scholarly journals Numerical simulation of fiber-matrix debonding in single fiber pull-out tests

2020 ◽  
Vol 2 (1) ◽  
pp. 21-35
Author(s):  
Lukas Hoppe
Keyword(s):  
Crack Initiation ◽  
Cohesive Zone ◽  
Single Fiber ◽  
Displacement Curve ◽  
Fe Model ◽  
Pull Out ◽  
Peridynamic Model ◽  
Reference Experiment ◽  
Fiber Matrix ◽  
Force Displacement

The present work deals with the numerical crack simulation of fiber-matrix debonding in single fiber pull-out tests. For this purpose, two models are used: a finite element model (FE model) with the cohesive zone approach and a peridynamic model. For calibration a reference experiment is applied. In addition analytical equations are used for reference values. The influence of the model parameters and the material parameters of the cohesive zone model on the force-displacement curve is investigated. Besides the free fiber length, the critical interface strength, the critical energy release rate as well as the initial interface stiffness have a great influence on the force-displacement curve of the pull-out test. From the crack simulation it can be seen that Mode I has an influence on the crack initiation, but further crack growth after initiation is dominated by Mode II. The FE model can be calibrated in a way that the crack initiation point and the maximum force correspond to the reference experiment. The peridynamic model depicts a comparable crack formation process.

Interface Properties for Ceramic Composites from a Single-Fiber Pull-Out Test

1989 ◽  
Vol 170 ◽  
Author(s):  
Elizabeth P. Butler ◽  
Edwin R. Fuller ◽  
Helen M. Chan
Keyword(s):  
Friction Coefficient ◽  
Shear Resistance ◽  
Ceramic Composites ◽  
Single Fiber ◽  
Displacement Curve ◽  
Interface Properties ◽  
Model Composite ◽  
Pull Out ◽  
Fiber Matrix ◽  
Clamping Pressure

AbstractAn experimental approach has been developed using a single-fiber pullout test to measure intrinsic interface properties for ceramic composites. The properties are determined from a pull-out, force-displacement curve, which is directly related to reinforcement toughening via fiber/matrix debonding and frictional pull-out. They were evaluated for a model composite system of continuous SiC fibers with various surface treatments in a borosilicate glass matrix. For the processing conditions used, the interface fracture toughness and the interface frictional shear resistance were found to be 1.0 ± 0.5 J/m2 and 3.3 ± 0.6 MPa, respectively, for as-received fibers. Experiments conducted with long embedded fiber lengths allowed the shear resistance to be deconvolved into an interface friction coefficient of 0.05 ± 0.01 and an initial fiber-clamping pressure of 65 ± 6 MPa. Nitric acidwashed fibers gave an increased interface toughness of 3.6 ± 0.1 J/m2 and friction coefficient of 0.08 ± 0.02, but nearly the same initial clamping pressure, 72 ± 12 MPa. Calculations of the clamping pressure from the fiber/matrix thermal expansion mismatch and from stress birefringence measurements in the glass were in general agreement with this value.

scholarly journals Dynamic Single-Fiber Pull-Out of Polypropylene Fibers Produced with Different Mechanical and Surface Properties for Concrete Reinforcement

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 722
Author(s):  
Enrico Wölfel ◽  
Harald Brünig ◽  
Iurie Curosu ◽  
Viktor Mechtcherine ◽  
Christina Scheffler
Keyword(s):  
Tensile Strength ◽  
Dynamic Loading ◽  
Melt Spinning ◽  
Structural Changes ◽  
High Surface ◽  
Single Fiber ◽  
Scanning Calorimetry ◽  
Matrix Interaction ◽  
Pull Out ◽  
Fiber Matrix

In strain-hardening cement-based composites (SHCC), polypropylene (PP) fibers are often used to provide ductility through micro crack-bridging, in particular when subjected to high loading rates. For the purposeful material design of SHCC, fundamental research is required to understand the failure mechanisms depending on the mechanical properties of the fibers and the fiber–matrix interaction. Hence, PP fibers with diameters between 10 and 30 µm, differing tensile strength levels and Young’s moduli, but also circular and trilobal cross-sections were produced using melt-spinning equipment. The structural changes induced by the drawing parameters during the spinning process and surface modification by sizing were assessed in single-fiber tensile experiments and differential scanning calorimetry (DSC) of the fiber material. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements were applied to determine the topographical and wetting properties of the fiber surface. The fiber–matrix interaction under quasi-static and dynamic loading was studied in single-fiber pull-out experiments (SFPO). The main findings of microscale characterization showed that increased fiber tensile strength in combination with enhanced mechanical interlocking caused by high surface roughness led to improved energy absorption under dynamic loading. Further enhancement could be observed in the change from a circular to a trilobal fiber cross-section.

scholarly journals Why Should the “Alternative” Method of Estimating Local Interfacial Shear Strength in a Pull-Out Test Be Preferred to Other Methods?

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2406
Author(s):  
Serge Zhandarov ◽  
Edith Mäder ◽  
Uwe Gohs
Keyword(s):  
Shear Strength ◽  
Interfacial Shear Strength ◽  
Traditional Approach ◽  
Interfacial Shear ◽  
Frictional Stress ◽  
Displacement Curve ◽  
Pull Out ◽  
Alternative Method ◽  
Fiber Reinforced Materials ◽  
Force Displacement

One of the most popular micromechanical techniques of determining the local interfacial shear strength (local IFSS, τd) between a fiber and a matrix is the single fiber pull-out test. The τd values are calculated from the characteristic forces determined from the experimental force–displacement curves using a model which relates their values to local interfacial strength parameters. Traditionally, the local IFSS is estimated from the debond force, Fd, which corresponds to the crack initiation and manifests itself by a “kink” in the force–displacement curve. However, for some specimens the kink point is hardly discernible, and the “alternative” method based on the post-debonding force, Fb, and the maximum force reached in the test, Fmax, has been proposed. Since the experimental force–displacement curve includes three characteristic points in which the relationship between the current values of the applied load and the crack length is reliably established, and, at the same time, it is fully determined by only two interfacial parameters, τd and the interfacial frictional stress, τf, several methods for the determination of τd and τf can be proposed. In this paper, we analyzed several theoretical and experimental force–displacement curves for different fiber-reinforced materials (thermoset, thermoplastic and concrete) and compared all seven possible methods of τd and τf calculation. It was shown that the “alternative” method was the most accurate and reliable one, while the traditional approach often yielded the worst results. Therefore, we proposed that the “alternative” method should be preferred for the experimental force–displacement curves analysis.

Electromechanical study of carbon fiber composites

1998 ◽  
Vol 13 (11) ◽  
pp. 3081-3092 ◽  
Author(s):  
Xiaojun Wang ◽  
Xuli Fu ◽  
D. D. L. Chung
Keyword(s):  
Carbon Fiber ◽  
Electrical Resistance ◽  
Fiber Composites ◽  
Single Fiber ◽  
Fiber Direction ◽  
Carbon Fiber Composites ◽  
Fiber Waviness ◽  
Pull Out ◽  
The Matrix ◽  
Fiber Matrix

Electromechanical testing involving simultaneous electrical and mechanical measurements under load was used to study the fiber-matrix interface, the fiber residual compressive stress, and the degree of marcelling (fiber waviness) in carbon fiber composites. The interface study involved single fiber pull-out testing while the fiber-matrix contact electrical resistivity was measured. The residual stress study involved measuring the electrical resistance of a single fiber embedded in the matrix while the fiber was subjected to tension through its exposed ends. The marcelling study involved measuring the electrical resistance of a composite in the through-thickness direction while tension within the elastic regime was applied in the fiber direction.

The Pull-Out Method For On-Site Estimation of the Elastic Modulus of Concrete

2005 ◽  
Vol 40 (6) ◽  
pp. 505-511 ◽  
Author(s):  
P Antonaci ◽  
P Bocca
Keyword(s):  
Elastic Modulus ◽  
Concrete Strength ◽  
Displacement Curve ◽  
Concrete Mass ◽  
Existing Structures ◽  
Pull Out ◽  
Site Evaluation ◽  
Displacement Transducers ◽  
Force Displacement

The paper describes a new experimental mechanical method for the on-site evaluation of the elastic modulus of concrete. It is based on a modification of the well-known pull-out test, which is currently used for the estimation of concrete strength. The method consists in pulling out a metal insert embedded in the concrete mass and measuring the force-displacement curve consequent to the extraction. Three displacement transducers were used in order to correctly detect the displacement of the insert. Moreover, an adequate number of loading-unloading cycles was performed in order to stabilize the system and eliminate possible phenomena of mutual sliding between the mechanical parts of the apparatus and between the insert and the concrete mass. By performing a certain number of pull-out tests the stiffness value of the system is obtained. The material deformability is then estimated through an appropriate correlation curve between pull-out stiffness and elastic modulus, which has been worked out on the basis of finite element simulations and experimental results. The proposed method offers interesting possibilities of application for the characterization of existing structures at affordable costs.

Electromechanical Study of Carbon Fiber Composites

1997 ◽  
Vol 500 ◽  
Author(s):  
Xiaojun Wang ◽  
Xuli Fu ◽  
D.D.L. Chung
Keyword(s):  
Residual Stress ◽  
Carbon Fiber ◽  
Fiber Composites ◽  
Single Fiber ◽  
Fiber Direction ◽  
Carbon Fiber Composites ◽  
Fiber Waviness ◽  
Pull Out ◽  
The Matrix ◽  
Fiber Matrix

ABSTRACTElectromechanical testing involving simultaneous electrical and mechanical measurements under load was used to study the fiber-matrix interface, fiber residual stress and marcelling (fiber waviness) in carbon fiber composites. The interface study involved single fiber pull-out while the fiber-matrix contact resistivity was measured. The residual stress study involved measuring the resistance of a single fiber embedded in the matrix while the fiber was tensioned at its exposed ends. The marcelling study involved measuring the resistance of a composite in the through-thickness direction while tension was applied in the fiber direction.

scholarly journals Modelling of Crack Propagation in Layered Structures Using Extended Finite Element Method

2016 ◽  
Vol 2 (5) ◽  
pp. 180-188 ◽  
Author(s):  
Hesamoddin Nasaj Moghaddam ◽  
Ali Keyhani ◽  
Iman Aghayan
Keyword(s):  
Finite Element Method ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Young’S Modulus ◽  
Extended Finite Element Method ◽  
Young's Modulus ◽  
Displacement Curve ◽  
Extended Finite Element ◽  
Three Point Bending ◽  
Force Displacement

Crack propagation in structures is an important issue which is engineers and designers should consider. Modeling crack propagation in structures and study the behavior of this phenomenon can give a better insight to engineers and designers for selecting the construction’s materials. Extended finite element method (XFEM) was used successfully in the past few years for simulating crack initiation and propagation in sophisticated and complex geometries in elastic fracture mechanics. In this paper, crack propagation in three-point bending beam including initial crack was modeled based on ABAQUS software. The following consequences were attained through the study of simulation data. First, the effects of young’s modulus and fracture energy on force-displacement curve at three-point bending beam were investigated. It was observed that, by increasing the value of young’s modulus and fracture energy, three-point bending beam was showed more load carrying against initiation. Second, in multi-layer beam, the effect of young’s modulus on force-displacement curve was investigated. In case I (the thin upper layer is harder than the substrate) the value of young’s modulus in substrate was kept constant and the amount of young’s modulus in thin layer was risen in each step rather than the substrate, the peak in force-displacement curve was ascended and three-point bending beam resisted better against crack initiation. Next, similar conditions was considered in case II (the thin upper layer is softer than the substrate), by decreasing the value of young’ modulus in top layer, peak in force-displacement curve was declined and crack initiation was happened in lower loading in each step. Finally, sensitivity analysis for thickness of top layer was conducted and the impact of this parameter was studied.

Simulating Nanoindentation of Thin Cu Films Using Molecular Dynamics and Peridynamics

2016 ◽  
Vol 258 ◽  
pp. 25-28 ◽  
Author(s):  
Aylin Ahadi ◽  
Per Hansson ◽  
Solveig Melin
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamic ◽  
Displacement Curve ◽  
Dynamic Simulations ◽  
Cu Films ◽  
Cu Film ◽  
Peridynamic Model ◽  
Properties Of Materials ◽  
Deformation Patterns ◽  
Force Displacement

Nanoindentation is a useful experimental method to characterize the micromechanical properties of materials. In this study molecular dynamics and peridynamics are used to simulate nanoindentation, with a spherical indenter targeting a thin single crystal Cu film, resting on an infinitely stiff substrate. The objective is to compare the results obtained from molecular dynamic simulations to those obtained using a peridynamic approach as regards the force-displacement curves and the deformation patterns after that the material parameters in the peridynamic model have been fitted to the force displacement curve from the molecular dynamic simulation.

scholarly journals Deformation and Mechanical Properties of a Constant-Friction-Force Energy-Absorbing Bolt

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Tao Song ◽  
Tianbin Li ◽  
Lubo Meng ◽  
Chunchi Ma ◽  
Chaofei Li ◽  
...  
Keyword(s):  
Energy Absorption ◽  
Friction Force ◽  
Displacement Curve ◽  
Pull Out ◽  
Constant Friction ◽  
Combined Action ◽  
Face Plate ◽  
Energy Absorbing ◽  
Rock Tunnels ◽  
Force Displacement

The conventional bolts used in surrounding rock tunnels with large deformation often fail. As a solution to this problem, we developed an extensible bolt with energy-absorbing and constant-friction-force (EACF) characteristics. The EACF bolt mainly comprises a damping device, a hollow threaded bolt, a tightening nut, and a face plate. To reveal its working mechanism, the bolt was tested in terms of its friction, displacement, and energy absorption through a modified tensile test device in a laboratory. The static pull-out test results showed that the axial force-displacement curve of the bolt can be mainly divided into three stages: a conical extrusion stage, an elongation stage, and an elastic failure stage. The EACF bolts exhibited stable energy absorption behaviors when subjected to static loading. The maximum constant friction force could be adjusted by increasing the size and diameter of the straight section of the damping block, and the maximum elongation could be adjusted by increasing the length of the damping cylinder. When the properties of the bolt materials are kept constant, increasing the diameter of the damping block can help achieve a high constant resistance. The proposed EACF bolt has reliable deformation and energy-absorption properties, which ensure its stability when employed in tunnels under the combined action of support and surrounding rocks.

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