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Davis, Richard Anthony. "The Effects of a Damage Arrestment Device on the Mechanical Behavior of Sandwich Composite Beams Under Four-Point Bending". DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/506.
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The demand for an insert on composite sandwich structures to aid in the arrestment of face-core delamination is of great need. This research studies the use of a damage arrestment device (DAD) that connects the carbon fiber face sheets to the foam core to find whether an increase in the structural integrity of the sandwich beam results. Experimental analysis was employed to test the samples and was verified by a theoretical and finite element approach.
The mechanical properties of LTM45/CF1803 pre-impregnated carbon fiber and Last-A-foam FR 6710 polyvinylchloride foam were experimentally analyzed using ASTM D3039 and ASTM D1621 standards respectively to verify the manufacturer’s data for the given material. With all the mechanical data, the effects of adding DAD keys to a delaminated composite sandwich beam were studied under a four-point bending test using ASTM standard D6272 and compared with non-delaminated beams to see if an increase in ultimate strength could be achieved. The initial delamination in the beams under consideration was one inch in length and located in between the loaded span of the beam. Two control beams were utilized for comparison: one with no defects, and another with a one inch delamination introduced at the face-core interface. The DAD keys were added in two different configurations to potentially stop the delamination propagation and increase the ultimate strength. In the first configuration DAD keys were added 0.25 inches on either side of the initial delamination in the transverse direction and provided a significant increase in strength over the delaminated control beam. The second configuration had a DAD key running along the longitudinal axis of the sandwich beam and resulted in a significant increase in ultimate strength over the delaminated control beam. After testing ten successful samples for each of the six different configurations, it was concluded that the addition of DAD keys in both configurations significantly increased the structural integrity of both the delaminated and non-delaminated control beams.
With all the experimental data acquired, finite element models were created in COSMOS. The purpose of the finite element analysis was to validate the experimental results by comparing the deflections of the beam subjected to four-point bending during the experiment to the deflections found numerically. The deflections for the various DAD key configurations found in the experimental work were in agreement with the finite element results.
2
Glenn, Christopher Edward. "Fabrication and Structural Performance of Random Wetlay Composite Sandwich Panels". Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/43208.
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The random wetlay process is used to make fiber-reinforced thermoplastic sheets that can be compression molded into composite panels at little cost. By utilizing these composite panels as the facesheets of honeycomb sandwich structures, it is possible to greatly increase the bending stiffness of the composite without adding significant weight. The random wetlay composite facesheets used in this research consisted of 25% E-glass fibers and 75% PET by weight. The thickness uniformity of the facesheets was difficult to control. The core of the sandwich structure was HexWeb&174; EM. Three low-cost adhesives were examined for secondarily bonding the facesheets to the core: polyurethane glue; epoxy paste; and 3M Scotch-Grip&174; plastic adhesive. The polyurethane glue mixed with Cab-O-Sil filler was easiest to apply and provided the largest flatwise tensile strength. Mathematical models were developed to predict the static behavior of sandwich beams and plates in bending. Three-point bend tests were performed on a sandwich beam in accordance with ASTM C 393. A sandwich plate simply supported along two opposite edges and free along the other two edges was subjected to a line-load using weights and a wiffle tree arrangement. An effective facesheet modulus and Poissonâ s ratio were found by comparing the measured displacements to the sandwich plate theory. The shadow moiré technique was used to visualize the displacement of the line-loaded sandwich plate. The overall shape of the displacement was very similar to the shape predicted by the sandwich plate theory.Master of Science
3
Hove, Darlington. "Finite element analysis of a composite sandwich beam subjected to a four point bend". Thesis, Nelson Mandela Metropolitan University, 2011. http://hdl.handle.net/10948/1465.
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The work in this dissertation deals with the global structural response and local damage effects of a simply supported natural fibre composite sandwich beam subjected to a four-point bend. For the global structural response, we are investigating the flexural behaviour of the composite sandwich beam. We begin by using the principle of virtual work to derive the linear and nonlinear Timoshenko beam theory. Based on these theories, we then proceed to develop the respective finite element models and then implement the numerical algorithm in MATLAB. Comparing the numerical results with experimental results from the CSIR, the numerical model correctly and qualitatively recovers the underlying mechanics with some noted deviances which are explained at the end. The local damage effect of interest is delamination and we begin by reviewing delamination theory with more emphasis on the cohesive zone model. The cohesive zone model relates the traction at the interface to the relative displacement of the interface thereby creating a material model of the interface. We then carry out a cohesive zone model delamination case study in MSC.Marc and MSC.Mentat software packages. The delamination modelling is carried out purely as a numerical study as there are no experimental results to validate the numerical results.
4
Ho, Qhinhon D. "An Assessment Of The Accuracy Of The Euler-Bernoulli Beam Theory For Calculating Strain and Deflection in Composite Sandwich Beams". ScholarWorks@UNO, 2015. http://scholarworks.uno.edu/td/2084.
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This study focuses on assessing the accuracy of the Euler-Bernoulli beam theory as computational bases to calculate strain and deflection of composite sandwich beam subjected to three-point and four-point bending. Two groups of composite sandwich beams tests results will be used for comparison purposes. Mechanical properties for the laminated skin are provided by researchers from University of Mississippi (Ellen Lackey et al., 2000). Mechanical properties for the balsa wood core are provided by Alcan Baltek Corporation. Appropriate material properties and test geometries are then used in the Euler-Bernoulli-based algorithm in order to generate analytical data for comparison to experimental data provided by researchers from University of New Orleans (UNO, 2005). The resulting single material cross section is then analyzed in the traditional manner using the Euler-Bernoulli beam theory. In general, the Euler-Bernoulli beam theory provides an appropriate analytical approach in predicting flexural behavior of composite sandwich beams.
5
Petras, Achilles. "Design of sandwich structures". Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/236995.
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Failure modes for sandwich beams of GFRP laminate skins and Nomex honeycomb core are investigated. Theoretical models using honeycomb mechanics and classical beam theory are described. A failure mode map for loading under 3-point bending, is constructed, showing the dependence of failure mode and load on the ratio of skin thickness to span length and honeycomb relative density. Beam specimens are tested in 3-point bending. The effect of honeycomb direction is also examined. The experimental data agree satisfactorily with the theoretical predictions. The results reveal the important role of core shear in a sandwich beam's bending behaviour and the need for a better understanding of indentation failure mechanism. High order sandwich beam theory (HOSBT) is implemented to extract useful information about the way that sandwich beams respond to localised loads under 3-point bending. 'High-order' or localised effects relate to the non-linear patterns of the in-plane and vertical displacements fields of the core through its height resulting from the unequal deformations in the loaded and unloaded skins. The localised effects are examined experimentally by Surface Displacement Analysis of video images recorded during 3-point bending tests. A new parameter based on the intrinsic material and geometric properties of a sandwich beam is introduced to characterise its susceptibility to localised effects. Skin flexural rigidity is shown to play a key role in determining the way that the top skin allows the external load to pass over the core. Furthermore, the contact stress distribution in the interface between the central roller and the top skin, and its importance to an indentation stress analysis, are investigated. To better model the failure in the core under the vicinity of localised loads, an Arcan- type test rig is used to test honeycomb cores under simultaneous compression and shear loading. The experimental measurements show a linear relationship between the out-of-plane compression and shear in honeycomb cores. This is used to derive a failure criterion for applied shear and compression, which is combined with the high order sandwich beam theory to predict failure caused by localised loads in sandwich beams made of GFRP laminate skins and Nomex honeycomb under 3-point bending loading. Short beam tests with three different indenter's size are performed on appropriately prepared specimens. Experiments validate the theoretical approach and reveal the nature of pre- and post-failure behaviour of these sandwich beams. HOSBT is used as a compact computational tool to reconstruct failure mode maps for sandwich panels. Superposition of weight and stiffness contours on these failure maps provide carpet plots for design optimisation procedures.
6
ASCIONE, ALESSIA. "Synthetic models for the analysis and control of composite and sandwich aerospace structures in critical conditions". Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2751494.
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Isildak, Murat. "Use Of Helical Wire Core Truss Members In Space Structures". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610553/index.pdf.
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In an effort to achieve lighter and more economical space structures, a new patented steel composite member has been suggested and used in the construction of some steel roof structures. This special element has a sandwich construction composed of some strips of steel plates placed longitudinally along a helical wire core. The function of the helical core is to transfer the shear between the flange plates and increase the sectional inertia of the resulting composite member by keeping the flange plates at a desired distance from each other. Because of the lack of research, design engineers usually treat such elements as a solid member as if it has a full shear transfer between the flanges. However, a detailed analysis shows that this is not a valid assumption and leads to very unsafe results. In this context, the purpose of this study is to investigate the behavior of such members under axial compression and determine their effective sectional flexural rigidity by taking into account the shear deformations. This study applies an analytical investigation to a specific form of such elements with four flange plates placed symmetrically around a helical wire core. Five independent parameters of such a member are selected for this purpose. These are the spiral core and core wire diameters, the pitch of the spiral core, and the flange plate dimensions. Elements with varying combinations of the selected parameters are first analyzed in detail by finite element method, and some design charts are generated for the determination of the effective sectional properties to be used in the structural analysis and the buckling loads. For this purpose, an alternative closed-form approximate analytical solution is also suggested.
8
Maheri, M. R. "Vibration damping in composite/honeycomb sandwich beams". Thesis, University of Bristol, 1991. http://hdl.handle.net/1983/d96ba3e9-edb0-4a07-ac6e-69328ed22678.
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Joshi, Ninad Milind. "Study of the Effect of Unidirectional Carbon Fiber in Hybrid Glass Fiber / Carbon Fiber Sandwich Box Beams". University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1386188162.
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Frieda, Jan. "Administrativní budova". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226910.
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This thesis aims to design a bearing composite steel structure for five-storey administration building with ground plan dimensions 35,00 x 50,00 m. Designed building has L-shaped plan, flat roof and attic all the way around. The largest part of the plan area occupies office zone with dimensions of 48,60 x 18,90 m. Contiguous zone communication and sanitation has dimensions of 13,50 x 15,90 m. Floor height is designed 3,60 m, the total height of the building is 18,70 m. Composite steel floor structure consists of transverse primary beams and hinge-connected secondary beams. Integrated formwork (trapezoidal sheet) has ribs oriented perpendicular to the secondary beams. Coupling is bidirectional. Construction will be done in two variants. Variant No.1 assumes primary and secondary beams (at the columns) hinge-connected with columns. In variant No.2 will be frame connection between primary beams and columns and together they will create 2D transverse frames with hinge-connected secondary beams. The supporting structure of the roof is designed similarly to ceiling, but reinforced concrete slab will be replaced with bracing in the roof plane and self-bearing rib sandwich panels. Vertical sheathing of the building provide sandwich panels and strip windows. The type of steel is S355. The building is designed for the site Hradec Králové. Standards and documents used in design of the bearing structure are included in the list of sources. The result of this work is a static analysis with an assessment of all elements of the selected (best) variant of the structure, drawing documentation and technical report.
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Koike, Ayako. "Torsional and flexural control of sandwich composite beams with piezoelectric actuators". Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06232009-063235/.
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Worrall, Christopher Michael. "The behaviour of composite sandwich beams and panels under low velocity impact conditions". Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333578.
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Wahyuni, Ade Sri. "Structural characteristics of reinforced concrete beams and slabs with lightweight blocks infill". Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/1874.
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A Lightweight Sandwich Reinforced Concrete (LSRC) section has been developed with a novel use of prefabricated Autoclaved Aerated Concrete (AAC). This LSRC section is a reinforced concrete section in which AAC blocks are used as infill material in the section where concrete is considered ineffective under bending. This technology is suitable to be used for slab and beam.Five beams were prepared to investigate the flexural and shear capacity of the LSRC. Based on the test results, the flexural capacity was found to be almost identical to the capacity of the equivalent solid beam, while the shear capacity was reduced. The shear strength reduction was as expected due to the reduction in the compressive strength of AAC infill material.Furthermore, eight tests were also conducted on four slabs, one solid and three LSRC slabs. Based on the test results, all LSRC slabs exhibited similar behaviour to the equivalent solid slab and had varying shear capacities depending on the profile of AAC blocks infill. The obtained shear capacities were compared with the design values based on several major design codes and found to be within the safety predictions of the codes.ANSYS 12.1 was employed to develop nonlinear finite element models of LSRC beams and slabs. The numerical results agree well with the experimental one. The beams modelled with ANSYS followed the same trend as the actual beam in the linear range, however after the first cracking the loss of stiffness in ANSYS model caused the bigger deflection compared to the actual beam. For slab models, ANSYS overestimates the load deflection behaviour due to the cracks that already available in slabs from the previous test. The crack propagation modelled with ANSYS for beams and slabs shows the cracks in the area of AAC blocks which associates with the brittle failure of LSRC beams and slabs.In General ANSYS can predict the behaviour of the LSRC beams and slabs. The developed model can be used to investigate LSRC members with different structural and loading parameters.The proposed LSRC section will be suitable for large span construction. Themain benefits of this LSRC member are the cost and time savings due to theweight reduction and the less of supporting structure and foundation and the consequent ease of construction.
14
Wood, Yvette Vanessa. "EFFECTS OF DAMAGE ARRESTMENT DEVICES ON THE FATIGUE LIFE OF IMPACTED COMPOSITE SANDWICH BEAMS". DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/955.
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The use of composite sandwich panels is rapidly increasing in the aerospace industry. In these applications, thin composite face sheets are typically co-cured to foam or honeycomb cores. One of the greatest concerns in these types of applications is face-core delamination because it can ultimately lead to catastrophic failure of the structure. Further, the effects of foreign object damage on composite sandwich structures are often catastrophic. Damage to the structure is often undetectable through visual inspection, leading to concerns of unknown interlaminar damage through the life of the structure, which can cause a catastrophic failure. This research determines the effectiveness of a damage arrestment device (DAD) on the structural integrity of composite sandwich beams. The effects of these DADs on the fatigue life of these beams following a low-velocity impact will be considered.
Composite sandwich beams were constructed utilizing two layers of Advanced Composite Group LTM45EL/CF1803 bi-directional woven carbon fiber face sheets with a General Plastics Last-A-Foam FR-6710 rigid polyurethane core, and were cured utilizing an autoclave. Static 4-point bend testing following the ASTM standard D6272 was investigated to determine the flexural behavior of composite sandwich beams. Six different beam cases, with dimensions 1-inch wide by 11.75-inch long, were investigated. The cases considered were beams with and without initial delamination and also, with DAD keys placed transversely and longitudinally with and without delamination. A drop test was employed to simulate a low-velocity impact to the composite sandwich beams with and without delamination. The flexural behavior of these two cases was determined and used in fatigue testing. Experimental results showed that the addition of DAD keys to initially delaminated composite sandwich beams improved the ultimate strength values significantly.
Fatigue testing was investigated to determine the fatigue life of composite sandwich beams following a low velocity impact. Similar to static 4-point bend testing, six different beam cases, with dimensions 1-inch wide by 11.75-inch long, were investigated. The cases considered were exactly those seen in static 4-point bend testing - beams with and without initial delamination and also with DAD keys placed transversely and longitudinally with and without delamination. The three cases without delamination were investigated in the 4-point bend fatigue test, with and without impact. Experimental results showed that the addition of DAD keys had a significant effect on increasing the fatigue life of composite sandwich beams with initial damage from impact, and even improved the fatigue life of beams with initial delamination.
A numerical investigation was completed using a finite element model (FEM) as a means to validate the experimental results found in this research. Static 4-point bend testing was modeled using Abaqus, where maximum deflection values at a specific load were used as a comparison between the experimental and numerical results. Experimental and numerical results showed that the addition of DADs significantly improved the integrity and fatigue life of the composite sandwich design. All cases showed close agreement between the experimental and numerical results.
15
Lin, Yih Lan, i 林義嵐. "Analysis of Composite Sandwich Beam Subjected to Torsional Loading". Thesis, 1996. http://ndltd.ncl.edu.tw/handle/50976979163870121726.
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Sharma, Himanshu. "Optimization of a higher-order sandwich composite beam under uncertainties". Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5219.
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Optimization under uncertainties of structures is a challenging field due to the requirements of high computational resources. The typical approaches include reliability-based design optimization (RBDO) and robust design optimization (RDO), which provide more realistic optimal designs than the conventional deterministic optimization approaches. For complex engineering structures, performing RBDO and RDO becomes computationally intractable or even infeasible. Thus, there is a requirement to employ efficient uncertainty quantification methods to perform the optimization under uncertainty of advanced structures. This thesis investigates the reliable and robust optimum design of a higher-order sandwich composite beam under the effect of uncertainty in material properties. Sandwich composites are a unique class of composite materials that are quite popular in the aerospace, marine, and automobile industries, mainly due to their superior properties such as high stiffness, low weight to strength ratio, high corrosion resistance, and high energy absorption capabilities. The sandwich composite beam is modeled using the extended higher-order sandwich panel theory. The optimization procedure is performed using an accelerated particle swarm optimization. The efficiency of the optimization process is enhanced by using a novel time-domain spectral element method-based polynomial chaos surrogate model. The proposed surrogate model is based on the highly efficient hybrid stochastic time domain spectral element method (STSEM). STSEM couples the computational efficiencies of the spectral stochastic finite element method and the time-domain spectral element method. The uncertainty analysis of a higher-order sandwich composite beam using STSEM is performed to compare the numerical accuracy and the computational efficiency of the proposed method with the Monte Carlo simulation (MCS). Sobol indices-based global sensitivity analysis is also performed to identify the sensitive random parameters. The numerical results indicate the superior computational efficiency and excellent numerical accuracy of STSEM in comparison with MCS. Thus, a surrogate model is built using STSEM to perform the optimization of a higher-order sandwich composite beam under uncertainty. The proposed surrogate model alleviates the high computational requirements of RBDO and RDO procedures for sandwich composite. The numerical results of the reliable and robust optimal design are presented and discussed. Furthermore, the effect of load density and allowable deflection on the optimal design is also examined.
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Tseng, Chi-Feng, i 曾頎峰. "Bending stiffness analysis of composite sandwich beam with the application of Taguchi method". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/30569813797491075755.
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碩士國立臺灣大學
機械工程學研究所
93
The purpose of present study was to find out a best combination level of factors, which would give an optimal bending stiffness of a composite sandwich structure. Taguchi method was used for experiment planning, while bending test was applied based on a standard testing procedure, ASTM-C393, the force-displacement relationship was output. Output data were then used to do S/N ratio and ANOVA analysis, to investigate the contribution of each factor to bending stiffness, and the optimal combination of levels could be predicted. Verification experiment was then carried out to confirm the optimized sandwich beam. Sandwich beams made of composite laminate with foam core were brought to discussion, and the factors considered were: type of laminate, core, and adhesive, and each factor with three levels. After levels of factor were chosen, L9 orthogonal array was used to set each level of factor to form 9 sets of testament. Since the property of the objective function, bending stiffness, which is the larger-the-better, S/N ratio could be calculated, and AVOVA analysis was carried out. The results showed with the combination of CFRP lamination, and foam with density of 100kg/m3, and adhesive Kit 138, there would be an optimal stiffness. Verification test was then carried out to verify the accuracy of the predict value. With the application of Taguchi method, the contributions of each factor to objective function were investigated. Minimal numbers of tests were required to get the result. Without reducing accuracy, the cost and time could be effectively saved. The method was recommended to be a great tool to experiment design.
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Hsieh, Tsung-Han, i 謝宗翰. "Dynamic Properties of Composite Beam and Sandwich Structure with MWNTs Reinforcement in Polymer Matrix". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/61831863633226046566.
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碩士國立清華大學
動力機械工程學系
94
The carbon nanotubes (CNTs) have better mechanical and chemical properties. Researchers used CNTs as reinforcement to fabricate nano- composites. In this study, multi-walled nanotubes (MWNTs) were used to reinforce the polymer resin, and the dynamic properties of the nanocomposites were investigated experimentally. Dynamic properties such as natural frequency and loss factor were measured. When the structure was subjected to dynamic loading, the material used would influence the dynamic characteristics of the structure directly. The addition of MWNTs in the polymer matrix increased the stiffness and natural frequency of the structure, and decreased the effect of resonance. There is good interfacial characteristic between the MWNTs and polymer resin which increased the damping characteristic. In this study, finite element analysis was used to simulate the structural mode shape and natural frequency, and the results were compared to the results obtained from the vibration test. Moreover, Half-Power Bandwidth method was used to calculate the loss factor from the frequency spectrum response. At last, polymeric composites were applied to the core part of the sandwich structure, and graphite/epoxy laminates were applied to be surface material. The effects of different ply-angle on the dynamic characteristics of graphite/epoxy laminates were investigated. Material parameters should be defined in the analysis. The specimen was subjected to tension test. With the test, the mechanical properties of nanocomposites were discussed. Finally, SEM was used to observe the fractured surface of nanocomposites to understand the failure mechanism of the material subject to tension loading and the distribution of the MWNTs in the resin matrix.
19
Wei-LianDai i 戴維廉. "Applications of the Refined Zigzag Theorem (RZT) to exact solutions of cracked-sandwich-beam and composite beam with functionally graded materials". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/xttj3e.
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碩士國立成功大學
機械工程學系
107
In this thesis, the refined zigzag theory is used to solve the deflections and stresses of composite sandwich beam. According to the configurations of the sandwich beam, two parts are included in this study. In the first part, the cracked sandwich beam (CSB) is investigated by using the Refined Zigzag Theory (RZT). To solve the displacements, stresses, compliance and energy release reates, the continuity conditions at the crack tip and the boundary conditions are derived. By comparing the results between the theroretical predictions and finite element computations, the solutions by RZT are more accurate than those by FSDT (First-order Shear Deformation Theory). In the present study, parameters such as elastic modulus, shear modulus, layer thickness are considered to investigate their effects on the energy release rates of the CSB. In the second part, the RZT is extended to investigated the sandwich beam with functionally graded material. Various boundary conditions, loading conditions and spacial distribution models are considered to investigated their effects on the FGM sandwich beam. It reveals that the solutions by RZT agree very much with those by FEM and has low computational resources. Material properties equation in thickness direction and the effect of isotropic or orthotropic materials. In general, FGM is an isotropic material. Although FGM with orthotropic material has not developed on the market, it is expected that the numerical simulation results for FGM with orthotropic material presented of this paper will be applied to this new material in the future.
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Hu, Jian Shiun, i 胡建勳. "STRUCTURAL ANALYSIS OF DELAMINATED COMPOSITE SANDWICH BEAMS". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/47891724819711718190.
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Chang, Wen-Chi, i 章雯琦. "Vibration Analysis and Control of Composite Sandwich Beams". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/23791402175914974436.
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碩士國立成功大學
航空太空工程學系
88
Although some investigations such as buckling, free vibration of composite sandwich beams can be found, it’s rarely seen the research about control and vibration suppression. In our study, we get the closed form solution of free vibration and forced vibration equations and use the mathematical model to control the amplitude of vibration and achieve the vibration reduction in a short time. This investigation uses smart composite beams with surface bonded piezoelectric sensors and actuators. The piezoelectric sensors can respond to structural vibration and generate output voltage due to the direct piezoelectric effect. On the other hand, the actuators can induce force and moment and control the system due to the converse piezoelectric effect. We use linear quadratic Gaussian algorithm to be the classical control method and form a feedback control system, and we choose Kalman estimator as an optimal state observer for a system contaminated with plant noise and measurement noise. The numerical simulation of the vibration control was done with the assist of the software MATLAB toolbox simulink.
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Lin, Kai-Pei, i 林凱評. "Compressive Strength of Impact Damaged Composite Sandwich Beams". Thesis, 1995. http://ndltd.ncl.edu.tw/handle/20922434098332899324.
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碩士國立成功大學
航空太空工程學系
83
Because the composite sandwich structure is made of laminated plates and lack of transverse reinforcement, it is susceptible to damage under impact. Two of the most important damage mechanisms are delamination and buckling of the core. The strength and stiffness of the composite structure are always reduced as resul- ts of two damage types. This would be especically serious for the circumstance of the structure subjected to compression. Thus, delamination may proporgate due to local buckling.Composite sand- wich beams, with or without face-core delamination, objected to compression is studied in this thesis.The delamination on the core-face interface is theoretically computed by employing a fin- ite elemennt method which is based on the mindlin's plate theory and von Karman's large deformation hyperthesis. The two face plates are modeled as two mindlin plates which are connected by the core material. Stress compoments parallel to the face plates in the core are neglected. It is showed that the results have good correlation between the theoretical work and test results. The other important damage mechanism of impact is buckling of the core. This factor will affect the composite sandwish beam very much. Therefore, it is not sufficient to analyze the delamination under impact only con- sidering the delamination on the core-face interface.
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Bi, Tien-Yo, i 畢天祐. "The Buckling and Vibration Analysis of the Delaminated Composite Sandwich Beams". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/17543589408612649240.
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碩士國立成功大學
航空太空工程學系
87
A new theory always need the experiment or other ways to prove . In the literture, there are already having theories talking about the delaminated composite sandwich beams. However, proving it by experiments is necessary. In this thesis, in order to prove that the developed physical model of the delaminated composite sandwich beams is useful, we design the buckling and vibration experiments and reprove it by the results from the finite-element software NASTRAN. At the same time, the providing information in this thesis hopefully can be applied to designing and using the delaminated composite sandwich beams.
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Wright, Bryan K. "Validation of Point and Pressure Loading Models for Simply Supported Composite Sandwich Beams". Thesis, 2012. http://hdl.handle.net/1807/33590.
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Stiffness and strength models are derived for simply supported composite sandwich panels comprised of fibre-reinforced face sheets and polymer cores subject to symmetric four point bending and uniformly distributed loading. Optimal trajectories for minimum mass design are calculated using the models and situated on failure mechanism maps. A stiffness constraint is also derived to omit beam designs of excessive compliance. Analytical models were validated through an extensive series of experiments, considering beams comprised of GFRP face sheets with ROHACELL 51-IG and extruded polystyrene (EPS) polymer cores. An alternate loading fixture was used to simulate uniform pressure loads. In general, experiments were able to validate most analytical expressions for a range of experimental conditions. Though the predictions worked well with most beam cases, analytical models were noted to become unreliable for short or slender beams.