Full-field bulge test for planar anisotropic tissues: Part I – Experimental methods applied to human skin tissue

• Published in: Acta biomaterialia Vol. 9; no. 4; pp. 5913 - 5925
• Main Authors: Tonge, Theresa K., Atlan, Lorre S., Voo, Liming M., Nguyen, Thao D.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2013
• Subjects: Anisotropy; Bulge test; Computer Simulation; cytology; Digital image correlation; Elastic Modulus; Elastic Modulus - physiology; extraembryonic membranes; gastrointestinal system; Human skin; Humans; humidity; Inflation test; methods; Models, Biological; pericardium; Physical Stimulation; Physical Stimulation - methods; physiology; Reproducibility of Results; Sensitivity and Specificity; Skin; Skin - cytology; Skin Physiological Phenomena; Stress, Mechanical; Tensile Strength; Tensile Strength - physiology; Human skin; Bulge test; Inflation test; Anisotropy; Digital image correlation
• ISSN: 1742-7061; 1878-7568; 1878-7568
• DOI: 10.1016/j.actbio.2012.11.035

The nonlinear anisotropic properties of human skin tissue were investigated using bulge testing. Full-field displacement data were obtained during testing of human skin tissues procured from the lower back of post-mortem human subjects using 3-D digital image correlation. To measure anisotropy, the dominant fiber direction of the tissue was determined from the deformed geometry of the specimen. Local strains and stress resultants were calculated along both the dominant fiber direction and the perpendicular direction. Variation in anisotropy and stiffness was observed between specimens. The use of stress resultants rather than the membrane stress approximation accounted for bending effects, which are significant for a thick nonlinear tissue. Of the six specimens tested, it was observed that specimens from older donors exhibited a stiffer and more isotropic response than those from younger donors. It was seen that the mechanical response of the tissue was negligibly impacted by preconditioning or the ambient humidity. The methods presented in this work for skin tissue are sufficiently general to be applied to other planar tissues, such as pericardium, gastrointestinal tissue, and fetal membranes. The stress resultant–stretch relations will be used in a companion paper to obtain material parameters for a nonlinear anisotropic hyperelastic model.