Abstract
Dynamic crack propagation in elastomer membranes is investigated; the focus is laid on cracks reaching the speed of shear waves in the material. The specific experimental setup developed to measure crack speed is presented in details. The protocol consists in (1) stretching an elastomer membrane under planar tension loading conditions, then (2) initiating a small crack on one side of the membrane. The crack speed is measured all along the crack path in both reference and actual configurations, including both acceleration and deceleration phases, i.e. non steady-state crack propagation phases. The influence of the prescribed stretch ratio on crack speed is analysed in the light of both these new experiments and the few previously published studies. Conclusions previously drawn for steady-state crack growth are extended to non steady-state conditions: stretch perpendicular to the crack path governs crack speed in intersonic crack propagation regime, and the role of the stretch in crack direction is minor.
Highlights
High speed fracture of elastomer membranes is a rather unusual problem for both fracture mechanics and elastomer engineering communities, mainly because of the narrow range of application and the complex context of both large strain and dynamics
As common in fracture mechanics, the velocity of mechanical waves in the material is used as a scaling factor
The shear wave speed in the material depends on the strain state
Summary
High speed fracture of elastomer membranes is a rather unusual problem for both fracture mechanics and elastomer engineering communities, mainly because of the narrow range of application and the complex context of both large strain and dynamics. To our knowledge, only a dozen experimental studies on cracks combine large strain (> 100 %) and high speed propagation (close to the shear wave speed of the material) since the pioneering work of Treloar (1944) Peculiar features of such cracks have been highlighted, from wavy crack path (Stevenson and Thomas 1979; Deegan et al 2001) to the role of strain-induced crystallisation in natural rubber (Zhang et al 2009). Following the extension of the Griffith theory of fracture to elastomers by Rivlin and Thomas (1953), the relationship between crack speed and energy release rate is measured (Lake et al 2000; Morishita et al 2016) Alongside with this energetic approach, the precise role of strain in the membrane is investigated with both inflated (Stevenson and Thomas 1979; Moulinet and Adda-Bedia 2015) or plane (Gent and Marteny 1982a; Petersan et al 2004) sheets of elastomer. Following the first observations of Gent and Marteny (1982a) and the theoretical derivation of Marder (2006), Chen et al (2011) experimentally confirm
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