A series of mechanical experiments were performed to quantify the strength and fracture toughness of human amnion and chorion. The experiments were complemented with computational investigations using a 'hybrid' model that includes an explicit representation of the collagen fibre network of amnion. Despite its much smaller thickness, amnion is shown to be stiffer, stronger and tougher than chorion, and thus to determine the mechanical response of fetal membranes, with respect to both, deformation and fracture behaviour. Data from uniaxial tension and fracture tests were used to inform and validate the computational model, which was then applied to rationalize measurements of the tear resistance of tissue samples containing crack-like defects. Experiments and computations show that the strength of amnion is not significantly reduced by defects smaller than 1 mm, but the crack size induced by perforations for amniocentesis and fetal membrane suturing during fetal surgery might be larger than this value. In line with previous experimental observations, the computational model predicts a very narrow near field at the crack tip of amnion, due to localized fibre alignment and collagen compaction. This mechanism shields the tissue from the defect and strongly reduces the interaction of multiple adjacent cracks. These findings were confirmed through corresponding experiments, showing that no interaction is expected for multiple sutures for an inter-suture distance larger than 1 mm and 3 mm for amnion and chorion, respectively. The experimental procedures and numerical models applied in the present study might be used to optimize needle and/or staple dimensions and inter-suture distance, and thus to reduce the risk of iatrogenic preterm premature rupture of the membranes from amniocentesis, fetoscopic and open prenatal surgery.

中文翻译：

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对胎膜的耐受性差。

进行了一系列机械实验，以量化人类羊膜和绒毛膜的强度和断裂韧性。使用“混合”模型进行的计算研究对实验进行了补充，该模型包括羊膜胶原纤维网络的明确表示。尽管羊膜的厚度要小得多，但它显示出比绒毛膜更硬，更坚固和更坚韧，因此可以确定胎儿膜在变形和断裂行为方面的机械响应。使用单轴拉伸和断裂试验的数据来告知和验证计算模型，然后将其用于合理化测量包含裂纹样缺陷的组织样品的抗撕裂强度。实验和计算表明，小于1 mm的缺陷不会明显降低羊膜的强度，但是在羊膜穿刺术和胎膜缝合过程中，胎儿手术中羊膜穿刺和胎膜缝合引起的裂纹尺寸可能大于该值。与以前的实验观察一致，该计算模型预测出由于局部纤维排列和胶原蛋白压缩，羊膜裂纹尖端的近场非常狭窄。这种机制可保护组织免受缺陷的侵害，并大大减少多个相邻裂纹的相互作用。这些发现通过相应的实验得到了证实，表明对于缝线间距离大于1 mm和3 mm的羊膜和绒毛膜，预期多条缝线不会发生相互作用。