Publikace v odborných časopisech

The fatigue of rubber products is usually accompanied by undesirable transformation in their properties. The present work was dedicated to the investigation of consequences of fatigue loading on volume electric conductivity of natural rubber (NR) reinforced with 30 phr of fillers composed from various weight combinations of carbon nanotubes (CNTs) and carbon black (CB). Special attention was paid to study the influence of CNTs content on residual electric conductivity and a possible mechanism of fatigue driven rearrangement of hybrid filler network inside of rubber matrix was propounded forward. An increase in the CNTs content over the complete range of concentrations, enhanced the conductivity of fabricated samples up to two orders of magnitude in comparison to rubber compounds without CNTs. All the samples were subjected to harmonic sinusoidal loading at a frequency of 5 Hz up to 105 loading cycles at three different strains of 0.1, 0.25 and 0.5. Despite very little transformation in the polymer matrix, fatigue caused a progressive degradation of conductivity with an increase in applied strain. It was also found that with the addition and a subsequent increase in the concentration of CNTs, the undesirable reduction of conductivity was significantly arrested. This novel finding added another number to the list of the outstanding properties of CNTs.

In this work a new laboratory test equipment is presented, that allows for the definition of suitable load conditions (force, rotational speed, impact incidence). The Instrumented Chip & Cut Analyzer (ICCA) collects all relevant data during the test. Using a mathematical algorithm, realistic and reliable answers on CC behaviour of the rubber are derived from the measurements.

Tyre treads are exposed to rolling and sliding impacts which lead to damages, known as chip and cut (CC) effects. Reliable prediction of the CC behaviour of new tyre tread compounds is very difficult without field testing. The traditional CC test methods used in laboratories employ simple devices, where loading conditions cannot be applied sufficiently and reproducibly. In this work a new laboratory test equipment is presented that allows for the definition of suitable load conditions (force, rotational speed, impact incidence). The Instrumented Chip & Cut Analyzer (ICCA) produces wear patterns like the ones observed on surfaces of tyre treads that have been operated in the field for a while. The relevant data are collected during the test. Using a mathematical algorithm, realistic and reliable answers on CC behaviour of the rubber are derived from the measurements in a short time with very little effort.

The traditional CC test methods used in laboratories employ simple devices, where loading conditions cannot be applied sufficiently and reproducibly. Only the sample weight loss and the damaging total energy are provided as results after the test, which is not sufficient to describe the complexity of CC phenomenon [3]. That is the reason why the reliable prediction of CC behaviour is very difficult without field experiments. Therefore, it becomes necessary to perform time and cost consuming development programs involving iterative tyre building and field testing of new candidates for tread compounds. A recently launched laboratory test equipment, the Instrumented Chip & Cut Analyzer (ICCA) manufactured by Coesfeld GmbH & Co. KG, Germany, allows the definition of suitable load conditions (force, rotational speed, impact incidence). It produces wear patterns as those observed on surfaces of tyre treads that have been operated in the field for a while. The relevant data values are collected during the test. Using a mathematical algorithm, realistic and reliable answers on CC behaviour of the rubber are derived from the measurements in a short time with very little effort.

The capability of the new laboratory test method employing the ICCA to determine the CC resistance is shown on carbon black reinforced compounds based on NR and SBR. Speed and loads were varied over a wide range. The measuring results evidence a very high sensitivity of this laboratory appliance. This rubber impact testing approach allows to quantify the CC behaviour using a new classifier “P” which is the reciprocal equivalent to CC resistance. According to the P-value determined in the tests, NR ranks higher than SBR regarding CC resistance at higher applied loading, whereas for lower applied loadings an inverse ranking has been determined. This ranking matches the ranking of known crack growth resistance of the analysed rubbers. Thus, the methodology and equipment provide a successful tool to investigate the durability of rubber compounds used for tyre tread rubber in the laboratory already.

Tires require rubber compounds capable of enduring more than 108 deformation cycles without crack growth. One strategy for evaluating candidate compounds is to measure the intrinsic strength. The intrinsic strength is the residual strength remaining in the material after the strength-enhancing effects of energy dissipation in crack tip fields are removed.  If loads stay below the intrinsic strength (taking proper account of the possibility that the intrinsic strength may degrade with aging), then cracks cannot grow. Using the cutting protocol proposed originally by Lake and Yeoh, as implemented on a commercial Intrinsic Strength Analyzer, the intrinsic strength is determined for a series of carbon black (CB) reinforced blends of natural rubber (NR) and butadiene rubber (BR) typical of tire applications.  The intrinsic strength benefits of the blends over the neat NR and BR compounds are only observed after aging at temperatures in the range from 50°C to 70°C, thus providing fresh insights into the widespread durability success of CB-filled NR/BR blends in tire sidewall compounds and commercial truck tire treads.

Understanding the cut and chip (CC) effect in rubber is important for successful product development for tires used in off-road or poor road conditions and for other demanding applications of rubber. This research describes a laboratory testing method for characterising the CC fracture behaviour of rubber using a device that controls and records multiple applied loads and displacements during cyclic impact to the surface of a solid rubber specimen to mimic and quantify the CC damage experienced by tire tread compounds. To study the capabilities of the instrument, three model compounds were studied that are based on carbon black reinforced compounds of common elastomers used in tire treads: natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR). These polymers have well-established CC tendencies in field performance of tire treads, with NR exhibiting the best CC resistance followed by SBR and finally BR. The same trend was found with the rubber impact testing approach that allowed the CC behaviour to be quantified using a new physical parameter which is the CC propensity (P). The relative ranking for CC resistance for the three compounds followed the fatigue crack growth resistances of the materials but was exactly opposite to the ranking of DIN abrasion resistance. This provides evidence that CC damage from impact by mm-scale asperities and abrasion of rubber against μm-scale asperities exhibit distinct characteristics in rubber.

KEYWORDS: rubber, tire, chipping, chunking, testing, equipment, friction, wear

Dry friction and wear properties of natural rubber (NR), containing multi-walled carbon nanotubes (MWCNT) and carbon black (CB), were investigated. Natural rubber (NR)-based composites containing all common additives and curatives, and a fixed amount (30 phr—parts per 100 rubber by weight) of hybrid fillers  (MWCNTx + CB30−x) were prepared by simple mixing procedure and tested. The main goal was to study the behaviours of composites at different tribological testing con-ditions, such as friction speed and normal load. It was found that with an increase of concentration of MWCNT from x =  0 phr to x =   5 phr in studied composites, there was a decrease in the coefficient of friction (COF) with no significant change in wear in the framework of each used combination of testing parameters. Generally, higher friction speed at certain normal force led to the increase of COF of all the samples and wear reflected deliberate value fluctuation. Also, it was established that considerable growth of wear and unexpected reducing of friction coefficient ensued from increasing of applied load for every fixed sliding speed.

The phenomena of chipping and chunking have been effectively characterized in the laboratory.

Three different batches of ground tyre rubber (GTR), obtained from end of life (EOL) tyres, in the form of powder, were subjected to quantitative analysis using simple non-pyrolytic Fourier Transform Infrared (FT-IR) spectroscopy and derivative thermogravimetric (DTG) analysis. Two batches were based on EOL truck tyres varying in particle size, and one batch was based on EOL passenger car tyres. The focus was to derive a general method for finding multiple polymer blend compositions in different types of GTR for future efficient recycling applications of EOL tyres. The secondary aim was to evaluate the validity of the methodology independent of particle size. IR studies detected the presence of NR, SBR and BR characterized by peaks at 1375, 699 and 738 cm(-1), respectively, in all the batches. Each of the blends was ternary, in which the ratio of two rubbers was exactly calculated by combined use of an existing infrared blend parameter (P-IR) and the absorbance ratio of the characteristic peaks of the two rubbers in a baseline corrected IR spectrum. Then, using this calculated ratio on the results obtained from DTG, all three rubbers were quantified. (C) 2017 Elsevier Ltd. All rights reserved.

The present paper deals with the development of a progressive rubber-suspension system as light weight construction substituting a combination of a steel spring and rubber bushing system for sports equipment application. The new developed rubber suspension element uses the V-element geometry with respect to well-known non-linear mechanical behaviour of rubber and the expected non-linear relationship between required forces and the deformation of the suspension system. As example for application a mountain boardin kiting sports was selected. The approach is based on the correlation between the kinematics of the athlete and the viscoelastic behaviour of rubber-suspension elements.

The aim of this study is focused on the experimental investigations of wear behavior caused by cyclic impact loading of carbon black filled rubber compounds comprising pristine styrene butadiene rubber (SBR) together with incorporated SBR ground rubber (rubber powder).

The experimental approach is based on the energy evaluation of a hard abrader, which impacts and slides with constant cyclic loading force at the surface of a rubber test specimen. Experimental studies were performed using an instrumented cyclically working equipment, which is labeled Chip&Cut-Analyzer.

The fracture mechanical characterization of elastomeric materials is based on a global energy balance. Tearing energy was introduced in 1953 by Rivlin and Thomas to characterize the energy required for an infinitesimal increase in surface area during crack propagation. Enhancing the contributions of various energy dissipation mechanisms during the process of crack propagation is crucial for the understanding and modification of elastomeric materials with respect to an enhanced service life. Apart from the tearing energy, alternative fracture mechanical quantities based on the global energy balance are reviewed and discussed with respect to various influencing factors such as geometrical constraints of the specimen, specific loading conditions, and the specific material and its structural details. Finally, the application of advanced experimental methods characterizing the stages of crack initiation, propagation, and wear under more practical loading conditions are reviewed.

In the present work, binary blends of carbon black-filled cured rubber, composed of natural rubber (NR) and styrene butadiene rubber (SBR) at three different blend ratios, were subjected to Fourier Transform Infrared (FT-IR) spectroscopic study in attenuated total reflection (ATR) mode. The objective was to use the infrared spectra obtained to calculate a simple general infrared blend parameter (PIR), a characteristic of the NR-SBR blend. The calculation for determining PIR required finding the exact infrared (IR) peak heights for NR and SBR, at 1375 and 699 cm
1 , respectively. To obtain the exact peak heights, each of the spectra originally obtained from the IR spectrophotometer was modified using a newly developed numerical algorithmic method of baseline creation on and subsequent subtraction from the original spectrum. A very good baseline fit was achieved using this method. As a result, the numerical calculation of PIR for the NR-SBR blend was possible.

The aim of this work is to explore the influence of thermal ageing on wear resistance of cured rubber which has been based on varied composition of Natural rubber/Styrene butadiene rubber compounds. The thermal ageing process has been performed in a heating chamber at the temperature 80 degrees C during 4 and 16 days, respectively. The wear behaviour has been analysed at steady state as well as at dynamic conditions. The qualitative parameter "weight loss" has been observed during the analysis based on both of methods. We demonstrate the relationship between rubber composition, based on varied ratio of rubber types, and varied wear processes in dependence on thermal ageing.

The present work aims to characterize fatigue crack growth (FCG) behaviour for comparative durability prediction of NR/BR and NR/SBR blend based compounds. The influence of strain, temperature, r-ratio and waveform was studied to simulate realistic service life condition by using aTear and Fatigue Analyser (TFA). Both of these blends shown higher FCG rate at higher temperature, but the effect is comparatively higher in NR/SBR compound. The influence of r-ratio towards FCG rate was found to be very less in NR/BR blend, whereas NR/SBR blend shown considerable decrease in FCG rate at positive r-ratio. The higher FCG rate was observed in pulse mode compared to sine mode in both the blends.

ABSTRACT: The present paper proposes a new fracture experimental approach to rubber resistance against cutting by sharp objects based on newly developed instrumental testing equipment. In this work the effect of cutting velocity 25 and 100 mm.min-1 on varied pre-force 50 and 100 N cured rubber test specimens based on NR/BR/SBR blends has been studied. The experimental approach represents an application of cutting imple-ment (razor blade) to the tip of a crack in a time-dependent stretched test specimen. The fracture mechanic’s phenomena has been based on the definition of test specimen geometry with respect to the geometry ratio L0/W (Length/Width) = 1/8, whereas the common pure-shear test specimens have been used for the study. For lower cutting velocity, there also were found lower tearing energies at fracture process, which seems to be very important parameter. As a specific result we introduce the relationship between elastic energy of crack in-itiation in dependence on cutting velocity and crack length.

Abstract: Rubber is a widely used material in industry because of the unique viscoelastic behavior of rubber matrix.  In practice, rubber products are exposed to complex dynamic loading conditions caused due to various effects. Technical rubber products are mainly used for high dynamic applications especially in automotive as well as mechanical engineering, thus the factors affecting the rubber matrix behavior mostly are the dynamic inertia, profile of a contact surface of solid parts affecting rubber as well as influence of ozone concentration, solar radiation, different temperature etc. These complex processes constitute the initiation of micro-cracks, which is the fundamental fracture element of rubber-matrix responsible for various failure mechanisms of rubber products. Tests and determination of rubber product failure in the real usage are time and money consuming and thus effective testing methods in laboratory condition are highly appreciated. This work focuses on advanced methods for experimental characterization of complex rubber fracture mechanisms and parameters in the laboratory with respect to real loading conditions of rubber products in the field. Thus the rubber product failure in the real usage could be predicted. Finally, we have introduced theoretical approaches, new methods and testing equipment for characterization of complex rubber failure process from the phase of the crack initiation, its propagation up to the total rupture of rubber matrix.

Keywords: Rubber, Failure, Fracture, Crack, Testing Equipment

The aim of this study is concentrated on the experimental investigation of crack initiation during dynamic wear process and its correlation with fatigue crack growth of reinforced rubber materials. The analyzed rubber compounds suitable for applications such as treads for truck tires were based on natural rubber (NR) and polybutadiene rubber (BR). The dynamic wear behavior has been studied using an own developed testing equipment based on gravimetric determination of mass loss of test specimen. Fatigue crack growth (FCG) analysis was performed under pulse loading in accordance with real dynamic loading conditions of rolling tires using the Tear Analyser (TA). We show the crack initiation process during dynamic wear with respect to different impact energies and correlate the liability of crack initiation with FCG data at given tearing energy as a function of the rubber compositions. We demonstrate the higher crack initiation resistance of rubber blends with increased content of BR, while a predominant influence of NR improves the resistance against crack propagation especially at higher strain levels due to strain induced crystallization.

ABSTRAKT: Pneumatiky jsou v praxi vystavovány extrémnímu dynamickému, cyklickému zatěžování, zapříčiněnému zejména pohybem vozidla a to v závislosti na profilu povrchu vozovky, přičemž vzniklé reakce dynamických sil jsou přenášeny mezi vozidlem a vozovkou právě pneumatikami. Chování pneumatiky při přenosu dynamických sil je dáno převážně její konstrukcí, složením použitých pryží zejména pak běhounu, který je v přímém kontaktu s vozovkou. Dále její chování podléhá vlivům, jako je sluneční záření či změna povětrnostních podmínek, teplot atd., při kterých dochází k degradaci a procesu stárnutí pryže. Tyto zatěžující podmínky způsobují vznik mikrotrhlin, které z důvodu cyklicky opakujících se deformací rolující pneumatiky vedou k jejich dalšímu šíření v makrotrhliny. Zejména se pak makrotrhliny projevují v nejvíce exponované běhounové části pneumatiky jako jeho oděr a v kritickém případě můžou tyto trhliny vést k nezvratnému a totálnímu poškození pneumatiky. Testování a charakterizace poškození pneumatik v reálných podmínkách na testovacích vozidlech je však časově a finančně velmi náročné, proto se tyto testy přesouvají do laboratoří, kde je možné na měřících strojích zajistit shodné okrajové podmínky s podmínkami chování reálných pneumatik. Získané výsledky však popisují pouze komplexní chování daného typu pneumatiky bez přímého vztahu k použité pryži. Právě proto jsou vyvíjena laboratorní měřící zařízení, která se zaměřují na přímou analýzu a charakterizaci použitého pryžového materiálu při simulaci dynamického zatěžování odpovídající reálnému zatěžování pneumatiky a tím zajišťují značnou finanční tak jako časovou úsporu prováděných testů. V této práci jsou představovány průmyslem nejvyužívanější dostupné pokročilé experimentální metody a zařízení pro charakterizaci a předpověď poškození pneumatik, které jsou založeny na přímých analýzách pryžového materiálu použitého pro následnou výrobu pneumatiky. Hlavním smyslem této práce je pak představit a názorně porovnat výsledky lomového chování získané různými měřícími metodami a to jak na bubnové stolici při testování reálné pneumatiky, tak na stroji De-Mattia a Tear Analyzer při analýze zkušebních těles.

KEYWORDS: Pneumatika, Pryž, Poškození, Trhlina, Testování

We concentrate our work to the description of the state-of the-art and future trends in experimental laboratory characterization concerning structure-property relationship of unfilled and filler reinforced elastomers with respect to the micro-crack’s initiation and its propagation under the behavior simulating the real loading conditions in practice. We theoretically describe the fracture mechanism leading to the micro-crack initiation and summarize the criterions, which are available for experimental characterization of rubber fracture. We describe how the micro-crack initiation could experimentally be analysed with common testing equipment. Finally we show how the experimental fracture analysis and surface investigation could contribute to a description of the interaction between micro-cracks initiation, fatigue and fracture crack propagation in rubber under the real dynamic loading conditions.

This work focuses on the experimental investigation of rubber fracture behavior due to fatigue crack growth (FCG) as well as on the dynamic chip and cut (CC) analysis. We firstly show a relationship between FCG and CC for rubber blends composed of natural rubber (NR), styrene-butadiene rubber (SBR) and ethylene-propylene-diene-monomer rubber (EPDM). As specific results the rate of crack growth rate at given tearing energy and of dynamic rubber wear depending on the corresponding blend compositions are shown. A comprehensive description is also presented of a newly developed advanced CC measuring concept that allows an exactly quantified determination of the relation between damaging energy and its effects.

The understanding of fracture behavior of rubber-like materials is of great practical importance for the prediction of rubber-like product’s life time. The aim of this work is concentrated to mechanism of tyre tread failure working in hard terrain based on the experimental determination of the fracture data with respect to real loading conditions. The relationship between Fatigue Crack Growth (FCG) and Chip & Cut (CC) behaviors of blends based on Natural Rubber (NR) and Polybutadiene Rubber (BR) suitable for tyre tread ap-plication has been investigated. The fracture mechanical analyses under real pulse as well as commercially used sinusoidal cyclic loading conditions were performed using Tear Analyzer (TA). The Chip & Cut behavior has been studied using a own developed dynamic wear testing equipment based on gravimetric determination of mass loss of test specimen and energy-input during the testing period. We demonstrate the specific re-lationship between crack growth rate at given tearing energy as well as crack growth exponent and dynamic rubber wear in dependence of blend composition.

The understanding of dynamic behavior as well as fracture behavior of rubber-like materials is of great practical importance for the prediction of rubber-like product’s life time. The aim of this work is concentrated (i) to the description of mechanisms leading to rubber failure with respect to real loading conditions of the products and (ii) to a proposal resp. discussion of future trends in practical rubber characterization. We firstly demonstrate a relationship between Fatigue Crack Growth (FCG) behaviors under different loading conditions. Concluding we introduce a closed characterization method of dynamic rubber behavior with respect to tyre tread wear including the specific role of the FCG behavior of the rubber materials.

In this study, organo-montmorillonite (OMt) was treated with long alkyl chain containing docosanoic acid in order to obtain expanded organo-montmorillonite (EOMt) with increased interlayer distance. The X-ray diffraction (XRD) patterns confirmed the widening of the interlayer space of clay after intercalation of long alkyl chain docosanoic acid. The role of EOMt nanoparticles on the microstructure and fracture mechanical behavior of carbon black (CB) filled natural rubber (NR) composites was investigated. The microstructure of these clay filled NR/CB composites were revealed by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Tear Fatigue Analysis (TFA) tests were carried out using pure-shear test specimen under cyclic conditions to explicate the crack growth behavior of CB filled NR in the presence of EOMt. A significant reduction in crack growth rate was noticed in the presence of only 5 phr of EOMt. The viscoelastic properties obtained from the dynamic mechanical analysis (DMA) for different CB filled NR–clay composites were utilized to estimate the tearing energy qualitatively using the ‘Persson–Brener’ equation. The reinforcement of rubber matrix was investigated by both the static and dynamic mechanical properties. A synergy in reinforcement between clay nanoparticles and CB was attested by the marked enhancement in both mechanical properties.

Dochází-li v materiálu k lomu, jedná se o nežádoucí jev, který výrazně snižuje životnost výrobku. Lomové chování a tak i životnost pryžového výrobku je závislá na struktuře a složení gumárenské směsi. Cílem této práce byla příprava sady gumárenských směsí s různou škálou houževnatosti na bázi přírodního kaučuku (NR) a styren butadienového kaučuku (SBR). Pro každý kaučuk byly připraveny dvě sady směsí, u nichž byl variován obsah síry a sazí. Připravené vulkanizáty byly podrobeny mechanickým zkouškám a následně vzniklé lomové plochy byly analyzovány pomocí optické mikroskopie. Cílem práce je připravit jednoduchou metodu charakterizující lomovou plochu v závislosti na složení směsi, která by se dala využít v praxi.

The present paper proposes a new fracture mechanical testing concept for determination of dynamic crack propagation of rubber materials based on the method of simultaneous SENT- and pure-shear-mode testing. The fracture mechanic’s approach is based on the definition of pure-shear states according to the test specimen’s geometry ratio L0:W. We show how the tearing energy, T, and the crack growth rate, da/dn, depend on the test specimen’s geometry ratio and crack length. It is also demonstrated that the values for tearing energies and also crack growth rates for short crack lengths in SENT- as well as in pure-shear test specimens are identical.

The objective of the research presented in this paper is to investigate and to define the minimal  length of notch for the initiation of crack propagation in the pure-shear test specimen for the analysis of dynamic crack propagation in elastomers. Test specimens with different geometry factors L0:W (length to width of test piece) in the range from 1:12 to 1:4 and with or without initial crack have been investigated. The new developed experimental method has been supplemented by an appropriate FE–analysis. A minimal allowed notch length in the test piece, independent from its geometry, could be defined. This definition forms the theoretical basis for the improvement of efficiency for the analysis of dynamic crack propagation in rubbers.

Die Rissausbreitung in Elastomerwerkstoffen für technische Anwendungen wurde und wird aufgrund ihrer großen Bedeutung hinsichtlich der Lebensdauer von Bauteilen intensiv unter-sucht. Dazu werden bruchmechanische Untersuchungen herangezogen, wobei bekannt ist, dass derartige Ergebnisse von der Geometrie der Prüfkörper und der Kerbgeometrie beein-flusst werden können. Im Rahmen dieser Arbeit wird ein Verfahren zur definierten und stan-dardisierbaren Kerbeinbringung als Basis für die zuverlässige Ermittlung von bruchmechani-schen Kennwerten für Elastomere vorgestellt. Um die Rissausbreitungscharakteristik in Ab-hängigkeit von der Kerbeinbringung quantitativ zu beschreiben, wurden Elastomerprüfkörper mit unterschiedlichen Kerben hergestellt, wobei die Kerbeinbringung insbesondere hinsicht-lich der möglichen Winkel definiert erfolgte. Nach der Kerbeinbringung wurden Experimente unter zyklischer Beanspruchung durchgeführt. Die Ergebnisse zeigen die Bedeutung einer reproduzierbaren und definierten Kerbeinbringung.

Die Arbeit beschäftigt sich mit der Entwicklung eines Verfahrens zur definierten und standardisierbaren Kerbeinbringung als Basis für die zuverlässige Ermittlung von bruchmechanischen Kennwerten für Elastomere. Im Rahmen der Untersuchungen wurden unterschiedliche Metallklingenkerben definiert erzeugt. Dabei kamen drei verschiedene Elastomere zur Anwendung. Nach der Kerbeinbringung wurden Experimente unter quasistatischer Beanspruchung durchgeführt. Es wurde festgestellt, dass eine Veränderung der Winkel bei der Kerbeinbringung einen teilweise signifikanten Einfluss auf den Rissausbreitungsverlauf hatte. Dieses Ergebnis zeigt die Bedeutung einer reproduzierbaren und definierten Kerbeinbringung auf.

Die Rissausbreitung in Elastomerwerkstoffen für technische Anwendungen wurde und wird aufgrund ihrer großen Bedeutung hinsichtlich der Lebensdauer von Bauteilen intensiv untersucht. Dazu werden bruchmechanische Untersuchungen herangezogen, wobei bekannt ist, dass derartige Ergebnisse von der Geometrie der Prüfkörper und der Kerbgeometrie beeinflusst werden können. Im Rahmen dieser Arbeit wird ein Verfahren zur definierten und standardisierbaren Kerbeinbringung als Basis für die zuverlässige Ermittlung von bruchmechanischen Kennwerten für Elastomere vorgestellt. Um die Rissausbreitungscharakteristik in Abhängigkeit von der Kerbeinbringung quantitativ zu beschreiben, wurden Elastomerprüfkörper mit unterschiedlichen Kerben hergestellt, wobei die Kerbeinbringung insbesondere hinsichtlich der möglichen Winkel definiert erfolgte. Nach der Kerbeinbringung wurden Experimente unter zyklischer Beanspruchung durchgeführt. Die Ergebnisse zeigen die Bedeutung einer reproduzierbaren und definierten Kerbeinbringung. 

A description of a new high speed falling-dart impact machine is presented. The machine, instrumentation and also some experimental analysis of elastomers are described. Important factors influencing the impact behaviour of elastomers are impact velocity and temperature during the tests. The machine allows a velocity between 2 and 50 m/s and temperature from -40 to 180 °C. Some testing results on TPE, SBR, NBR/SBR, EPDM at velocities of 10, 20 and 30 m/s are presented. Results show that the dynamic behaviour of elastomer materials is different when testing at low, medium or high speeds.

Crack growth characteristics of rubber materials are important for determination of strength and durability of the materials. In classical studies of fracture mechanics of rubber, it was featured tensile- and prominently pure-shear-test pieces. In this paper a fatigue crack growth of rubber materials is determined by using a method of simultaneous Tensile- and Pure-shear-Mode Testing. Measurement were made in order to characterize the fatigue crack growth behavior as a function of the tearing energy, determined by strain energy density in test piece of tensile- and pure-shear geometry. Measurements were made to observe the effects of loading frequency and amplitude. Comparison of the fatigue crack growth behavior between tensile- and pure-shear-test pieces was observed for verification of experimental data measured by simultaneous tensile- and pure-shear-mode testing.

In dieser Arbeit wird  die Entwicklung einer Methode zur Analyse des dynamischen Risswachstums von  Elastomeren im simultanen Zug- und Pure-shear-Prüfmodus aufgezeigt. Die Entwicklung basiert auf der mechanischen Aufrüstung und Weiterentwicklung eines Tear Fatigue Analyzers (TFA, Fa. Coesfeld) und der weiteren Ausstattung dieser Prüfmaschine mit neuer Hardware, sowie an Veränderungen in Bezug auf Erkennung und Analyse der Rissbilderfassung. Mit der neuen Prüfmaschine können erstmals  simultan zwei Prüfmoden realisiert werden. Mittels dieser zwei Methoden wird gleichzeitig die Rissausbreitung in Probekörpern unterschiedlicher Geometrie unter gleicher Belastung gemessen.  Dadurch wird ein genauer Vergleich zwischen den experimentell ermittelten Prüfwerten ermöglicht.

The technical rubber is high filled and cross-linked polymeric material. It can be applied in many applications in the industry because of its unique and variable elastic and damping behaviours. The rubber is set the high requirements about efficiency and stability for the characteristic value of material due to the typical dynamic loading of the rubber. The long durability could be generally reduced through damage of materials and wear mechanism, which are nearly always the cause of crack creation and propagation.

The most important technical rubber is often based on natural rubber (NR) and styrene butadiene rubber (SBR). The matrix of rubber could be reinforced with the active fillers. The most important active fillers are carbon black and silicic acid. The specific quantity addition of this filler combined with the vulcanization gives various possibilities for the setting of mechanical behaviors of rubber.

The review describes recent research about crack propagation of vulcanized rubber filled with waste rubber powder where the main intention is to gain insight into relationship between concentration of rubber powder in vulcanized rubber on critical stress by crack propagation.