the high-quality of multi-layered composite. Composite specimens were axially compressed in laboratory tests by means of static testing unit of Instron upgraded with Zwick/Roel control software. Electromechanical strength testing machine had a maximum capacity of 200kN for which applied screw type testing machine provided a displacement control loading. During experimental tests, deformations were measured by Aramis 3D non-contact optical equipment based on digital image correlation (DIC) which allowed investigating columns behaviour in full load range until fracture. The behaviour of thin-walled GLARE members was analysed with the main attention to postbuckling response. Simultaneously, numerical simulations by FEM were performed to predict the post-buckling equilibrium paths of the multi-layered GLARE structures modelled by SHELL element type. The non-linear problem was solved initially by the incremental Newton– Raphson procedure whereby the stiffness matrix was updated with each iteration and equilibrium paths were calculated based on nominal stress state in non-degraded structure. Secondly, the damage evolution law was introduced by the material property degradation method (MPDG). Hence, based on the damage variables the stiffness was gradually reduced in the area where failure was initiated which had a significant impact on the samples’ post-buckling response. Therefore, the influence of damage variables on the laminate's post-buckling equilibrium paths was also considered. For various GLARE lay-ups, numerical results were found to be in a good agreement with experimental tests. Acknowledgments The author has obtained funding as part of financing a doctoral scholarship from the National Science Center, No. UMO-2019/32/T/ST8/00605

A Modeling Method of Continuous Fiber Paths for Additive Manufacturing (3D Printing) of Variable Stiffness Composite Structures

A modeling method of variable stiffness composite structures (VSCSs) with curved fiber trajectories has been developed. The fiber trajectories are aligned in the direction of maximum principal stress, and the VSCSs with variable fiber orientation and the variable fiber volume fraction are modeled on the basis of these trajectories. A material property degradation method taking into account the heterogeneity of material properties of the VSCSs is used to predict the ultimate load and model the progressive failure for a composite plate with a hole under tensile loading. It is shown that a transition from rectilinear reinforcement to curvilinear results in an increase in the ultimate load of the plate. The opportunity for simulation of a continuous fiber path for the VSCSs is presented, and the path could be used to produce the VSCSs by additive manufacturing (3D printing).

Damage analysis of thin-walled GLARE members under axial compression – Numerical and experiment investigations

This paper presents an investigation of the progressive damage and failure behaviour of thin-walled Glare – Fibre Metal Laminate (FML) short columns subjected to in-plane compressive loading. The study concerns 7-layered top-hat-shaped open cross-section members that consist of aluminium and angle-ply composite plies. The compression tests were conducted by means of an ultimate static testing strength machine with displacement control loading, whereas wall deflections were monitored by a Digital Image Correlation (DIC) system Aramis®. Laboratory procedures also included ultrasonic non-destructive testing to assess the quality of specimens produced by the autoclave technique. Failure tests were compared with FE simulations with the implementation of the progressive failure algorithm. Based on the material property degradation method (MPDG) and Hashin failure criterion, damage variables were used to control material stiffness reduction after damage initiation. Progressive failure assessment of top-hat members by FEM included an attempt to estimate the post-buckling equilibrium paths and failure loads that were found to be in a good agreement with experiment evidence. High consistency of numerical and experiment damage modes was also achieved.

A literature review of failure prediction and analysis methods for composite high-pressure hydrogen storage tanks

With the development of hydrogen fuel cell vehicles, the on-board hydrogen storage technology with safety, efficiency and economy has become a fundamental part. Low cost, light weight and good safety performance are required for the on-board hydrogen storage tanks. The composite high-pressure hydrogen storage tank has been recognized as an efficient solution that could address these problems. However, the complex working environment of hydrogen-thermo-mechanism presents challenge to the failure analysis and predictive model establishment of the composite hydrogen storage tanks. The crucial parameters or indicators for tank's failure analysis include burst pressure, damage state and fatigue lifetime, etc. So this paper gives a comprehensive review on the failure behavior analysis methods and prediction models of composite high-pressure hydrogen storage tanks from the literature. First, the failure analysis methods of composite high-pressure hydrogen storage tanks are summarized. Second, the latest literature regarding failure mode predictive methods and models of type III and type IV tanks are reviewed. The different failure criteria are compared and summarized, including some new failure criteria. These criteria enable failure analysis methods to obtain the interaction information on the interaction between the microscopic and macroscopic aspects of the composite. Damage evolution model and constitutive model are summarized. The post-initial failure behavior of the composite laminates structure is simulated by the material property degradation method (MPDM), especially the continuum damage mechanics (CDM) in conjunction with commercial finite element (FE) analysis method. The process of progressive failure analysis of composite tank is summarized as a reference for subsequent failure analysis. The future work of progressive failure analysis should focus on the initial failure of the composite material and microscopic failure mechanisms. The burst, fiber damage and fatigue life are the mainly investigated failure modes for type III composite hydrogen storage tank. For Type IV, the mainly researched failure modes are the collapse and blistering of the liner, burst and damage. The different finite element analysis methods and failure predictive models were classified and summarized. Further improvements were required for the simulation models of full-scale structure of the tank in the working environment or under the complex fiber winding modes. The liner of the type IV cylinder is completely distinct from that of the type III, therefore the behavior of collapse and blistering of the liner needs to be further investigated. The factors that affect collapse and blistering should be explored. The future research need focus on controlling these factors and monitoring the effects of these factors towards structural strength.

A damage model based on the introduction of a crack direction parameter for FRP composites under quasi-static load

Continuum damage mechanics model with consideration of crack direction is developed for the prediction of fracture behavior in fiber reinforced polymer (FRP) composites under quasi-static load. Traditional continuum damage mechanics (CDM) models cannot well predict the crack propagation path in the development state of discrete crack. The crack direction parameter is introduced as a major factor with damage variable for damage propagation and failure analysis. The CDM model, which has the capability to reliably predict the initiation and direction of crack propagation while analysing the multi failure of FRP composites, is proposed by introducing crack direction parameter to material property degradation method. Failure criteria is set up according to the behavior of FRP composites for damage initiation, and fracture-mechanics-based energy release rate criteria is employed for damage evolution. APDL is used to simulate crack propagation, ultimate strength and complex failure behavior of FRP composite structure for this model. Results from the previous researches, when compared with those of this model, showed good agreement, thus demonstrating that proposed methodology can be used for simulation of FRP composite damage failure and strength prediction.

Collapse of channel section composite profile subjected to bending. Part I: Numerical investigations

The paper deals with four-point bending tests of thin-walled channel section beams, made of eight-layer GFRP laminate. In the performed tests two scenarios were investigated: beams were bent in the plane with lowest second moment of area and beams were subjected to bending in the plane passing through the geometrical centre of the flanges of channel section profile and parallel to the plane with the highest second moment of area. Six arrangements of layers were analysed: [0/−45/45/90]S, [90/−45/45/0]S, [90/0/90/0]S, [0/90/0/90]S, [45/−45/45/−45]S, [45/−45/90/0]S. The experimental research was conducted with the use of the ultimate testing machine, additionally designed test stand and the digital image correlation system Aramis®. Numerical analyses have been performed in the Ansys® software, based on the finite element method. In geometrically nonlinear analysis two algorithms, indicating failure mechanisms, were applied: progressive failure analysis with material property degradation method and anisotropic Hill potential theory with assumption of perfect plasticity.

An advanced continuum damage mechanics model for predicting the crack progress process based on the consideration of the influence of crack direction under quasi-static load

In reality the wrong crack path can be generally obtained in the case of arbitrary crack propagation by traditional continuum damage mechanics (CDM). In this paper a novel advanced continuum damage mechanics (ACDM) method is proposed, which can predict the crack propagation and fracture behavior correctly for the structures. The material property degradation method, which is usually used when simulating the structures within the framework of CDM, is advanced based on considering the influence of crack direction. The maximum tensile stress criterion is used to predict the damage initiation and crack propagation direction and the advanced CDM used to predict the damage evolution process in meso-level under the quasi-static load. It can directly evaluate the propagation process of the discrete crack and the fracture strength for structures using the continuum model as well as not using discontinuum model. The algorithm for the application of our advanced CDM theory in the numerical simulation based on finite element method (FEM) is presented. ACDM model is not only a simple and useful model which can easily be used in FEM framework but also a phenomenological model based on the concept of crack propagation. The simulation results by our ACDM are compared with the experiment results and the ones and from cohesive zone method and extended finite element method for good agreements to be achieved.

Progressive failure analysis of thin-walled composite columns subjected to uniaxial compression

The paper deals with estimating the load capacity of thin-walled composite columns with C-shaped cross-section subjected to uniform compression. The discussed columns were made of eight-layer GFRP laminate. Three symmetric arrangements of layers were taken into consideration: [0/−45/45/90]S, [90/0/90/0]S, [45/−45/45/−45]S. The experimental research was conducted with the use of the ultimate testing machine and the DIC system Aramis®. Additionally, the numerical analyses were performed employing the Ansys® software. The numerical calculations were conducted with the implementation of the progressive failure algorithm, based on the material property degradation method and implementation of the Hashn’s criterion as the damage initiation criterion. In all analyzed cases high consistency of numerical and experimental results was achieved and the failure mechanism included the initiation of the fiber failure in the corner of the columns and its propagation in the direction of the web and the flange of the columns.

Micromechanics-based progressive failure analysis of carbon fiber/epoxy composite vessel under combined internal pressure and thermomechanical loading

A progressive failure analysis algorithm based on micromechanics of failure (MMF) theory and material property degradation method (MPDM) is developed, wherein the MMF is used to predict the failure initiation at constituent level and the MPDM is employed to account for the post failure behavior of the damaged materials. The progress of damage is controlled by a linear damage evolution law, which is based on the fracture energy dissipating during the process. This micromechanics-based approach is implemented by a user-material subroutine (UMAT) in ABAQUS, which is sufficiently general to predict the ultimate strength and complex failure behaviors of the composite vessel subject to both high pressure and thermal loading. In addition, the predictions of the model are also compared with those by experiment and traditional finite element analysis.

Continuum damage modeling and progressive failure analysis of carbon fiber/epoxy composite pressure vessel

This paper presents a progressive damage model, which is sufficiently general to predict the ultimate load-bearing ability and complex failure behaviors of the aluminum–carbon fiber/epoxy composite vessel structure. The model is implemented in the commercial finite element software ABAQUS based on the integration of material property degradation method (MPDM) and cohesive element (CE) method. The MPDM is implemented by ABAQUS user subroutine UMAT to model the intralaminar failure of composite laminates, while CEs are employed to simulate the delamination initiation and evolution at the interfaces. The progression of damage is controlled by a linear damage evolution law, which is based on the fracture energy dissipating during the process. In addition, the predictions of the model are also compared with experiments and reasonably good agreements are obtained.

Study on stress concentration in notched cross-ply laminates under tensile loading

This article presents a detailed analysis on stress concentration in notched unidirectional fiber-reinforced composites. Due to the formation of longitudinal splitting at notch tips along the fiber direction, the extremely high stress concentrations ahead of the notch tips could be drastically reduced for composites under remote tension. The inability of the widely used material property degradation method to accurately redistribute the local stresses at the notch tips is examined. The notch blunting effect is investigated by modeling the longitudinal splitting as a thin plastic cohesive layer or debonding, and results for the stress redistribution in the unnotched section directly ahead of the notch tips are presented. By introducing the intra- and inter-ply damage modes, the failure of a double-notched cross-ply laminate is predicted and compared with the experimental results from open literature.

Biaxial tensile-compressive loading of unnotched and open-hole carbon epoxy crossply laminates

Although most tests on composites are conducted uniaxially, they are subjected to multi-axial loads in real-life applications. In this paper, the behavior of unnotched and open-hole unidirectional carbon epoxy crossply laminates under various off-axis biaxial tension-compression loadings is studied using a mixed experimental and numerical approach. Strain measurements made using digital image correlation technique in cruciform test specimens show overall good correlation with finite element predictions based on the micromechanics of failure theory and material property degradation method. It is shown that an aligned mesh concept where element edges are aligned with ply fiber direction is necessary for accurate prediction of progressive failure patterns. The finite element model is shown to be capable of predicting critical and sub-critical damage mechanisms governing failure in these laminates. Furthermore, the detrimental effect of off-axis loading and the introduction of an open-hole in carbon epoxy crossply laminates under the biaxial loading are investigated quantitatively.

Strength prediction and progressive failure analysis of carbon fiber reinforced polymer laminate with multiple interacting holes involving three dimensional finite element analysis and digital image correlation

Composites are finding lot of applications in aerospace, automobile and many other sectors due to their high strength to weight ratio and longer fatigue life. For assembly or electrical wiring purposes, often hole(s) are drilled into the laminate thereby reducing its strength. The strength prediction and damage mechanics study is of great importance in such structural applications. In this work, a three-dimensional finite element based progressive damage model (PDM) is presented for unidirectional carbon fiber reinforced polymer (CFRP) laminates having two holes in different configurations subjected to tensile loading. The developed model is suitable for predicting failure and post failure behavior of fiber reinforced composite materials. The material is assumed to behave as linear elastic until final failure. The three broad steps involved in this study are stress analysis, failure analysis and damage propagation which are implemented as a PDM involving finite element analysis. Hashin’s failure criteria for unidirectional fiber composite is used for the damage prediction. It utilizes a set of appropriate degradation rules for modeling the damage involving material property degradation method. Digital image correlation (DIC) experiment is also carried out to perform whole field strain analysis of CFRP panel with different hole configurations. Whole field surface strain and displacement from finite element prediction are compared with DIC results for validation of the finite element model. Load–deflection behavior as well as path of damage progression is predicted by both PDM simulation and experiment. They are found to be in good agreement thereby confirming the accuracy of PDM implementation. Effect of spacing between the holes on stress concentration factor (SCF) is also further investigated.

EXPERIMENTAL AND COMPUTATIONAL STUDIES ON PROGRESSIVE FAILURE ANALYSIS OF NOTCHED CROSS-PLY CFRP COMPOSITE

This work presents experimental and computational studies on progressive failure analysis of notched cross-ply carbon fiber reinforced polymer (CFRP) composite. The carbon/epoxy composite laminated with [90/0]s layup is tested using double-notched specimens loaded in tension. The load-displacement curve, failure load and damage patterns of all tested specimens are discussed. In addition, a numerical analysis approach based on material property degradation method (MPDM) and cohesive elements (CE) is illustrated to capture complex failure mechanisms and damage progression as observed in the tested specimens. The MPDM is used to model the in-plane failure of 90° plies and 0° plies while the cohesive elements are used to account for the delamination at the [90/0] interfaces. Different progressive failure models employing fracture mechanics, continuum mechanics and micromechanics of failure are presented based on the MPDM-CE approach. The failure analyses by these progressive models are performed and their predictions are compared with the experimental results of notched [90/0]s CFRP composite. Reasonably good agreement between experimental results and simulation results is obtained and it is shown that the MPDM-CE approach can effectively predict the progressive failure of double-notched [90/0]s composite laminate.

Progressive Failure Analysis of Scaled Double-Notched Carbon/Epoxy Composite Laminates

This article presents progressive failure analysis of double-notched carbon/epoxy composite laminates with different scales. A numerical analysis strategy based on material property degradation method (MPDM) and cohesive elements (CE) is developed to model progressive failure of scaled double-notched composite laminates, where the material property degradation method is used to model the intralaminar failure and the cohesive elements are employed to account for the delamination at the interfaces. Different failure theories are considered in the material property degradation method–cohesive element approach and a comparative study of these failure theories is presented. The mesh dependency of the material property degradation method–cohesive element approach is investigated with different notch and element types for the double-notched composite laminates. Size scaling effects are also studied by traditional fracture models and the material property degradation method–cohesive element approach, significantly revealing a trend in strength reduction of notched composites with increasing specimen size. The predictions are compared with the experimental results and reasonably good agreement is observed.

Failure Progression and Mesh Sensitivity Analyses by the Plate Element-Failure Method

Despite the fact that fiber-reinforced composite materials have been extensively used in aerospace, defense and marine structures for many years, the high stiffness and strength properties of these materials have not yet been fully exploited. In many instances, overly rigid adherence to conservative design rules based on ‘black aluminum’ (symmetric quasi-isotropic graphite-epoxy laminates) has eroded these advantages significantly. Efforts to better understand the failure mechanisms and develop efficient and robust computational tools will lend more confidence to designers and engineers to realize better weight savings and improve damage tolerance. The search for efficient computational tools for the modeling of progressive damage in composites should be coupled with sufficient fidelity to ensure that the mechanisms of the complex failure modes are accurately represented. In an effort towards this goal, the authors have proposed the element-failure method (EFM) using 3D solid finite elements, which has been successfully applied to failure analysis of composite laminates. The EFM has advantages over the traditional material property degradation method (MPDM) because the stiffness matrix of the element is not changed, thereby improving computational convergence and saving in computational efforts. In this article, a plate element-based EFM (PEFM) is presented for modeling progressive damage in fiber-reinforced composites. The implementation in plate elements further improves the efficiency of computation, when compared to analyses with 3D elements. In conjunction with several different failure theories, the plate EFM is applied to model progressive damage in quasi-isotropic composite laminates with open-holes, subjected to remote tensile loading. A mesh sensitivity study shows that the EFM results are relatively independent of mesh size effects. When compared with experimental data, the predicted ultimate strengths and damage patterns show good agreement.