Design and Analysis of Composite Structures

Design and Analysis of Composite Structures enables graduate students and engineers to generate meaningful and robust designs of complex composite structures. Combining analysis and design methods for structural components, the book begins with simple topics such as skins and stiffeners and progresses through to entire components of fuselages and wings.

Starting with basic mathematical derivation followed by simplifications used in real-world design, Design and Analysis of Composite Structures presents the level of accuracy and range of applicability of each method. Examples taken from actual applications are worked out in detail to show how the concepts are applied, solving the same design problem with different methods based on different drivers (e.g. cost or weight) to show how the final configuration changes as the requirements and approach change.

Provides a toolkit of analysis and design methods to most situations encountered in practice, as well as analytical frameworks and the means to solving them for tackling less frequent problems.
Presents solutions applicable to optimization schemes without having to run finite element models at each iteration, speeding up the design process and allowing examination of several more alternatives than traditional approaches.
Includes guidelines showing how decisions based on manufacturing considerations affect weight and how weight optimization may adversely affect the cost.
Accompanied by a website at a href='hosting lecture slides and solutions to the exercises for instructors.

Leseprobe

Preface

This book is a compilation of analysis and design methods for structural components made of advanced composites. The term advanced composites is used here somewhat loosely and refers to materials consisting of a high-performance fiber (graphite, glass, Kevlar®, etc) embedded in a polymeric matrix (epoxy, bismaleimide, PEEKetc). The material in this book is the product of lecture notes used in graduate-levelclasses in Advanced Composites Design and Optimization courses taught at the Delft University of Technology.

The book is aimed at fourth year undergraduate or graduate level students and starting engineering professionals in the composites industry. The reader is expected to be familiar with classical laminated-plate theory (CLPT) and first ply failure criteria. Also, some awareness of energy methods, and Rayleigh Ritz approaches will make following some of the solution methods easier. In addition, basic applied mathematics knowledge such as Fourier series, simple solutions of partial differential equations, and calculus of variations are subjects that the reader should have some familiarity with.

A series of attractive properties of composites such as high stiffness and strength-to-weight ratios, reduced sensitivity to cyclic loads, improved corrosion resistance, and, above all, the ability to tailor the configuration (geometry and stacking sequence) to specific loading conditions for optimum performance has made them a prime candidate material for use in aerospace applications. In addition, the advent of automated fabrication methods such as advanced fiber/tow placement, automated tape laying, filament winding, etc. has made it possible to produce complex components at costs competitive with if not lower than metallic counterparts. This increase in the use of composites has brought to the forefront the need for reliable analysis and design methods that can assist engineers in implementing composites in aerospace structures. This book is a small contribution towards fulfilling that need.

The objective is to provide methodology and analysis approaches that can be used in preliminary design. The emphasis is on methods that do not use finite elements or other computationally expensive approaches in order to allow the rapid generation of alternative designs that can be traded against each other. This will provide insight in how different design variables and parameters of a problem affect the result.

The approach to preliminary design and analysis may differ according to the application and the persons involved. It combines a series of attributessuch as experience, intuition, inspiration and thorough knowledge of the basics. Of these, intuition and inspiration cannot be captured in the pages of a book or itemized in a series of steps. For the first attribute, experience, an attempt can be made to collect previous best practices which can serve as guidelines for future work. Only the last attribute, knowledge of the basics, can be formulated in such away that the reader can learn and understand them and then apply them to his/her own applications. And doing that is neither easy nor guaranteed to be exhaustive. The wide variety of applications and the peculiarities that each may require in the approach, preclude any complete and in-depth presentation of the material. It is only hoped that the material presented here will serve as a starting point for most types of design and analysis problems.

Given these difficulties, the material covered in this book is an attempt to show representative types of composite structure and some of the approaches that may be used in determining the geometry and stacking sequences that meet applied loads without failure. It should be emphasized that not all methods presented here are equally accurate nor do they have the same range of applicability. Every effort has been made to present, along with each approach,

Inhalt
Preface 1. Applications of advanced composites in aircraft structures References 2. Cost of Composites- A qualitative discussion 2.1 Recurring cost 2.2 Non-recurring cost 2.3 Technology selection 2.4 Summary and conclusions Exercises References 3. Review of Classical Laminated-Plate Theory 3.1 Composite Materials - Definitions, symbology and terminology 3.2 Constitutive equations in three dimensions 3.3 Constitutive equations in two dimensions - Plane stress Exercises References 4. Review of laminate strength and failure criteria 4.1 Maximum stress failure theory 4.2 Maximum strain failure theory 4.3 Tsai-Hill failure theory 4.4 Tsai-Wu failure theory 4.5 Other failure theories References 5. Composite structural components and mathematical formulation 5.1 Overview of composite airframe 5.2 Governing equations 5.3 Reductions of governing equations - Applications to specific problems 5.4 Energy methods Exercises References 6. Buckling of composite plates 6.1 Buckling of rectangular composite plate under biaxial loading 6.2 Buckling of rectangular composite plate under uniaxial compression 6.3 Buckling of rectangular composite plate under shear 6.4 Buckling of long rectangular composite plates under shear 6.5 Buckling of rectangular composite plates under combined loads 6.6 Design equations for different boundary conditions and load combinations Exercises References 7. Post-buckling 7.1 Post-buckling analysis of composite panels under compression 7.2 Post-buckling analysis of composite plates under shear Exercises References 8. Design and analysis of composite beams 8.1 Cross-section definition based on design guidelines 8.2 Cross-sectional properties 8.3 Column buckling 8.4 Beam on elastic foundation under compression 8.5 Crippling 8.6 Importance of radius regions at flange intersections 8.7 Inter-rivet buckling of stiffener flanges 8.8 Application - Analysis of stiffener in a stiffened panel under compression Exercises References 9. Skin-stiffened structure 9.1 Smearing of stiffness properties (equivalent stiffness) 9.2 Failure modes of a stiffened panel 9.3 Additional considerations of stiffened panels Exercises References 10. Sandwich structure 10.1 Sandwich bending stiffness 10.2 Buckling of sandwich structure 10.3 Sandwich wrinkling 10.4 Sandwich crimping 10.5 Sandwich intra-cellular buckling …