Academic literature on the topic 'Stiff Fiber-reinforced Structures'
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Journal articles on the topic "Stiff Fiber-reinforced Structures"
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Ruotsalainen, Pasi, Petter Kroneld, Kalervo Nevala, Timo Brander, Tomi Lindroos, and Merja Sippola. "Shape Control of a FRP Airfoil Structure Using SMA-Actuators and Optical Fiber Sensors." Solid State Phenomena 144 (September 2008): 196–201. http://dx.doi.org/10.4028/www.scientific.net/ssp.144.196.
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The aim of this work was to design a control system for the shape memory alloy (SMA) actuator operated airfoil (a cross section of wind turbine blade). Design of SMA control is focused on the reliable operation of the SMA actuators. The actuator should follow the targeted shape accurately and without too much delay. Another objective is to avoid overheating which is the most critical damage to the structure. SMA actuator shape control is in principle possible to do with any position control method, but the specific properties of the SMA actuators, like the hysteresis, the first cycle effect and the long term changes, need to be taken into account. In this work, a wing profile prototype was measured using optical fiber sensors and traditional strain gauges. Also, external laser sensors were used to measure displacements of upper/lower surface and trailing edge. Shape change was obtained by embedding SMA wire actuators into fiber reinforced polymer (FRP) composite structure. SMA actuators were laminated in such way that bending of trailing edge is always downwards. Actuators are activated with Joule heating and the temperature is measured with integrated thermocouples and optical fiber temperature sensors. As a result, this work gave information about the usability of optical fibers sensors in active FRP composite structures. Measurements also give information about the efficiency of SMA actuators in shape control of relatively stiff FRP structures.
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Eskenati, Amir Reza, Amir Mahboob, Ernest Bernat-Maso, and Lluís Gil. "Characterizing the Structural Behavior of FRP Profiles—FRCM Hybrid Superficial Elements: Experimental and Numerical Studies." Polymers 14, no. 6 (March 8, 2022): 1076. http://dx.doi.org/10.3390/polym14061076.
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Composite materials have been increasingly used to produce hybrid structures together with concrete. This system is commonly applied to bridges and roof structures. The main idea of the current research was to extend this approach by replacing the concrete with a fabric-reinforced cementitious matrix (FRCM) composite, resulting in a combination of composite materials. The main aim was to characterize the structural behavior of fiber-reinforced polymer (FRP) profiles and FRCM hybrid superficial elements. Two different prototypes of the hybrid superficial structural typology were tested to cover bidimensional and three-dimensional application cases of the proposed technology. After mortar cracking, the experimental results revealed a ductile response and a high mechanical capacity. A finite element model was implemented, calibrated, and validated by comparing numerical data with experimental results of the two prototypes. The output was a validated model that correctly captured the characteristic response of the proposed technology, which consisted of changing the structural response from a stiff plate configuration to a membrane type due to cracking of the FRCM composite part of the full solution. The suggested numerical model adequately reflected the experimental response and proved valuable for understanding and explaining the resistive processes established along this complicated FRP-FRCM hybrid structure.
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Machado, Marina, Mateus Hofmann, Mário Garrido, João R. Correia, João C. Bordado, and Inês C. Rosa. "Incorporation of Lignin in Bio-Based Resins for Potential Application in Fiber–Polymer Composites." Applied Sciences 13, no. 14 (July 19, 2023): 8342. http://dx.doi.org/10.3390/app13148342.
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Bio-based resins, obtained from renewable raw materials, are a more sustainable alternative to oil-based resins for fiber-reinforced polymer (FRP) composites. The incorporation of lignin in those resins has the potential to enhance their performance. This paper presents results of an experimental study about the effects of Lignoboost lignin incorporation on a partially bio-based vinyl ester (VE) resin. Two resins were prepared—without (reference) and with lignin addition (4% by weight) to its main chain—and their chemical, thermophysical, and mechanical properties were compared using Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and tensile and shear tests. Results suggest that the addition of lignin to the base resin resulted in a copolymer of increased heterogeneity and higher molecular weight, incorporating stiff and complex aromatic structures in the polymer chain. While requiring high-temperature curing, the VE–lignin copolymer presented improvements of 27% in tensile strength, 4% in shear strength, and increased glass transition temperature by about 8 °C, thus confirming the potential of this natural biopolymer for FRP composite applications.
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Scheurer, Martin, Matthias Kalthoff, Thomas Matschei, Michael Raupach, and Thomas Gries. "Analysis of Curing and Mechanical Performance of Pre-Impregnated Carbon Fibers Cured within Concrete." Textiles 2, no. 4 (December 6, 2022): 657–72. http://dx.doi.org/10.3390/textiles2040038.
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In carbon-reinforced concrete, the commonly used steel reinforcement is replaced with carbon fiber reinforcement textiles, enabling thin-walled elements by using new construction principles. The high drapability of textiles offers design opportunities for new concrete structures. However, commonly utilized textiles are impregnated with comparatively stiff polymeric materials to ensure load transmission into the textile, limiting drapability. In this paper, a new approach is analyzed: the use of pre-impregnated textiles cured within the concrete matrix. This enables the production of filigree, highly curved components with high mechanical performance, as needed for novel additive manufacturing methods. In the presented trials, rovings were successfully impregnated with potential impregnation materials, cured within the concrete, and compared to rovings cured outside of the concrete. The analysis of the curing process using a rolling ball test determines that all materials have to be placed in concrete 4 to 24 h after impregnation. The results of uniaxial tensile tests on reinforced concrete show that maximum load is increased by up to 87% for rovings cured within concrete (compared to non-impregnated rovings). This load increase was higher for rovings cured outside of concrete (up to 185%), indicating that the concrete environment interferes with the curing process, requiring further analysis and adaptation.
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Sessner, Vincent, Matthias Stoll, Arnaud Feuvrier, and Kay André Weidenmann. "Determination of the Damping Characteristics of Fiber-Metal-Elastomer Laminates Using Piezo-Indicated-Loss-Factor Experiments." Key Engineering Materials 742 (July 2017): 325–32. http://dx.doi.org/10.4028/www.scientific.net/kem.742.325.
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. In technical applications components are often exposed to vibrations with a broad range of frequencies. To ensure structural integrity and a convenient usage for the customer, materials with good damping characteristics are desirable. Especially stiff and lightweight structures tend to be prone to vibrations. Fibre metal laminates (FML) offer great potential for lightweight design applications due to their good fatigue behavior. By using carbon fiber reinforced plastics (CFRP) as part of the laminates very good strength and stiffness to weight ratios can be obtained. To improve the damping characteristics of this hybrid material an additional layer of elastomer can be added between the CFRP and the metal, generating a fiber-metal-elastomer laminate (FMEL). In this present study the damping behavior of different layups of FMEL was examined. Two different metal sheets and two types of elastomer were used, also the layup of the constituents was variated. Vibrations were induced with a frequency range from 100 Hz to 20 kHz by mounting the laminates onto a speaker. The vibration response was measured with a piezoelectric accelerometer. Eventually the different laminate layups were compared with each other to determine the influence of the individual constituents regarding the damping characteristics. The different elastomer types and prepreg layups affected the damping of vibrations, whereas the use of different metal sheet materials showed only little influence.
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Danilov, Alexander I. "Cascade Strengthening of Bent Elements by Polymers with Adhesive Joints." Materials Science Forum 974 (December 2019): 583–88. http://dx.doi.org/10.4028/www.scientific.net/msf.974.583.
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The subject of the article is to give a full analysis of the cascade type layouts in elements strengthening design in bending by gluing the fiber reinforced polymer (FRP) materials on their surfaces’ applicability and effectiveness. The research objectives are the substantiation elements cascade method application reinforcement with adhesive joints. Materials and methods are revealed in a few variants of FRP-reinforcement with application of FEM simulation. A number of diagrams and tables represent the results. The results are defined in the cost-effective efficient method presentation of the bent elements strengthening to increase their bearing capacity reserves, the features of the bonded joint behavior, the equations and formulae for the glue joint analysis and design. Conclusions are formulated in depicting the “cascade” reflects, the features of the proposed strengthening design, the base element unloading, which is gradual with each successive element attached. The design examples are oriented on the adhesive joints’ application possibility analysis of attaching the FRP elements. The results suggest the effective use possibility of the adhesive joints to strengthen rather stiff, including steel, elements in bending. The cascade method eliminates the indispensability of highly expensive high-strength materials, thereby reducing the reinforcement structures cost.
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Porcu, Maria Cristina, Juan Carlos Vielma Pérez, Gavino Pais, Diego Osorio Bravo, and Juan Carlos Vielma Quintero. "Some Issues in the Seismic Assessment of Shear-Wall Buildings through Code-Compliant Dynamic Analyses." Buildings 12, no. 5 (May 23, 2022): 694. http://dx.doi.org/10.3390/buildings12050694.
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Due to their excellent seismic behavior, shear wall-type concrete buildings are very popular in earthquake-prone countries like Chile. According to current seismic regulations, the performance of such structures can be indifferently assessed through linear or non-linear methods of analysis. Although all the code-compliant approaches supposedly lead to a safe design, linear approaches may be in fact less precise for catching the actual seismic performance of ductile and dissipative structures, which can even result in unconservative design where comparatively stiff buildings like reinforced-concrete shear-wall (RC-SW) buildings are concerned. By referring to a mid-rise multistory RC-SW building built in Chile and designed according to the current seismic Chilean code, the paper investigates the effectiveness of the linear dynamic analyses to predict the seismic performance of such kind of structures. The findings show that the code-compliant linear approaches (Modal Response Spectrum Analysis and Linear Time-History Analysis) may significantly underestimate the displacement demand in RC-SW buildings. This is highlighted by the comparison with the results obtained from the Non-Linear Time-History Analysis, which is expected to give more realistic results. A set of ten spectrum-consistent Chilean earthquakes was considered to carry out the time-history analyses while a distributed-plasticity fiber-based approach was adopted to model the non-linear behavior of the considered building. The paper highlights how the risk of an unsafe design may become higher when reference is made to the Chilean code, the latter considering only the Modal Response Spectrum Analysis (MRSA) without even providing corrective factors to estimate the inelastic displacement demand. The paper checks the effectiveness of some amplifying factors taken from the literature with reference to the case-study shear-wall building, concluding that they are not effective enough. The paper also warns against the danger of local soft-story collapse mechanisms, which are typical of reinforced concrete frames but may also affect RC-SW buildings when weaker structural parts made by column-like walls are present at the ground floor.
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Huang, Runzhou, Xian Zhang, Zhuangzhuang Teng, and Fei Yao. "Properties of core-half wrapped shell structure wood-polymer composites containing glass fiber-reinforced shells." BioResources 15, no. 4 (October 16, 2020): 9088–102. http://dx.doi.org/10.15376/biores.15.4.9088-9102.
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Glass fiber (GF) is commonly applied as a filler in the preparation of polymer composites. Due to the presence of GF, composite mechanical performance, flame resistance, and thermal performance could be greatly improved. The influence of a GF-filled polymer shell layer was investigated relative to the morphology, mechanical, thermal, and fire flammability performance of the core-half wrapped shell structured wood high-density polyethylene (HDPE) composites prepared via co-extrusion. The use of the relatively less-stiff pure HDPE with high linear coefficients of thermal expansion (LCTEs) lowered the general thermal stability and modulus of the wood polymer composites (WPCs). Flexural and thermal expansion properties were improved for the GF-filled HDPE shells in comparison to the unmodified material, enabling a well-balanced performance of this novel core–shell material. Implementation of GF-modified HDPE or unmodified HDPE layers as a shell for WPC core remarkably improved the impact resistance of the co-extruded WPCs. In comparison with composites possessing unmodified HDPE shell, the flame resistance performance of the shell layer was slightly improved in case that the GF content was below 25 wt%. A slight decrease in composite general heat release and rate was discovered in case that the GF content was greater than 25 wt%.
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Pando, Miguel, George Filz, Carl Ealy, and Edward Hoppe. "Axial and Lateral Load Performance of Two Composite Piles and One Prestressed Concrete Pile." Transportation Research Record: Journal of the Transportation Research Board 1849, no. 1 (January 2003): 61–70. http://dx.doi.org/10.3141/1849-08.
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Composite piles use fiber-reinforced polymers (FRPs), plastics, and other materials to replace or protect steel or concrete, with the intent being to produce piles that have lower maintenance costs and longer service lives than those of conventional piles, especially in marine applications and other corrosive environments. Well-documented field loading tests of composite piles are scarce, and this lack of a reliable database may be one reason that composite piles are not in widespread use for load-bearing applications. The purpose of this research is to compare the axial and lateral load behavior of two different types of composite test piles and a conventional prestressed concrete test pile at a bridge construction site in Hampton, Virginia. One of the composite piles is an FRP shell filled with concrete and reinforced with steel bars. The other composite pile consists of a polyethylene plastic matrix surrounding a steel reinforcing cage. The axial structural stiffnesses of the prestressed concrete pile and the FRP pile are similar, and they are both much stiffer than the plastic pile. The flexurel stiffness of the prestressed concrete pile is greater than that of the FRP pile, which is greater than the flexural stiffness of the plastic pile. The axial geotechnical capacities of the test piles decreased in order from the prestressed concrete pile to the FRP pile to the plastic pile. The prestressed concrete pile and the FRP pile exhibited a similar response for lateral load versus deflection, and the plastic pile was much less stiff in lateral loading.
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Desai, Akshay, Mihir Mogra, Saketh Sridhara, Kiran Kumar, Gundavarapu Sesha, and G. K. Ananthasuresh. "Topological-derivative-based design of stiff fiber-reinforced structures with optimally oriented continuous fibers." Structural and Multidisciplinary Optimization, October 6, 2020. http://dx.doi.org/10.1007/s00158-020-02721-1.
Full textDissertations / Theses on the topic "Stiff Fiber-reinforced Structures"
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Desai, Akshay. "Topological Derivative-based Optimization of Fiber-reinforced Structures, Coupled Thermoelastic Structures, and Compliant Mechanisms." Thesis, 2020. https://etd.iisc.ac.in/handle/2005/5158.
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The topological derivative of a functional quantifies the sensitivity with respect to an infinitesimal domain perturbations such as a hole, an inclusion, a source term, a crack, etc. In this thesis, topological derivatives are used in conjunction with level-set methods to optimize stiff structures and compliant mechanisms. In the first part of the thesis, we use topological derivatives in polar form to obtain fiber-reinforced structural designs with non-periodic continuous fibers that are optimally arranged in specific patterns. The distribution of anisotropic fiber material within isotropic matrix material is determined for given volume fractions of void and material as well as fiber and matrix simultaneously, for maximum stiffness. In this three-phase material distribution approach, we generate a Pareto surface of stiffness and two volume fractions by adjusting the level-set plane in the topological sensitivity field. The next part of the thesis deals with the topology optimization of thermally coupled elastic structures. In this, we present two design examples: (i) a stiff battery pack for heat dissipation; and (ii) a thermomechanical actuator. In addition to the design of stiff structures, we perform topology optimization of compliant mechanisms using topological derivatives. In such elastically deformable structures, we adopt a multicriteria formulation that aims to simultaneously attain desired displacement with adequate overall stiffness. The resulting compliant topologies reduce the occurrence of undesirable discrete compliance, particularly at low volume fraction of material. Finally, we derive topological derivative for a homogeneous Dirichlet condition prescribed on the boundary of a hole. Here, we address the rationale behind the proposed ansätz in the asymptotic analysis of the solution using a second-order Green’s tensor. In summary, the analytically derived topological derivative-based optimization approach makes it unique in terms of its computational efficiency and wide applicability for a variety of problems.
Conference papers on the topic "Stiff Fiber-reinforced Structures"
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Ebna Hai, Bhuiyan Shameem Mahmood, and Markus Bause. "Finite Element Approximation of Wave Propagation in Composite Material With Asymptotic Homogenization." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-26314.
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Advanced composite materials such as carbon fiber reinforced plastics are being applied to many aerospace or automotive structures in order to improve material performances and save weight. Most composites have strong, stiff fibres in a matrix which is weaker and less stiff. But these structures can be damaged due to fluid-structure interaction (FSI) oscillations or material fatigue. To design integrated structural health monitoring (SHM) systems in a lightweight structure, it is important to understand wave propagation phenomena in composite material, and the influence of the material properties of the structures. In non-destructive test (NDT), piezoelectric induced ultrasonic waves can be used for damage detection. In this work, we focus on mathematical modeling and numerical approximation of the propagation of time-harmonic elastic waves in a fiber-reinforced composite material. The fibers are assumed to be parallel to each other and statistically uniformly distributed. In this work we study higher order continuous finite element approximation of the elastic wave equation and the implementation is carried out by means of the FEM library deal.II. (Differential Equations Analysis Library)
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Hübler, Moritz, Sebastian Nissle, Martin Gurka, Sebastian Schmeer, and Ulf Paul Breuer. "Smart Crash Management by Switching the Crash Behavior of Fiber-Reinforced Plastic (FRP) Energy Absorbers With Shape Memory Alloy (SMA) Wires." In ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/smasis2013-3049.
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In this paper two innovative concepts for adjustable energy absorbing elements are presented. These absorbers can serve as an essential element in a smart crash management system e.g. for automotive applications. The adaptability is based on the basic idea of adjusting the stiffness of the absorber in relation to the actual load level in a crash event. Therefore the whole length of the absorber element can be used for energy dissipation. The adjustable absorbers are made from fiber reinforced plastics and shape memory alloy wires as actuating elements. Two possibilities for the basic design of the absorber elements are shown, the performance of the actuating SMA elements is characterized in detail and the switching behavior of the whole elements, between a stiff “on” state and a flexible “off” state, is measured.
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Baker, Brendon M., Grace D. O’Connell, Sounok Sen, Ashwin S. Nathan, Dawn M. Elliott, and Robert L. Mauck. "Multi-Lamellar and Multi-Axial Maturation of Cell-Seeded Fiber-Reinforced Tissue Engineered Constructs." In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176434.
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The architecture of load-bearing fibrous tissues is optimized to enable a specific set of mechanical functions. This organization arises from a complex process of cell patterning, matrix deposition, and functional maturation [1]. In their mature state, these tissues span multiple length scales, encompassing nanoscale interactions of cells with extracellular matrix to the centimeter length scales of the anatomic tissue volume and shape. Two structures that typify dense fibrous tissues are the meniscus of the knee and the annulus fibrosus (AF) of the intervertebral disc (IVD). The mechanical function of the wedge-shaped knee meniscus is based on its stiff prevailing circumferential collagen architecture that resists tensile deformation [2,3]. Adding to its complexity, radial tie fibers and sheets are interwoven amongst these fibers, increasing stiffness in the transverse direction and binding the tissue together [4]. In the annulus fibrosus, multiple anisotropic lamellae are stacked in concentric rings with their prevailing fiber directions alternating above and below the horizontal axis in adjacent layers [5]. The high circumferential tensile properties of this laminate structure allow it to resist bulging of the nucleus pulposus with compressive loading of the spine. Given their structural properties, unique form, and demanding mechanical environments, the knee meniscus and the AF region of the IVD represent two of the most challenging tissues to consider for functional tissue engineering.
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Nguyen, Thao D., Reese E. Jones, and Brad L. Boyce. "Modeling the Anisotropic Finite-Deformation Viscoelastic Behavior of Soft Fiber-Reinforced Tissues." In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176919.
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This paper presents a constitutive model for the anisotropic, finite-deformation viscoelastic behavior of soft fiber-reinforced tissues. Soft fiber-reinforced tissues, such as the cornea, tendons, and blood vessels, have a unique combination of mechanical properties that enables them to perform important structural, protective, and energy-absorbing functions. Because of their fiber-reinforced microstructure, these tissues are extraordinarily stiff and strong for their weight. Many are also flexible and tough. The toughness of these tissues arises from the ability of both the soft fiber and matrix phases to dissipate energy through large viscoelastic deformations. The viscoelastic behavior of the matrix of soft tissues can arise from fluid flow through a swollen polymer network and/or the diffusive motion of polymer segments within the network. The time-dependent behavior of the fiber reinforcements, which themselves can be composite structures, stems from the viscoelastic nature of the fiber material and/or the dissipative mechanisms of the fiber/matrix interface. To model the distinct time-dependent behavior of both fiber and matrix constituents, the tissue is represented as a continuum mixture consisting of a variety of fiber families embedded in an isotropic matrix. Both phases are required to deform with the continuum deformation gradient. However, the model attributes a different viscous stretch measure and free energy density to the matrix and fiber phases. Separate viscous flow rules are specified for the matrix phase and the individual fiber families. The flow rules for the fiber families are combined to give an anisotropic effective viscous flow rule for the fiber phase. An attractive feature of model is that key parameters can be related to the material properties (i.e., moduli, viscosities, volume fraction) of the fiber and matrix phases. Also, the anisotropy exhibited by both the elastic and viscous response of the composite arises directly from the fiber arrangement.
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Ebna Hai, Bhuiyan Shameem Mahmood. "Numerical Approximation of Fluid Structure Interaction (FSI) Problem." In ASME 2013 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fedsm2013-16013.
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Nowadays, advanced composite materials such as carbon fiber reinforced plastics (CFRP) are being applied to many aircraft structures in order to improve performance and reduce weight. Most composites have strong, stiff fibres in a matrix which is weaker and less stiff. However, aircraft wings can break due to Fluid-Structure Interaction (FSI) oscillations or material fatigue. The airflow around an airplane wing causes the wing to deform, while a wing deformation causes a change in the air pattern around it. Due to thrust force, turbulent flow and high speed, fluid-structure interaction (FSI) is very important and arouses complex mechanical effects. Due to the non-linear properties of fluids and solids as well as the shape of the structures, only numerical approaches can be used to solve such problems. The principal aim of this research is to explore and understand the behaviour of the fluid-structure interaction during the impact of a deformable material (e.g. an aircraft wing) on air. This project focuses on the analysis of Navier-Stokes and elastodynamic equations in the arbitrary Lagrangian-Eulerian (ALE) frameworks in order to numerically simulate the FSI effect on a double wedge airfoil. Since analytical solutions are only available in special cases, the equation needs to be solved by numerical methods. Of all methods, the finite element method was chosen due to its special characteristics and for its implementation, the software package DOpElib.
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Ebna Hai, Bhuiyan Shameem Mahmood, and Markus Bause. "Finite Element Approximation of Fluid Structure Interaction (FSI) Optimization in Arbitrary Lagrangian-Eulerian Coordinates." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-62291.
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Advanced composite materials such as Carbon Fiber Reinforced Plastics (CFRP) are being applied to many aircraft structures in order to improve performance and reduce weight. Most composites have strong, stiff fibers in a matrix which is weaker and less stiff. However, aircraft wings can break due to Fluid-Structure Interaction (FSI) oscillations or material fatigue. This paper focuses on the analysis of a non-linear fluid-structure interaction problem and its solution in the finite element software package DOpElib: the deal.II based optimization library. The principal aim of this research is to explore and understand the behaviour of the fluid-structure interaction during the impact of a deformable material (e.g. an aircraft wing) on air. Here we briefly describe the analysis of incompressible Navier-Stokes and Elastodynamic equations in the arbitrary Lagrangian-Eulerian (ALE) frameworks in order to numerically simulate the FSI effect on a double wedge airfoil. Since analytical solutions are only available in special cases, the equation needs to be solved by numerical methods. This coupled problem is defined in a monolithic framework and fractional-step-θ time stepping scheme are implemented. Spatial discretization is based on a Galerkin finite element scheme. The non-linear system is solved by a Newton method. The implementation using the software library package DOpElib and deal.II serves for the computation of different fluid-structure configurations.
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Guest, James K. "Projection-Based Topology Optimization Using Discrete Object Sets." In ASME 2014 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/detc2014-35213.
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We look to expand the reach of continuum topology optimization to include the design of ‘structures’ that gain functionality or are specifically manufactured from discrete, non-overlapping objects. While significant advancements have been made in restricting the geometric properties of topology-optimized structures, including restricting the minimum and maximum length scale of features, continuum topology optimization is still largely limited to monolithic structures. A wide variety of structures and materials, however, gain their stiffness or functionality from discrete objects, such as fiber-reinforced composites. This work examines a recently developed method for optimizing the distribution of discrete objects (2d inclusions) across a design domain and extends the approach to variable shape and variable sized objects that must be selected from a designer-defined set. This essentially enables simultaneous optimization of object sizes, shapes, and/or locations within the projection framework, without need for additional constraints. As in traditional topology optimization, gradient-based optimizers are used with sensitivity information estimated via the adjoint method, solved using finite element analysis. The algorithm is demonstrated on benchmark problems in structural design for the case where the objects are stiff inclusions embedded in a compliant matrix material.
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Sedlmair, Roman, and Lothar Stempniewski. "CFRP strengthening system to increase fatigue resistance of bridges." In IABSE Congress, New York, New York 2019: The Evolving Metropolis. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2019. http://dx.doi.org/10.2749/newyork.2019.1464.
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<p>Carbon fiber reinforced polymers (CFRP) laminates externally bonded with epoxy resins are an often used strengthening technique of aged and overloaded structures, e.g. bridges. A well-known, though not commonly discussed, problem is the stiff bond behavior of the used adhesives. Their use leads to stress concentrations in the CFRP and concrete at the location of cracks and an uneven strain distribution of internal and external reinforcement. On that basis, the usage of such a strengthening technique for components subjected to dynamic loads is limited or almost impossible due to premature debonding of the CFRP.</p><p>The present paper focuses on numerical analysis of reinforced concrete bending beams strengthened with CFRP using the finite element method. In our analysis we focus on contact modelling techniques. The effect of differing adhesives on the overall behavior of the strengthened beams and strain distribution of internal and external reinforcement is shown. Numerical investigations demonstrate the relevance of the used adhesive on the static and fatigue behavior of the strengthened component. Modified and optimized material properties of the adhesive lead to a strengthening system which is even capable of carrying dynamic loads.</p>
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Hervin, Flora, and Paul Fromme. "Anisotropy Influence on Guided Wave Propagation and Steering in Unidirectional CFRP." In 2022 49th Annual Review of Progress in Quantitative Nondestructive Evaluation. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/qnde2022-98375.
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Abstract Carbon fiber reinforced composite laminates (CFRP) are often selected for aerospace structures due to their low weight and high strength compared to their metallic counterparts. They consist of very stiff and highly anisotropic fiber matrix ply layers, resulting in high in-plane strength. However, composite laminates are prone to barely visible impact damage when subjected to low velocity impacts during service. Undetected impact damage can cause significant strength reduction of the laminate. Effective structural health monitoring (SHM) of composite panels is therefore required to prevent component failure, which can be achieved using guided waves propagating along the structure. A number of guided wave propagation effects occur in composite laminates due to the high material anisotropy of the ply layers, such as directionality of phase and group velocity and wave steering effects. If unaccounted for, these anisotropic effects could lead to inaccurate localization of damage, and potential regions of the structure where guided waves do not provide sufficient defect detection sensitivity. Propagation of the A0 Lamb mode was investigated for multiple incident wave directions in an undamaged unidirectional CFRP panel. Full 3D Finite Element (FE) models were developed using homogenized anisotropic material properties to investigate the directional dependency of velocity. Non-contact guided wave velocity measurements were obtained using a laser vibrometer to validate the FE model. Both a point and line source were modelled to investigate the influence of the excitation source on the guided wave evaluation and signal processing. Significant wave skewing behavior was predicted from the numerical simulations for several wave propagation directions, with good agreement with theoretical values.
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Stabile, P., F. Ballo, M. Gobbi, and G. Mastinu. "Innovative Chassis Made From EPP and CFRP of an Urban-Concept Vehicle." In ASME 2020 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/detc2020-22244.
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Abstract The paper presents a fully new chassis of a high efficiency vehicle for the Shell Eco-marathon competition. The chassis is realized by a sandwich structure with an expanded polypropylene (EPP) core and carbon fiber reinforced plastic (CFRP) external skins. The chassis is connected to the body to realize a safe and stiff structure. Numerical analyses have been performed to assess the stiffness, safety and dynamic eigenfrequencies of the chassis. A Finite Element model of the entire chassis and body was developed. The manufacturing process of the entire chassis and body is described in the paper and some data obtained during on-track tests of the vehicle are presented. The vehicle reached the 4th place at the 2019 edition of the Shell Eco-marathon competition, with an equivalent energy consumption of 184 km/kWh.