Estimating the Cohesive Zone Model Parameters for Carbon Nanotube–Polymer Interface Using Inverse Finite Element Approach

2012 ◽  
Author(s):  
Lingyun Jiang ◽  
Chandra Nath ◽  
Johnson Samuel ◽  
Shiv G. Kapoor
Keyword(s):  
Finite Element ◽  
Carbon Nanotube ◽  
Fracture Energy ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Interfacial Strength ◽  
Model Parameters ◽  
Zone Model ◽  
Displacement Curve ◽  
Polymer Interface

During machining of carbon nanotube (CNT)-polymer composites, the failure of the polymer elements occurs at the CNT-polymer interface. The interfacial behavior that can be represented by a cohesive zone model (CZM) is mainly influenced by two parameters, viz., interfacial strength and fracture energy. The objective of this study is to estimate these two specific CZM parameters using an inverse finite element (FE) simulation approach that works based on an iterative error minimization procedure. Nanoindentation tests have been conducted on a CNT-polyvinyl alcohol (PVA) composite sample containing 4 wt% multi-walled nanotubes (MWNTs). A 2D axisymmetric FE model of nanoindentation has been developed. This micro-structure based model considers the CNT, the PVA, and the cohesive zone of interface as three individual phases. The unknown interfacial parameters are determined by minimizing the error between the simulation load-displacement curve and the experimental results. The interfacial strength and the fracture energy at the CNT-PVA interface are estimated to be approximately 40 MPa and 16e−3 J/m2, respectively. This approach provides a convenient framework to understand the role of the CZM parameters at the interface between the CNT and polymer matrix.

Estimating the Cohesive Zone Model Parameters of Carbon Nanotube–Polymer Interface for Machining Simulations

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Lingyun Jiang ◽  
Chandra Nath ◽  
Johnson Samuel ◽  
Shiv G. Kapoor
Keyword(s):  
Carbon Nanotube ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Interfacial Strength ◽  
Weight Fraction ◽  
Model Parameters ◽  
Zone Model ◽  
Fe Model ◽  
Polymer Interface ◽  
Two Parameters

The failure mechanisms encountered during the machining of carbon nanotube (CNT) polymer composites are primarily governed by the strength of the CNT–polymer interface. Therefore, the interface should be explicitly modeled in microstructure-level machining simulations for these composites. One way of effectively capturing the behavior of this interface is by the use of a cohesive zone model (CZM) that is characterized by two parameters, viz., interfacial strength and interfacial fracture energy. The objective of this study is to estimate these two CZM parameters of the interface using an inverse iterative finite element (FE) approach. A microstructure-level 3D FE model for nanoindentation simulation has been developed where the composite microstructure is modeled using three distinct phases, viz., the CNT, the polymer, and the interface. The unknown CZM parameters of the interface are then determined by minimizing the root mean square (RMS) error between the simulated and the experimental nanoindentation load–displacement curves for a 2 wt. % CNT–polyvinyl alcohol (PVA) composite sample at room temperature and quasi-static strain state of up to 0.04 s−1, and then validated using the 1 wt. % and 4 wt. % CNT–PVA composites. The results indicate that for well-dispersed and aligned CNT–PVA composites, the CZM parameters of the interface are independent of the CNT loading in the weight fraction range of 1–4%.

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 Model to Study the Effect of Interfaces in Carbon Nanotube-Based Composites

2005 ◽  
Vol 127 (2) ◽  
pp. 222-232 ◽  
Author(s):  
S. Namilae ◽  
N. Chandra
Keyword(s):  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Finite Element ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Interfacial Region ◽  
Model Parameters ◽  
Zone Model ◽  
Pullout Tests ◽  
Nanoscale Interfaces

In order to fully harness the outstanding mechanical properties of carbon nanotubes (CNT) as fiber reinforcements, it is essential to understand the nature of load transfer in the fiber matrix interfacial region of CNT-based composites. With controlled experimentation on nanoscale interfaces far off, molecular dynamics (MD) is evolving as the primary method to model these systems and processes. While MD is capable of simulating atomistic behavior in a deterministic manner, the extremely small length and time scales modeled by MD necessitate multiscale approaches. To study the atomic scale interface effects on composite behavior, we herein develop a hierarchical multiscale methodology linking molecular dynamics and the finite element method through atomically informed cohesive zone model parameters to represent interfaces. Motivated by the successful application of pullout tests in conventional composites, we simulate fiber pullout tests of carbon nanotubes in a given matrix using MD. The results of the pullout simulations are then used to evaluate cohesive zone model parameters. These cohesive zone models (CZM) are then used in a finite element setting to study the macroscopic mechanical response of the composites. Thus, the method suggested explicitly accounts for the behavior of nanoscale interfaces existing between the matrix and CNT. The developed methodology is used to study the effect of interface strength on stiffness of the CNT-based composite.

Effects of asphalt concrete characteristics on cohesive zone model parameters of hot mix asphalt mixtures

2016 ◽  
Vol 43 (3) ◽  
pp. 226-232 ◽  
Author(s):  
S. Pirmohammad ◽  
H. Khoramishad ◽  
M.R. Ayatollahi
Keyword(s):  
Asphalt Concrete ◽  
Cohesive Energy ◽  
Cohesive Zone ◽  
Hot Mix Asphalt ◽  
Cohesive Zone Model ◽  
Experimental Tests ◽  
Model Parameters ◽  
Zone Model ◽  
Binder Type ◽  
Air Void

In this paper, the effects of the main asphalt concrete characteristics including the binder type and the air void percentage on the cohesive zone model (CZM) parameters were studied. Experimental tests were conducted on semi-circular bend (SCB) specimens made of asphalt concrete and the fracture behavior was simulated using a proper CZM. The CZM parameters of various hot mix asphalt (HMA) mixtures were determined using the SCB experimental results. Five types of HMA mixtures were tested and modeled to consider the effects of binder type and air void percentage on the CZM parameters. The results showed that as the binder in HMA mixture softened, the cohesive energy strength increased, whereas enhancing the air void percentage led to reduction of the cohesive energy and strength values. Among the studied HMA mixtures, the highest values of CZM parameters were found for the HMA mixture containing a copolymer called styrene-butadiene-styrene.

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.

Effects of adhesive thickness on the mode I cohesive zone model parameters of a high toughness structural adhesive

2018 ◽  
Author(s):  
M. H. R. de Oliveira ◽  
A. F. Ávila ◽  
R. R. Chaves ◽  
H. Nascimento Júnior ◽  
F. D. Passos
Keyword(s):  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Model Parameters ◽  
Mode I ◽  
Zone Model ◽  
High Toughness ◽  
Adhesive Thickness ◽  
Structural Adhesive

Crack Growth Modelling in the Silicon Nitride Ceramics by Application of the Cohesive Zone Approach

2013 ◽  
Vol 592-593 ◽  
pp. 193-196
Author(s):  
Vladislav Kozák ◽  
Zdeněk Chlup
Keyword(s):  
Finite Element ◽  
Silicon Nitride ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Zone Model ◽  
Interface Elements ◽  
Practical Applications ◽  
Damage Models ◽  
Cohesive Models ◽  
Finite Element Package

Specific silicon nitride based materials are considered according to certain practical requirements of process, the influence of the grain size and orientation on the bridging mechanisms was found. Crack-bridging mechanisms can provide substantial increases in toughness coupled with the strength in ceramics. The prediction of the crack propagation through interface elements based on the fracture mechanics approach and cohesive zone model is investigated and from the amount of damage models the cohesive models seem to be especially attractive for the practical applications. Using cohesive models the behaviour of materials is realized by two types of elements. The former is the element for classical continuum and the latter is the connecting cohesive element. Within the standard finite element package Abaqus a new finite element has been developed; it is written via the UEL (users element) procedure. Its shape can be very easily modified according to the experimental data for the set of ceramics and composites. The new element seems to be very stable from the numerical point a view. The shape of the traction separation law for three experimental materials is estimated from the macroscopic tests, JR curve is predicted and stability of the bridging law is tested.

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