Debonding Process In Composites Using BEM

Indian Journal of Engineering and Materials Sciences

In this paper, a numerical model developed for the analysis of a cylindrical element of matrix containing a single fibre is presented. A ring-shaped crack is assumed at the interface of fibre and matrix. Both layers in the model are bonded perfectly with the exception of the crack faces. Contact elements, which have bonded feature, are used between fibre and matrix. Displacement correlation method is used to calculate opening-mode and sliding-mode stress intensity factors. These results obtained from the analysis help to understand the debonding phenomenon between fibre and matrix interface.

Computers & Structures, 2006

In this paper the behaviour of unidirectional fiber-reinforced composites with imperfect interfacial bonding is investigated by using the finite element method. The matrix and the fibers are considered homogeneous, isotropic and linearly elastic; an interfacial failure model is implemented by connecting the fibers and the matrix at the finite element nodes by normal and tangential brittle-elastic springs. Numerical analyses are carried out on a unit cell extracted from a composite model characterized by a periodic microstructure. The micromechanical simulations provide the first failure loci (FFL), i.e. the envelopes of the composite average strains corresponding to the initiation of the debonding, and the instantaneous overall moduli of the damaged composite corresponding to several interface damage configurations. The results show that the intersections of the FFL with prescribed planes are defined by curves associated with different interface failure modes. Besides, damage induced by fiber-matrix debonding is strongly anisotropic and dependent on the load history.

International Journal of Engineering Science, 2011

The finite element model of progressive debonding in fiber reinforced composite is developed based on the cohesive zone model of interface. An interface crack nucleation, onset and growth has been studied in detail for a single fiber and comparison is made with the linear fracture mechanics model. Then, the effect on debonding progress of local stress redistribution due to interaction between the fibers was studied in the framework of two-inclusion model. Simulation of progressive debonding in fiber reinforced composite using the many-fiber models of composite has been performed. It has been shown that the developed model provides detailed analysis of the progressive debonding phenomenon including the interface crack cluster formation, overall stiffness reduction and induced anisotropy of the effective elastic moduli of composite.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1993

The previous analytical solution, which was presented in part I of this series of papers, for the transfer of elastic stress from a bonded fiber to the matrix is improved in the present study. The present analysis resolves the following limitations, which existed in the previous analysis. (1) The radial dimension of the matrix is much greater than that of the fiber. (2) The radial dependence of the axial stress in the fiber is ignored. (3) The approximate shear stress distribution, which is used to derive the radial dependence of the axial stress in the matrix, satisfies the free surface condition only in an approximate sense. (4) A plane strain condition is assumed in the equilibrium equation in order to relate the tangential stress to the radial stress at the interface. The most significant improvement of the present analysis is that it is applicable for any radial dimension of matrix.

Journal of Solid Mechanics and …, 2008

In this paper, the debonding initiation and propagation in the bundled fibers-matrix composite is studied by utilizing a finite element method, which incorporates the bilinear cohesize zone model. The cohesive zone model parameters are adjusted so that the mechanical response of the model fits to that obtained in an experiment. Furthermore, the model performance is verified against three additional experimental datasets. The study reveals that for this particular specimen and loading condition, the interface debonding stably propagates until the applied load reaches its maximum. After the maximum applied load, the debonding propagates rapidly, and finally, the bundled fibers breaks completely.

Journal of Engineered Fibers and Fabrics

Fiber/matrix debonding behavior of steel fiber composites is analyzed using a parametric finite element modeling procedure and compared with conventional composites with carbon and glass fibers. Cohesive surfaces are applied to fiber–matrix interface to simulate the debonding behavior, while the interface strength properties of steel fiber are obtained with and without surface treatment. The effect of various parameters on the debonding behavior is investigated, including stress concentrations, fiber diameter, fiber shape, and fiber volume fraction, using the parametric model. The influence of stress concentrations is determined to be much lower than the debonding strength. Debonding damage is more evident in larger fibers compared to smaller ones. Earlier and sudden interface separation is observed with the polygonal steel fibers compared to the circular ones. Increase in the fiber volume ratio increases the debonding opening distance but does not affect the opening angle significa...

Mechanics of Materials, 2000

Decohesion at multiple ®ber interfaces of elastic ®ber reinforced composites is modeled by the Voronoi cell ®nite element model (VCFEM) in this paper. Interfacial debonding is accommodated by cohesive zone models, in which normal and tangential springs tractions are expressed in terms of interfacial separation. Model simulations are compared with results from experiments using cruciform specimens, of single and multiple ®ber polymer-matrix composites. An inverse problem is solved to calibrate the cohesive zone parameters. Debonding at ®ber-matrix interfaces is simulated for dierent architectures, volume fractions and boundary conditions, to understand the in¯uence of microstructural morphology and boundary conditions on the decohesion process.

Composites Science and Technology, 2001

The paper focuses on the identi®cation of the parameters of a time-dependent elastic-damage interface model for the simulation of debonding in composites. Model parameters are identi®ed by means of the extended Kalman ®lter and of a numerical approximate computation of the gradient of the system response in the state variable space. For the identi®cation use is made of pseudoexperimental data both at the constitutive (material) level and at the structural level.

Advanced Composites Letters, 1996

A shear-lag analysis based on energy is used to predict the amount of debonding that occurs when a fiber fragment breaks into two fragments. The shear-lag analysis reproduces all features of more sophisticated analyses. A drawback of the shear-lag analysis, however, is that it depends on an unknown parameter which can be expressed in terms of an effective fiber volume fraction. If the effective fiber volume fraction can be determined (by experiments or by advanced stress analyses), the shear-lag model can be used to interpret debonding experiments.

Mathematics and Computers in Simulation, 2007

We show how we can exploit our recently proposed algorithms for the solution of contact problem of elasticity to the 2D analysis of the interfacial debonding of samples that consist of several fibres embedded in a homogeneous matrix, aligned in the longitudal direction. The performance of the algorithm is demonstrated on analysis of deformations of samples of the fibrous composite material.