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)
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)
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)
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)
—This paper identifies dynamic excitation parameters that promote decohesion of stiction-failed microcantilevers. The dynamic response of " s-shaped " adhered beams subjected to harmonic loading is described using modal analysis; this model is then used to predict the onset of debonding in the context of a critical interface energy. These theoretical(More)
We present experimental measurements of the mechanical properties of nanoscale-thick materials using a recently developed free-standing membrane test. Freestanding membranes of gold and a nano-porous silicate were centrally deflected using a spherical indenter attached to a microfabricated fixed-fixed beam device. Experiments of this type allow us to(More)
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