Waldman Stephen D, Lee J Michael
Department of Mechanical and Materials Engineering, Queen's University, McLaughlin Hall, Room 205, Kingston, Ont., Canada K7L 3N6.
Biomaterials. 2005 Dec;26(35):7504-13. doi: 10.1016/j.biomaterials.2005.05.056.
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.
为工程材料开发的机械测试方法，如果应用于柔软的平面结缔组织，可能会导致人为的材料特性。使用高纵横比的单轴组织样本或带有细长十字形臂的双轴样本，可能会导致仅对在夹具之间完全伸展的离散细胞外纤维子集进行优先加载。为了验证这一假设，对显示出明显不同材料特性的十字形双轴结缔组织样本（牛心包、鱼皮）以及具有预定义纤维取向的模型纺织层压板，随着样本臂长度的减小进行了反复测试。在样本中心确定力学性能后，结果表明，随着样本几何形状变粗，材料似乎变得更硬且延展性更小，这表明随着样本臂长度的减小，纤维募集增加。还注意到观察到的剪切行为和刚体旋转的变化。确定材料特性的唯一真正可靠的方法是通过体内测试，但这并不总是方便的，而且通常在实验上要求很高。对于双轴材料特性的体外测定，应采用合适的样本几何形状，使所有纤维都对力学响应有贡献。
