Abstract: Elastic wave transmission characteristics through a fiber-reinforced composite layer are
studied by the two-dimensional steady-state finite element analysis. To this purpose, boundary
conditions are formulated which account for the connection of the model domain to the semi-infinite
regions as well as a certain periodicity of the fiber arrangement. The transmission characteristics
through a composite layer are computed for the longitudinal and transverse wave incidence, assuming
a finite number of fiber alignments in a square array. The analysis delineates the existence of clear
stop bands in the case of transverse wave incidence, even with a few lines of fibers aligned normal to
the propagation direction. These stop bands are discussed on the basis of the interference effects of
neighboring fiber alignments as well as neighboring fibers in each alignment.
Abstract: Nowadays, researches for replacing material systems for cryogenic propellant tanks by
composites have been being performed for the purpose of light weight of a launch vehicle. In this
paper, a type III propellant tank, which is composed of the composite developed for cryogenic use and
an aluminum liner, was fabricated and tested considering actual operating environment, that is,
cryogenic temperature and pressure. For this aim, liquid nitrogen (LN2) was injected into the
fabricated tank and in turn, gaseous nitrogen (GN2) was used for pressurization. During this test
procedure, strains and temperatures on the tank surface were measured. ESG (electric strain gage) and
thermocouple were used for the measurement of strain and temperature, respectively. Delamination
between hoop layer and helical one, was detected during the experiment. Finally, Tsai-Wu criterion
for the tank and microscopy for the composite/aluminum ring specimen were carried out to
investigate the reason why delamination had happened.
Abstract: The composite, based on a polymer matrix such as Bisphenol A glycol dimethacrylate
(Bis-GMA), urethane dimethacrylate (UDMA), and triethyleneglycoldimethacrylate (TEGDMA) and
a reinforced-ceramic filler has been used in dental restorative materials. The light curing composite
consists of Bis-GMA, TEGDMA, UDMA, Bis-GMA/TEGDMA, Bis-GMA/UDMA, or
UDMA/TEGDMA polymer systems and a fumed silica filler with 35 weight ratio loading was
synthesized using camphorquinone (CQ) and 2-(dimet6hyloamino)ethyl methacrylate (DMAEMA)
as an initiator system. FTIR spectroscopy was used to determine the degree of conversion (DC) of the
composites. Polymerization shrinkage and physical properties such as hardness strength and flexural
strength were correlated with the composites containing different polymer systems.
Abstract: Laminated composite plates have lower interlaminar strength making it difficult to apply
interference-fit rivet joining. In this paper, a three-dimensional finite element model has been
developed in order to simulate the riveting process on composite plates. The finite element model is
based on continuum elements and accounts for some important mechanisms involved in a whole
riveting process. The stresses around the rivet hole and the deformed shapes of the rivet are presented
together with the effects of the interference fit and the geometry of the washer when the rivet joints are
subjected to the compressive load. The numerical results show the applicability of an interference-fit
riveting in composite laminates.
Abstract: Ankle Foot Orthosis (A.F.O) should endure the uncountable repeating impact and fatigue
loadings due to the gait characteristics. This study investigated the impact deflection and relationship
between the absorbed energy and the residual strength rate using the cross ply GFRP (glass/epoxy)
and the woven AFRP (aramid/epoxy) for the leaf spring in A.F.O. In conclusion, the equation was
suggested to evaluate the absorbed energy and the residual strength rate by the different impact
velocities. When the cross ply GFRP and the woven AFRP was selected for the leaf spring in A.F.O,
it was reasonable to use the cross ply GFRP for the parts subject to the large impact and the woven
AFRP for the parts to require the high elastic energy such as the large deformation.
Abstract: The applicable bending moment equation of LIPCA is necessary even though the fiber
layer ply orientation is changed. The aim of this research is to evaluate the relationship between the
total effective moment (ME) and Bernoulli-Euler bending moment (M) when the ply orientations of
unidirectional CFRP, which is one of the various laminate configurations in LIPCA, are changed.
Since the related previous equation between the performance stroke range (h) and the radius of
curvature (ρ) was just applicable to the CFRP ply orientation , it will be modified using these
results. The related modified equation, which has nothing to do with the various CFRP ply orientation,
is also suggested and compared with the previous equation.
Abstract: Nature has developed many novel solutions and extracting these design solutions from
nature is known as biomimetics. Cancellous bone contains trabecular bone (solid) and marrow
(fluid), plays an important role for load transfer of the knee joint.
The objective of this research is to mimick the solid-liquid composition of the cancellous bone and
to develop the material that has the excellent load dispersion ability. In the previous research, the
solid-liquid composition of the cancellous bone has been modeled as solid-air composites that was
made with Al honeycomb and silicon films. Air pressure in cells affected the load dispersion
characteristic under static loading condition. In this study, to investigate the influence of the
compression speed, impact tests were carried out. We investigated the influence of directions of holes
to cell walls, foil thickness, hole diameter and the number of holes on the load dispersion ability.
Presence of silicon film and air in cells affected the load dispersion characteristic under dynamic
loading condition. Solid - air composition and relaxing local deformation by optimal design improve
load dispersion ability.
Abstract: Sulphoaluminate-alite cement (SAAC) was successfully prepared from high alumina fly
ash. XRD analysis indicated that the optimal mineralogical phase of cement clinker was obtained
under condition of MG=1.05, MS =0.95 at 1300oC, and C4A3 S reached the strongest intensity and
is 58.73% in the phase of calcined clinckers. SEM observation showed that C4A3 S are well
developed into regular diamond/hexagon-shaped crystal with the size of 1~3.5 μm in the clinker.
Hydrated clinker exhibited its new formed dominant phases in AFt, C-S-H and Afm. Pillar shaped
AFt and sheet shaped AFm coexisted among the colloidal C-S-H substrate. It is demonstrated that
the prepared cement shows a compressive strength of 27 MPa (1d), 36 MPa (3d), 49 MPa (28d),
and flexural strength of 5.9 MPa (1d), 5.9 MPa (3d), 6.1 MPa (28d), indicated that the hydration
product owned a good mechanical strength at early ages and increased steadily in the later stages.
Abstract: TiCp/ZA-12 composites have been fabricated by XDTM method and stirring-casting
techniques. The behavior of TiC particle in the solidification interface has been studied through
conventional and directional solidification techniques. The results demonstrate that under
conventional solidification conditions, the particles with lower content mainly distribute in eutectic
phases; while when at a larger content of TiC particles, they exist both in eutectic phases and in
primary phases. Under directional solidification, due to the repulsion of primary phases of alloy on
TiC particles, the particles congregate and form band structure, and extent of the congregation in
band structure relates to TiC particles content. With the increasing of TiC particles content, their
congregation in band structure decreases, and the band structure disappears when the content of TiC
particles exceeds 6%. The tests for mechanical properties reveal that the tensile strength and yield
strength increase with increasing fraction of TiC particles. When the fraction of TiC particles
increase up to 10%, the tensile strength and yield strength are 390MPa and 340MPa, respectively
and they increase by 11% and 17% than that of matrix respectively.
Abstract: A novel retrofitting method using extremely prestressed carbon fiber sheets, MLML
(Multi-Layer Multi-Tensioning) method, was proposed for improving the flexural strength of
reinforced concrete structures. The experimental results suggested that the crack initiation strength
and the energy absorbing capacity of RC beams could be largely improved by the MLMT method.
However, the advantage of the MLMT method was not so clear on the rebars yielding strength and
the ultimate flexural strength of RC beams, compared with the conventional methods.