ABSTRACT
Because it yields numerous material structure properties, Wide Angle X-ray Diffraction (Huneau 2011) has been the main tool used, among the numerous existing techniques, in order to characterize strain-induced crystallization in rubber. Most of this work was focused on uniaxial quasi-static tension-retraction tests. Besides, very few studies considered SIC under fatigue loading conditions. In the 1970s, (Kawai 1975) successfully measured SIC in fatigue using a stroboscopic method in order to accumulate the weak diffracted intensity over hundreds of cycles. More recently, (Rouviere 2007) performed interrupted fatigue tests, WAXD acquisitions being performed at a fixed strain level during 45 min; this method renders difficult the split between SIC due to fatigue and SIC due to maintained stretch during measurements. Beurrot (Beurrot 2012) overcame this difficulty using synchrotron radiation to reduce the exposure
The study of fatigue crack propagation in elastomers is of major importance for the tyre industry; the goal is to improve the service life of products. Vulcanized cis-1,4-polyisoprene (natural rubber; NR) is a key compound in tyres; it exhibits remarkable mechanical properties and more particularly a very good resistance to fatigue crack growth as compared with synthetic rubbers, especially for large strain (Mars 2004). It is widely recognized that these excellent fatigue properties are related to the ability of NR to crystallize under strain (Saintier 2011). This property is usually referred to as Strain-Induced Crystallization (SIC); the reader may consult Huneau (Huneau 2011) for details on this subject.
