Guan Juan, Zhu Wenshu, Liu Binghe, Yang Kang, Vollrath Fritz, Xu Jun
School of Materials Science and Engineering and Intl. Research Center for Advanced Structural and Biomaterials, Beihang University, Beijing 100191, China; State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200433, China.
School of Materials Science and Engineering and Intl. Research Center for Advanced Structural and Biomaterials, Beihang University, Beijing 100191, China.
Acta Biomater. 2017 Jan 1;47:60-70. doi: 10.1016/j.actbio.2016.09.042. Epub 2016 Sep 30.
Silkworm cocoon material is a natural composite consisting of silk fibres and sericin glues. Both domestic and wild silkworms produce cocoons but with different functionality - one selected by man for textile manufacture whereas the other selected by Nature to provide damage-tolerant housing. To understand the structure--property relationship of cocoons, we evaluated and compared the microstructure and mechanical properties of two representative cocoon walls. It appears that a "brittle and weak" composite is produced by domestic Bombyx mori (B. mori) while a "tough and strong" composite is made by wild Antheraea pernyi (A. pernyi). The superior mechanical performance of A. pernyi cocoons can be attributed to both the material properties and the fibre network microstructures. Failure mechanisms and different failure modes for cocoon fibre composites were also proposed. A finite element model revealed qualitatively the effect of fibre properties and inter-fibre bonding strength on the mechanical properties of the fibre network. It emerged that both good mechanical properties of fibres and robust inter-fibre bonding were required for tough and strong fibre composites. The new insights could inspire new designs of synthetic fibre composites with enhanced mechanical properties.
Natural cocoons are an important group of natural fibre composites with versatile functionalities. Previous studies have focused on the diversity of cocoon species and different morphological and mechanical features. It was suggested that the cocoon network structure determined the final mechanical properties of the cocoon composite. Nevertheless, the full structure-propertyfunction relationships for the cocoon composite are not understood. By studying two distinct cocoon species with specific functionalities, we prove that the mechanical properties of two cocoons are determined by both network properties and fibre properties. A robust fibre network is the prerequisite, within which the good mechanical properties of the fibres can play a part. The finding will inspire new designs of synthetic composites with desirable and predictable mechanical properties.
蚕茧材料是一种由丝纤维和丝胶组成的天然复合材料。家蚕和野蚕都会结茧，但功能不同——一种是人类选择用于纺织制造，而另一种是自然选择用于提供耐损伤的住所。为了理解茧的结构与性能关系，我们评估并比较了两种代表性茧壁的微观结构和力学性能。结果表明，家蚕（Bombyx mori，B. mori）产生的是一种“脆性且脆弱”的复合材料，而野蚕（Antheraea pernyi，A. pernyi）产生的是一种“坚韧且强壮”的复合材料。柞蚕茧优异的力学性能可归因于材料特性和纤维网络微观结构。还提出了茧纤维复合材料的失效机制和不同失效模式。有限元模型定性地揭示了纤维特性和纤维间粘结强度对纤维网络力学性能的影响。结果表明，坚韧强壮的纤维复合材料既需要纤维具有良好的力学性能，也需要强大的纤维间粘结。这些新见解可能会激发具有增强力学性能的合成纤维复合材料的新设计。
天然茧是一类具有多种功能的重要天然纤维复合材料。以往的研究集中在茧种类的多样性以及不同的形态和力学特征上。有人认为茧网络结构决定了茧复合材料的最终力学性能。然而，茧复合材料完整的结构 - 性能 - 功能关系尚不清楚。通过研究两种具有特定功能的不同茧种类，我们证明了两种茧的力学性能由网络特性和纤维特性共同决定。强大的纤维网络是前提条件，在此基础上纤维良好的力学性能才能发挥作用。这一发现将激发具有理想且可预测力学性能的合成复合材料的新设计。
