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Experimental investigations of crack propagation in rubber under dif-ferent loading rates, temperatures and fracture modes
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
2015 (English)Report (Other academic)
Abstract [en]

In the present paper, the fracture behavior of carbon-black natural rubber material is experimentally studied. The cracked pure shear and the single edge notch specimens were used for investigating both pure mode I and mixed mode I and II fracture behavior, respectively. Further, different testing conditions were employed in the case of the cracked pure shear specimens. The specimens were subjected to three different loading rates and they were tested in two different temperatures. For studying the crack growth, a high speed camera at up to 7000 frames/s was used to follow the progress of the crack and later a post-processor was used to obtain the crack trajectory and velocity at different stages. The method introduced previously by the present author (Elmukashfi in report 580, Department of Solid Mechanics, Royal Institute of Technology (KTH), 2015) was used to obtain the critical tearing energy using the cracked pure shear specimens. Hence, the uncracked pure shear specimens were subjected to cyclic loading history in order to obtain the true elastic energy in pure shear. The single edge notch specimens were tested in room temperature under quasi-static loading. The pure mode I results suggest that the critical tearing depends strongly on the loading rate as well as the temperature. The tearing behavior shows stick-slip pattern at low tearing rates and smooth propagation at high velocities. The size of the stick-slip region is reduced significantly by increasing the loading rate as well as the temperature. In the mixed mode I and II, the transition from the stick-slip to smooth propagation and the transition from mixed mode I and II take place approximately simultaneously.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2015.
Series
TRITA-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 580
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-178051OAI: oai:DiVA.org:kth-178051DiVA: diva2:876372
Note

QC 20151203

Available from: 2015-12-03 Created: 2015-12-03 Last updated: 2015-12-10Bibliographically approved
In thesis
1. Modeling of fracture and damage in rubber under dynamic and quasi-static conditions
Open this publication in new window or tab >>Modeling of fracture and damage in rubber under dynamic and quasi-static conditions
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Elastomers are important engineering materials that have contributed to the different technical developments and applications since the 19th century. The study of crack growth mechanics for elastomers is of great importance to produce reliable products and therefore costly failures can be prevented. On the other hand, it is fundamental in some applications such as adhesion technology, elastomers wear, etc. In this thesis work, crack propagation in rubber under quasi-static and dynamic conditions is investigated.

In Paper A, theoretical and computational frameworks for dynamic crack propagation in rubber have been developed. The fracture separation process is presumed to be described by a cohesive zone model and the bulk behavior is assumed to be determined by viscoelasticity theory. The numerical model is able to predict the dynamic crack growth. Further, the viscous dissipation in the continuum is found to be negligible and the strength and the surface energy vary with the crack speed. Hence, the viscous contribution in the innermost of the crack tip has been investigated in Paper B. This contribution is incorporated using a rate-dependent cohesive model. The results suggest that the viscosity varies with the crack speed. Moreover, the estimation of the total work of fracture shows that the fracture-related processes contribute to the total work of fracture in a contradictory manner.

A multiscale continuum model of strain-induced cavitation damage and crystallization in rubber-like materials is proposed in Paper C. The model adopts the network decomposition concept and assumes the interaction between the filler particles and long-chain molecules results in two networks between cross-links and between the filler aggregates. The network between the crosslinks is assumed to be semi-crystalline, and the network between the filler aggregates is assumed to be amorphous with the possibility of debonding. Moreover, the material is assumed to be initially non-cavitated and the cavitation may take place as a result from the debonding process. The cavities are assumed to exhibit growth phase that may lead to complete damage. The comparison with the experimental data from the literature shows that the model is capable to predict accurately the experimental data.

Papers D and E are dedicated to experimental studies of the crack propagation in rubber. A new method for determining the critical tearing energy in rubber-like materials is proposed in Paper D. The method attempts to provide an accurate prediction of the tearing energy by accounting for the dissipated energy due to different inelastic processes. The experimental results show that classical method overestimates the critical tearing energy by approximately 15%. In Paper E, the fracture behavior of carbon-black natural rubber material is experimentally studied over a range of loading rates varying from quasi-static to dynamic, different temperatures, and fracture modes. The tearing behavior shows a stick-slip pattern in low velocities with a size dependent on the loading rate, temperature and the fracture mode. Smooth propagation results at high velocities. The critical tearing depends strongly on the loading rate as well as the temperature.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xv, 37 p.
Series
TRITA-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 0581
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:kth:diva-178048 (URN)978-91-7595-749-4 (ISBN)
Public defence
2015-12-18, sal B2, Brinellvägen 23 (02 tr), KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150203

Available from: 2015-12-03 Created: 2015-12-03 Last updated: 2015-12-31Bibliographically approved

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