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1
Lei, Sheng-Yuan. "Deformation micromechanics in composite structures." Thesis, University of Manchester, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488306.
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Do, Nascimento Oliveira Jose Emidio. "Deformation and damage analysis of composite beams equipped with polyvinylidene fluoride film sensors /." [S.l. : s.n.], 2008. http://dk.cput.ac.za/cgi/viewcontent.cgi?article=1001&context=td_cput.
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Sinclair, Chad. "Co-deformation of a two-phase FCC/BCC material /." *McMaster only, 2001.
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4
Derian, Edward J. "Large deformation dynamic bending of composite beams." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45678.
Full textAbstract:
The large deformation response of composite beams subjected to a
dynamic axial load was studied. The beams were loaded with a moderate
amount of eccentricity to promote bending. The study was primarily
experimental but some finite element results were obtained. Both the
deformation and the failure of the beams were of interest. The static
response of the beams was also studied in order to determine the
difference between the static and dynamic failure. Twelve different
laminate types were tested. The beams tested were 23 in. by 2 in. and
generally 30 plies thick. The beams were loaded dynamically with a
gravity-driven impactor traveling at 19.6 ft./sec. and quasi-static
tests were done on identical beams in a displacement controlled
manner. For laminates of practical interest, the failure modes under
static and dynamic loadings were identical. Failure in most of the
laminate types occurred in a single event involving 40% to 50% of the
plies. However, failure in laminates with 30° or 15° off axis plies occurred in several events. All laminates exhibited bimodular
properties. The compressive flexural moduli in some laminates was
measured to be 1/2 the tensile flexural modulus. No simple relationship
could be found among the measured ultimate failure strains of the
different laminate types. Using empirically determined flexural
properties, a finite element analysis was reasonably accurate in
predicting the static and dynamic deformation response.Master of Science
5
do, Nascimento Oliveira Jose Emidio. "Deformation and damage analysis of composite beams equipped with polyvinylidene fluoride film sensors." Thesis, Cape Peninsula University of Technology, 2008. http://hdl.handle.net/20.500.11838/1284.
Full textAbstract:
In many engineering applications, it is desirable to know the behaviour of structures and
systems under loading conditions. One reason is to help optimize the design and prevent
damage and failure which might occur during in service and operation. Damage represents a
serious problem which can cause catastrophic failure of structures, machines and systems.
Therefore for safe operation, efficient and reliable methods for inspection and monitoring of
damage are required. Different methods for health monitoring of structures such as non
destructive testing (NDT) and strain gauges are widely used. These methods have proven to
be efficient in terms of resolution and response. However, some disadvantages associated
with them include the vicinity of the area under inspection which must be well known,
equipment to acquire the necessary information is expensive and in many cases high skills
are required for operation. On the other hand, advances in materials science and MEMS
systems has promoted the use of new materials with piezoelectric properties. This include
mainly polymeric and ceramic materials which after processed can be used for structural
health monitoring. These materials offer a number of advantages such as lightweight,
sensitivity, toughness, durability, and low cost.
The present research work investigates the feasibility of using a polymeric material,
Polyvinylidene Fluoride (PVDF) as a sensor for deformation and defect detection in
structures. The sensors are embedded in composite cantilevered type beams to detect
defects at distinct locations along the beam’s length. The defect detection method proposed
is based on experimental tests and Finite Element simulations.
Experimental tests on defect free and beams with manufactured internal flaws were
conducted. Numerical (FEM) simulations of defect free and flawed beam models containing
sections of reduced elastic modulus to represent the damage were conducted using ANSYS
software. The experimental tests have been used for the validation of the numerical solution.
Results have shown that the defect location changes the stiffness and indeed the frequency
of vibration. For flaws near the fixed end of the beams, lower frequencies are obtained as
compared to flaws away from the fixed end. PVDF sensors were used to acquire the natural
frequencies of the beams for the first mode of vibration. Good agreement was verified
between experimental and numerical simulation results. The work has demonstrated that
PVDF film sensors can be used as possible candidates for defect detection.
The analysis of the behaviour embedded PVDF sensors near the fixed end of cantilever
beams, represents an initial and important step towards the application of measuring static
and dynamic behaviour of structures as part of a health monitoring process.
6
Bocchieri, Robert Thomas. "Time-dependent deformation of a nonlinear viscoelastic rubber-toughened fiber composite with growing damage /." Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008280.
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Lo, Kin Man. "Surface deformation on composite patches by constrained morphing." Thesis, University of Macau, 2010. http://umaclib3.umac.mo/record=b2493981.
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Lee, Kok Loong. "Deformation behaviour of Cu-Cr in-situ composite." Thesis, University of Leicester, 2004. http://hdl.handle.net/2381/11077.
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With the increasing requirements for higher strength materials with high electrical conductivity, a lot of interest has been paid to develop Cu-based composites in the last 25 years. These composites have superior tensile strength, combined with good electrical conductivity, to that exhibited by pure Cu and conventional Cu alloys. To date, much of the research carried out on this composite has focused on the mechanical and electrical properties of the as processed material. However, there is a basic lack of understanding of the way in which the properties may change or degrade during service. Without this knowledge, these composites cannot be fully and safely exploited. Thus the objective of this study was to investigate the thermo-mechanical behaviour of a Cu-Cr composite, and the nature and extent of any damage mechanisms occurring within the composite over a wide range of experimental conditions. Neutron diffraction was used to investigate the deformation behaviour of the individual phases in the composite and their interaction through elastic and plastic loading at room temperature. For the composite, a fairly good agreement was observed in the phase strains predicted by the Eshelby theory and measured by neutron diffraction. In-situ tensile tests in the SEM were also performed to study the damage mechanism of the composite. Tensile and creep tests were carried out in air and in vacuum over a wide range of temperatures. To provide data for comparison with the composite material, pure Cu specimens were tested whenever possible. Creep resistance increases significantly with the introduction of Cr fibres into Cu. The higher creep rate of the composite in air than in vacuum is due to the gradual decrease of the cross-sectional area of the matrix due to increasing thickness of the oxide layer. Damage characteristics and distributions were found to be similar during tensile and creep testing.
9
Momken, Bahareh. "Fluid flow and deformation in composite porous media /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004343.
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Derisi, Bijan. "Development of thermoplastic composite tubes for large deformation." Thesis, Connect to online version, 2008. http://proquest.umi.com/pqdweb?did=1675143241&sid=1&Fmt=2&clientId=10306&RQT=309&VName=PQD.
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Hazzard, Mark Kenneth. "Composite armour : an investiagion of the deformation and failure mechanisms of Dyneema® composites." Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.723515.
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Ahmad, M. K. M. "Shear lag effect in composite box girders." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237869.
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Nagappan, Govindan. "Analysis of composite moving beams using higher order shear deformation theory." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3463.
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Thesis (M.S.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains xi, 126 p. : ill. Includes abstract. Includes bibliographical references (p. 123-126).
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Jun, Fan Li. "Deformation and stress analysis of rubber/metal composite components." Thesis, Queen Mary, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337873.
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Osman, Todd Michael. "Deformation and fracture in a laminated metallic composite system." Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1062603827.
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Shah, Sneha. "Coupled heat conduction and deformation in a viscoelastic composite cylinder." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2008-08-62.
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Antolovich, Bruce F. "Deformation response of ARALL under uni-axial loading conditions." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/19456.
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Wung, Pey M. "Large deformation analysis of laminated composite structures by a continuum-based shell element with transverse deformation." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54815.
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In this work, a finite element formulation and associated computer program is developed for the transient large deformation analysis of laminated composite plate/shell structures. In order to satisfy the plate/shell surface traction boundary conditions and to have accurate stress description while maintaining the low cost of the analysis, a newly assumed displacement field theory is formulated by adding higher-order terms to the transverse displacement component of the first-order shear deformation theory. The laminated shell theory is formulated using the Updated Lagrangian description of a general continuum-based theory with assumptions on thickness deformation. The transverse deflection is approximated through the thickness by a quartic polynomial of the thickness coordinate. As a result both the plate/shell surface tractions (including nonzero tangential tractions and nonzero normal pressure) and the interlaminar shear stress continuity conditions at interfaces are satisfied simultaneously. Furthermore, the rotational degree of freedoms become layer dependent quantities and the laminate possesses a transverse deformation capability (i.e. the normal strain is no longer zero).
Analytical integration through the thickness direction is performed for both the linear analysis and the nonlinear analysis. Resultants of the stress integrations are expressed in terms of the laminate stacking sequence. Consequently, the laminate characteristics in the normal direction can be evaluated precisely and the cost of the overall analysis is reduced. The standard Newmark method and the modified Newton Raphson method are used for the solution of the nonlinear dynamic equilibrium equations.
Finally, a variety of numerical examples are presented to demonstrate the validity and efficiency of the finite element program developed herein.Ph. D.
19
Wiggers, Joram. "Analysis of textile deformation during preforming for liquid composite moulding." Thesis, University of Nottingham, 2007. http://eprints.nottingham.ac.uk/10414/.
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Fibre Reinforced Plastics offer several advantages over other materials such as decreased part counts, weight savings, and flexibility. The obstacles to the further expansion of composites use, particularly in cost-conscious industries such as the car industry, include volume, cost, and quality. Liquid Composite Moulding, where the dry textile reinforcement is shaped prior to application of the plastic matrix, offers to address these drivers by offering potential for automation, speed, and quality control. However, the preforming of the dry reinforcement is rarely automated, and its results are variable and hard to predict or control. This thesis aims to facilitate better preforming process design and control. The dominant deformation mechanism that allows reinforcements to conform to a 3D surface is trellis shear. Work is therefore presented on shear characterisation of textile reinforcements using the picture frame and the bias extension tests. Several approaches to normalising these tests to achieve method-independent shear data are proposed, and compared. Of these, a normalisation technique for the bias extension test based on energy considerations appears to be the most appropriate. A constitutive modelling approach, based on the meso-mechanical deformation mechanisms identified in the reinforcement, is developed for characterising the asymmetric shear properties exhibited by non-crimp fabrics. The results from this model are compared with experimental data. Finally, an energy minimising kinematic drape method is developed to account for the use of automated reinforcement blank-holders, and methods for modelling process variability using the code are investigated.
20
Wong, Chun Lok. "Cardiac motion estimation with finite deformation and composite material models /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202004%20WONGCL.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 84-87). Also available in electronic version. Access restricted to campus users.
21
Johannesson, Birgir. "Internal stresses and the cyclic deformation of an aluminium matrix composite." Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/843903/.
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The development of internal stresses in planar random Saffil fibre reinforced aluminium with a range of fibre volume fractions has been studied theoretically and in monotonic and cyclic deformation (Bauschinger) experiments at room temperature and 77K. The conventional method of analysing Bauschinger experiments is extended to allow for a separation of the mean and thermal stresses. This analysis is applied to experimental results enabling the mean stress hardening rate and the magnitude of the thermal stress to be measured. The experimental results are compared with predictions of the mean field model, which is based on the Eshelby method of determining internal stresses. For that purpose the Eshelby S tensor for a planar random array of fibres is calculated. Because the aluminium/Saffil composites are not isotropic in the transverse directions, the plastic strain used in the calculations has to be determined experimentally. A method for quantifying the anisotropic plastic flow of the aluminium/Saffil composites is proposed and the results are used in calculations of the mean stress hardening rate. A comparison of predictions for the mean stress hardening rate with results of the experimental analysis proposed here shows that good agreement is obtained for low fibre volume fractions at 77 K. The results also show that relaxation of the mean stress increases with fibre volume fraction and that at 77 K the mean stress hardening rate is about a factor of two larger than at room temperature. The measurements of the thermal stresses obtained in the Bauschinger experiments are in quantitative agreement with results obtained in monotonic tests. The magnitude of the thermal stress at room temperature or 77 K is independent of fibre volume fraction and a comparison with predictions shows that relaxation of the thermal stress increases with fibre volume fraction. Cycling in the Bauschinger experiments reduces the thermal stress and hence the separation of the mean and thermal stresses is essential for a reliable measurement of the mean stress hardening rate. Matrix hardening contributes considerably to the overall hardening of the composite, both at room temperature and 77 K. The modified Orowan-Wilson model, which enables the plastic friction coefficient to be measured in copper-tungsten composites, has been applied to the aluminium\Saffil composites. The model requires both the mean stress and the peak stress curves obtained in Bauschinger experiments to be linear in plastic strain. Most of the peak stress curves for the aluminium/Saffil composites are non-linear but for the curves which are linear the predictions of the model are not in quantitative accord with experimental results. This may be because relaxation reduces the mean stress and the source shortening stress in different proportions. The diameter of the Saffil fibres is also close to the lower end of applicability of the model. The temperature dependence of the mean stress hardening rate suggests that relaxation is thermally activated. A model for relaxation of the mean stress is proposed. An equation is derived for the number of Orowan loops per fibre and it is assumed that the rate controlling mechanism of relaxation is cross slip of screw dislocations. The estimated activation energy is independent of fibre volume fraction but the activation volume decreases with increasing fibre volume fraction. The magnitudes of activation energy and activation volume support the assumptions of the model. A preliminary study on the early stages of fatigue shows that persistent slip bands form in the matrix of the aluminium/Saffil composites.
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Tao, Min Ravichandran G. "High temperature deformation of Vitreloy bulk metallic glasses and their composite /." Diss., Pasadena, Calif. : Caltech, 2006. http://resolver.caltech.edu/CaltechETD:etd-03022006-005723.
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Rogacki, John R. "A combined experimental analytical methodology for characterizing the thermoviscoplastic deformation of a metal matrix composite /." Thesis, Connect to this title online; UW restricted, 1992. http://hdl.handle.net/1773/7083.
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Liu, Chorng-Fuh. "Geometrically nonlinear analysis of composite laminates using a refined shear deformation shell theory." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/54453.
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The theory is based on an assumed displacement field, in which the surface displacements are expanded in powers of the thickness coordinate up to the third order. The theory allows parabolic description of the transverse shear stresses, and therefore the shear correction factors of the usual shear deformation theory are not required in the present theory. The theory accounts for small strains but moderately large displacements (i.e., von Karman strains). Exact solutions for certain cross-ply shells and finite-element models of the theory are also developed. The finite-element model is based on independent approximations of the displacements and bending moments (i.e., mixed formulation), and therefore only C°-approximations are required. Further, the mixed variational formulations developed herein suggest that the bending moments can be interpolated using discontinuous approximations (across inter-element boundaries). The finite element is used to analyze cross-ply and angle-ply laminated shells for bending, vibration, and transient response. Numerical results are presented to show the effects of boundary conditions, lamination scheme (i.e., bending-stretching coupling and material anisotropy) shear deformation, and geometric nonlinearity on deflections and frequencies. Many of the numerical results presented here for laminated shells should serve as references for future investigations.Ph. D.
25
Osooly, Amir. "Development and implementation of robust large deformation and contact mechanics capabilities in process modelling of composites." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/747.
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Autoclave processing of large scale, one-piece structural parts made of carbon fiber-reinforced polymer composite materials is the key to decreasing manufacturing costs while at the same time increasing quality. Nonetheless, even in manufacturing simple flat parts, residual strains and stresses are unavoidable. For structural design purposes and to aid in the assembly procedures, it is desirable to have proven numerical tools that can be used to predict these residual geometrical and material properties in advance, thus avoid the costly experimental trial and error methods.
A 2-D finite element-based code, COMPRO, has previously been developed in-house for predicting autoclave process-induced deformations and residual stresses in composite parts undergoing an entire cure cycle. To simulate the tool-part interaction, an important source of residual deformations/stresses, COMPRO used a non-zero thickness elastic shear layer as its only interface option. Moreover, the code did not account for the large deformations and strains and the resulting nonlinear effects that can arise during the early stages of the cure cycle when the material is rather compliant.
In the present work, a contact surface employing a penalty method formulation is introduced at the tool-part interface. Its material-dependent parameters are a function of temperature, degree of cure, pressure and so forth. This makes the stick-slip condition plus separation between the part and the tool possible. The large displacements/rotations and large shear strains that develop at the early stages of the cure cycle when the resin has a very low elastic modulus provided the impetus to include a large strain/deformation option in COMPRO. A new “co-rotational stress formulation” was developed and found to provide a robust method for numerical treatment of very large deformation/strain problems involving anisotropic materials of interest here.
Several verification and validation examples are used to calibrate the contact interface parameters and to demonstrate the correctness of implementation and the accuracy of the proposed method. A number of comparisons are made with exact solutions, other methods, other experiments and the same models in other commercial codes. Finally, several interesting cases are examined to explore the results of COMPRO predictions with the added options.
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Mathaudhu, Suveen Nigel. "Fabrication of amorphous metal matrix composites by severe plastic deformation." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4389.
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Bulk metallic glasses (BMGs) have displayed impressive mechanical properties, but
the use and dimensions of material have been limited due to critical cooling rate
requirements and low ductility. The application of severe plastic deformation by equal
channel angular extrusion (ECAE) for consolidation of bulk amorphous metals (BAM)
and amorphous metal matrix composites (AMMC) is investigated in this dissertation.
The objectives of this research are a) to better understand processing parameters which
promote bonding between particles and b) to determine by what mechanisms the
plasticity is enhanced in bulk amorphous metal matrix composites consolidated by
ECAE.
To accomplish the objectives BAM and AMMCs were produced via ECAE
consolidation of Vitreloy 106a (Zr58.5Nb2.8Cu15.6Ni12.8Al10.3-wt%), ARLloy #1
(Hf71.3Cu16.2Ni7.6Ti2.2Al2.6 -wt%), and both of these amorphous alloys blended with
crystalline phases of W, Cu and Ni. Novel instrumented extrusions and a host of postprocessing
material characterizations were used to evaluate processing conditions and
material properties. The results show that ECAE consolidation at temperatures within the supercooled liquid region gives near fully dense (>99%) and well bonded millimeter
scale BAM and AMMCs. The mechanical properties of the ECAE processed BMG are
comparable to cast material: ÃÂf = 1640 MPa, õf = 2.3%, E = 80 GPa for consolidated
Vitreloy 106a as compared to ÃÂf = 1800 MPa, õf = 2.5%, E = 85 GPa for cast Vitreloy
106, and ÃÂf = 1660 MPa, õf = 2.0%, E = 97 GPa for ARLloy #1 as compared to ÃÂf = 2150
MPa, õf < 2.5%, E = 102 GPa for Hf52Cu17.9Ni14.6Ti5Al10. The mechanical properties of
AMMCs are substandard compared to those obtained from melt-infiltrated composites
due to non-ideal particle bonding conditions such as surface oxides and crystalline phase
morphology and chemistry. It is demonstrated that the addition of a dispersed crystalline
phase to an amorphous matrix by ECAE powder consolidation increases the plasticity of
the amorphous matrix by providing locations for generation and/or arrest of adiabatic
shear bands. The ability of ECAE to consolidated BAM and AMMCs with improved
plasticity opens the possibility of overcoming the size and plasticity limitations of the
monolithic bulk metallic glasses.
27
McKinley, Brett. "Large deformation structural performance of double skin composite construction using British Steel's 'Bi-Steel'." Thesis, City University London, 1999. http://openaccess.city.ac.uk/8071/.
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Double skin composite construction consists of two relatively thin steel plates with the space between filled with, usually, normal weight concrete. The transfer of shear between the steel and concrete is possible through the use of steel shear connectors that are welded to the steel plates. A study of previously published information revealed that the areas to market double skin composite construction would be submerged tube tunneling and floating offshore structures, particularly those used for the storage of crude oil. Double skin composite construction was traditionally fabricated with headed studs, as used in composite bridge construction. These were welded to each of the steel plates which were then temporarily held in place whilst the concrete was cast. This method of construction was costly in time and labour so British Steel PIc and The Steel Construction Institute developed an idea of using continuous friction welded bars. These connect to both plates to form a continuous steel structure. By manufacturing steel panels, up to 12m by 3m in a factory environment that requires no additional formwork allows great savings in time and labour during the construction process. Research on Bi-Steel, as it is known, is being carried out on numerous fronts with that detailed in this thesis being part of it. This thesis covers the overall performance aspects of strength and stiffness throughout the elastic and plastic regions of deformation and includes local buckling of the compression plate. Analytical solutions are developed for all aspects dealt with by this thesis which are supported with an experimental test programme. The test programme uses 16 full-scale, wide beam specimens that are tested in three point bending. The first series of tests carried out, which used the first two prototype Bi-Steel panels, compared the existing method of construction of double skin composites with Bi-Steel, the new method of construction. The second series of tests, divided into two parts, helped to develop the strength, stiffness and local buckling equations. The first series of tests showed that Bi-Steel was structurally the better performer. This was due to the continuous nature of the steelwork, which allowed the full strength of the steel to be achieved and structural continuity even after buckling failure. The traditional method of constructing DSC was no weaker or less stiff than its Bi-Steel counterpart, but the headed shear studs prematurely pulled out of the concrete. The second test series, which only used Bi-Steel panels, showed that an Euler analysis can be carried out to determine the buckling load of the compression plate. It also showed that the post yield gain in strength of the panels was due to strain hardening of the steel tension plate. In conclusion, it has been structurally and financially beneficial to develop Bi-Steel. The factory fabrication of the steelwork increases quality control and the unit type product allows easy on-site assembly. The structural performance of Bi-Steel is now well understood with few areas left to study which are now being addressed. The first design code has now been produced by SCI for the design of Bi-Steel components.
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Hayes, Michael David. "Characterization and Modeling of a Fiber-Reinforced Polymeric Composite Structural Beam and Bridge Structure for Use in the Tom's Creek Bridge Rehabilitation Project." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/35852.
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Fiber reinforced polymeric (FRP) composite materials are beginning to find use in construction and infrastructure applications. Composite members may potentially provide more durable replacements for steel and concrete in primary and secondary bridge structures, but the experience with composites in these applications is minimal. Recently, however, a number of groups in the United States have constructed short-span traffic bridges utilizing FRP members. These demonstration cases will facilitate the development of design guidelines and durability data for FRP materials. The Tom's Creek Bridge rehabilitation is one such project that utilizes a hybrid FRP composite beam in an actual field application.
This thesis details much of the experimental work conducted in conjunction with the Tom's Creek Bridge rehabilitation. All of the composite beams used in the rehabilitation were first proof tested in four-point bending. A mock-up of the bridge was then constructed in the laboratory using the actual FRP beams and timber decking. The mock-up was tested in several static loading schemes to evaluate the bridge response under HS20 loading. The lab testing indicated a deflection criterion of nearly L/200; the actual field structure was stiffer at L/450. This was attributed to the difference in boundary conditions for the girders and timber panels.
Finally, the bridge response was verified with an analytical model that treats the bridge structure as a wood beam resting upon discrete elastic springs. The model permits both bending and torsional stiffness in the composite beams, as well as shear deformation. A parametric study was conducted utilizing this model and a mechanics of laminated beam theory to provide recommendations for alternate bridge designs and modified composite beam designs.
Master of Science
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Melin, L. Gunnar. "Moiré techniques for measurement of the deformation field at crack tips in fiber composite materials." Licentiate thesis, Luleå tekniska universitet, 1995. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26502.
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Khdeir, Ahmed Adel. "Analytical solutions for the statics and dynamics of rectangular laminated composite plates using shearing deformation theories." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/49808.
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Begg, Henry S. "Processing, structure and properties of Al-matrix composites." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:6b825394-f5a0-4087-a89a-1ec6ca091426.
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Three classes of Al-matrix composite were manufactured to combine dissimilar metals and incorporate structural hierarchy, in an attempt to develop unusual combinations of mechanical properties. The first class combined a brittle, nano-quasicrystalline forming Al-3Fe-2Cr-2Ti phase with a ductile Al-4Cu phase into a layered structure using low pressure plasma spraying (LPPS). By using a substrate with multi-scale topological features, an ultra-thick (>2mm) deposit was successfully sprayed, which was subsequently consolidated by hot rolling to reduce residual porosity. The microstructure comprised a 'brick-wall' structure consisting of a convoluted arrangement of inter-leaved discreet droplet splats. Structure-property relationships were studied for four volume fractions of ductile additions and in-situ electron microscopy of beams subjected to 3-point bending suggested the ductile additions were providing additional toughening to the composite by a crack-bridging mechanism. The second class of composite investigated highly deformed microstructures of Al with 20vol% additions of either Sn or Ti. Nano-scale fibrous structures of the minority additions were achieved via an accumulative extrusion method, where extruded rod was abraded, degreased, bundled and re-extruded. This process was repeated to create refined microstructures while retaining a large material section. Fracture properties were studied in three point bending and crack growth monitored using Digital Image Correlation (DIC) to produce strain fields of the deforming beam surface. Modest changes were observed in mechanical properties with weak interfaces between poorly bonded extruded rods dominating fracture behaviour. Whiskers formed on polished surfaces of extruded Al-20vol%Sn and were monitored in real time by electron microscopy. Growth rates of up to 2.8nm/s were measured, which exceeds re- ported values in the literature on electroplated coatings by at least one order of magnitude. This may provide a convenient new means of studying whisker formation and calls into question current growth models. The third class of composite combined heavily rolled sheets of Al-20vol%Sn and Al-20vol%Ti with glass fibre/epoxy sheets to produce a laminate with multi-scale architecture. This laminate was designed as a proof-of-concept hierarchical material with structures ranging from the near millimetre scale of the metal-polymer layers, to the micro-sized glass fibre reinforcement of the epoxy and the nano-scale filamentary/lamellar microstructure of the highly deformed metal sheets. Fracture of such laminates was investigated in 3-point bending with continuous optical monitoring.
32
Johnston, Andrew A. "An integrated model of the development of process-induced deformation in autoclave processing of composite structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0030/NQ27172.pdf.
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Zhang, Hong. "Plastic deformation and chip formation mechanisms during machining of copper, aluminum and an aluminum matrix composite." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ62306.pdf.
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Bhumbla, Ravinder. "A study of vibrations in rotating laminated composite plates accounting for shear deformation and rotary inertia." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/43291.
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A ftrst-order shear deformation plate theory is used to predict free vibration frequencies in rotating laminated composite plates. The theory accounts for geometric non-linearity in the form of von Karman strains. The plate is permitted to have arbitrary orientation and offset from the axis of rotation.
A finite element model is developed to obtain a solution to the problem. The model is validated
by comparing the results for free vibration of non-rotating plates for various boundary conditions
and material properties with the exact results based on the classical plate theory and the first-order shear deformable plate theory. Results are presented for free vibration of isotropic and laminated composite plates rotating at different angular velocities. A study has also been made on the change in the free vibration frequencies of the plate with angular velocity for different plate thicknesses and for different modulus ratios.Master of Science
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Lee, Seung Joon. "Nonlinear analysis of smart composite plate and shell structures." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/2218.
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Theoretical formulations, analytical solutions, and finite element solutions for laminated composite plate and shell structures with smart material laminae are presented in the study. A unified third-order shear deformation theory is formulated and used to study vibration/deflection suppression characteristics of plate and shell structures. The von K??rm??n type geometric nonlinearity is included in the formulation. Third-order shear deformation theory based on Donnell and Sanders nonlinear shell theories is chosen for the shell formulation. The smart material used in this study to achieve damping of transverse deflection is the Terfenol-D magnetostrictive material. A negative velocity feedback control is used to control the structural system with the constant control gain. The Navier solutions of laminated composite plates and shells of rectangular planeform are obtained for the simply supported boundary conditions using the linear theories. Displacement finite element models that account for the geometric nonlinearity and dynamic response are developed. The conforming element which has eight degrees of freedom per node is used to develop the finite element model. Newmark's time integration scheme is used to reduce the ordinary differential equations in time to algebraic equations. Newton-Raphson iteration scheme is used to solve the resulting nonlinear finite element equations. A number of parametric studies are carried out to understand the damping characteristics of laminated composites with embedded smart material layers.
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Yildiz, Tuba. "Development Of A Shell Finite Element For Large Deformation Analysis Of Laminated Composites." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609943/index.pdf.
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The objective of the present work is to investigate the behavior of laminated fiber -reinforced polymer matrix composite shell structures under bending load with the help of a modified finite element computer code which was previously developed for the analysis of pseudo-layered single material shells. The laminates are assumed to be orthotropic and the formulation is adapted to first order shear deformation theory. The aim is to determine the large deformation characteristics numerically, and to predict the modes of failure by the illustration of the critical elements of the model. Therefore, several failure theories are also integrated to the code to detect first ply failure. Triangular shell elements are used and all the related data are generated from the mid-plane. Laminates under transverse loading are analyzed through several boundary conditions and ply orientations. To verify the numerical results obtained, a commercial finite element program is used to compare the outputs of the study, and the comparison is found to have shown good agreement. The onset of damage is investigated by using different failure criteria consisting of maximum stress, Tsai-Wu, and Tsai- Hill theories and close results are obtained.
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Kwon, Jonghan. "Characterization of deformation mechanisms in pre-strained NiAl-Mo composites and α-Ti alloy." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343796987.
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de, Falco Paolino. "Mechanisms of deformation and energy dissipation in antler and arthropod cuticle with bio-inspired investigations." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/54050.
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Bio-composite hierarchical materials have attracted the interest of the academic community operating in the field of bio-inspired materials for their outstanding mechanical properties achieved via lightweight structural designs. Antler and mantis shrimp's cuticle are extreme examples of materials naturally optimised to resist impacts and bear dynamic loading. Firstly, a class of finite-element fibril models was developed to explain the origin of heterogeneous fibrillar deformation and hysteresis from the nanostructure of antler. Results were compared to synchrotron X-ray data and demonstrated that the key structural motif enabling a match to experimental data is an axially staggered arrangement of stiff mineralised collagen fibrils coupled with weak, damageable interfibrillar interfaces. Secondly, the cuticle of the crustacean Odontodactylus scyllarus, known as peacock mantis shrimp, was investigated. At the nanoscale it consists of mineralised chitin fibres and calcified protein matrix, which form plywood layers at the microscale. Lamination theory was used to calculate fibrillar deformation and reorientation and, in addition, an analytical formulation was used to decouple in-plane fibre reorientation from diffraction intensity changes induced by 3D lamellae tilting. This animal also attracted my attention for using its hammer-like appendages to attack and destroy the shells of prey with a sequence of two strikes. Inspired by this double impact strategy, I performed a set of parametric finite-element simulations of single, double and triple mechanical hits, to compute the damage energy of the target. My results reveal that the crustacean attack strategy has the most damaging effect among the double impact cases, and lead me to hypothesise, that optimal damaging dynamics exists, depending on the sequence of consecutive impacts and on their time separation values. These new insights may provide useful indications for the design of bio-inspired materials for high load-bearing applications.
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Sahin, Hakan. "Addressing Adaptive Structure Technology to Reduce the Airframe Noise(Link)." Thesis, KTH, Hållfasthetslära (Avd.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-132231.
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ABSTRACTThe purpose of this thesis is to design and analyze the new generation leading edge slat of a commercial jet to reduce the structural noise with the application of new conceptual design approaches. Recent scientific research show that the leading edge slats account for the structural noise during the flight operation therefore, when the leading edge slat is deployed under different flight conditions, an open gap/slot is formed between the high lift device and the wing box. However, since the leading edge slat includes flexible sections, it is assumed that defining an adaptive system inside the leading edge slat may reduce the structural noise by utilizing bending properties of these flexible sections. Hence, electromechanical actuator designing gains also great importance in the whole process. In this study, we have used, finite element modelling of the slat structure to examine the required structural deformations and strengths; our work is based on the software ANSYS/Workbench. To be realistic in deciding the right geometry in the follow up steps, we have first studied a generic geometry having no aerodynamics or actuator forces application. The whole simulation was performed by defining dummy forces and dummy material properties. The simulation lead to having a global overview of the mechanical behaviour of the structure; further, once the influent parameters were tested, realistic aerodynamic forces and material properties were defined, and as a result of bending of the flexible sections the required gap closure was formed between the trailing edge of the slat and the wing box. Subsequently, the suitable actuator design and required strength analysis are also performed on the last section. This study has also proved that the use of adaptive systems on the leading edge slats improves flight comfort by reducing the structural noise and provides less fuel consumption; this is significant for the long run considerations of aeroplane manufacturers.es Zentrum für Luft- und Raumfahrt e. V. (DLR)
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Schniepp, Timothy John. "Design Manual Development for a Hybrid, FRP Double-Web Beam and Characterization of Shear Stiffness in FRP Composite Beams." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/34550.
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Fiber-reinforced polymeric (FRP) composites are being considered for structural members in bridge construction as lighter, more durable alternatives to steel and concrete. Extensive testing and analysis of a pultruded, hybrid double web beam (DWB) developed for use in bridge construction has been conducted at Virginia Tech. A primary purpose of this testing is the development of a structural design guide for the DWB, which includes stiffness and strength data. The design manual also includes design allowables determined through a statistical analysis of test data.
Static testing of the beams, including failure tests, has been conducted in order to determine such beam properties as bending modulus, shear stiffness, failure mode, and ultimate capacity. Measuring and calculating the shear stiffness has proven to be an area of particular interest and difficulty. Shear stiffness is calculated using Timoshenko beam theory which combines the shear stiffness and shear area together along with a shear correction factor, k, which accounts for the nonuniform distribution of shear stress/strain through the cross-section of a structure. There are several methods for determining shear stiffness, kGA, in the laboratory, including a direct method and a multi-span slope method. Herein lays the difficulty as it has been found that varying methods produces significantly different results. One of the objectives of current research is to determine reasons for the differences in results, to identify which method is most accurate in determining kGA, and also to examine other parameters affecting the determination of kGA that may further aid the understanding of this property.
This document will outline the development of the design guide, the philosophy for the selection of allowables and review and discuss the challenges of interpreting laboratory data to develop a complete understanding of shear effects in large FRP structural members.Master of Science
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Subbarayan, Sapthagireesh. "Fabrication of a Novel Al/Mg Composite: : Processing and Characterization of Pure Aluminium, Al/AZ31 Alloy Bi-Metal and Aluminium based Sheet Composites by Severe Plastic Deformation." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23778.
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Schwark, Tabea Gisela [Verfasser]. "Deformation and Fracture Properties of the Soft Magnetic Composite Somaloy 700 3P on Different Length Scales / Tabea Gisela Schwark." Karlsruhe : KIT Scientific Publishing, 2018. http://www.ksp.kit.edu.
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Gunel, Murat. "Linear And Nonlinear Progressive Failure Analysis Of Laminated Composite Aerospace Structures." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12614033/index.pdf.
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This thesis presents a finite element method based comparative study of linear and geometrically non-linear progressive failure analysis of thin walled composite aerospace structures, which are typically subjected to combined in-plane and out-of-plane loadings. Different ply and constituent based failure criteria and material property degradation schemes have been included in a PCL code to be executed in MSC Nastran. As case studies, progressive failure analyses of sample composite laminates with cut-outs under combined loading are executed to study the effect of geometric non-linearity on the first ply failure and progression of failure. Ply and constituent based failure criteria and different material property degradation schemes are also compared in terms of predicting the first ply failure and failure progression. For mode independent failure criteria, a method is proposed for the determination of separate material property degradation factors for fiber and matrix failures which are assumed to occur simultaneously. The results of the present study show that under combined out-of-plane and in-plane loading, linear analysis can significantly underestimate or overestimate the failure progression compared to geometrically non-linear analysis even at low levels of out-of-plane loading.
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Muturi, Christopher. "Characterization of viscoelastic properties of an epoxy composite and simulation of time dependent deformation of an annulus seal under load." Thesis, KTH, Hållfasthetslära (Inst.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176400.
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A new sealing stand-alone tool, i.e. CannSeal to produce a barrier packer or zonal isolation in oil/gas wells has been developed by a Norwegian company (AGR CannSeal AS). The tool allows injection of a fluid into the annulus between the production casing and the surroundings in an oil/gas well. After injection the fluid will solidify and form an annulus solid plug which will prevent/reduce axial flow in the annulus volume. During operation and testing of well integrity the plug may be subjected to high pressure gradients, e.g. 250 bar. AGR CannSeal has developed epoxy formulations for different applications for use with the CannSeal tool. After curing the epoxy will form a solid, or more specifically a cross-linked polymer. Since the epoxy plug may be exposed to large differential pressure for long times it is of great interest to study the viscoelastic properties and estimate the severity of the time dependent deformation (creep) by FEA simulations, considering the load scenarios expected in an oil or gas well. An annulus shaped epoxy plug intended for use as a barrier seal at 70°C was manufactured by injection of an epoxy formulation at 70°C and 150 bar hydrostatic pressure into the annulus of two steel tubings (5 1/2" and 9 5/8") on top of a defect packer. Curing was interrupted after 3 weeks well beyond the Gel point. Test specimens were prepared and subjected for post-curing at 120°C for 2 days after which extensive material testing at 70°C was performed, i.e. tensile testing, relaxation testing, creep testing and compression testing. The degree of curing (conversion) was estimated to be 67 % and the glass transition to about 80°C by means of DMA, DSC and HFC. Different material models were evaluated of which the Generalized Maxwell model, which assumes linear viscoelastic properties, was found to adequately describe all experimental results. The model parameters were determined by means of the method of Non-linear least squares. FEA simulations were made using the model selected and the parameters determined. Two load cases, one simulating the most sever predicted load scenario of an epoxy plug and the second simulating loading under ideal circumstances were evaluated. The simulations predicted that the most severe load case of the epoxy plug would have a safety factor of approximately 1.8 - 2,3 before reaching the estimated fracture strain, after one year of exposure to a differential pressure of 250 bar.Ett nytt sorts verktyg kallat CannSeal har utvecklats av ett norskt bolag (AGR CannSeal AS)för att skapa barriärpackningar och zon-isolation inom olje- och gasbrunnar. Verktyget tillåter injicering av en reaktiv vätska mellan produktionsröret och omgivande underlag i en olje-/gasbrunn. Efter injicering stelnar vätskan och formar en solid annulär epoxitätning som förhindrar eller minskar axiella flöden i utrymmet. Under användning och testning av brunnintegriteten kan tätningen utsättas för höga tryckgradienter som kan uppgå till 250 bar. AGR CannSeal har utvecklat ett flertal olika epoxiformuleringar avsedda för olika typer av applikationer, som injiceras med CannSeal. Efter härdning kommer epoxin att forma en solid eller mer specifikt en tvärbunden polymer, en så kallad härdplast. Eftersom epoxitätningen är utsatt för höga tryckgradienter under långa perioder är det av stort intresse att undersöka de viskoelastiska egenskaperna och utgående från FEA simuleringar, simulera graden av tidsberoende deformation (krypdeformation) vid lastfall uppskattade att inträffa under applikation. Ett annulärt formad epoxitätning avsedd till användning som barriärpackning vid 70oC, tillverkades via en inmatning av en epoxiformel vid 150 Bar hydrostatiskt tryck. Tätningen placerades mellan två stålrör (5 1/2" och 9 5/8"), befinnande ovanpå en redan befintlig defekt barriärspackning. Härdningen var avbruten efter 3 veckors tid och därför även långt efter uppnådd gelpunkt. Provstavar förberedes och utsattes för en efterhärdning vid 120oC under 2 dagars tid, efterföljt av omfattande mekaniskprovning vid 70oC. Provningen bestod av dragprov, relaxationsprov, krypprov samt kompressionsprov. Graden av härdning uppskattades till 67 % och en glasomvanlingstemperatur på cirka 80oC, uppskattningen utfördes med hjälp av DMA-, DSC- samt HFC-provning. Olika materialmodeller evaluerades varav den Generaliserade Maxwell modellen valdes. Modellen ansätter linjära viskoelastiska egenskaper som passade bra med avseende på experimentella resultat. Modellens parametrar kalibrerades med hjälp av en olinjär-minstakvadratmetod. Två typer av lastfall med FEA simuleringarna utfördes sedan med den definierade materialmodellen. Ena lastfallet skulle representera belastning under värst uppskattade förhållanden var den andra skulle modellera belastning under ideala förhållanden, i en olje-/gasbrunn. Simuleringarna visade att vid värsta förhållanden, under 1års belastning av 250 bar differentialtryck, skulle epoxitätningen ha en säkerhetsfaktor mellan 1.8 - 2,3 innan den estimerade brottöjningen är uppnådd.
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Pauer, Brett Arnold. "Development of a finite element method program for the analysis of laminated composite plates using first-order shear deformation theory." Connect to resource, 1993. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1232807239.
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Peng, Xuan. "Co-deformation and bonding of multi-component billets with application to Nb-Sn based superconductor processing." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1127096847.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xix, 182 p.; also includes graphics (some col.). Includes bibliographical references (p. 177-182). Available online via OhioLINK's ETD Center
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Strömbro, Jessica. "Micro-mechanical mechanisms for deformation in polymer-material structures." Doctoral thesis, KTH, Hållfasthetslära (Inst.), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4626.
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In this thesis, the focus has been on micro-mechanical mechanisms in polymer-based materials and structures. The first part of the thesis treats length-scale effects on polymer materials. Experiments have showed that the smaller the specimen, the stronger is the material. The length-scale effect was examined experimentally in two different polymers materials, polystyrene and epoxy. First micro-indentations to various depths were made on polystyrene. The experiments showed that length-scale effects in inelastic deformations exist in polystyrene. It was also possible to show a connection between the experimental findings and the molecular length. The second experimental study was performed on glass-sphere filled epoxy, where the damage development for tensile loading was investigated. It could be showed that the debond stresses increased with decreasing sphere diameter. The debonding grew along the interface and eventually these cracks kinked out into the matrix. It was found that the length to diameter ratio of the matrix cracks increased with increasing diameter. The experimental findings may be explained by a length-scale effect in the yield process which depends on the strain gradients. The second part of the thesis treats mechano-sorptive creep in paper, i.e. the acceleration of creep by moisture content changes. Paper can be seen as a polymer based composite that consists of a network of wood fibres, which in its turn are natural polymer composites. A simplified network model for mechano-sorptive creep has been developed. It is assumed that the anisotropic hygroexpansion of the fibres leads to large stresses at the fibre-fibre bonds when the moisture content changes. The resulting stress state will accelerate creep if the fibre material obeys a constitutive law that is non-linear in stress. Fibre kinks are included in order to capture experimental observations of larger mechano-sorptive creep effects in compression than in tension. Furthermore, moisture dependent material parameters and anisotropy are taken into account. Theoretical predictions based on the developed model are compared to experimental results for anisotropic paper both under tensile and compressive loading at varying moisture content. The important features in the experiments are captured by the model. Different kinds of drying conditions have also been examined.QC 20100910
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Khadraoui, Fouzia. "Incidence du renforcement à l'aide de plaques en matériau composite sur le comportement différé du mortier." Thesis, Rouen, INSA, 2009. http://www.theses.fr/2009ISAM0018/document.
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Les ouvrages du génie civil ont une durée de vie limitée, et plusieurs d’entre eux nécessitent aujourd’hui une réparation, voire une reconstruction partielle. Ainsi le domaine des réparations et des renforcements en béton connaît depuis une dizaine d’années, une croissance importante dans le secteur du bâtiment et des travaux publics. Plusieurs études ont montré que le retrait et le fluage peuvent mener à de sévères problèmes liés à la durabilité. En effet, ces phénomènes peuvent être à l’origine de la fissuration, et même plus rarement de la ruine de l’ouvrage. Cette thèse a pour objectif d’étudier le comportement au retrait et au fluage d’éléments renforcés. Ce travail est divisé en deux parties principales. Dans la première partie, nous effectuons une étude expérimentale sur des éléments renforcés. Nous nous intéressons, dans la deuxième partie,à la modélisation du séchage afin de prévoir les transferts hydriques au sein du matériau, et le retrait de celui-ci. L’étude expérimentale vise à étudier l’effet du renforcement sur le comportement différé d’éprouvettes en mortier normalisé. L’approche théorique et numérique permet d’analyser les transferts hydriques et la diffusion de l’humidité au sein du matériau, et de calculer ainsi les déformations différées. Les essais expérimentaux montrent que le renforcement avec des matériaux composites réduit considérablement la déformation au fluage, mais n’apporte pas d’amélioration quant au retrait de séchageThe works of civil engineering have one limited life span, and several of them require a repair today, even a partial rebuilding. Thus the field of the concrete repairs and strengthening knowssince ten years, a considerable growth in the sector of the building and public works. Several studies showed that the shrinkage and creep can lead to severe problems involved indurability. Indeed, these phenomena can be at the origin of cracking, and even more rarely of the ruin of the work. This thesis aims to study the shrinkage and creep behaviour of strengthened elements. This work is divided into two principal parts. In the first part, we carry out an experimental study on strengthened elements. We are interested, in the second part, to the modelling of drying in orderto envisage the hydrous transfers within material, and the shrinkage of this one. In the experimental study, we are interested to the strengthening effect on the differed behaviour of mortar specimens. The theoretical and numerical approach allows to analyze the hydrous transfers and the diffusion of humidity within material, and thus to calculate the differed deformations. The experimental tests show that the strengthening with composite materials reduced considerably the creep strain, but does not make improvement as for the shrinkage ofdrying
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Lopez-Pamies, Oscar. "Sur le comportement effective, l'évolution de microstructure et la stabilité macroscopique des composite élastomères." Phd thesis, Ecole Polytechnique X, 2006. http://pastel.archives-ouvertes.fr/pastel-00002978.
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Les composites élastomères sont actuellement utilisés dans de nombreuses applications commerciales et ont montré de grandes promesses pour l'utilisation dans les nouvelles technologies. Cela soulève la pratique, ainsi que théorique nécessaire pour comprendre le lien entre la microstructure sous-jacente de composites en élastomère et de leurs propriétés mécaniques et physiques, et comment celui-ci peut être améliorée avec des changements dans l'ancienne. Dans ce contexte, l'objectif principal de cette thèse est le développement d'une analyse, le cadre homogénéisation non linéaire pour déterminer la réponse globale des composites élastomères soumis à des déformations finies. Les comptes-cadre pour l'évolution de la microstructure sous-jacente, ce qui entraîne des changements dans la géométrie finie induite par la charge appliquée. Ce point est essentiel que l'évolution de la microstructure peut avoir un assouplissement significatif géométrique (ou raidissage) effet sur la réponse globale du matériau, qui, à son tour, peut conduire à l'élaboration éventuelle d'instabilités macroscopiques. Le concept principal derrière la méthode d'homogénéisation non linéaire proposé est la construction de principes variationnels appropriés en utilisant l'idée d'un "portail composite linéaire», qui a finalement permettre la conversion des estimations disponibles homogénéisation linéaire dans les estimations analytiques pour la grande déformation de réponse global de l' non linéaire des composites en élastomère. Cette thèse comprend des applications de la théorie proposée pour les différentes classes des élastomères renforcés et poreux aléatoire et des microstructures périodiques. Une analyse complète du comportement efficace, l'évolution de la microstructure et le développement d'instabilités macroscopiques est prévu pour toutes ces applications.
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Waldron, Christopher J. "Determination of the Design Parameters for the Route 601 Bridge: A Bridge Containing the Strongwell 36 inch Hybrid Composite Double Web Beam." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34414.
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The Route 601 Bridge spans 39 ft over Dickey Creek in Sugar Grove, VA and represents the first use of Strongwell's 36 in. double web beam (DWB) as the main load carrying members for a traffic bridge. The bridge was designed for AASHTO HS20-44 and AASHTO alternate military loading with a targeted deflection limit of L/800. For the preliminary design, conservative properties for the 36 in. DWB were assumed based on experience at Virginia Tech with Strongwell's 8 in. DWB used in the Tom's Creek Bridge. An elastic modulus (E) of 6,000 ksi and a shear stiffness (kGA) of 20,000 ksi-in2 were assumed and used with Timoshenko shear deformable beam theory to characterize the beams and determine the deflections.
This thesis details the experimental work conducted in conjunction with the design of the Route 601 Bridge, which had two goals. First, a deck-to-girder connection was tested to determine if a bolted connection could develop composite action between the girder and the deck. This connection was shown to provide a significant amount of composite action when used with the 8 in. DWB and a composite deck, but little or no composite action when used with the 36 in. DWB and a glue-laminated timber deck. Second, eleven 36 in. DWB's were tested to determine their stiffness properties (EI and kGA) to insure that these properties were above the values assumed in the preliminary design, and all the beams had stiffness properties that were close to or above the assumed values. The eleven beams were also proof tested to a moment equivalent to five times the service load moment to insure the safety of the Route 601 Bridge, and one beam was tested to failure to determine the failure mode and residual stiffness of the 36 in. DWB. Finally, based on these results eight beams were chosen for the Route 601 Bridge.Master of Science