Tensile and shear mechanical properties of laver (Porphyra yezoensis Ueda)

Abstract

ABSTRACT The tensile and shear mechanical properties of laver were investigated in order to reduce the tensile and shear forces, tensile and shear energies consumption during the harvesting and processing. Loading rate, harvest time and origin were selected as the effect factors for laver tensile and shear tests, while mathematical models of the variation of tensile and shear mechanical properties with three factors were also developed. The following results were obtained: tensile force, shear force, tensile energy and shear energy of laver are affected by loading rate, harvest time and origin. Tensile force, shear force and shear energy were generally inversely proportional to the loading rate, while tensile energy was generally positively proportional to the loading rate. The minimum values are 0.0557 N, 0.1650 N, 0.7267 N.mm and 0.7393 N.mm, respectively. Tensile force, shear force and tensile energy all increased with increasing harvest time, while shear energy decreased with increasing harvest time. The maximum values are 0.1581 N, 0.4437 N, 1.5367 N.mm and 1.5177 N.mm, respectively. Both tensile and shear forces (0.0857 N, 0.2549 N) were greatest in Dalian for the first harvest of laver. However, the first harvest of Qingdao laver has the lowest tensile and shear energy. The microstructure after stretching and shearing changed significantly with normally shaped cells deformed and ruptured. The changes in microstructure were consistent with the macro-mechanical properties, verifying the reliability of the test data.