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Author: Paul A. Lagace
Publisher:
ISBN:
Category :
Languages : en
Pages : 19
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Book Description
Introduction: The aircraft industry continues to pursue the use of advanced composite materials in aircraft structures in order to save weight and produce more efficient, and potentially cost-effective, aircraft. In the more than two decades in which composite materials have been applied, such application to aircraft structures has progressed from secondary structures to "medium-primary" structures and now has pushed into the use in primary structures. The Boeing 777 with its "all-composite" empennage structure represents an important achievement in such regard. However, despite such successes and ambitious programs such as NASA's ACT (Advanced Composite Technology), application of composite materials to the largest parts of the airframe, the wing and fuselage, is still inhibited by a number of issues. Among these issues is the overriding concern of safety. Safety is a very wide-ranging issue. But, with regard to structure, safety generally deals with the ability of the structure to maintain its integrity while subjected to the loads and environment experienced in operation. The central issue in the case of a primary load-bearing structure is damage. There are three facets to this issue of damage: damage resistance, which involves the ability of a structure to undergo events without (minimal) damage occurring and which thus addresses the question "how does damage get there"; damage tolerance, which involves the ability of a structure to undergo loading with damage present without failing and which thus addresses the question of "when does damage propagate/cause failure?"; and damage arrest, which involves the ability of a structural configuration to stop propagating damage before such damage causes catastrophic failure and which thus addresses the question "how can the propagating damage be stopped?". Answers to these three questions must be provided in order for a safe structure to be designed. There are many "events" that can cause damage and must therefore be addressed within the framework just described. A key issue in the design of composite structures is impact [1]. This is of special concern in laminated composite structures due to the relatively low through-thickness strength. Furthermore, the damage caused by impact may be "hidden" beneath the surface of the laminate. Events such as runway kickup, tool drop, encounter with a hailstorm, and engine damage can cause damage in these laminated structures that can result in a significant decrease in their load-carrying capability or can promote further damage growth under cyclic loads thereby reducing the life of the part. It is therefore important to consider the issue of impact, particularly with regard to composite structural configurations that are likely to be utilized in fuselage and wing applications. Since the effects of impact, damage resistance, and damage tolerance are structural responses [2], this must be considered both for generic application as well as with particular structural configurations in mind.
Author: Paul A. Lagace
Publisher:
ISBN:
Category :
Languages : en
Pages : 19
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Book Description
Introduction: The aircraft industry continues to pursue the use of advanced composite materials in aircraft structures in order to save weight and produce more efficient, and potentially cost-effective, aircraft. In the more than two decades in which composite materials have been applied, such application to aircraft structures has progressed from secondary structures to "medium-primary" structures and now has pushed into the use in primary structures. The Boeing 777 with its "all-composite" empennage structure represents an important achievement in such regard. However, despite such successes and ambitious programs such as NASA's ACT (Advanced Composite Technology), application of composite materials to the largest parts of the airframe, the wing and fuselage, is still inhibited by a number of issues. Among these issues is the overriding concern of safety. Safety is a very wide-ranging issue. But, with regard to structure, safety generally deals with the ability of the structure to maintain its integrity while subjected to the loads and environment experienced in operation. The central issue in the case of a primary load-bearing structure is damage. There are three facets to this issue of damage: damage resistance, which involves the ability of a structure to undergo events without (minimal) damage occurring and which thus addresses the question "how does damage get there"; damage tolerance, which involves the ability of a structure to undergo loading with damage present without failing and which thus addresses the question of "when does damage propagate/cause failure?"; and damage arrest, which involves the ability of a structural configuration to stop propagating damage before such damage causes catastrophic failure and which thus addresses the question "how can the propagating damage be stopped?". Answers to these three questions must be provided in order for a safe structure to be designed. There are many "events" that can cause damage and must therefore be addressed within the framework just described. A key issue in the design of composite structures is impact [1]. This is of special concern in laminated composite structures due to the relatively low through-thickness strength. Furthermore, the damage caused by impact may be "hidden" beneath the surface of the laminate. Events such as runway kickup, tool drop, encounter with a hailstorm, and engine damage can cause damage in these laminated structures that can result in a significant decrease in their load-carrying capability or can promote further damage growth under cyclic loads thereby reducing the life of the part. It is therefore important to consider the issue of impact, particularly with regard to composite structural configurations that are likely to be utilized in fuselage and wing applications. Since the effects of impact, damage resistance, and damage tolerance are structural responses [2], this must be considered both for generic application as well as with particular structural configurations in mind.
Author: Brian Lee Wardle
Publisher:
ISBN:
Category :
Languages : en
Pages : 42
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Book Description
The response of various composite structures to transverse loading was studied through impact and quasi-static testing. The AS4/3501-6 graphite/epoxy composite structures considered have a [±45n/0n]s layup configuration and include convex and concave shell sections, plates, and full cylinders. The impact tests fall within the so-called large-mass, low-velocity regime where previous findings for composite plates indicate that quasi-static tests accurately represent the impact response, i.e., impact and quasi-static tests can be considered equivalent. This equivalence includes damage if the same peak force is reached in both the impact and quasi-static tests. The present work extends the impact and quasi-static equivalence from composite plates to various composite (shell) structures, even when the shell response exhibits an instability. Over nearly the entire range of impact events and shell structures tested, impact and quasi-static response (including damage extent and distribution) is found to be equivalent. A small number of the most flexible (large span, thin) specimens displayed a large-amplitude oscillatory impact loading response which was not observed for the quasi-static tests. These few specimens indicate a regime which may limit the general equivalence of impact and quasi-static testing demonstrated herein. The general equivalence of impact and quasi-static response demonstrated herein for a wide range of composite structures, especially in regard to damage resistance, has important implications for testing and design of damage tolerant aerospace components. Furthermore, the findings suggest that quasi-static experimentation can often be used to simulate the impact response (including damage) of composite shell structures.
Author: Robert L. Sierakowski
Publisher: Routledge
ISBN: 1351456709
Category : Technology & Engineering
Languages : en
Pages : 170
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Book Description
This recent book provides a detailed presentation of damage tolerance assessment and characterization methods for advanced composites, as well as an examination of the role of damage tolerance in the design of composites. Included are analytical models for different types of damage in different composite materials. Tables provide helpful reference
Author: Brian Lee Wardle
Publisher:
ISBN:
Category :
Languages : en
Pages : 42
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Book Description
The response of various composite structures to transverse loading was studied through impact and quasi-static testing. The AS4/3501-6 graphite/epoxy composite structures considered have a [±45n/0n]s layup configuration and include convex and concave shell sections, plates, and full cylinders. The impact tests fall within the so-called large-mass, low-velocity regime where previous findings for composite plates indicate that quasi-static tests accurately represent the impact response, i.e., impact and quasi-static tests can be considered equivalent. This equivalence includes damage if the same peak force is reached in both the impact and quasi-static tests. The present work extends the impact and quasi-static equivalence from composite plates to various composite (shell) structures, even when the shell response exhibits an instability. Over nearly the entire range of impact events and shell structures tested, impact and quasi-static response (including damage extent and distribution) is found to be equivalent. A small number of the most flexible (large span, thin) specimens displayed a large-amplitude oscillatory impact loading response which was not observed for the quasi-static tests. These few specimens indicate a regime which may limit the general equivalence of impact and quasi-static testing demonstrated herein. The general equivalence of impact and quasi-static response demonstrated herein for a wide range of composite structures, especially in regard to damage resistance, has important implications for testing and design of damage tolerant aerospace components. Furthermore, the findings suggest that quasi-static experimentation can often be used to simulate the impact response (including damage) of composite shell structures.
Author: Brian Lee Wardle
Publisher:
ISBN:
Category :
Languages : en
Pages : 11
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Book Description
The damage resistance of thin composite structures was investigated experimentally. Specifically, surface damage in the form of dent-depth measurements are compared with internal damage states obtained by the X-radiography technique to better understand the implications of "barely visible impact damage" (BVID). Impact and quasi-static tests were conducted on plate and shell graphite/epoxy specimens between 0.804 mm and 2.412 mm thick in a [±45n/On]s layup configuration. Damage was measured via visual, transducer, and X-ray methodologies. No correlation was found between internal (nonvisible) damage from the X-ray data and measured characteristics of the surface damage, specifically the depth of the dent. The results indicate that the use of dent depth as a metric can be misleading, particularly in that no dent depth can be found in cases where substantial subsurface damage exists. Other examples are given wherein substantial (relative to other specimens) dent depths are measured with no corresponding internal damage. In previous work peak force was found to correlate the resulting internal damage for both shell and plate specimens. However, dent depth shows no such general trend or correlation with peak force. This, coupled with previous damage tolerance work, places into question the use of dent-depth for thin (less than 2.4 mm, or 0.10") composite plate and shell structures in current damage tolerance methodologies.
Author: Vadim Silberschmidt
Publisher: Woodhead Publishing
ISBN: 0081000839
Category : Technology & Engineering
Languages : en
Pages : 618
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Book Description
Composite materials, with their higher exposure to dynamic loads, have increasingly been used in aerospace, naval, automotive, sports and other sectors over the last few decades. Dynamic Deformation, Damage and Fracture in Composite Materials and Structures reviews various aspects of dynamic deformation, damage and fracture, mostly in composite laminates and sandwich structures, in a broad range of application fields including aerospace, automotive, defense and sports engineering. As the mechanical behavior and performance of composites varies under different dynamic loading regimes and velocities, the book is divided into sections that examine the different loading regimes and velocities. Part one examine low-velocity loading and part two looks at high-velocity loading. Part three then assesses shock and blast (i.e. contactless) events and the final part focuses on impact (contact) events. As sports applications of composites are linked to a specific subset of dynamic loading regimes, these applications are reviewed in the final part. - Examines dynamic deformation and fracture of composite materials - Covers experimental, analytical and numerical aspects - Addresses important application areas such as aerospace, automotive, wind energy and defence, with a special section on sport applications
Author: Paul A. Lagace
Publisher:
ISBN:
Category :
Languages : en
Pages : 5
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Book Description
A key design issue in the design of composite structures continues to be impact. Due to the limited capability of laminated composites to withstand transverse loadings and the subsequent reduction in their overall load-carrying capacity, impact can, in fact, be a/the limiting design issue in many applications. In order to effectively utilize composites, it is necessary to understand the impact issue and to develop techniques to assess the damage and resultant capability of composite laminates subjected to impact. The overall issue of impact and related issues have, therefore, received considerable attention in the structural design process, in the materials development world, and in the research community [Abrate, 1991]. Engineers and researchers have recently realized that it is necessary to divide the behavior of composite laminates and structures with regard to impact into the two separate aspects of damage resistance and damage tolerance [Cairns and Lagace, 1992]. Damage resistance is a measure of the damage incurred by a material or structure due to a particular event such as impact, while damage tolerance involves a measure of the ability of a material or structure to "perform", given particular requirements, with damage present. These two aspects are related only in that the damage tolerance of a structure depends upon the type, location, and extent of the damage present. The damage tolerance is not affected by how the damage got there (the damage resistance aspect) [Cairns and Lagace, 1990]. Although understanding and predicting the residual performance capability of the structure is the ultimate goal in considering impact, it has become clear [Lee and Zahuta, 1991, Guy and Lagace, 1992] that it is first necessary to characterize, on a three-dimensional basis, the damage which results due to an impact event. Only then can the proper models be formulated to characterize the performance of the composite structure based on the damage which actually exists. This can be facilitated by understanding the mechanics of the impact event and how the damage occurs such that methods can be developed to predict the damage state based on the characteristics of the impact event. In order to simplify the assessment of the behavior of composites subjected to impact, approaches have been formulated which treat the behavior as the sequential effect of a number of events. The flow of such an approach is shown in Figure 1 [Cairns and Lagace, 1992]. In this figure, italicized descriptions refer to output from a model to be used as input to the next step.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 652
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Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: Hyonny Kim
Publisher:
ISBN:
Category :
Languages : en
Pages : 508
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Book Description
Author: S.R. Reid
Publisher: CRC Press
ISBN: 9780849308475
Category : Technology & Engineering
Languages : en
Pages : 328
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Book Description
Much of the early, pioneering work on the properties of composites under impact is still conceptually relevant, yet the results of many such analyses are outdated. The accuracy of these results depend specifically on the materials used (fibre, resin), interface, and method of fabrication. Development of new materials, cost effective design, and analysis and prediction of structural behaviour have all established a need for timely, wide ranging research on impact behaviour. Impact Behaviour of Fibre-Reinforced Composite Materials and Structures brings together - for the first time - state-of-the-art research from the most recent works of leading, international experts. An important new study, this book extensively investigates impact response, damage tolerance, and failure of fibre-reinforced composite materials and structure, from a number of expert viewpoints. This book explores the nature of modern polymer composites based on glass, carbon, aramid, ceramic and polymer fibres in a polymer matrix, and details various ways of analysing the impact process. Impact Behaviour of Fibre-Reinforced Composite Materials and Structures will prove itself a valuable tool for research and development engineers, structural engineers, materials scientists, designers, and students and researchers of related disciplines.
