The mechanical and thermal properties of silk fiber/PLA and CFF/PLA biocomposites have been investigated in depth in the past few years. The mechanical properties in terms of elastic modulus and ductility of these biocomposites increased substantially compared to the neat polymers. From the DMA results, incorporation of the fibers gave rise to a considerable increase in their storage modulus (stiffness) and to a decrease of their tan delta values. These results demonstrated the reinforcing effect of CFF on PLA matrix. The TGA thermograms reveal the thermal stability of the composites with respect to the pure PLA resin. In addition, the TMA results suggest that the biocomposite with a small amount of animal fiber provided also better thermal properties as compared with pristine polymer. The SEM investigations confirm that both fibers were well dispersed in the PLA matrix. However, concerns have been raised on their interfacial bonding properties, as normally it is difficult to have consistent physical properties between fibers collected from different suppliers. The surface of the fibers are rough, which enables a mechanical interlocking with surrounding matrix to be generated. Moisture absorption is another issue that restricts the wide usage of natural fibers for primarily structural components in industry.
Although plant- and animal-based fibers have attracted much attention in product design and engineering and bioengineering industries and have undergone comprehensive research in the past few years, many factors, such as their interfacial bonding and stress transfer properties, have not yet been solved to date. To broaden the application of these fibers in solving environmental problems, more studies have to be done in the future.