Effect of the Distribution of Fiber Orientation on the Mechanical Properties of Silk Fibroin/Polycaprolactone Nanofiber Mats

Abstract

In this study, Silk Fibroin (SF)/Polycaprolactone (PCL) composite nanofiber mats were fabricated using an electrostatic spinning technology employing different drum rotation speeds. The morphology and tensile performance of the resulting nanofiber mats were characterized using thermal field emission scanning electron microscopy, multi-layer image fusion technology, pore size distribution analysis and uniaxial and biaxial tensile tests. The analytical results showed that the drum rotation speed had little effect on the diameter of the nanofibers, but it did effect the physical orientation of the nanofibers. When the drum rotating speed was lower than 2.38 m s^-1, the nanofibers were randomly distributed, and there was no obvious mechanical anisotropy in the fiber mats. However, when the rotation speed was as high as 11.88 m s^-1, the nanofibers were fully uniaxially oriented, which provided high mechanical anisotropy to the fiber mats. The distribution of the size of the aperture of the nanofiber mats was related to the distribution in the fiber orientation. If the degree of orientation of the fibrous layer was high, the variation in the individual fibers was low and the pore diameter of fibrous mats was smaller as a result of the centralized fiber distribution. In the case of the SF/PCL composite nanofiber mats fabricated with different drum rotation speeds, the variation in the mechanical performance of the resulting mat in biaxial tension was consistent with its performance in uniaxial tension; however, it was found that the fracture mechanism of fiber mats varied in biaxial tension and uniaxial tension.