Resolving cavitation in silica-filled styrene-butadiene rubber composites upon cyclic tensile testing

Abstract

Cavitation phenomena were resolved in silica-filled styrene-butadiene-rubber composite upon cyclic tensile testing, prior to and after an accelerated thermal exposure. To this end, 3D digital image correlation (3D-DIC) and micro-computed x-ray tomography (μCT) were employed with in-situ approaches. It was found that thermal exposure induced structural changes in the composite similar to those occurring in real tires, such as the increase of the crosslink density of the rubber matrix, and the increase of its stiffness. The 3D-DIC measurements revealed that the mechanical hysteresis and volume strain were higher in the thermally-treated composite. The μCT results indicated three types of cavitation phenomenon as sources of volume change: i) debonding at the agglomerate poles, ii) internal agglomerate fracture and iii) a combination of both of them. Cavities were initially oblate and became more spherical when stretching the materials. The μCT measurements confirmed a faster increase in size and sphericity of voids for the thermally-treated composite when deformed, which is probably due to the higher stiffness of the rubber matrix.

Keywords

• Rubber
• Silica filler
• Tensile testing
• Digital image correlation
• Volume strain
• Tomography