Microcharacterization of Creep Behavior of Carbon Nanofiber Reinforced HDPE Nanocomposites using a Depth Sensing Method

S. Xu, T. Liu, X.W. Tangpong, I. Akhatov, W-H. Zhong
North Dakota State University, US

Keywords: nanocomposites, creep, carbon nanofiber


Depth-sensing indentation at micro- and nano-scale levels is a useful tool for material characterization due to its simplicity. There are many well-established methods for determining local mechanical properties including elastic modulus, hardness, and fracture toughness of small volumes of solids by indentation. Most Polymer or polymeric composites usually exhibit time-dependent mechanical behavior even at room temperature which reduces its applicability as load-bearing components. Creep would not be desirable, particularly when the material, such as ultra-high molecular weight polyethylene (UHMWPE) or high density polyethylene (HDPE), is applied in artificial joints as the bearing material. This work reports an investigation on creep behavior of UHMWPE, HDPE and its nanocomposites (HDPE/CNF) by a micro-indentation technique instead of the traditional uniaxial tensile creep test. Compared with UHMWPE, the HDPE and HDPE/CNF nanocomposites exhibited higher creep resistance. The addition of pristine CNF (P-CNF) exhibited subtle effects on creep; however, the creep compliance was obviously increased with the addition of silane treated CNF (T-CNF). A second-order Kelvin Chain Model was determined through curve fitting to experimental data and can be used to predict the creep deformation behavior of the materials.