Thin
Films, Interfaces, and Composites Characterization Laboratory at UCLA
Research Fields
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| ACADEMICS |
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| INDUSTRIAL
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| Our lab is involved in the following academic fields: | |
| Applied Mechanics Modeling | |
A progressive damage
growth model for failure of rocks under compression has been developed.
This model considers incremental growth and eventual instability
of a shear fault nucleus, which in turn, is considered as an elliptical
inhomogeneity composed locally of a cluster of grain boundary cracks,
using the concept of stress enhancement factors. Model predictions
with consideration of statistical grain boundary strength distribution
for each rock-type, correlated dramatically with the widely available
failure data on different rocks. Read
more >> |
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Biomechanics/Orthopaedics |
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Biomechanics-related
research addresses both fundamental and applied problems. On the
fundamental level, we are seeking to understand the adhesion of
chondrocytes and osteoblasts (bone-forming cells) to various implant
surfaces, with an ultimate goal to design better knee and hip prostheses.
Also of interest is to understand how adhesion controls the cell’s
own biochemical processes. To appreciate the loading environment,
the anatomy and physiology of the joints is also considered in calculating
the local joint forces using applied mechanics. Read
more >> |
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Composites |
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Microscopic examination of load-interrupted samples has established the local shear instability in fiber and matrix as the failure initiation mechanism in biaxially-loaded graphite epoxy cross-ply laminates under compression. The failure data for all material orientations (with respect to loading axes) and in-plane biaxiality ratios correlated remarkably well using a local pressure-dependent matrix and fiber shear failure criterion. Read more >> |
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Construction of Reliable
Steel/Composite Joints |
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Recent unpublished work has
established chemical recipes for joining stainless steel and E-glass
composite surfaces for composite shipbuilding application. Combination
of self-assembled monolayer (silane) coverings on steel surfaces,
and epoxy has led to remarkable joint sections that fail through
the substrate (composite delamination), when loaded using the double
cantilever beam test geometry. Read
more >> |
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Interface Science and
Engineering |
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Novel techniques to measure
the intrinsic tensile strength and intrinsic toughness of interfaces
have been developed. Notable among these is a laser spallation experiment
for interface strength measurement. The latter is a synthesis of
two inventions, (1) nanosecond rise-time stress pulses with tailless
profiles, and (2) a wide-angle interferometer for non-specular surfaces.
Read
more >> |
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MEMS |
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Stiction (adhesion of suspended
structures and the underlying surface) is a considerable problem
for batch fabricated MEMS devices. MEMS devices are often released
through wet etching. As the wafer is removed from the wet etch liquid
is trapped between the small space separating the MEMS device and
the substrate. This liquid, through capillary forces, pulls the
cantilevered MEMS device down to the substrate where it remains.
The purpose of this study was repair the stiction by using a laser-induced
stress wave. |
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Pattern Transfer Technology |
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The basic idea of this study
is based on a previously developed laser spallation technology in
which a transient compressive stress pulse of 1-2 nanoseconds (ns)
rise-time and 16-20 ns total duration is generated on the backside
of a substrate by exfoliating a constrained metallic film by using
a 3 ns-long Nd:YAG laser pulse (Fig. 1). The stress pulse is made
to propagate towards a test coating deposited on the substrate’s
front surface, and whose fundamental interface tensile strength
(adhesion) is to be measured. Read
more >> |
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Other Contributions |
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Other contributions include
measurement and recording of the highest interface crack velocity
(J. Mechanics and Physics of Solids 48,3 (2000) 609-619),
measurement of grain boundary tensile strength in ice polycrystals,
measurement of in-situ fiber/matrix interface strength, dynamic
characterization of laminates at ultrahigh strain rate loadings,
and development of an efficient deicing coating for structural surfaces. |
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Technology Transfer |
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The fundamental interface mechanical
characterization work has been integrated all the way to technology
transfer. The first beta unit of the laser spalltion experiment
now exists at the Chandler facility of Intel Corporation. Further
development are in progress inside Intel Corporation, with the aim
of transferring the industrial version of the technology to other
semiconductor technology partners, such as Motorolla, IBM, Texas
Instruments, and AMD, among others. Through consulting and collaborative research, the laser spallation technology has been used for product development in companies worldwide, belonging not to one, but a number of different industries such as semiconductor (Intel Corporation, Hitachi, Dow Corning Corporation), Automobile (Delphi Corporation), Television (LG Gould in Korea), Biomedical (Pacesetter Inc., Baxter Corporation), Aircraft Engines (Pratt and Whitney, Westinghouse Corporation), Paint (Boeing: multilayer polymer-based paint assembly on aircraft, Du Pont), and Dentistry (University of Nijmegen Dental School: improved Ti implants with highly adherent calcium-phosphate coating). |