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Author: Sotiris Kellas
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages :
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Book Description
"A stand-alone, crash-energy absorbing structure and fabrication method are provided. A plurality of adjoining rigid cells are each constructed of resin-cured fiber reinforcement and are arranged in a geometric configuration. The fiber reinforcement can be in the form of a fabric or braided fibers wrapped about a core that is either left in place or removed from the ultimate cured structure. The geometric configuration of cells is held together with more fiber reinforcement (in the form of fabric or braided fibers) in order to integrate the cells in the geometric configuration. The additional fiber reinforcement is resin-cured to the cells. Curing of the cells and ultimate structure can occur in a single step. In applications where post-crash integrity is necessary, ductile fibers can be used to integrate the cells in the geometric configuration. The novelty of the present invention is that simple fabrication techniques are used to create structures that can be formed in a variety of net stable shapes without additional reinforcement and can withstand combined loading while crushing in a desired direction."--Page i.
Author: Sotiris Kellas
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages :
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Book Description
"A stand-alone, crash-energy absorbing structure and fabrication method are provided. A plurality of adjoining rigid cells are each constructed of resin-cured fiber reinforcement and are arranged in a geometric configuration. The fiber reinforcement can be in the form of a fabric or braided fibers wrapped about a core that is either left in place or removed from the ultimate cured structure. The geometric configuration of cells is held together with more fiber reinforcement (in the form of fabric or braided fibers) in order to integrate the cells in the geometric configuration. The additional fiber reinforcement is resin-cured to the cells. Curing of the cells and ultimate structure can occur in a single step. In applications where post-crash integrity is necessary, ductile fibers can be used to integrate the cells in the geometric configuration. The novelty of the present invention is that simple fabrication techniques are used to create structures that can be formed in a variety of net stable shapes without additional reinforcement and can withstand combined loading while crushing in a desired direction."--Page i.
Author: A.G. Mamalis
Publisher: CRC Press
ISBN: 1351457551
Category : Technology & Engineering
Languages : en
Pages : 270
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Book Description
FROM THE INTRODUCTION Vehicle crashworthiness has been improving in recent years with attention mainly directed towards reducing the impact of the crash on the passengers. Effort has been spent in experimental research and in establishing safe theoretical design criteria on the mechanics of crumpling, providing to the engineers the ability to design vehicle structures so that the maximum amount of energy will dissipate while the material surrounding the passenger compartment is deformed, thus protecting the people inside. During the last decade the attention given to crashworthiness and crash energy management has been centered on composite structures. The main advantages of fibre reinforced composite materials over more conventional isotropic materials, are the very high specific strengths and specific stiffness which can be achieved. Moreover, with composites, the designer can vary the type of fibre, matrix and fibre orientation to produce composites with proved material properties. Besides the perspective of reduced weight, design flexibility and low fabrication costs, composite materials offer a considerable potential for lightweight energy absorbing structures; these facts attract the attention of the automotive and aircraft industry owing to the increased use of composite materials in various applications, such as frame rails used in the apron construction of a car body and the subfloor of an aircraft, replacing the conventional materials used. Our monograph is intended to provide an introduction to this relatively new topic of structural crashworthiness for professional engineers. It will introduce them to terms and concepts of it and acquaint them with some sources of literature about it. We believe that our survey constitutes a reasonably well-balanced synopsis of the topic.
Author: A. Praveen Kumar
Publisher: Springer Nature
ISBN: 9819952891
Category : Technology & Engineering
Languages : en
Pages : 121
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Book Description
This book summarizes many of the recent advances in the design and application of thin-walled composite protective structures. The past few decades have seen outstanding advances in the use of composite materials in structural applications. Composites have revolutionized traditional design concepts and made possible an unparalleled range of new and exciting possibilities as viable materials for construction. This book presents an extensive survey on recent improvements in the research and development of composites and biocomposites that are used to make structures in various applications. This book deals with design, research and development studies, experimental investigations, theoretical analysis, and fabrication techniques relevant to the application of composites in load-bearing components for assemblies, ranging from individual components such as plates and shells to complete composite structures. This book also focuses the recent advances in biocomposite materials from renewable resources and introduces a potential application of this material. The content is this book benefits the academics, researchers, scientists, engineers, and students in the field of epoxy blends for application as lightweight advanced composite structures.
Author: Sotiris Kellas
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 28
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Book Description
Author: Ahmed Elmarakbi
Publisher: John Wiley & Sons
ISBN: 111853526X
Category : Technology & Engineering
Languages : en
Pages : 487
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Book Description
The automotive industry faces many challenges, including increased global competition, the need for higher-performance vehicles, a reduction in costs and tighter environmental and safety requirements. The materials used in automotive engineering play key roles in overcoming these issues: ultimately lighter materials mean lighter vehicles and lower emissions. Composites are being used increasingly in the automotive industry due to their strength, quality and light weight. Advanced Composite Materials for Automotive Applications: Structural Integrity and Crashworthiness provides a comprehensive explanation of how advanced composite materials, including FRPs, reinforced thermoplastics, carbon-based composites and many others, are designed, processed and utilized in vehicles. It includes technical explanations of composite materials in vehicle design and analysis and covers all phases of composite design, modelling, testing and failure analysis. It also sheds light on the performance of existing materials including carbon composites and future developments in automotive material technology which work towards reducing the weight of the vehicle structure. Key features: Chapters written by world-renowned authors and experts in their own fields Includes detailed case studies and examples covering all aspects of composite materials and their application in the automotive industries Unique topic integration between the impact, crash, failure, damage, analysis and modelling of composites Presents the state of the art in composite materials and their application in the automotive industry Integrates theory and practice in the fields of composite materials and automotive engineering Considers energy efficiency and environmental implications Advanced Composite Materials for Automotive Applications: Structural Integrity and Crashworthiness is a comprehensive reference for those working with composite materials in both academia and industry, and is also a useful source of information for those considering using composites in automotive applications in the future.
Author: Bonnie Wade
Publisher:
ISBN:
Category : Absorption
Languages : en
Pages : 368
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Book Description
As fiber reinforced composite material systems become increasingly utilized in primary aircraft and automotive structures, the need to understand their contribution to the crash worthiness of the structure is of great interest to meet safety certification requirements. The energy absorbing behavior of a composite structure, however, is not easily predicted due to the great complexity of the failure mechanisms that occur within the material. Challenges arise both in the experimental characterization and in the numerical modeling of the material/structure combination. At present, there is no standardized test method to characterize the energy absorbing capability of composite materials to aide crash worthy structural design. In addition, although many commercial finite element analysis codes exist and offer a means to simulate composite failure initiation and propagation, these models are still under development and refinement. As more metallic structures are replaced by composite structures, the need for both experimental guidelines to characterize the energy absorbing capability of a composite structure, as well as guidelines for using numerical tools to simulate composite materials in crash conditions has become a critical matter. This body of research addresses both the experimental characterization of the energy absorption mechanisms occurring in composite materials during crushing, as well as the numerical simulation of composite materials undergoing crushing. In the experimental investigation, the specific energy absorption (SEA) of a composite material system is measured using a variety of test element geometries, such as corrugated plates and tubes. Results from several crush experiments reveal that SEA is not a constant material property for laminated composites, and varies significantly with the geometry of the test specimen used. The variation of SEA measured for a single material system requires that crush test data must be generated for a range of different test geometries in order to define the range of its energy absorption capability. Further investigation from the crush tests has led to the development of a direct link between geometric features of the crush specimen and its resulting SEA. Through micrographic analysis, distinct failure modes are shown to be guided by the geometry of the specimen, and subsequently are shown to directly influence energy absorption. A new relationship between geometry, failure mode, and SEA has been developed. This relationship has allowed for the reduction of the element-level crush testing requirement to characterize the composite material energy absorption capability. In the numerical investigation, the LS-DYNA composite material model MAT54 is selected for its suitability to model composite materials beyond failure determination, as required by crush simulation, and its capability to remain within the scope of ultimately using this model for large-scale crash simulation. As a result of this research, this model has been thoroughly investigated in depth for its capacity to simulate composite materials in crush, and results from several simulations of the element-level crush experiments are presented. A modeling strategy has been developed to use MAT54 for crush simulation which involves using the experimental data collected from the coupon- and element-level crush tests to directly calibrate the crush damage parameter in MAT54 such that it may be used in higher-level simulations. In addition, the source code of the material model is modified to improve upon its capability. The modifications include improving the elastic definition such that the elastic response to multi-axial load cases can be accurately portrayed simultaneously in each element, which is a capability not present in other composite material models. Modifications made to the failure determination and post-failure model have newly emphasized the post-failure stress degradation scheme rather than the failure criterion which is traditionally considered the most important composite material model definition for crush simulation. The modification efforts have also validated the use of the MAT54 failure criterion and post-failure model for crash modeling when its capabilities and limitations are well understood, and for this reason guidelines for using MAT54 for composite crush simulation are presented. This research has effectively (a) developed and demonstrated a procedure that defines a set of experimental crush results that characterize the energy absorption capability of a composite material system, (b) used the experimental results in the development and refinement of a composite material model for crush simulation, (c) explored modifying the material model to improve its use in crush modeling, and (d) provided experimental and modeling guidelines for composite structures under crush at the element-level in the scope of the Building Block Approach.
Author: Sotiris Kellas
Publisher:
ISBN:
Category : Space vehicles
Languages : en
Pages : 52
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 18
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Book Description
This research aims to develop, analyze, and evaluate a new type of structural element that will enhance the crashworthiness of naval vehicles by providing outstanding energy absorption with minimal weight. The structural element is an array of concentric fiber reinforced composite tubes with extension-twist coupling and ultra-high Poisson's ratio. The tubes are configured to crush or shear internal foam as a means of absorbing energy. This interim report includes technical progress, plans, publications, and various administrative matters. In the current period, work has focused on evaluating the mechanisms of energy absorption in composite tubular structures and the development of analytical models for predicting the deformation and damage in these tubular structures. A significant effort was dedicated towards developing the manufacturing and testing technology for tubes having extension-twist coupling. This effort culminated in the successful demonstration, for the first time, of energy dissipation in extension-twist coupled tubes with sandwich foam.
Author:
Publisher:
ISBN:
Category : Patents
Languages : en
Pages : 1300
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 270
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Book Description
In passenger vehicles, the ability to absorb impact energy and be survivable for the occupant is called the "crashworthiness" of the structure. The ACC (Automotive Composite Consortium) has been and continues to be very interested in investigating the use of fiber-reinforced composites as crash energy absorbers. It would have been ideal if the composite structure to be used as a crash energy absorber were manufactured as an integral, monolithic component, but limitations in the present day manufacturing technology necessitate the presence of joints in composite structures. While many scientists have investigated the energy absorption characteristics in various fiber reinforced composite materials, there is no literature available on the energy absorption and crushing characteristics of these materials when they are used in a bonded structure. The influence of having a bonded joint within the crush zone of a composite structure has not been adequately characterized in the past. After reviewing the existing literature and based on our own work done in automotive crashworthiness studies it can be concluded that investigating the strain rate dependence of fiber reinforced polymer composites and bonded structures made from them are also very important since the amount of energy they absorb and their performance properties vary with loading rate. The above is the last stage in crashworthiness research, where in one would like to determine how best fiber composite structures can be bonded together in the pursuit of designing the most crashworthy adhesively bonded automotive composite structure. Hence, a comprehensive experimental methodology to analyze and design adhesively bonded automotive composite structures made of carbon fiber polymer composites to sustain axial, off-axis and lateral crash/impact loads is developed and strain rate effects on the crashworthiness of these bonded carbon fiber composite structures are studied. The experimental results from this work are being used to provide the building blocks for model developments - first the coupon level, then progressing in complexity to component level. Correlation with experimental results will provide the basis for which the analytical developments including development of constitutive laws, materials models, damage algorithms and new finite elements, are made.
