New Direction Of Application Of Natural Silk Fiber: Wild Tussah Silk / Carbon Fiber Hybrid Composites

Beijing time on August 22, 2019, Nature Communications published the latest research results of Beihang University's associate professor Guan Juan's research group entitled "wild tussah silk / carbon fiber hybrid building impact resistant composite material" (Integrating tough Antheraea pernyi silk and strong carbon fibres carbon). For the first time, the mixture of wild tussah silk and carbon fiber was used as a tough and tough phase. A series of high stiffness and high strength epoxy matrix composites were constructed, which realized the perfect combination of two kinds of high energy fibers and opened up a new direction for the application of natural silk fibers.

The first author of this article is Dr. Yang Kang, who is the first correspondence author, associate professor Guan Juan, Institute of materials science and engineering, advanced structural materials and biomaterials research center, and senior communications author. He is a fellow of Robert Ritchie, University of California at Berkeley, Fudan University Shao Zhengzhongjiao, and Keiji Numata researcher of the Japanese Institute of physical chemistry. This study is supported by the Beihang University's excellent 100 person program and youth top talent program.

Fig. 1 the functions of silkworm cocoon and tussah cocoon produced in China and corresponding to two kinds of silk are textile and protecting silkworm chrysalis respectively.

Nature's gift to Chinese people -- wild tussah silk

Wild tussah silk is mainly produced in China's Liaoning and Shandong. After thousands of years of natural selection, its protein sequence structure (oligoalanine fragment), aggregated structure and nanofiber structure are closer to spider silk than mulberry silk. In addition, although the tensile strength of tussah silk is only slightly higher than that of mulberry silk (higher than ordinary epoxy resin), the tensile fracture energy of tussah silk is 150 MJ M-3, much higher than that of mulberry silk ~70 MJ M-3 [2], so it is very strong and tough. However, tussah silk is not used to toughen and strengthen composite materials. This paper focuses on tussah silk with excellent mechanical properties to enhance the toughness and energy absorption properties of composites. It may provide new ideas for the selection of lightweight, high toughness and impact resistant materials in aviation and automotive fields.

Fig. 2 the microstructure of A. tussah silk fabric; the 2D synchrotron radiation pattern of B. tussah silk shows the structure of beta folded crystal; and the molecular structure of C. tussah silk protein.

FritzVollrath, an animal silk expert at University of Oxford, predicts that silk fiber composites are most likely to be applied to structural materials such as military helmets and wind turbines. In 2014, Guan Juan research group carried out systematic research on silk fiber composites (SFRP). The results showed that [3-5] had a very excellent impact property and had a low temperature toughness of -50 C at a volume fraction of 50%. The flax plant fiber could effectively control the mechanical properties of silkworm composite materials and enhance the rigidity and strength of silk composites. Coincidentally, the YoussefK. Hamidi research group of Houston University on the other side of the ocean has also carried out research on silk fiber composite materials, and developed a more matching resin [6] for silk reinforcement. The strength and toughness of hybrid fiber composites with strength and toughness are still lower than that of most high performance structural materials. In this paper, carbon fibers and wild tussah silk fibers were mixed, and carbon fibers were stiffened and tussah silk toughened. The interlaminar / interlaminar composites were successfully constructed, which ensured the toughness of silk fiber composites under flexural and impact modes. Meanwhile, the strength and stiffness requirements of engineering structural materials were achieved. The researchers also studied the influence of classical hybrid methods, such as interlaminar mixing and interlaminar intermingling, and hybrid ratio on the mechanical properties of composites.

Fig. 3 high toughness tussah silk / high rigid carbon fiber blended fabric.

Industrialization oriented comprehensive performance evaluation

In this paper, the researchers believe that the research of engineering materials should ultimately point to the application of industrialization. Therefore, they comprehensively evaluated the properties of tussah silk / carbon fiber hybrid composites: tensile, bending, interlaminar shear, impact, dynamic mechanical thermal analysis, aging behavior of water absorption, tensile creep, bending creep and so on. Abundant experimental data show that the alternate layer of tussah silk / carbon fiber hybrid composites has the best fiber matrix interface in all the hybrid materials, with 2 times the impact strength of carbon fiber composites with the same volume fraction, and shows excellent mechanical properties.

Fig. 4 A. impact resistance index; B. various mechanical properties of radar chart. CFRP: carbon fiber reinforced composite; 5C5S-1: alternate layer of silk fiber / carbon fiber hybrid reinforced composite; SFRP: tussah silk fiber reinforced composite.

Article official website link: https://www.nature.com/articles/s41467-019-11520-2

Reference:

[1]Yang K, et al, Nature Communications, 2019, 10; doi.org/10.1038/s41467-019-11520-2.[2]Fu C et al. Advanced al. Nal Materials, 2015, 21 (4): 729-737.[3]Yang K et al. Materials & Design, 2016, 108: 470-478.[4]Yang K, 108:, 729-737.[3]Yang, 2017