Mei-po Ho

Study on the Mechanical Properties of Different Silkworm Silk Fibers

Mechanical properties of Bombyx mori, twisted B. mori, and Tussah silk fibers were investigated. Their ultimate tensile strength, elongation at break, and Young’s modulus were examined by performing a uniaxial tensile test on a single fiber. Scanning electron microscopy was used to observe the morphology of two different types of silk fiber, and to measure their apparent diameters from which the cross-sectional area of the silk fiber for stress-strain analysis can be determined. Based on experimental results obtained, it was found that Tussah silk fiber has a relatively high extensibility as compared to B. mori silk fiber and other natural fibers. Weibull analysis was also used to quantify tensile strength reproducibility of the silk fiber. Both single and twisted B. mori silk fibers have a better reproducibility of tensile properties than Tussah silk fiber.

Structural health monitoring of an asymmetrical SMA reinforced composite using embedded FBG sensors

Embedded actuator and sensor technology provides accurate structural health monitoring and proper structural response of a structure in any harsh servicing situation. This paper describes the fabrication of a smart composite by embedding shape memory alloy (SMA) wires and fibre Bragg grating (FBG) sensors into a glass fabric reinforced polymeric composite. Mechanical performances of the composite under martensitic and austenitic stages of the SMA wires were studied, and its natural frequencies were also measured accordingly. The result shows that the shift of the natural frequency arises from temperature change, thus changing the mechanical properties of the SMA wires. The changes of strain, stress, curvature, and damping ratio were predicted from an asymmetrical lamination model. It was found that this model demonstrates certain attractive effects, including mechanical properties, the change of shape, and the natural frequency upon activation of the SMA wires.