Koh Ching Theng, Tonsomboon Khaow, Oyen Michelle L
Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK.
Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 81310 Parit Raja, Johor, Malaysia.
Interface Focus. 2019 Oct 6;9(5):20190012. doi: 10.1098/rsfs.2019.0012. Epub 2019 Aug 16.
Amnion is a membrane that surrounds and structurally protects the developing fetus during pregnancy. The rupture of amniotic membranes prior to both normal and preterm deliveries involves stretch forces acting on a biochemically triggered weak zone of the membranes. Fracture toughness is an important mechanical property describing how the membranes containing a defect resist fracture, but this property has never been investigated in amniotic membranes. In this work, the fracture toughness of many samples cut from four pieces of amniotic membrane from different mothers was examined by uniaxial and pure shear (mode I) fracture tests. The measurement was checked for dependence on the sample geometry and notch length. Results from the uniaxial tensile test show J-shaped stress-strain curves and confirm that the amniotic membrane is a nonlinear material. The measured fracture toughness of four amniotic membranes ranged from 0.96 ± 0.11 to 1.83 ± 0.18 kJ m. Despite considering the effect of the presence of the defect on mechanical property measurement, similar fracture behaviour was observed for pre-notched and unnotched specimens, indicating that the membranes were extremely tolerant to defects. This defect-tolerant characteristic provides insight into the understanding of fetal membrane rupture.
羊膜是一种在孕期环绕并在结构上保护发育中胎儿的膜。在正常分娩和早产之前，羊膜破裂涉及作用于膜的生化触发薄弱区的拉伸力。断裂韧性是描述含缺陷膜抵抗断裂能力的一项重要力学性能，但这一性能从未在羊膜中得到研究。在这项工作中，通过单轴和纯剪切（I型）断裂试验，对从不同母亲的四张羊膜上切割得到的许多样本的断裂韧性进行了检测。检查了测量结果对样本几何形状和切口长度的依赖性。单轴拉伸试验结果显示出J形应力-应变曲线，并证实羊膜是一种非线性材料。四张羊膜的测量断裂韧性范围为0.96±0.11至1.83±0.18 kJ/m²。尽管考虑了缺陷存在对力学性能测量的影响，但预切口和未切口样本观察到了相似的断裂行为，表明这些膜对缺陷具有极强的耐受性。这种耐缺陷特性为理解胎膜破裂提供了思路。
