Silk Fibers and their Unidirectional Polymer Composites - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 81

tensile testing of Composites
Stress-strain curves of unidirectional fiber-reinforced composites under longitudinal
loading are represented in Figure 10. It is seen from this Figure that ultimate tensile
strength (UTS), modulus and percentage elongation are maximum for fiber volume
fraction at highest end (45%), because the load applied to the fiber direction. Longi-
tudinal strength is dominated by fiber strength. The stress-strain mode that operates
for a specific composite will depend on fiber and matrix properties, and the nature
and strength of the fiber-matrix interfacial bond. Figure 11 represents the comparison
between theoretical and experimental strength and modulus; the experimental values
are lower than theoretical values. This is due to the poor fiber-matrix interface and
misalignment of continuous unidirectional fibers. Figure 12 shows that longitudinal
strain increases with fiber volume fraction.
Figure 10. Stress-strain curve for composites under longitudinal loading.
Figure 11. Comparison between theoretical and experimental longitudinal strength and modulus.