Nanomechanical Behaviors of Nanoparticle Incorporated Nanofiber

Author

• Ashfaqul Hoque KhademFollow

Date of Award

8-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Committee Chair/Advisor

Dr. Lihua Lou

Committee Member

Dr. Xin Zhao

Committee Member

Dr. Zhaoxu Meng

Abstract

Poly(vinylidene fluoride) (PVDF) nanofibers have attracted significant interest for flexible, lightweight, and functional polymer-based systems because of their favorable mechanical, piezoelectric, and processing characteristics. Incorporating inorganic nanoparticles such as iron oxide (Fe₃O₄) into PVDF nanofibers can further modify their surface and nanomechanical behavior. However, the role of particle size on local modulus, adhesion, roughness, and fiber morphology remains insufficiently understood. In this thesis, electrospun PVDF and PVDF/Fe₃O₄ nanocomposite fibers were fabricated and analyzed to investigate how Fe₃O₄ nanoparticles with different sizes (20 nm and 50 nm) affect nanoscale mechanical and surface properties. Atomic force microscopy (AFM) was used to evaluate fiber morphology, surface roughness, adhesion force, and local elastic modulus through force mapping. The results showed that Fe₃O₄ incorporation altered both the topographical and nanomechanical response of PVDF nanofibers. The 20 nm Fe₃O₄ composite exhibited the smallest average fiber diameter, approximately 1056.30 ± 214.46 nm, compared with 1630.72 ± 482.46 nm for neat PVDF and 1362.57 ± 288.31 nm for the 50 nm Fe₃O₄ composite. Surface roughness also depended on particle size, with the 50 nm composite showing the highest roughness. In contrast, the 20 nm composite exhibited a smoother surface than both neat PVDF and the 50 nm composite. Adhesion force increased after Fe₃O₄ addition, indicating modified tip–sample interaction and surface characteristics.

Nanomechanical mapping revealed a load-dependent decrease in modulus for all samples, consistent with polymer deformation behavior under increasing indentation depth. The PVDF/Fe₃O₄ composite containing 20 nm particles showed the highest modulus with average values of 2.74, 2.19, and 2.10 MPa at 500, 750, and 1000 nN, respectively. In comparison, the 50 nm Fe₃O₄ composite showed modulus values of 2.38, 2.16, and 1.91 MPa under the same loading conditions. These findings suggest that smaller Fe₃O₄ particles provide more effective nanoscale reinforcement. To interpret the indentation response, this work developed a modified Voigt–Reuss–Hill (VRH) framework by introducing a load-dependent strain-sharing parameter, n, linked to AFM contact mechanics. This parameter accounts for the changing contribution of the interphase region as the applied indentation load increases. For the 20 nm PVDF/Fe₃O₄ composite, the modified VRH framework yielded a MAPE of 9.29%, which was comparable to or slightly better than the Reuss, Halpin–Tsai, Guth–Gold, and Mori–Tanaka models, with MAPE values of 15.14%, 15.86%, 14.76%, and 15.48%, respectively. For the 50–100 nm PVDF/Fe₃O₄ composite, the modified VRH framework produced a MAPE of 15.26%, while the Voigt, Reuss, Halpin–Tsai, Guth–Gold, and Mori–Tanaka models yielded MAPE values of 66.38%, 14.24%, 14.89%, 14.78%, and 14.58%, respectively. Although several conventional models showed similar average errors, the modified VRH framework provides a more physically meaningful interpretation by incorporating AFM contact geometry and load-dependent strain sharing. Hence, it enables the description of the localized, interphase-sensitive nanomechanical response of Fe₃O₄-reinforced PVDF nanofibers.

Recommended Citation

Khadem, Ashfaqul Hoque, "Nanomechanical Behaviors of Nanoparticle Incorporated Nanofiber" (2026). All Theses. 4818.
https://open.clemson.edu/all_theses/4818

Author ORCID Identifier

https://orcid.org/0000-0003-4464-2868