Effect of sample geometry on the apparent biaxial mechanical behaviour of planar connective tissues.
Mechanical testing methodologies developed for engineering materials may result in artifactual material properties if applied to soft planar connective tissues. The use of uniaxial tissue samples with high aspect ratios or biaxial samples with slender cruciform arms could lead to preferential loading of only the discrete subset of extracellular fibres that fully extend between the grips. To test this hypothesis, cruciform biaxial connective tissue samples that display distinctly different material properties (bovine pericardium, fish skin), as well as model textile laminates with predefined fibrous orientations, were repeatedly tested with decreasing sample arm lengths. With mechanical properties determined at the sample centre, results demonstrated that the materials appeared to become stiffer and less extensible with less slender sample geometries, suggesting that fibre recruitment increases with decreasing sample arm length. Alterations in the observed shear behaviour and rigid body rotation were also noted. The only truly reliable method to determine material properties is through in vivo testing, but this is not always convenient and is typically experimentally demanding. For the in vitro determination of the biaxial material properties, appropriate sample geometry should be employed in which all of the fibres contribute to the mechanical response.
Waldman
Stephen D
SD
Department of Mechanical and Materials Engineering, Queen's University, McLaughlin Hall, Room 205, Kingston, Ont., Canada K7L 3N6. waldman@me.queensu.ca
Lee
J Michael
JM
D000818:Animals; D016477:Artifacts; D002417:Cattle; D003238:Connective Tissue / Q000502:physiology*; D004548:Elasticity; D005399:Fishes / Q000502:physiology*; D008422:Materials Testing / Q000379:methods*; D010496:Pericardium / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods*; D018401:Sample Size; D012879:Skin Physiological Phenomena; D013314:Stress, Mechanical; D013718:Tensile Strength; D046509:Tissue Culture Techniques / Q000379:methods*