Composite Damage Model Research Articles

Nonlocal dynamic damage modelling of quasi-brittle composites using the scaled boundary finite element method

In this contribution, a nonlocal approach is proposed to model the dynamic damage of quasi-brittle composites within the framework of the scaled boundary finite element method (SBFEM). The image-based quadtree decomposition is used to automatically achieve multi-level mesh of a domain with geometric as well as material discontinuities. By enforcing a 2:1 balanced condition, only limited types of S-domains are used. Owning to the salient capability of the SBFEM in constructing polygons with arbitrary edges and nodes, there is no extra burden on dealing with hanging nodes between neighbouring S-domains in different sizes. Furthermore, the strain modes and the original stiffness matrix of each S-domain and the weighting matrix for nonlocal formulation are all pre-computed initially and extracted in subsequent time steps. Consequently, the computational efficiency of the proposed approach is considerably accelerated. The mesh dependence is well eliminated by using an integral-type nonlocal model. Several benchmarks are simulated to demonstrate the efficiency, robustness and variability of the proposed approach for macroscale and mesoscale problems. It is found that the proposed method can model multiple crack propagation and crack branching as well. Compared with the case under static load, the failure mode of quasi-brittle materials under dynamic load depends not only on the strength of each component but also on the propagation of stress wave.

Meso-FE modelling of textile composites and X-ray tomography

Among the recent advances made in the analysis and simulation of the mechanical behaviour of composite materials, calculations on a mesoscopic scale make it possible to take into account the internal architecture of a textile and to compute its deformations. The mesoscopic analysis covers the reinforcement behaviour during manufacturing (draping and permeability) and performance in-service (response to applied loads and strains, including damage development). X-ray tomography (lCT) is a tool well suited for determining the 3D internal geometry of the composite. The current characteristics of the lCT devices allow micrometrescale characterization, providing high-quality geometrical models. The paper presents an overview of lCT-based meso-modelling of textile composites, illustrated by novel modelling results. It covers two segmentation methods (structural tensor and texture analysis), models of the behaviour (deformation response) at meso-scale of textile reinforcements and damage models for textile composites. A set of cases is analysed where X-ray tomography provides the definition of the initial models and the validation of the results obtained by mesoscopic analysis.

Strain-softening composite damage model of rock under thermal environment

To ensure the safe and effective application of deep geotechnical engineering, it is necessary to establish a suitable constitutive model of the rocks in thermal environment, including geothermal energy mining, and deep geological treatment of nuclear waste and tunnel fire. A strain-softening damage model of the rocks with defect growth is established based on damage evolution. According to the change in the tangent modulus from the compression phase to the elastic stage, we established a constitutive model reflecting the nonlinearity characteristics of the compression phase. According to the change in the energy conversion, the energy consumption coefficient is introduced to describe the deformation characteristics of the rocks when the residual stress is reached. The specific physical meaning and the calculation method of the energy consumption coefficient are given to correct the shortcomings of the evolution of the damage variable. We then analyzed the relationship between parameters in the constitutive model of the rocks at high temperature and normal temperature. Based on the constitutive model of the rocks at normal temperature, we established a constitutive model reflecting the influence of high temperature. Finally, the established model fit the stress-strain curves of several kinds of the rocks at different temperatures and generated desired results. The established model can be used to describe the stress-strain curve characteristics of the rocks at different temperatures.

Simulation of edge impact and compression after edge impact in CFRP laminates

This paper presents the application of a composite damage model to predict the edge impact and compression after edge impact (CAEI) response of CFRP laminates. First, a mesh sensitivity analysis is performed showing that the mesh needs to be sufficiently fine to accurately capture the permanent out-of-plane deformation at the impact location, which acts as the initiation site that induces laminate compressive failure at early stages in the deformation process. The simulations of edge impact are correlated with the impactor load-displacement data, impact area, and visible crack length data available in the literature. The experimentally measured stress-displacement curves are used to validate the residual strength predictions. The shape and size of the damage inflicted by the edge impact events on different laminates is well predicted, as well as the residual strength of the laminates subjected to CAEI. The model proposed can accurately capture stacking sequence effects, predicting significant changes in the shape of the damaged area when only the stacking sequence changes, in agreement with the experimental observations.

A micromechanics based elasto-plastic damage model for unidirectional composites under off-axis tensile loads

Nonlinear properties of composite materials are essential for their engineering application. In this work, a three-phase micromechanics bridging model is employed to evaluate the nonlinear behavior of a composite from properties of fiber, matrix and interphase. It is assumed that the matrix elastoplasticity and the interface damage are two major sources of the nonlinearity. The former is described by the J2 flow rule. The latter is approximated by an interphase with stiffness degradation. For an interphase, an equivalent damage stress is introduced to account for the effect of normal and shear stress on the interface damage growth. Further, an explicit empirical equation is developed to relate the equivalent damage stress and the stiffness degradation of an interphase. The present elasto-plastic damage model is validated by comparing with experimental data of a series of composites under off-axis tensile loads.

Multiscale ceramic matrix composite thermomechanical damage model with fracture mechanics and internal state variables

This work presents a multiscale damage model that accounts for ceramic matrix composite (CMC) length scale dependent behavior, including scale-specific brittle matrix damage initiation and propagation. Internal state variable theory is implemented to obtain the stress–strain constitutive relationship for damaged ceramic matrix material using damage variables which capture the effects of matrix cracking and nucleation and growth of matrix porosity. Matrix cracking is modeled using a damage variable determined using fracture mechanics and the self-consistent scheme. This methodology provides an effective way to model the effects of matrix cracks which initiate when stress intensity factors exceed the fracture toughness of the material, and whose growth is governed by crack growth kinetics. An additional source of material nonlinearity, matrix porosity, occurs as a result of material diffusion around grain boundaries and is related to the material entropy dissipation. These effects are captured using a porosity state variable that is explicitly related to the volumetric strain. The nonlinear predictive capabilities of the material model are demonstrated for monolithic silicon carbide, unidirectional (UD) carbon fiber/silicon carbide matrix (C/SiC) CMC, and five-harness satin (5HS) woven C/SiC CMC. The model predictions are in excellent agreement with experimental observations for 2D woven C/SiC CMCs from literature.

A modified composite fatigue damage model considering stiffness evolution for wind turbine blades

Proper fatigue life prediction is very essential for the safety of structural design, operation, and maintenance. This paper presents a modified composite fatigue damage model considering stiffness evolution aimed at simulating the three periods of damage development. The proposed model containing two parameters avoids the trouble and complexity of multiparameter. Meanwhile, the stiffness degradation model and the life prediction model of two-stage loading have a good agreement and high fitting accuracy with experiment data considering different types of composites. For better assessment, four existing models are also compared, demonstrated that the values predicted by the modified model are much closer to the experimental data upon most occasions. Moreover, this model is applied to the fatigue test of a full-size wind turbine blade to show its availability and future prospect on real-time monitoring in service.

A novel mesoscopic progressive damage model for 3D angle-interlock woven composites

In this paper, a novel mesoscopic progressive damage model is proposed to investigate the effective properties and damage mechanisms of 3D angle-interlock woven composites. The damage activation is based on the three-dimensional version of Puck criterion. Given that there may be multiple cracks in the transverse direction of the fiber yarns, a set of fracture angle-dependent damage variables are introduced to eliminate the stress abnormal phenomenon. In addition, an innovative exponential damage evolvement scheme, based on the equivalent displacement and stress, characteristic element length and fracture toughness, is proposed to govern the damage variables. Furthermore, a representative mesoscopic volume cell model, accounting for the fluctuation, distortion and actual cross-section size of fiber yarns, is constructed to represent the realistic interlaced architecture of the woven composites. The anisotropic damage model is applied to investigate the failure behavior of the 3D woven composites subjected to uniaxial tensile loading along the warp and weft directions. Some typical quasi-static tension experiments are performed to validate the accuracy of the simulations. The numerical predictions including failure strength and damage accumulation process are coincident with the corresponding experimental results.

Assessment of the load carrying performance of composite cross joints

Composite cross joints are common structures in an airframe. When this type of joint is used on an air inlet stiffened structure, it will undertake large bending moment, especially under overpressure of the engine. In this paper, two types of cross joints are tested experimentally and simulated to investigate the load bearing characteristics and make comparative remarks. Four-point bending tests are conducted and the load deflection curves are obtained; besides, the damage pattern of the joints is reported. Based on composite progressive damage model, the numerical simulations have a good agreement with experimental results, revealing the joint failure mechanism and fastener force feature of various joints. The comparative assessment of two types of joints is summarized.

A progressive damage model for three-dimensional woven composites under ballistic impact loading

Ballistic impact damage of three-dimensional woven composites have not been sufficiently studied. Numerical and experimental methods were used to evaluate the ballistic penetration behavior of three dimensional woven carbon fiber reinforced composites in this paper. A one-stage light gas gun apparatus was employed to conduct impact tests. Based on the nonhomogeneous elements method, a finite element model considering the strain rate effect of the matrix was established to analyze the damage mechanisms of 3D woven composites subjected to ballistic impact loading. The speed history and acceleration history of the projectile were obtained during the impact, as well as the damage process of fiber yarns and the matrix. The simulation results showing good agreement with experimental observations, in terms of damage patterns, residual velocities and damage morphology. The results show that the finite element model in this paper is reasonable for ballistic performance design of 3D woven composites.

Progressive damage modeling and optimization of fibrous composites under ballistic impact loading

Failure prediction modeling and optimization of composite structure under impact loading is reported in the paper. A methodology is presented to optimize the composite laminate subjected to impact loading considering fiber arrangement as a design variable and residual velocity as an objective function. The fitness function is evaluated using ABAQUS/Explicit that works on the continuum damage mechanics model. The damage behavior of composites obtained through this model is validated with simulation and experiments. The results show a substantial impact of fiber arrangement on residual velocity, penetration, energy absorption capacity and ballistic limit of the plate.

The crashworthiness prediction of 2D triaxially braided composite fuselage frame under transverse impact load

The fuselage frame, an apron construction of the typical transport aircraft fuselage, manufactured with carbon fibre/epoxy 2D triaxially braided composites, hinders the crashworthy aircraft analysis and design for the complicated failure behaviour under transverse impact loading. To capture the intricate details, the crashworthiness performance is investigated and compared with different damage models including enhanced composite damage model, composite failure shell model and laminated composite fabric model. Based on the continuum damage mechanics and irreversible thermodynamics, the progressive failure behaviour is implemented to predict the damage behaviour. The damaged constitutive equations with damage state variables and Hashin’s criteria are adopted. Results show that the presence of non-physical parameters in the damage models make it challenging to predict the peak and post-peak responses using enhanced composite damage model and composite shell failure models. The laminated composite fabric model demonstrates good functionality to capture the failure sequences and the load response of the frame under transverse impact loading.

Establishment and damage analysis for steel deck pavement composite beam fatigue model

Different from high-grade asphalt pavement, steel bridge thin layer pavement share traffic load with orthotropic steel deck pavement and its fatigue damage is related to the latter. Based on deformation characteristics of orthotropic steel deck pavement, we established a corresponding composite beam fatigue test model. Based on damage mechanics, we put up with a steel bridge composite beam fatigue damage model. Through steel deck pavement composite beam fatigue experiments, composite beam fatigue damage equation was established. Results show that the fatigue damage test model can well reflect local mechanics response of steel deck pavement; composite beam made of different paving materials have different damage rules: stiffening pavement system has the smallest fatigue damage rate, modified asphalt SMA has the biggest fatigue damage rate and epoxy asphalt concrete has a middle level.

Progressive damage modelling and experimental investigation of three-dimensional orthogonal woven composites with tilted binder

This paper investigates the tensile properties of 3D orthogonal woven carbon fiber composites with tilted binder by experiment and simulation. The tensile failure strain and fracture mode of this composite show distinguished discrepancy with idealized 3D orthogonal woven composites experimentally. In order to explain this specific failure mechanism, a unit cell finite element model incorporated with damage models of constituents is established to reproduce the damage initiation and propagation of 3D orthogonal woven composites with tilted binder during tensile test. A three-dimensional failure criterion based on Hashin's criterion and Pinho's criterion is utilized to describe the progressive damage of yarns, while the non-linear behavior of the matrix is predicted by Drucker-Prager yield criterion. Besides, a traction-separation law is applied to predict the damage of yarn-matrix interface. The proposed unit cell model is correlated and validated by global stress–strain curves, DIC full-field strain distributions and modulus history curve. The damage evolution process of 3D orthogonal woven carbon fiber composites with tilted binder, including fiber tow failure, matrix cracking, and interfacial debonding, is recorded and investigated by the modulus history curve from simulation.

Numerical modeling of high velocity impact in sandwich panels with honeycomb core and composite skin including composite progressive damage model

In this paper, a numerical model is developed to simulate the ballistic impact of a projectile on a sandwich panel with honeycomb core and composite skin. To this end, a suitable material model for the aluminum honeycomb core is used taking the strain-rate dependent properties into account. To validate the ballistic impact of the projectile on the honeycomb core, numerical results are compared with the experimental results available in literature and ballistic limit velocities are predicted with good accuracy. Moreover, to achieve composite skin material model, a VUMAT subroutine including damage initiation based on Hashin’s seven failure criteria and damage evolution based on MLT approach modulus degradation is used. To validate the composite material model VUMAT subroutine, the ballistic limit velocities of the projectile impact on the composite laminates are predicted similar to the numerical results presented by other researchers. Next, the numerical model of the sandwich panel ballistic impact at different velocities is compared with the available experimental results in literature, and energy absorption capacity of the sandwich panel is predicted accurately. In addition, the numerical model simulated the sandwich panel damage mechanisms in different stages similar to empirical observations. Also, the composite skin damages are investigated based on different criteria damage contours.

Thermodynamical consistency of an anisotropic meanfield damage model for SMC composites

AbstractThis contribution investigates the thermodynamic consistency of a meanfield damage model published by the authors [1]. The model is based on an empirical description of the fiber orientation distribution function (FODF). Due to a combination of matrix damage and fiber‐matrix interface debonding, the model is able to predict the inhomogeneous and anisotropic evolution of the overall behavior of the considered Sheet Molding Compound (SMC) composite.

A microscale energy-based fatigue damage model for unidirectional composites under multiaxial loading at different stress ratios

The off-axis fatigue behavior of unidirectional composites has been studied using an energy based model. The fatigue model is based on average stresses in fiber and matrix derived from a micromechanical approach. Different fatigue damage modes are identified on the basis of physical interpretation of the driving forces defined from Continuum Damage Mechanics. The model is able to distinguish between damage in fiber and matrix and predict the residual stiffness in transverse and longitudinal direction. The proposed model is verified and validated by studying the fatigue behavior of unidirectional carbon/epoxy and glass/epoxy laminates under non-negative mean stresses. The predictions are in good agreement with the experimental data regardless of stress ratio, stress level and fiber orientation.

A hysteresis energy dissipation based model for multiple loading damage in continuous fiber-reinforced ceramic-matrix composites

In this paper, a hysteresis energy dissipation based damage model for fiber-reinforced ceramic-matrix composites (CMCs) subjected to multiple loading stress levels is developed. Considering the combination effects of multiple loading sequences and multiple fatigue damage mechanisms, i.e., matrix cracking, fiber/matrix interface debonding and interface wear, the evolution of the fiber/matrix interface debonding and sliding, fatigue hysteresis loops, fatigue hysteresis dissipated energy and fatigue hysteresis modulus changing with increasing applied cycles are analyzed. The effects of fiber volume fraction, matrix crack spacing, fatigue peak stress and fatigue stress range on the damage development inside of CMCs are discussed. The difference of the fiber/matrix interface shear stress existed between the interface wear region and new interface debonded region affects the fiber/matrix interface debonded length and loading carrying ability of intact and broken fibers. The damage evolution for C/SiC and SiC/SiC composites subjected to multiple fatigue loading sequences are predicted using the hysteresis energy dissipation damage model. Under multiple loading stress, the fatigue hysteresis dissipated energy increases when high peak stress and stress range increases due to the increase of fiber/matrix interface sliding range. However, when the low peak stress increases, the evolution of fatigue hysteresis dissipated energy depends on the interface debonding and sliding state.

A progressive damage model for 3D woven composites under compression

A progressive damage model is proposed to investigate the damage initiation and evolution of 3D woven composites under uniaxial compression at a micromechanical level. The typical compressive experiments were carried out. Based on the observations, the compression failure modes of 3D woven composites mainly include fiber kinking, transverse failure of fiber tow, matrix fracture, and interfacial debonding. The initial damage criteria are according to the physically based failure criteria for the fiber kinking, the Puck criteria for the transverse failure of fiber tow, and the maximum stress criterion for the matrix. The damage of fiber tow–matrix interfacial is simulated through cohesive contact. Particularly, the fiber’s initial misalignment angle is taken into account in the damage model. The simulated compression results agree well with the experimental ones. The compressive stress–strain response of the 3D woven composite is forecasted. The damage evolution of each constituent of the 3D woven composite is obtained. The results show that the influence of the fiber’s initial misalignment angle on the compression strength of the 3D woven composite needs to be considered.

Meso-scale progressive damage modeling and life prediction of 3D braided composites under fatigue tension loading

3D braided composites have broad potential applications in the high-tech industries because of their superior mechanical properties. Fatigue is an essential design factor for their use in those engineering applications. The fatigue damage accumulation during cyclic loading should be involved in the numerical models in order to predict the fatigue life accurately. In this paper, a unit-cell based finite element model in conjunction with continuum damage mechanics (CDM) is developed for simulating the fatigue damage evolution process and predicting the fatigue life of 3D braided composites under fatigue tension loading. This meso-scale fatigue modeling, including stress analysis, failure criteria and material property degradation scheme, is implemented via a user-material subroutine UMAT based on ABAQUS/Standard platform with FORTRAN code. The fatigue damage initiation and propagation processes of 3D braided composites with typical braiding angles on the unit-cell model as a function of number of cycles are presented in detail. The fatigue life of 3D braided composites is predicted from the computed S-N curve and the stiffness degradation process is also investigated. The obtained numerical results indicate that the present model can provide a suitable reference to the numerical study of the fatigue issues in other textile composites.