scholarly journals Problem of Delamination in RC Beams Strengthened by FRP with Rheological Model of Adhesive Leyer

2016 ◽  
Vol 23 (4) ◽  
pp. 103-110 ◽  
Author(s):  
Krzysztof Kula ◽  
Tomasz Socha
Keyword(s):  
Finite Element ◽  
Rheological Model ◽  
Failure Modes ◽  
Cohesive Zone Model ◽  
Adhesive Layer ◽  
Epoxy Adhesive ◽  
Zone Model ◽  
Time Behavior ◽  
Long Time ◽  
Shell Finite Element

Abstract This paper deals with one of the most dangerous failure modes in layered structures, namely delamination. The strengthening layer is modelled by a solid-shell finite element. The mechanical modelling of delamination onset and propagation is based upon a cohesive zone model implemented into a cohesive element located between adhesive layer and a concrete structure. The long time behavior of epoxy adhesive layer is modelled with the five-parameter rheological model. The numerical simulations are accomplished within the commercial software package Abaqus by the implementation of a user-written finite element and user-written material.

Optimization of composite patch repair for maximum stability of crack growth in an aluminum plate

2016 ◽  
Vol 231 (20) ◽  
pp. 3690-3701
Author(s):  
B Talebi ◽  
A Abedian
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Cohesive Zone Model ◽  
Adhesive Layer ◽  
Patch Repair ◽  
Aluminum Plate ◽  
Uniaxial Tensile ◽  
Zone Model ◽  
Composite Patch ◽  
The Stability

In this paper, the configuration parameters of pre-designed composite patch repair are optimized with the aim of achieving the highest level of stability of crack growth in aluminum in the presence of some constraints such as weight, load sustainability, shear stress in the adhesive layer and maximum stress in the patch. For this purpose, the patch is modeled in full scale by ABAQUS, a commercial finite element code. The crack growth process is simulated with the extended finite element method under uniaxial tensile loading, and the Cohesive Zone Model is used to model the progressive damage in the adhesive of the composite patch repair. Also, sensitivity analysis is performed on the configuration parameters and it is shown that three parameters, i.e. width, stiffness ratio, and height of the patch are more important. Nonlinear fracture mechanics concepts have been used in calculating the stability of crack in the cracked aluminum plate. The results show that optimization based on the method proposed in this paper causes the stability of crack growth to increase by 21% while the patch weight is reduced by 52%.

scholarly journals Numerical and Experimental Study of Tensile Strength of Single and Double-Strap Repairs

2012 ◽  
Vol 730-732 ◽  
pp. 1018-1023
Author(s):  
Arnaldo M.G. Pinto ◽  
Raul D.S.G. Campilho ◽  
Isabel R. Mendes ◽  
A.G. Magalhães ◽  
A.P.M. Baptista
Keyword(s):  
Adhesive Bonding ◽  
Failure Modes ◽  
Cohesive Zone Model ◽  
Fatigue Cracks ◽  
Adhesive Layer ◽  
Elastic Stiffness ◽  
Zone Model ◽  
Shear Stresses ◽  
Adhesively Bonded ◽  
Shear Modes

Adhesive bonding as a joining or repair method has a wide application in many industries. Repairs with bonded patches are often carried out to re-establish the stiffness at critical regions or spots of corrosion and/or fatigue cracks. Single and double-strap repairs (SS and DS, respectively) are a viable option for repairing. For the SS repairs, a patch is adhesively-bonded on one of the structure faces. SS repairs are easy to execute, but the load eccentricity leads to peel peak stresses at the overlap edges. DS repairs involve the use of two patches, one on each face of the structure. These are more efficient than SS repairs, due to the doubling of the bonding area and suppression of the transverse deflection of the adherends. Shear stresses also become more uniform as a result of smaller differential straining. The experimental and Finite Element (FE) study presented here for strength prediction and design optimization of bonded repairs includes SS and DS solutions with different values of overlap length (LO). The examined values ofLOinclude 10, 20 and 30 mm. The failure strengths of the SS and DS repairs were compared with FE results by using the Abaqus®FE software. A Cohesive Zone Model (CZM) with a triangular shape in pure tensile and shear modes, including the mixed-mode possibility for crack growth, was used to simulate fracture of the adhesive layer. A good agreement was found between the experiments and the FE simulations on the failure modes, elastic stiffness and strength of the repairs, showing the effectiveness and applicability of the proposed FE technique in predicting strength of bonded repairs. Furthermore, some optimization principles were proposed to repair structures with adhesively-bonded patches that will allow repair designers to effectively design bonded repairs.

Progressive failure analysis of scarf-repaired composite laminate based on damage constitutive model

2016 ◽  
Vol 233 (2) ◽  
pp. 180-188 ◽  
Author(s):  
Qiuyi Shen ◽  
Zhenghao Zhu ◽  
Yi Liu
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Composite Laminate ◽  
Damage Mechanics ◽  
Cohesive Zone Model ◽  
Load Capacity ◽  
Three Dimensional ◽  
Zone Model ◽  
State Variables ◽  
Element Analysis

A three-dimensional finite element model for scarf-repaired composite laminate was established on continuum damage model to predict the load capacity under tensile loading. The mixed-mode cohesive zone model was adopted to the debonding behavior analysis of adhesive. Damage condition and failure of laminates and adhesive were subsequently addressed. A three-dimensional bilinear constitutive model was developed for composite materials based on damage mechanics and applied to damage evolution and loading capacity analyses by quantifying damage level through damage state variables. The numerical analyses were implemented with ABAQUS finite element analysis by coding the constitutive model into material subroutine VUMAT. Good agreement between the numerical and experimental results shows the accuracy and adaptability of the model.

scholarly journals COMPUTATION FOR THE DELAMINATION IN THE LAMINATE COMPOSITE MATERIAL USING A COHESIVE ZONE MODEL BY ABAQUS

2020 ◽  
Vol 57 (6A) ◽  
pp. 61
Author(s):  
Hoa Cong Vu
Keyword(s):  
Finite Element ◽  
Cohesive Zone Model ◽  
Constitutive Relations ◽  
Damage Zone ◽  
Damage Model ◽  
Zone Model ◽  
Element Formulation ◽  
Cohesive Elements ◽  
Element Mesh ◽  
Variable Mode

In this paper, a damage model using cohesive damage zone for the simulation of progressive delamination under variable mode is presented. The constitutive relations, based on liner softening law, are using for formulation of the delamination onset and propagation. The implementation of the cohesive elements is described, along with instructions on how to incorporate the elements into a finite element mesh. The model is implemented in a finite element formulation in ABAQUS. The numerical results given by the model are compare with experimental data

Examination of the Transferability of CTOA From Small-Scale DWTT to Full-Scale Pipe Geometries Using a Cohesive Zone Model

2020 ◽  
Author(s):  
Chris Bassindale ◽  
Xin Wang ◽  
William R. Tyson ◽  
Su Xu
Keyword(s):  
Finite Element ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Element Model ◽  
Full Scale ◽  
Opening Angle ◽  
Small Scale ◽  
Zone Model ◽  
Pipe Model ◽  
Good Agreement

Abstract In this work, the cohesive zone model (CZM) was used to examine the transferability of the crack tip opening angle (CTOA) from small-scale to full-scale geometries. The pipe steel STPG370 was modeled. A drop-weight tear test (DWTT) model and pipe model were studied using the finite element code ABAQUS 2017x. The cohesive zone model was used to simulate crack propagation in 3D. The CZM parameters were calibrated based on matching the surface CTOA measured from a DWTT finite element model to the surface CTOA measured from the experimental DWTT specimen. The mid-thickness CTOA of the DWTT model was in good agreement with the experimental value determined from E3039 and the University of Tokyo group’s load-displacement data. The CZM parameters were then applied to the pipe model. The internal pressure distribution and decay during the pipe fracture process was modeled using the experimental data and implemented through a user-subroutine (VDLOAD). The mid-thickness CTOA from the DWTT model was similar to the mid-thickness CTOA from the pipe model. The average surface CTOA of the pipe model was in good agreement with the average experimental value. The results give confidence in the transferability of the CTOA between small-scale specimens and full-scale pipe.

Finite Element Simulation of Delamination in Carbon Fiber/Epoxy Laminate Using Cohesive Zone Model: Effect of Meshing Variation

2019 ◽  
Vol 964 ◽  
pp. 257-262
Author(s):  
Victor D. Waas ◽  
Mas Irfan P. Hidayat ◽  
Lukman Noerochim
Keyword(s):  
Finite Element ◽  
Carbon Fiber ◽  
Cohesive Zone ◽  
Composite Laminate ◽  
Cohesive Zone Model ◽  
Critical Force ◽  
Zone Model ◽  
Interface Elements ◽  
Dcb Specimen ◽  
Carbon Fiber Epoxy

Delamination or interlaminar fracture often occurs in composite laminate due to several factors such as high interlaminar stress, stress concentration, impact stress as well as imperfections in manufacturing processes. In this study, finite element (FE) simulation of mode I delamination in double cantilever beam (DCB) specimen of carbon fiber/epoxy laminate HTA/6376C is investigated using cohesive zone model (CZM). 3D geometry of DCB specimen is developed in ANSYS Mechanical software and 8-node interface elements with bi-linear formulation are employed to connect the upper and lower parts of DCB. Effect of variation of number of elements on the laminate critical force is particularly examined. The mesh variation includes coarse, fine, and finest mesh. Simulation results show that the finest mesh needs to be employed to produce an accurate assessment of laminate critical force, which is compared with the one obtained from exact solution. This study hence addresses suitable number of elements as a reference to be used for 3D simulation of delamination progress in the composite laminate, which is less explored in existing studies of delamination of composites so far.

Fracture energy characterisation of a structured interface by means of a novel J-Integral procedure

2019 ◽  
Vol 54 (7-8) ◽  
pp. 364-378
Author(s):  
Lorenzo García-Guzmán ◽  
Luis Távara ◽  
José Reinoso ◽  
Federico París
Keyword(s):  
Finite Element ◽  
Fracture Energy ◽  
Cohesive Zone Model ◽  
Integral Formulation ◽  
Evaluation Procedure ◽  
Crack Advance ◽  
Energy Calculation ◽  
Zone Model ◽  
Displacement Curve ◽  
J Integral

In the present investigation, a J-Integral formulation for non-flat crack paths, in the framework of the cohesive zone model, is developed. The formulation allows fracture energy properties in a direction that is not necessarily coplanar with the global crack advance to be analysed. Specifically, the effective fracture energy, [Formula: see text], has been examined based on the horizontal projection of the crack advance, [Formula: see text] (also called effective crack length). The use of [Formula: see text] is convenient in several situations as the case of patterned interfaces in adhesive joints. Finite-element analysis of double cantilever beam specimens including a trapezoidal patterned interface were employed to check the accuracy of this new definition of the contour integral. Post-process of the finite-element model, including those variables involved in the fracture energy calculation, is discussed together with some considerations that distinguish the energy evaluation procedure for flat profiles from structured designs. Finally, [Formula: see text] values obtained using the modified J-Integral formulation are compared with [Formula: see text] values obtained from the load–displacement curve method for comparison purposes.

Multiscale Finite Element Modeling of Alumina Ceramics Undergoing Laser-Assisted Machining

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Xiangyang Dong ◽  
Yung C. Shin
Keyword(s):  
Finite Element ◽  
High Temperatures ◽  
Cutting Forces ◽  
Cohesive Zone Model ◽  
Multiscale Approach ◽  
Zone Model ◽  
Alumina Ceramics ◽  
Weight Percentage ◽  
Laser Assisted Machining ◽  
Wide Range

Alumina ceramics, due to their excellent properties of high hardness, corrosion resistance, and low thermal expansion coefficient, are important industrial materials with a wide range of applications, but these materials also present difficulty in machining with low material removal rates and high tool wear. This study is concerned with laser-assisted machining (LAM) of high weight percentage of alumina ceramics to improve the machinability by a single point cutting tool while reducing the cutting forces. A multiscale model is developed for simulating the machining of alumina ceramics. In the polycrystalline form, the properties of alumina ceramics are strongly related to the glass interface existing in their microstructure, particularly at high temperatures. The interface is characterized by a cohesive zone model (CZM) with the traction–separation law while the alumina grains are modeled as continuum elements with isotropic properties separated by the interface. Bulk deformation and brittle failure are considered for the alumina grains. Molecular dynamics (MD) simulations are carried out to obtain the atomistic structures and parameterize traction–separation laws for the interfaces of different compositions of alumina ceramics at high temperatures. The generated parameterized traction–separation laws are then incorporated into a finite element model in Abaqus to simulate the intergranular cracks. For validation purposes, simulated results of the multiscale approach are compared with the experimental measurements of the cutting forces. The model is successful in predicting cutting forces with respect to the different weight percentage and composition of alumina ceramics at high temperatures in LAM processes.

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