Hygromechanical characterization of sunflower stems

S. Sun (1) , Jean-Denis Mathias (2) , Evelyne Toussaint (1) , Michel Grediac (1)

1 IP - Institut Pascal
2 UR LISC - Laboratoire d'ingénierie pour les systèmes complexes

This study concerns the determination of hygromechanical properties of sunflower stems. Mechanical tests were carried out on specimens of sunflower bark and pith. Particular attention was paid to the influence on the mechanical properties of (i) specimen location along the stem and (ii) moisture content of specimens. For this purpose, specimens were taken from the bottom, middle, and top of the stems. The influence of humidity on the mechanical properties was studied by testing specimens conditioned at three different relative humidities: 0% RH, 33% RH and 75% RH. Moisture diffusion coefficients of bark and pith were deduced assuming Fick's law to predict the variation in moisture content of the specimens during the mechanical test. The Young's modulus of the bark was found to be higher than that of the pith, whereas the moisture diffusion coefficient of the bark was lower than that of the pith. Mechanical and hygroscopic properties of specimens depended on their location along the stem. In order to explain these results, morphological observations have been carried out on the specimen at each location. It was found that porosity of both the bark and the pith are lower at the top of the stem. The presence of sclerenchyma in the bark is also higher at the top of the stem.

Mots clés: PROPRIETE MECANIQUE; HUMIDITE; TOURNESOL; MORPHOLOGIE; MOISTURE CONTENT; MOISTURE DIFFUSION COEFFICIENTS; SPECIMEN LOCATION; SUNFLOWER STEMS; FICK'S LAW; HYGRO-MECHANICAL PROPERTIES; HYGROSCOPIC PROPERTIES; INFLUENCE OF HUMIDITY; MECHANICAL TESTS; MOISTURE DIFFUSION COEFFICIENT; MORPHOLOGICAL OBSERVATIONS; YOUNG'S MODULUS; MOISTURE; MOISTURE DETERMINATION; MORPHOLOGY; DIFFUSION; FLOWER; HYGROSCOPICITY; MECHANICAL PROPERTY; POROSITY; STEM; YOUNG MODULUS

Domaines: Sciences de l'environnement

S. Sun, Jean-Denis Mathias, Evelyne Toussaint, Michel Grediac. Hygromechanical characterization of sunflower stems. Industrial Crops and Products, 2013, 46, p. 50 - p. 59. ⟨10.1016/j.indcrop.2013.01.009⟩. ⟨hal-00923258⟩