Evaluation of Mechanical Properties of Silk Fiber Reinforced Biodegradable Plastic Composites (Part 1, Effect of Fiber Surface Treatment on Mechanical Properties of Unidirectional Composites)

Abstract

Researches on the natural fiber reinforced “green” composites have been increasing in recent years due to concern over exhaustible petroleum resources and environmental destruction, and demands for energy saving and carbon dioxide reduction. Green composites are also expected as alternative materials for traditional fiber reinforced composites. Although green composites comprised of plant-derived natural fibers have been investigated by many researchers, use of animal-based natural fibers such as silk fiber (SF) in green composites has been rarely reported. In this regard, the mechanical properties and stress-strain relationships of silk fiber reinforced poly(butylene succinate) (PBS) biodegradable composites (SF/PBS) are evaluated in the present study. In order to investigate the effects of surface treatment of the silk fiber on the mechanical properties of SF/PBS, four types of surface treatment has been applied to the silk fiber. Tensile tests are conducted on the single silk fiber and unidirectional SF/PBS laminates. From the experimental results it has been found that removal of sericin in the silk fiber by the surface treatment improves Young's modulus but decreases fracture strain of the silk fiber. Predictions by generalized method of cells (GMC) micromechanics have shown good agreement with experimental results of the stress-strain relationship of 0° unidirectional laminates. However, nonlinear behavior in high stress region of 45° and 90° unidirectional laminates have not been predicted precisely due to internal damages such as interfacial debonding in the plates.