By Vamika Perumal (Instagram: @chaozinorder)
Green composites have gained popularity in the recent decades as solutions for several engineering problems, with the growing concern about environmental issues, crisis of crude oil and petroleum resources. Biocomposites and Hybrid composites with natural fibers have had noticeable industrial applications in the contemporary world. For instance, Mercedes Benz cars of Daimler Company have used a door panel made from sisal epoxy composites with a weight reduction of 20%.
Despite their lower performance as compared to the synthetic materials, the demand for bio-composites arises from their attractive properties like high strength to weight ratio, ease of design, wide availability, economical methods of processing and fabrication. They could be plant based like flax, hemp, jute, bamboo or animal based like silk. Plant fiber reinforced composites have been well studied and their use in commercial applications has been on the rise. Among the natural fibers, silk fibers are found to have exceptional mechanical properties and they act as a rival to many engineering materials. Limited scientific investigations are available in the literature on silk based composites and hence there is a need to study them.
The utility of silk has expanded in the recent past into domains of tissue engineering, smart wearable, optical sensors and medical devices. The lucrative qualities of silk from an engineering perspective are tunable degradability, hygroscopic nature, morphological flexibility, natural flame resistance, non abrasive nature, reasonable strength; high elongation at break similar to stainless steel; and higher toughness than Kevlar, carbon and glass fibers. Because of its low specific gravity, silk tends to have higher specific tensile and energy absorption properties.
Silk composites are a promising choice of candidate for energy absorption of one time high loads in short periods of time. For example they can be used in making high impact strength - body adaptive armor and foldable helmets. My study involved the synthesis of a novel composite with silk using strategic design criteria based on composite mechanics. The composite with optimal mechanical properties are found using TOPSIS - Multi Response Optimization method. A DOE-TOPSIS is performed to understand the effect of the variables chosen on the desired composite responses
Silk is very useful in biomedical applications because it is extremely compatible with the human body. It can be fabricated in multiple forms - hydrogels, sponges, films, etc. It is quite expensive, but the benefits are justified. I focus on non-biomedical applications of Silk as well. Specifically, Spider Silk can exceed the performance of many other synthetic materials!