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Measurement of anisotropic fracture energies in periodic templated silica/polymer composite coatings
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View: Figures


Image of FIG. 1.
FIG. 1.

Schematic of the periodic surfactant-templated silica/polymer composite films with a hexagonal honeycomb structure. The films consist of a fully interconnected silica framework, surrounding the cylindrical polymer micelles.

Image of FIG. 2.
FIG. 2.

(a) AFM image of an aligned hexagonal silica/polymer film showing uniaxial orientation of the domains along the dip-coating direction. (b) In-plane diffraction data collected in transmission mode showing alignment of the nanoscale cylinders, also along the dip-coating direction. The cylinders are aligned along the horizontal axis so that diffraction occurs on the vertical axis.

Image of FIG. 3.
FIG. 3.

Schematic setup of the microfilm tester.

Image of FIG. 4.
FIG. 4.

Typical stress-strain curves for a hexagonal silica/polymer composite film strained parallel (◻) and perpendicular (●) to the axis of the cylindrical micelles.

Image of FIG. 5.
FIG. 5.

A stress-strain curve for a 100-nm-thick silica/polymer composite film pulled in the parallel orientation, with images in the inset showing the evolution of a crack very near the failure strain.

Image of FIG. 6.
FIG. 6.

Schematic of the steady-state channeling crack problem (a), with corresponding plane strain problem geometries used for determining the energy far ahead (b) and far behind (c) of the crack tip.

Image of FIG. 7.
FIG. 7.

(a) Geometry and boundary conditions for the plain strain crack model implemented using finite element method (FEM). (b) Details of the meshing scheme near the crack tip that was used in the FEM model.

Image of FIG. 8.
FIG. 8.

Aligned hexagonal mesoporous silica films showing anisotropic fracture behavior. When such a film is cracked using a razor blade, fibers can be observed in SEM (part A). These same fibers can also be observed using TEM (part B). A high resolution TEM image (part C) shows the individual silica nanopores and confirms that the pores run parallel to the fiber axis. It thus appears that the fracture parallel the pore axis is a significantly lower energy process than the fracture perpendicular to the pore axis.


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Scitation: Measurement of anisotropic fracture energies in periodic templated silica/polymer composite coatings