Energy release rates for interlaminar delamination in laminates considering transverse shear effects (original) (raw)
Related papers
Energy release rate and stress intensity factors for delaminated composite laminates
International Journal of Solids and Structures, 1997
AbstnC't-A procedure of total energy release rate and stress intensity factors is developed for general non-homogeneous laminated composite laminates. The total energy release rate is obtained by using the J-integral for a one dimensional model of plane stress, plane strain and cylindrical bending. Decomposition of it into mode I and mode II, by which the mode mixity calculation is carried out, is based on the assumption of equivalent orthotropic properties through the laminate thickness. The process is straightforward and can be used as a criterion for delamination onset and growth of one dimensional structural model under general loading in the pre-and post-buckling states.
On the calculation of energy release rates for cracked laminates with residual stresses
International Journal of Fracture, 2006
Prior methods for calculating energy release rate in cracked laminates were extended to account for heterogeneous laminates and residual stresses. The method is to partition the crack tip stresses into local bending moments and normal forces. A general equation is then given for the total energy release rate in terms of the crack-tip moments and forces and the temperature difference experienced by the laminate. The analysis method is illustrated by several example test geometries. The examples were verified by comparison to numerical calculations. The residual stress term in the total energy release rate equation was found to be essentially exact in all example calculations.
Composite Structures, 2007
The aim of this paper is the analytical determination of the strain energy release rates in a delaminated laminate by means of a model of plates which provides no singular stresses. The strain energy release rates are expressed as quadratic functions of the interfacial stresses at the crack tip. These expressions and relevant delamination criteria can help predict delamination onset and growth. As an application example, data from edge delamination tests on carbon-epoxy laminates are used for determining a mode III delamination criterion involving the corresponding energy release rate. This criterion yields very accurate predictions and its analytical expression validates from an energy point of view a maximum stress criterion proposed in an earlier paper.
Loading rate dependency of strain energy release rate in mode I delamination of composite laminates
Theoretical and Applied Fracture Mechanics, 2021
This work aims at studying the loading rate dependency of mode I delamination growth in CFRPs, using typical fracture toughness analysis through both the R-curve and the crack tip opening rate. The average SERR is a method of data reduction based on energy balance which has been previously introduced to characterize delamination growth under different types of loading conditions in a similar manner. In the present research, the application of this method was extended to further analyze the results of delamination experiments at different loading rates. Mode I delamination tests on double cantilever beam specimens were performed at displacement rates varying from standard quasi-static testing up to 400 mm/s. A clear decrease in the propagation fracture toughness as well as in the average SERR was observed at high loading rates. The reduced fracture resistance at elevated rates was physically explained in correlation with fiber bridging, fiber breakage, and matrix cleavage observed in fracture surfaces via scanning electron microscopy.
Calculation of stress intensity factors for interlaminar cracks in composite laminates
Composites Science and Technology, 1997
Using Beom and Atluri's complete eigen-function solutions for stresses and displacements near the tip of an interfacial crack between dissimilar anisotropic media, a hybrid crack tip finite-element is developed. This element, as well as a mutual integral method are used to determine the stress intensity factors for an interfacial crack between dissimilar anisotropic media. The hybrid element has, for its Galerkin basis functions, the eigen-function solutions for stresses and displacements embedded within it. The "mutual integral" approach is based on the application of the path-independent J integral to a linear combination of two solutions: one, the problem to be solved, and the second, an "auxiliary" solution with a known singular solution. A comparison with exact solutions is made to determine the accuracy and efficiency of both the methods in various mixed mode interfacial crack problems. The size of the hybrid element was found to have very little effect on the accuracy of the solution: an acceptable numerical solution can be obtained with a very coarse mesh by using a larger hybrid element. An equivalent domain integral method is used in the application of the "mutual" integral instead of the line integral method. It is shown that the calculated mutual integral is domain independent. Therefore, the mutual integral can be evaluated far away from the crack-tip where the finite element solution is more accurate. In addition, numerical examples are given to determine the stress intensity factors for a delamination crack in composite lap joints and at plate-stiffener interfaces.
WIT transactions on engineering sciences, 1998
Layer debonding (delamination) is one of the most frequent cracking mode in laminated composite materials. This paper applies the concept of strain energy release rate (G) for the analysis of edge delamination growth in laminates [0TM, 90n]s (m, n 2, 4, 6) under tension loads. Analytical and numerical (finite element method) models were employed in order to study the effects of laminate stacking sequence on G evaluation. Finally, correlation studies between numerical and analytical approaches give support to the accomplishment of stress analyses near to the free edge. Nomenclature EXXlamina axial stiffness EZZ lamina transversal stiffness Gxz lamina shear modulus G strain energy release rate associated with delamination growth h ply thickness s distance between two adjacent microcracks T temperature Transactions on Engineering Sciences vol 21, © 1998 WIT Press, www.witpress.com, ISSN 1743-3533
Interlaminar stresses and delamination of composite laminates under extension and bending
Structural …, 2007
The metis element method has been applied to analyse free edge interlaminar stresses and delamination in composite laminates, which are subjected to extension and bending. The paper recalls Lekhnitskii's solution for generalized plane strain state of composite laminate and Wang's singular solution for determination of stress singularity order and of eigen coefficients C m for delamination problem. Then the formulae of metis displacement finite element in two-dimensional problem are established. Computation of the stress intensity factors and the energy release rates are presented in details. The energy release rate, G, is computed by Irwin's virtual crack technique using metis elements. Finally, results of interlaminar stresses, the three stress intensity factors and the energy release rates for delamination crack in composite laminates under extension and bending are illustrated and compared with the literature to demonstrate the efficiency of the present method.
Analytic formulas of energy release rates for delamination using a global–local method
International Journal of Solids and Structures, 2012
This article presents analytic solutions of energy release rates of a cracked laminate by using a globallocal method. Deformations of a cracked laminate subjected to pure bending moments are analyzed and then a new mode partition equation is proposed. By using this partition equation, closed-form solutions of energy release rates G I and G II are derived by using a global method. For a cracked laminate subjected to axial forces and bending moments, a local method based on the crack-tip force model is used and the unknown coefficient is solved by combining the present analytic solutions for the bending moment loading case. Numerical results of the mode mixity predicted by the present closed-form formulations correlate well with those numerically calibrated on the basis of the singular field and crack-tip force models.