title: Capturing tensile size-dependency in polymer nanofiber elasticity.
abstract: As the name implies, tensile size-dependency refers to the size-dependent response under uniaxial tension. It defers markedly from bending size-dependency in terms of onset and magnitude of the size-dependent response; the former begins earlier but rises to a smaller value than the latter. Experimentally, tensile size-dependent behavior is much harder to capture than its bending counterpart. This is also true in the computational effort; bending size-dependency models are more prevalent and well-developed. Indeed, many have questioned the existence of tensile size-dependency. However, recent experiments seem to support the existence of this phenomenon. Current strain gradient elasticity theories can accurately predict bending size-dependency but are unable to track tensile size-dependency. To rectify this deficiency a higher-order strain gradient elasticity model is constructed by including the second gradient of the strain into the deformation energy. Tensile experiments involving 10 wt% polycaprolactone nanofibers are performed to calibrate and verify our model. The results reveal that for the selected nanofibers, their size-dependency begins when their diameters reduce to 600 nm and below. Further, their characteristic length-scale parameter is found to be 1095.8 nm.
authors.affiliation: Department of Mechanical Engineering, Guangdong College of Industry & Commerce, Guangzhou 510510, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Yuan
authors.affiliation: Department of Materials Science, Fudan University, Shanghai 200433, China. Electronic address: jun_wang@fudan.edu.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Materials Science & Engineering, Peking University, Beijing 100871, China. Electronic address: ray-han@pku.edu.cn.
authors.forename: Ray P S
authors.initials: RP
authors.lastname: Han
mesh_terms: D004548:Elasticity; D008422:Materials Testing; D008962:Models, Theoretical; D057139:Nanofibers; D011091:Polyesters / Q000737:chemistry*; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D011091:Polyesters; C016240:polycaprolactone
keywords: Characteristic length-scale parameter; Effective modulus; Higher-order strain gradient elasticity; Tensile size-dependency