Matthew R. Begley

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Simulation of the nonlinear mechanical response of materials with explicit representation of microstructural features is extremely challenging. These models typically involve a very large number of degrees of freedom, and are prone to convergence difficulties when searching for roots to nonlinear equilibrium equations. We focus on an idealized material(More)
This paper describes a micromechanical analysis of the uniaxial response of composites comprising elastic platelets (bricks) bonded together with thin elastic perfectly plastic layers (mortar). The model yields closed-form results for the spatial variation of displacements in the bricks as a function of constituent properties, which can be used to calculate(More)
Neural electrodes are essential tools for the study of the nervous system and related diseases. Low electrode impedance is a figure of merit for sensitive detection of neural electrical activity and numerous studies have aimed to reduce impedance. Unfortunately, most of these efforts have been tethered by a combination of poor functional coating adhesion,(More)
Nanoporous gold (np-Au) has intriguing material properties that offer potential benefits for many applications due to its high specific surface area, well-characterized thiol-gold surface chemistry, high electrical conductivity, and reduced stiffness. The research on np-Au has taken place on various fronts, including advanced microfabrication and(More)
Stiff ceramic platelets (or bricks) that are aligned and bonded to a second ductile phase with low volume fraction (mortar) are a promising pathway to produce stiff, high-toughness composites. For certain ranges of constituent properties, including those of some synthetic analogs to nacre, one can demonstrate that the deformation is dominated by relative(More)
The mechanical behavior of thin elastic _lms deposited onto structural alloys plays a critical role in determining _lm durability[ This paper presents analysis of an impression experiment designed to evaluate some of the relevant properties of these _lms[ The modeling provides quantitative strain information which can be used to estimate the fracture(More)
Three-dimensional (3-D) images of two ceramic-matrix textile composites were captured by X-ray micron-resolution computed tomography (lCT) on a synchrotron beamline. Compared to optical images of sections, CT data reveal comprehensive geometrical information about the fiber tows; information at smaller scales, on matrix voids, individual fibers, and fiber(More)
We present a new experimental method for measuring the mechanical properties of nanoscale-thick materials using the free-standing membrane test. Freestanding circular membranes are centrally deflected using a spherical indenter attached to a microfabricated fixed-fixed beam device. Experiments of this type allow us to extract mechanical properties of the(More)
ÐThe adhesion between thin elastic ®lms/coatings and ductile substrates can be measured using a wedge test, wherein a long sharp edge is impressed through the ®lm into the substrate. The resulting plastic deformation causes delamination between the ®lm and the substrate. The extent of the delamination can be correlated with the crack driving force to(More)
An analytical solution is presented for the nonlinear pressure-flow relationship of deformable passive valves, which are formed by bonding a deformable film over etched channels separated by a weir. A fluidic pathway connecting the channels is opened when the upstream pressure creates a tunnel along a predefined narrow strip where the film is not bonded to(More)