Toughness Optimization of SBR Elastomers – Use of Fracture Mechanics Methods for Characterization

Abstract

Elastomer materials are used in a wide application range and subjected to different loading from which failure of the material results. Because this failure is caused by initiation and propagation of cracks, the application of fracture mechanics methods for the assessment of the material is obvious. A short summary of the methods of technical fracture mechanics including possibilities of determination of crack resistance curves is given. Vulcanizates on the basis of SBR 1500 with various sulfur and carbon black contents were investigated. For describing the crack initiation and crack propagation behavior, several fracture mechanics examination methods were applied. Tear‐analyzer results were used to assess the crack propagation behavior under fatigue‐like loading conditions. Furthermore, for the characterization of the crack resistance of the materials under impact‐like loading conditions, instrumented tensile‐impact tests were performed. To obtain information about the initiation and propagation of a stable crack, quasi‐static fracture mechanics tests were applied. The results of the several tests are discussed in dependence on sulfur and carbon black contents. We found a non‐monotonous behavior of the toughness as a function of carbon black loading. An explanation is given in connection with a percolation‐like transition in filler morphology on larger length scales. Schematic crack propagation curve for characterizing the fatigue behavior of the vulcanizates recorded in a TFA test.magnified imageSchematic crack propagation curve for characterizing the fatigue behavior of the vulcanizates recorded in a TFA test.

Prediction of Crack Toughness of Rubber Under Impact Loading Conditions

“…Since its introduction by Rivlin and Thomas in 1954, T is the fracture mechanics parameter most used for rubbers. Compared with T, J is relatively seldom used as material parameter for these materials, for example in ref …”

“…In respect of major application fields of rubbery materials, fracture mechanics investigations of those are mainly focused on the fatigue crack growth behaviour under cyclic loading conditions . However, such investigations for elastomers under impact‐like loading conditions are relatively rarely performed …”

Fracture toughness of poly(lactic acid)/ ethylene acrylate copolymer/wood‐flour composite ternary blends

“…The fracture mechanics approach is one of the methods suitable for testing the fracture toughness of a material by taking its imperfections into consideration, and produces parameters that are true material constants, independent of both size and geometry . In addition, fracture mechanics concepts have been shown to establish morphology–property correlations for thermoplastic materials, and hence the use of fracture mechanics as an assessment tool for PLA/ethylene acrylate copolymer (EAC)/wood‐flour ternary composites is preferred …”

“…For most brittle materials such as polystyrene these requirements are easy to achieve. However, in toughened materials large‐scale plastic deformation may occur ahead of the crack tip during testing violating the validity requirements of LEFM . Such toughened materials require post‐yield fracture mechanics approaches such as the J ‐integral method to quantitatively characterize their fracture toughness…”

Procesado, modelización y caracterización de mezclas industriales de SEBS con materiales con cambio de fase (PCM) para la mejora del confort térmico en aplicaciones de ortopedia y puericultura

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