Silk Fibers and their Unidirectional Polymer Composites - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 86

Secondly, variation of properties by varying fiber volume fraction in the compos-
ites was observed. From the test results, it can also be concluded that composite con-
taining 45% volume percentage shows higher strength than other lower fiber volume
fraction composites. It was expected that with the increase of fiber volume fraction,
strength of the composites will increase. As fiber contains inherent defects, strength
of single fibers is not constant and poor adhesion exists between fiber and matrix;
strength is less than theoretical strength. Hardness measurement shows not much vari-
ation in varying fiber volume fractions. Impact energy was greater in higher volume
fraction composites as compared to lower volume fraction ones. In conclusion, it can
be said that silk fibers should be incorporated in highly aligned manner and parallel
to each other to get substantial mechanical properties. Fiber volume fraction may be
increased keeping in mind that these fibers are not entangled, defect free and do not
impair proper wetting with the matrix phase.

KeyWords

• longitudinal strength

• Natural fibers

• Polypropylene

• scanning electron microscope

• siricin

• thermo-gravimetric analysis

• ultimate tensile strength