Julien Gauffreteau’s research while affiliated with Sigma Clermont and other places

Leather materials are subjected to various deformation states during their elaboration and their use as a final product. Although the mechanical response of leathers under tension has been studied in the literature for decades, scarce information is available on the nature of their elasticity and more generally on their thermomechanical behavior. In the present study, four leathers were tested under uniaxial loading conditions while temperature changes were measured at the specimen surface using infrared thermography. Two types of tests were performed at constant ambient temperature: monotonous displacement-controlled tests until failure, and cyclic load-unload tests with increasing amplitudes. The heat sources at the origin of the temperature changes were also determined by using a version of the heat diffusion equation applicable to homogeneous tests. Results enabled us to discuss the nature of thermoelastic couplings in leathers. Intrinsic dissipation caused by mechanical irreversibility was also detected and quantified. Distinct responses are evidenced depending on the type of leather tested.

Leather materials are able to undergo various strain and stress states during their elaboration process and their use in numerous applications. Although the experimental mechanical response in tension of leathers has been studied in the literature for decades, scarce information is available on the nature of their elasticity and more generally on their thermo-mechanical behaviors. In the present study, two leathers were tested under uniaxial cyclic loading while temperature changes were measured at the specimens’ surface by infrared thermography. The heat power at the origin of the temperature changes was then determined by using an adequate version of heat diffusion equation which is applicable to homogeneous tests. Results enabled us to discuss on the physical nature of the thermoelastic coupling in leathers. Intrinsic dissipation caused by the mechanical irreversibility was also detected. Distinct behaviors are evidenced as a function of the type of leathers.

Leather materials undergo various strain and stress states during their elaboration process and their application in numerous different functions. Among the key properties required for such materials, tearing resistance appears as one of the most important. In this paper, the tearing behavior of two types of leather, a grain pigskin leather and a grain calf leather, was investigated at the local scale using full-field techniques. During the tests, thermal fields were measured at the surface of the two leathers by means of an infrared camera. Measurements of the displacement and deformation fields were also performed at the surface of the pigskin sample using the digital image correlation technique, which was not possible for the calf sample due to surface wrinkling. The results obtained enable us to discuss and compare the tearing resistance of both leathers in terms of the thermal activity in the zone of influence of the crack. The best tearing resistance was obtained for the grain calf leather that has undergone a retanning operation and whose matrix contained a plasticizer.

Leather materials are able to undergo various strain and stress states during their elaboration process and their use in numerous applications. Although the experimental mechanical response in tension of leathers has been studied in the literature for decades, scarce information is available on the nature of their elasticity and more generally on their thermo-mechanical behaviors. In the present study, two leathers were tested under uniaxial cyclic loading while temperature changes were measured at the specimens' surface by infrared thermography. The heat power at the origin of the temperature changes was then determined by using an adequate version of heat diffusion equation which is applicable to homogeneous tests. Results enabled us to discuss on the physical nature of the thermoelastic coupling in leathers. Intrinsic dissipation caused by the mechanical irreversibility was also detected. Distinct behaviors are evidenced as a function of the type of leathers.