Creep Compliance Characterization of Vapor-Grown Carbon Nanofiber/Vinyl Ester Nanocomposites Using a Central Composite Design of Experiments

Drake, D., Simsiriwong, J., Sullivan, R. W., Lacy, T., Pittman, C., Toghiani, H., DuBien, J. L., & Nouranian, S. (2013). Creep Compliance Characterization of Vapor-Grown Carbon Nanofiber/Vinyl Ester Nanocomposites Using a Central Composite Design of Experiments. 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. Boston, MA. DOI:10.2514/6.2013-1585.

Abstract

The tensile creep behavior of nanocomposites prepared from a vinyl ester resin (Derakane 441‐400) with oxidized vapor-grown carbon nanofibers (VGCNFs) was characterized for composites containing 0.00 to 1.00 parts of nanofiber per hundred parts resin (phr). These nano-composites were fabricated by high shear mixing, casting, and curing the test articles in an open face mold under nitrogen for a prescribed heating and post-curing cycle. A response surface model (central composite design) was developed for predicting the viscoelastic behavior of VGCNF/vinyl ester nanocomposites. In a preliminary analysis, short-term creep/creep-recovery experiments were conducted to obtain the viscoelastic response at 43MPa and at 24 ºC. A non-contact digital image correlation technique was used to measure the creep strains in the longitudinal and transverse directions simultaneously. The creep compliances were calculated from the generalized 3-D viscoelastic constitutive equation with a Prony series representation. The effect of the VGCNF weight fraction on the ultimate tensile strength and creep compliance of the vinyl ester/VGCNF nanocomposites is discussed. At 24 ºC, increasing the VGCNF weight fraction decreased the creep compliance.