Matching Items (2)
Stochastic multiscale modeling and statistical characterization of complex polymer matrix composites
Description
There are many applications for polymer matrix composite materials in a variety of different industries, but designing and modeling with these materials remains a challenge due to the intricate architecture and damage modes. Multiscale modeling techniques of composite structures subjected to complex loadings are needed in order to address the scale-dependent behavior and failure. The rate dependency and nonlinearity of polymer matrix composite materials further complicates the modeling. Additionally, variability in the material constituents plays an important role in the material behavior and damage. The systematic consideration of uncertainties is as important as having the appropriate structural model, especially during model validation where the total error between physical observation and model prediction must be characterized. It is necessary to quantify the effects of uncertainties at every length scale in order to fully understand their impact on the structural response. Material variability may include variations in fiber volume fraction, fiber dimensions, fiber waviness, pure resin pockets, and void distributions. Therefore, a stochastic modeling framework with scale dependent constitutive laws and an appropriate failure theory is required to simulate the behavior and failure of polymer matrix composite structures subjected to complex loadings. Additionally, the variations in environmental conditions for aerospace applications and the effect of these conditions on the polymer matrix composite material need to be considered. The research presented in this dissertation provides the framework for stochastic multiscale modeling of composites and the characterization data needed to determine the effect of different environmental conditions on the material properties. The developed models extend sectional micromechanics techniques by incorporating 3D progressive damage theories and multiscale failure criteria. The mechanical testing of composites under various environmental conditions demonstrates the degrading effect these conditions have on the elastic and failure properties of the material. The methodologies presented in this research represent substantial progress toward understanding the failure and effect of variability for complex polymer matrix composites.
ContributorsJohnston, Joel Philip (Author) / Chattopadhyay, Aditi (Thesis advisor) / Liu, Yongming (Committee member) / Jiang, Hanqing (Committee member) / Dai, Lenore (Committee member) / Rajadas, John (Committee member) / Arizona State University (Publisher)
Created2016
Description
This dissertation is focused on the rheology scaling of metal particle reinforced polymermatrix composite made of solid and nanoporous metal powders to enable their
continuous 3D printing at high (>60vol%) metal content. There remained a specific
knowledge gap on how to predict successful extrusion with densely packed metals by
utilizing their suspension melt rheological properties. In the first project, the scaling of
the dynamic viscosity of melt-extrudate filaments made of Polylactic acid (PLA) and
gas-atomized solid NiCu powders was studied as a function of the metal’s volumetric
packing and feedstock pre-mixing strategies and correlated to its extrudability
performance, which fitted well with the Krieger-Dougherty analytical model. 63.4
vol% Filaments were produced by employing solution-mixing strategy to reduce
sintered part porosity and shrinkage. After sintering, the linear shrinkage dropped by
76% compared to the physical mixing. By characterizing metal particle reinforced
polymer matrix composite feedstock via flow-sweep rheology, a distinct extension of
shear-thinning towards high shear rates (i.e. 100 s-1) was observed at high metal content
– a result that was attributed to the improved wall adhesion. In comparison, physically mixed filament failed to sustain more than 10s-1 shear rate proving that they were prone
to wall slippage at a higher shear rate, giving an insight into the onset of extrusion
jamming. In the second project, nanoporous copper made out of electroless chemical
dealloying was utilized as fillers, because of their unique physiochemical properties.
The role of capillary imbibition of polymers into metal nanopores was investigated to
understand their effect on density, zero-shear viscosity, and shear thinning. It was
observed that, although the polymeric fluid’s transient concentration regulates its
wettability, the polymer chain length ultimately dictates its melt rheology, which consequentially facilitates densification of pores during vacuum annealing. Finally, it
was demonstrated that higher imbibition into nanopores leads to extrusion failure due
to a combined effect of volumetric packing increase and nanoconfinement, providing a
deterministic materials design tool to enable continuous 3D printing. The outcome of
this study might be beneficial to integrate nanoporous metals into binder-based 3D
printing technology to fabricate interdigitated battery electrodes and multifunctional 3D
printed electronics.
ContributorsHasib, Amm (Author) / Azeredo, Bruno (Thesis advisor) / Song, Kenan (Thesis advisor) / Nian, Qiong (Committee member) / Kwon, Beomjin (Committee member) / Li, Xiangjia (Committee member) / Arizona State University (Publisher)
Created2022