Fracture Mechanisms of Layer-By-Layer Polyurethane/Poly(Acrylic Acid) Nanocomposite.

Fracture Mechanisms;Layer-by-Layer Nanocomposite;Large Scale Deposition of Nanocomposites;Finite Element Modeling;Mechanical Engineering;Engineering;Mechanical Engineering

Kheng, Eugene R.Arruda, Ellen M. ;

University of Michigan

关键词: Fracture Mechanisms;    Layer-by-Layer Nanocomposite;    Large Scale Deposition of Nanocomposites;    Finite Element Modeling;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/107079/ekheng_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

A Layer-by-Layer (LBL) (layer-by-layer) manufactured material is examined in detailin this thesis. Improvements are made to the method of its manufacture. Efforts aremade to understand its fracture mechanisms and take advantage of these fracturemechanisms in the absorption of impact energy.A novel series of experiments has been performed on LBL manufactured thinfilms to demonstrate their unique fracture mechanisms. Polyurethane/Poly(AcrylicAcid) (PU/PAA) and PU/PAA/(PU/Clay)5 nanocomposite films readily undergoInterlaminar mode II fracture, because of the relatively weak elctrostatic bonds betweenmonolayers. Tensile tests performed while under observation by a scanningelectron microscope demonstrate the tendency of these nanocomposite films to undergointerlaminar mode II fracture even when loads are applied in the plane ofnanocomposite film. It is concluded that these mechanisms of energy dissipation areresponsible for the enhanced toughness of these films when used as layers betweenglass blocks in the prevention of impact damage to the glass.A novel automated manufacturing facility has been designed and built to depositlarge sheets of Layer-by-Layer nanocomposite film. These large sheets are incorporatedinto a borosillicate glass composite in order to compare the ballistic characteristicsof LBL PU based nanocomposite films to a single cast layer of polyurethane.It is demonstrated that shear fracture is the mode of failure in the blocks containingthe nanocomposite film. The shear fracture surface in the nanocomposite after it hasundergone a ballistic impact is characterized. Additional experiments are performedto characterize the interlaminar fracture stresses and toughnesses of the nanocompositeLBL layers, to assist in the implementation of a numerical crack band model thatdescribes the nanocomposite film. The computational model predicts the failure ofthe ballistic nanocomposite samples, and the predicted V50 velocity is found to be ingood agreement with experimental results.