1,720,970 research outputs found
Cohesive Crack Models and Finite Fracture Mechanics analytical solutions for FRP-concrete single-lap shear test: An overview
Full text linkIn the present paper we review and compare several analytical models describing the single-lap shear test, which is the most common test to determine the bonding behaviour between a strengthening FRP plates and the concrete substrate. The models are one-dimensional and formulated under the assumption that debonding occurs as a pure mode II cracking process throughout a zero-thickness interface between the FRP strip and the brittle substrate. As such, they are all amenable of an analytical treatment. The FRP-concrete interface is described by at most three parameters among the interfacial fracture energy, the tensile strength and the elastic stiffness. Particularly, we compare the effective bond length estimates provided by different models and compare them with the ones present in Design Codes. Finally, a comparison with experimental data sets available in the Scientific Literature is also given
Finite Fracture Mechanics at elastic interfaces
No full textAbstractIn the present paper we provide a method to determine the load causing delamination along an interface in a composite structure. The method is based on the elastic interface model, according to which the interface is equivalent to a bed of linear elastic springs, and on Finite Fracture Mechanics, a crack propagation criterion recently proposed for homogeneous structures. The procedure outlined is general. Details are given for the pull–push shear test. For such geometry, the failure load is obtained and compared with the estimates provided by stress concentration analysis and Linear Elastic Fracture Mechanics. It is seen that Finite Fracture Mechanics provides intermediate values. Furthermore, it is shown that the predictions provided by Finite Fracture Mechanics are almost coincident with the ones provided by the Cohesive Crack Model. As far as we are concerned with the determination of the failure load, the advantage of using Finite Fracture Mechanics with respect to the Cohesive Crack Model is evident, since a troublesome analysis of the softening taking place in the fracture process zone is not necessary. A final comparison with classical fracture criteria based on critical distances, such as the average stress criterion, concludes the paper
Implementation of a symmetric boundary integral formulation for cohesive cracks in homogeneous media and at interfaces
No full textInterface crack model using finite fracture mechanics applied to the double pull-push shear test
No full textAn analytical procedure predicting a debond (interface crack) onset and growth in an adhesive joint between two beams or plates is developed and applied to a specific configuration often used in reinforcement tests in civil engineering. The procedure is based on Timoshenko beam theory and Linear Elastic-(Perfectly) Brittle Interface Model (LEBIM) combined with the Coupled Criterion of the Finite Fracture Mechanics (CC-FFM) for mixed-mode fracture. First, a sixth order differential equation in the shear stresses along the adhesive layer is deduced and solved, leading to closed form expressions for both shear and normal stresses in the adhesive. Then, the critical value of the applied load necessary to produce debonding is predicted by coupling a stress and an energy condition based on: (i) the stress distribution produced in the interface before the debond onset and (ii) the energy released during the debonding process along the interface. Although the developed procedure can be applied to several types of joints with different geometries, materials and loads (e.g., double lap joint tests including adherents made of steel or composites), herein it is applied to the double pull-push shear test where the debond onset and growth between a Carbon Fibre Reinforced Polymer (CFRP) laminate and a concrete block occurs. For such a case, the debond is produced under predominant fracture mode II; nevertheless, it is shown that relevant normal (peeling) stresses associated to mode I may appear as well. A comparison of the present solution with a previous one by the shear-lag model is provided as well
A numerical implementation of the Coupled Criterion of Finite Fracture Mechanics for elastic interfaces
No full textA new numerical procedure for predicting interface failures between solids is developed. The procedure is based on the Linear Elastic-(Perfectly) Brittle Interface Model (LEBIM) combined with the Coupled Criterion of the Finite Fracture Mechanics (CCFFM). Although in the present investigation this procedure is implemented in a 2D BEM code, a general pseudocode is devised allowing its implementation in any BEM or FEM code. The pull-push shear test is used as a benchmark problem, where the fracture mode II is dominant. Nevertheless, the present procedure can tackle a debond growth occurring under any fracture mode mixity. The pull-push problem is chosen since it allows us to check the obtained numerical results against an available analytical solution based on a beam model. Additionally, the numerical results are compared with some experimental data from literature. Furthermore, an inverse analysis is applied to obtain the interface strength and fracture parameters that the model needs
Formulation and implementation of cohesive fracture models in the symmetric Galerkin boundary element method. Study of mode I crack growth
No full text
Single-Domain Cohesive-Zone-Model Formulation and Implementation using the Symmetric Galerkin Boundary Element Method
No full textA new symmetric boundary integral formulation
for embedded cohesive cracks growing in the interior
of homogeneous linear elastic isotropic media is
developed and implemented in a numerical code. The
use of an exponential cohesive law for 2D and the special
treatment about the way in which the law is included
in the Symmetric Galerkin Boundary Element
Method (SGBEM) allow us to develop a simple and efficient
formulation that includes a Cohesive Zone Model
(CZM). This formulation is only dependent on one variable
in the cohesive zone (relative displacement). The
corresponding constitutive cohesive equations present a
softening branch which induce to the problem a potential
instability. The development and implementation
of a suitable solution algorithm capable of following
the growth of the cohesive zone and subsequent crack
growth becomes an important issue. An arc-length control
combined with a Newton-Raphson algorithm for iterative
solution of nonlinear equations is developed.The
Boundary Element Method is very attractive for modeling
cohesive crack problems as all nonlinearities are located
along the boundaries (including the crack boundaries)
of linear elastic domains. A Galerkin approximation scheme, applied to a suitable symmetric integral
formulation, ensures an easy treatment of cracks in homogeneous
media and excellent convergence behavior of
the numerical solution. Numerical results for the wedge
split test are presented and compared with experimental
results available in the literature
- …
