A new overall nonlinear damage model for fiber metal laminates based on continuum damage mechanics (original) (raw)
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A study on fiber metal laminates by using a new damage model for composite layer
International Journal of Mechanical Sciences, 2017
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights A simple nonlinear damage model is introduced to modify the linear elastic model of GFRE to nonlinear elastic behavior. The damage model parameters have been determined by iterative simulation and GA. VOCE relation has been considered to describe the flow curve of Al 2024 and the model constants have been calculated by optimization. A simple tensile tests have been carried out to verify the tensile behavior of the FML. The results of the proposed model showed a reasonable agreement with the experiments.
A continuum damage model for composite laminates: Part I – Constitutive model
Mechanics of Materials, 2007
A continuum damage model for the prediction of the onset and evolution of intralaminar failure mechanisms and the collapse of structures manufactured in fiber-reinforced plastic laminates is proposed. The failure mechanisms occurring in the longitudinal and transverse directions of a ply are represented by a set of scalar damage variables. Crack closure effects under load reversal are taken into account by using damage variables that are established as a function of the sign of the components of the stress tensor. Damage activation functions based on the LaRC04 failure criteria are used to predict the different failure mechanisms occurring at the ply level.
An inelastic damage model for fiber reinforced laminates
Journal of composite materials, 2002
A new model for damage behavior of polymer matrix composite laminates is presented. The model is developed for an individual lamina, and then assembled to describe the nonlinear behavior of the laminate. The model predicts the inelastic effects as reduction of stiffness and increments of damage and unrecoverable deformation. The model is defined using Continuous Damage Mechanics coupled with Classical Thermodynamic Theory. Unrecoverable deformations and Damage are coupled by the concept of effective stress. New expressions of damage and unrecoverable deformation domains are presented so that the number of model parameters is small. Furthermore, model parameters are obtained from existing test data for unidirectional laminae, supplemented by cyclic shear stress-strain data. Comparison with lamina and laminate test data are presented to demonstrate the ability of the model to predict the observed behavior.
Mechanics of Materials, 2007
A continuum damage model for the prediction of the onset and evolution of intralaminar failure mechanisms and the collapse of structures manufactured in fiber-reinforced plastic laminates is proposed. The failure mechanisms occurring in the longitudinal and transverse directions of a ply are represented by a set of scalar damage variables. Crack closure effects under load reversal are taken into account by using damage variables that are established as a function of the sign of the components of the stress tensor. Damage activation functions based on the LaRC04 failure criteria are used to predict the different failure mechanisms occurring at the ply level.
Progressive damage and failure modeling in notched laminated fiber reinforced composites
International Journal of Fracture, 2009
A novel progressive damage and failure model for fiber reinforced laminated composites is presented in this work. The model uses the thermodynamically based Schapery Theory (ST) to model progressive microdamage in the matrix phase. Matrix failure is not governed with a matrix failure criterion, but rather matrix failure occurs naturally through the evolution of microdamage. A maximum strain criterion is used to dictate tensile failure in the fiber direction, while compressive failure is automatically accounted for by allowing local fiber rotations and tracking the evolution of rotation. The results of this model are compared to a previously developed model that used ST at the lamina level to calculate matrix microdamage, but used the Generalized Method of Cells to resolve the lamina level strains into constituent level stresses and strains and determines constituent failure by evaluating failure criteria at the micro, fiber/matrix level. Results for global load versus displacement and local strain from both models are compared to experimental data for notched laminates loaded in uniaxial tension. The results show remarkable agreement qualitatively, and in many cases the quantitative agreement is good. Accurate damage contours and failure paths are predicted.
A physically based continuum damage mechanics model for thin laminated composite structures
The present work focuses on the development, implementation, and verification of a plane-stress continuum damage mechanics (CDM) based model for composite materials. A physical treatment of damage growth based on the extensive body of experimental literature on the subject is combined with the mathematical rigour of a CDM description to form the foundation of the model. The model has been implemented in the commercial finite element code, LS-DYNA and the results of the application of the model to the prediction of impact damage growth and its effects on the impact force histories in carbon fibre reinforced plastic laminates are shown to be physically meaningful and accurate. Furthermore, it is demonstrated that the material characterization parameters can be extracted from the results of standard test methodologies for which a large body of published data already exists for many composite materials. commonly used strain equivalence approach, a material containing damage, subjected to a strain, e, and under a state of stress, r, can be represented as an equivalent undamaged material subject to the same strain, e, but under an effective stress state,r r. This can be expressed mathematically by the relation:
A new damage model for composite laminates
Composite Structures, 2012
Aircraft composite structures must have high stiffness and strength with low weight, which can guarantee the increase of the pay-load for airplanes without losing airworthiness. However, the mechanical behavior of composite laminates is very complex due the inherent anisotropy and heterogeneity. Many researchers have developed different failure progressive analyses and damage models in order to predict the complex failure mechanisms. This work presents a damage model and progressive failure analysis that requires simple experimental tests and that achieves good accuracy. Firstly, the paper explains damage initiation and propagation criteria and a procedure to identify the material parameters. In the second stage, the model was implemented as a UMAT (User Material Subroutine), which is linked to finite element software, ABAQUS™, in order to predict the composite structures behavior. Afterwards, some case studies, mainly off-axis coupons under tensile or compression loads, with different types of stacking sequence were analyzed using the proposed material model. Finally, the computational results were compared to the experimental results, verifying the capability of the damage model in order to predict the composite structure behavior.
Non-linear mechanical damage modelling for long fibre-reinforced laminates
2006
A computational methodology is presented for modelling the material non-linear mechanical behaviour of composite structures made of FRP (Fibre-Reinforced Plastic) laminates. The model is based on the appropriate combination of the constitutive models of component materials, considered to behave as isolated continua, together with additional ‘closure equations’ that characterize the micromechanics of the composite from a morphological point of view. To this end, any appropriate constitutive model may be selected for each phase. Each component is modelled separately and the global response is obtained by assembling all contributions taking into account the interactions between components in a general phenomenological way. To model the behaviour of a single unidirectional (UD) composite lamina, a Serial-Parallel continuum approach has been developed assuming that components behave as parallel materials in the fibres alignment direction and as serial materials in orthogonal directions. ...
Durability prediction of structural composites through a continuum damage mechanics approach
2010
The main objective of this research is to develop and implement a new analytical model that relies on a continuum-damage-mechanics approach to predict the evolution of plastic strain and mechanical damage until failure in a unidirectional fiber reinforced composite. The term "damage" is used only in the context of failure mechanisms associated with fracture, which are commonly associated with degradation in stiffness. Plastic and damage evolution are related to typical failure mechanisms in composite materials such as fiber, inter-fiber, and intra-fiber fracture. The plastic strain surface is defined based on the Tsai-Wu failure criterion, while the stiffness degradation damage surface is defined based on the energy-release crack growth. The coefficients that characterize the damage and the plastic surfaces are obtained from known material properties. Data obtained from inter-fiber shear load/unload experimental results are used to define the plastic and damage anisotropic associative evolution. The plastic and damage thresholds are obtained by using nonlinear extrapolation. The mathematical equations and physical principles underlying this model are formulated in the tensorial three-dimensional space and tailored to the primary objective of modeling damage evolution. This model is implemented as a new, user defined material in the commercial finite element analysis software ANSYS. The finite element results are validated by comparisons with published experimental data from shear load/unload in-plane tests, as well as with published experimental data from load/unload tension tests of a [±45°] 2S composite laminate. The comparison shows a good correlation between the model predictions and the experimental data. Finally, the new material model is implemented in ANSYS to predict the durability of a composite beam subjected to four-point bending, where the evolution of fiber, inter-laminar, and intra-laminar types of damage is quantified.
2017
In this study, an efficient combination of continuum and discrete damage mechanics based approaches is used to model the interacting effect of delamination and intra-laminar damage modes in notched composite laminates subjected to tensile loading [1]. Delamination is the only mode of damage captured by a discrete approach while all intra-laminar forms of damage are modelled using a nonlocal continuum damage approach. A series of open-hole specimens that have been tested under tensile loading [2] are simulated using the proposed approach. The specimens are made of quasi-isotropic IM7/8552 carbon fibre/epoxy laminates with varying hole diameter, ply and laminate thickness while keeping the ratios of the hole diameter to specimen width and length constant. The current approach is shown to capture the dominant failure mechanisms as well as the overall behaviour, including the size and layup effect on the notched strength of the laminate.