Abstract: A composite material with carbon fiber and polymer
matrix has been used as adherent for manufacturing adhesive joints.
In order to evaluate different fiber orientations on joint performance,
the adherents with the 0°, ±15°, ±30°, ±45° fiber orientations were
used in the single lap joint configuration. The joints with an overlap
length of 25 mm were prepared according to the ASTM 1002
specifications and subjected to tensile loadings. The structural
adhesive used was a two-part epoxy to be cured at 70°C for an hour.
First, mechanical behaviors of the adherents were measured using
three point bending test. In the test, considerations were given to
stress to failure and elastic modulus. The results were compared with
theoretical ones using rule of mixture. Then, the joints were
manufactured in a specially prepared jig, after a proper surface
preparation. Experimental results showed that the fiber orientations
of the adherents affected the joint performance considerably; the
joints with ±45° adherents experienced the worst shear strength, half
of those with 0° adherents, and in general, there was a great
relationship between the fiber orientations and failure mechanisms.
Delamination problems were observed for many joints, which were
thought to be due to peel effects at the ends of the overlap. It was
proved that the surface preparation applied to the adherent surface
was adequate. For further explanation of the results, a numerical
work should be carried out using a possible non-linear analysis.
Abstract: The purpose of this study is analyzing the relationship
between trust and social capital of people with using Social Network
Analysis. In this study, two aspects of social capital will be focused:
Bonding, homophilous social capital (BoSC), and Bridging,
heterophilous social capital (BrSC). These two aspects diverge each
other regarding to the social theories. The other concept of the study
is Trust (Tr), namely interpersonal trust, willing to ascribe good
intentions to and have confidence in the words and actions of other
people. In this study, the sample group, 61 people, was selected from
a private firm from the defense industry. The relation between
BoSC/BrSC and Tr is shown by using Social Network Analysis
(SNA) and statistical analysis with Likert type-questionnaire. The
results of the analysis show the Cronbach’s alpha value is 0.756 and
social capital values (BoSC/BrSC) is not correlated with Tr values of
the people.
Abstract: Companies face increasing challenges in research due
to higher costs and risks. The intensifying technology complexity and
interdisciplinarity require unique know-how. Therefore, companies
need to decide whether research shall be conducted internally or
externally with partners. On the other hand, research institutes meet
increasing efforts to achieve good financing and to maintain high
research reputation. Therefore, relevant research topics need to be
identified and specialization of competency is necessary. However,
additional competences for solving interdisciplinary research projects
are also often required. Secured financing can be achieved by
bonding industry partners as well as public fundings. The realization
of faster and better research drives companies and research institutes
to cooperate in organized research networks, which are managed by
an administrative organization. For an effective and efficient
cooperation, necessary processes, roles, tools and a set of rules need
to be determined. Goal of this paper is to show the state-of-art
research and to propose a governance framework for organized
research networks.
Abstract: Over the last two decades, externally bonded fiber
reinforced polymer (FRP) composites bonded to concrete substrates
has become a popular method for strengthening reinforced concrete
(RC) highway and railway bridges. Such structures are exposed to
severe cyclic loading throughout their lifetime often resulting in
fatigue damage to structural components and a reduction in the
service life of the structure. Since experimental and numerical results
on the fatigue performance of FRP-to-concrete joints are still limited,
the current research focuses on assessing the fatigue performance of
externally bonded FRP-to-concrete joints using a direct shear test.
Some early results indicate that the stress ratio and the applied cyclic
stress level have a direct influence on the fatigue life of the externally
bonded FRP. In addition, a calibrated finite element model is
developed to provide further insight into the influence of certain
parameters such as: concrete strength, FRP thickness, number of
cycles, frequency, and stiffness on the fatigue life of the FRP-toconcrete
joints.
Abstract: The 1:1 cocrystal of 2-amino-4-chloro-6-
methylpyrimidine (2A4C6MP) with 4-methylbenzoic acid (4MBA)
(I) has been prepared by slow evaporation method in methanol,
which was crystallized in monoclinic C2/c space group, Z = 8, and a
= 28.431 (2) Å, b = 7.3098 (5) Å, c = 14.2622 (10) Å and β =
109.618 (3)°. The presence of unionized –COOH functional group in
cocrystal I was identified both by spectral methods (1H and 13C
NMR, FTIR) and X-ray diffraction structural analysis. The
2A4C6MP molecule interact with the carboxylic group of the
respective 4MBA molecule through N—H⋯O and O—H⋯N
hydrogen bonds, forming a cyclic hydrogen–bonded motif R2
2(8).
The crystal structure was stabilized by Npyrimidine—H⋯O=C and
C=O—H⋯Npyrimidine types hydrogen bonding interactions.
Theoretical investigations have been computed by HF and density
function (B3LYP) method with 6–311+G (d,p)basis set. The
vibrational frequencies together with 1H and 13C NMR chemical
shifts have been calculated on the fully optimized geometry of
cocrystal I. Theoretical calculations are in good agreement with the
experimental results. Solvent–free formation of this cocrystal I is
confirmed by powder X-ray diffraction analysis.
Abstract: Novel wind-lens turbine designs can augment power
output. Vacuum-Assisted Resin Transfer Molding (VARTM) is used
to form large and complex structures from a Carbon Fiber Reinforced
Polymer (CFRP) composite. Typically, wind-lens turbine structures
are fabricated in segments, and then bonded to form the final structure.
This paper introduces five new adhesive joints, divided into two
groups: one is constructed between dry carbon and CFRP fabrics, and
the other is constructed with two dry carbon fibers. All joints and
CFRP fabrics were made in our laboratory using VARTM
manufacturing techniques. Specimens were prepared for tensile testing
to measure joint performance. The results showed that the second
group of joints achieved a higher tensile strength than the first group.
On the other hand, the tensile fracture behavior of the two groups
showed the same pattern of crack originating near the joint ends
followed by crack propagation until fracture.
Abstract: In this study, the commercial finite element software
ABAQUS was used to develop a three-dimensional nonlinear finite
element model capable of simulating the pull-out test of reinforcing
bars from underwater concrete. The results of thirty-two pull-out tests
that have different parameters were implemented in the software to
study the effect of the concrete cover, the bar size, the use of stirrups,
and the compressive strength of concrete. The interaction properties used in the model provided accurate
results in comparison with the experimental bond-slip results, thus
the model has successfully simulated the pull-out test. The results of
the finite element model are used to better understand and visualize
the distribution of stresses in each component of the model, and to
study the effect of the various parameters used in this study including
the role of the stirrups in preventing the stress from reaching to the
sides of the specimens.
Abstract: The study conducted a simulation of the effect of sea
water to the bonding capacity of GFRP sheet on the concrete beams
using a simulation tank. Fiber reinforced polymer (FRP) has been
developed and applied in many fields civil engineering structures on
the new structures and also for strengthening of the deteriorated
structures. The FRP has advantages such as its corrosion resistance as
well as high tensile strength to weight ratio. Compared to the other
FRP materials, Glass composed FRP (GFRP) is relatively cheaper.
GFRP sheet is applied externally by bonding it on the concrete surface.
The studies regarding the application of GFRP sheet have been
conducted such as strengthening system, bonding behavior of GFRP
sheet including the application as reinforcement in new structures. For
application to the structures with direct contact to sea environment, a
study regarding the effect of sea water to the bonding capacity of
GFRP sheet is important to be clarified. To achieve the objective of the
study, a series of concrete beams strengthened with GFRP sheet on
extreme tension surface were prepared. The beams then were stored on
the sea water tank for six months. Results indicated the bonding
capacity decreased after six month exposed to the sea water.
Abstract: Carbon nanotubes (CNTs) are known for having high elastic properties with high surface area that promote them as good candidates for reinforcing polymeric matrices. In composite materials, CNTs lack chemical bonding with the surrounding matrix which decreases the possibility of better stress transfer between the components. In this work, a chemical treatment for activating the surface of the multi-wall carbon nanotubes (MWCNT) was applied and the effect of this functionalization on the elastic properties of the epoxy nanocomposites was studied. Functional amino-groups were added to the surface of the CNTs and it was evaluated to be about 34% of the total weight of the CNTs. Elastic modulus was found to increase by about 40% of the neat epoxy resin at CNTs’ weight fraction of 0.5%. The elastic modulus was found to decrease after reaching a certain concentration of CNTs which was found to be 1% wt. The scanning electron microscopic pictures showed the effect of the CNTs on the crack propagation through the sample by forming stress concentrated spots at the nanocomposite samples.
Abstract: The first laboratory synthesis of hard materials such as
diamond proceeded to attack of developing materials with high
hardness to compete diamond. Boron rich solids are good candidates
owing to their short interatomic bond lengths and strong covalent
character. Boron containing hard material was synthesized by modifiedmicrowave
method under nitrogen atmosphere by using a fuel
(glycine or urea), amorphous boron and/or boric acid in appropriate
molar ratio. Characterizations were done by x-ray diffraction (XRD),
Fourier transform infrared (FTIR) spectroscopy, scanning electron
microscopy/energy dispersive analyze (SEM/EDS), thermo
gravimetric/differential thermal analysis (TG/DTA).
Abstract: The purpose of this research was to investigate the
creep behaviour of the heterogeneous Timber-UHPFRC beams. New
developments have been done to further improve the structural
performance, such as strengthening of the timber (glulam) beam by
bonding composite material combine with an ultra-high performance
fibre reinforced concrete (UHPFRC) internally reinforced with or
without carbon fibre reinforced polymer (CFRP) bars. However, in
the design of wooden structures, in addition to the criteria of
strengthening and stiffness, deformability due to the creep of wood,
especially in horizontal elements, is also a design criterion. Glulam,
UHPFRC and CFRP may be an interesting composite mix to respond
to the issue of creep behaviour of composite structures made of
different materials with different rheological properties. In this paper,
we describe an experimental and analytical investigation of the creep
performance of the glulam-UHPFRC-CFRP beams assembled by
bonding. The experimental investigations creep behaviour was
conducted for different environments: in- and outside under constant
loading for approximately a year. The measured results are compared
with numerical ones obtained by an analytical model. This model was
developed to predict the creep response of the glulam-UHPFRCCFRP
beams based on the creep characteristics of the individual
components. The results show that heterogeneous glulam-UHPFRC
beams provide an improvement in both the strengthening and
stiffness, and can also effectively reduce the creep deflection of
wooden beams.
Abstract: This study intends to show the influence of the
hydrolytic degradation on the properties of the e-PTFE/NOMEX®
membranes used in fire-protective clothing. The modification of
water vapour permeability, morphology and chemical structure was
examined by MOCON Permatran, electron microscopy scanning
(SEM), and ATR-FTIR, respectively. A decrease in permeability to
water vapour of the aged samples was observed following closure of
transpiration pores. Analysis of fiber morphology indicates the
appearance of defects at the fibers surface with the presence of micro
cavities. ATR-FTIR analysis reveals the presence of a new absorption
band attributed to carboxylic acid terminal groups generated during
the amide bond hydrolysis.
Abstract: Concrete is strong in compression however weak in
tension. The tensile strength as well as ductile property of concrete
could be improved by addition of short dispersed fibers. Polyethylene
terephthalate (PET) fiber obtained from hand cutting or mechanical
slitting of plastic sheets generally used as discrete reinforcement in
substitution of steel fiber. PET fiber obtained from the former process
is in the form of straight slit sheet pattern that impart weaker
mechanical bonding behavior in the concrete matrix. To improve the
limitation of straight slit sheet fiber the present study considered two
additional geometry of fiber namely (a) flattened end slit sheet and
(b) deformed slit sheet. The mix for plain concrete was design for a
compressive strength of 25 MPa at 28 days curing time with a watercement
ratio of 0.5. Cylindrical and beam specimens with 0.5% fibers
volume fraction and without fibers were cast to investigate the
influence of geometry on the mechanical properties of concrete. The
performance parameters mainly studied include flexural strength,
splitting tensile strength, compressive strength and ultrasonic pulse
velocity (UPV). Test results show that geometry of fiber has a
marginal effect on the workability of concrete. However, it plays a
significant role in achieving a good compressive and tensile strength
of concrete. Further, significant improvement in term of flexural and
energy dissipation capacity were observed from other fibers as
compared to the straight slit sheet pattern. Also, the inclusion of PET
fiber improved the ability in absorbing energy in the post-cracking
state of the specimen as well as no significant porous structures.
Abstract: In order to obtain efficient pollutants removal in
small-scale wastewater treatment plants, uniform water flow has to be
achieved. The experimental setup, designed for treating high-load
wastewater (leachate), consists of two aerobic biological reactors and
a lamellar settler. Both biological tanks were aerated by using three
different types of aeration systems - perforated pipes, membrane air
diffusers and tube ceramic diffusers. The possibility of homogenizing
the water mass with each of the air diffusion systems was evaluated
comparatively. The oxygen concentration was determined by optical
sensors with data logging. The experimental data was analyzed
comparatively for all three different air dispersion systems aiming to
identify the oxygen concentration variation during different
operational conditions. The Oxygenation Capacity was calculated for
each of the three systems and used as performance and selection
parameter. The global mass transfer coefficients were also evaluated
as important tools in designing the aeration system. Even though
using the tubular porous diffusers leads to higher oxygen
concentration compared to the perforated pipe system (which
provides medium-sized bubbles in the aqueous solution), it doesn’t
achieve the threshold limit of 80% oxygen saturation in less than 30
minutes. The study has shown that the optimal solution for the
studied configuration was the radial air diffusers which ensure an
oxygen saturation of 80% in 20 minutes. An increment of the values
was identified when the air flow was increased.
Abstract: Different designs of attenuator systems have been
studied in this research; new analysis have been done on existed
designs considering fibers effect on air flow; it was comprehended
that, at fibers presence, there is an air flow which agglomerates fibers
as a negative effect. So some new representations have been designed
and CFD analysis has been done on them. Afterwards, one of these
representations selected as the most optimum and effective design
which is brought in this paper.
Abstract: This paper presents the results obtained by numerical
simulation using the software ANSYS CFX-CFD for the air
pollutants dispersion in the atmosphere coming from the evacuation
of combustion gases resulting from the fuel combustion in an electric
thermal power plant. The model uses the Navier-Stokes equation to
simulate the dispersion of pollutants in the atmosphere. It is
considered as important factors in elaboration of simulation the
atmospheric conditions (pressure, temperature, wind speed, wind
direction), the exhaust velocity of the combustion gases, chimney
height and the obstacles (buildings). Using the air quality monitoring
stations it is measured the concentrations of main pollutants (SO2,
NOx and PM). The pollutants were monitored over a period of 3
months, after that the average concentration are calculated, which is
used by the software. The concentrations are: 8.915 μg/m3 (NOx),
9.587 μg/m3 (SO2) and 42 μg/m3 (PM). A comparison of test data
with simulation results demonstrated that CFX was able to describe
the dispersion of the pollutant as well the concentration of this
pollutants in the atmosphere.
Abstract: This study makes an integrated investigation on how
life satisfaction is associated with the Korean game users'
psychological variables (self-esteem, game and life self- efficacy),
social variables (bonding and bridging social capital), and
demographic variables (age, gender). The data used for the empirical
analysis came from a representative sample survey conducted in South
Korea. Results show that self-esteem and game efficacy were an
important antecedent to the degree of users’ life satisfaction. Both
bonding social capital and bridging social capital enhance the level of
the users’ life satisfaction. The importance of perspectives as well as
their implications for the game users and further associated research is
explored.
Abstract: Biodiesel is one of the alternative fuels that promising
for substituting petro diesel as energy source which is advantage on
sustainability and ecofriendly. Due to the raw material that tend to
decompose during storage, biodiesel also have the same characteristic
that tend to decompose and formed higher acid value which is the
result of oxidation to double bond on a chain of ester. Decomposition of biodiesel due to oxidation reaction could
prevent by introduce a small amount of antioxidant. The origin of raw
materials and the process for producing biodiesel will determine the
effectiveness of antioxidant. The quality degradation on biodiesel
could evaluate by measuring iodine value and acid number of
biodiesel. Biodiesel made from high fatty acid Jatropha curcas oil by using
esterification and transesterification process will stand on the quality
by introduce 90 ppm pyrogallol powder on the biodiesel, which could
increase Induction period time from 2 hours to more than 6 hours in
rancimat test evaluation.
Abstract: This paper presents modeling and simulation of
flexible robot in an underwater environment. The underwater
environment completely contrasts with ground or space environment.
The robot in an underwater situation is subjected to various dynamic
forces like buoyancy forces, hydrostatic and hydrodynamic forces.
The underwater robot is modeled as Rayleigh beam. The developed
model further allows estimating the deflection of tip in two
directions. The complete dynamics of the underwater robot is
analyzed, which is the main focus of this investigation. The control of
robot trajectory is not discussed in this paper. Simulation is
performed using Symbol Shakti software.
Abstract: This paper presents the experimental investigation on
the bond behavior of geo polymer concrete. The bond behavior of
geo polymer concrete cubes of grade M35 reinforced with 16 mm
TMT rod is analyzed. The results indicate that the bond performance
of reinforced geo polymer concrete is good and thus proves its
application for construction.