How To Analyse Composites

Marsden, W, and Irving, D J

First Published - July 2002
Softback - 58 Pages

Aesthetic, structural and financial constraints combine to demand continual improvements in design efficiency and optimisation. Engineers now increasingly look to advances in materials performance to meet a proportion of these demands. This has resulted in a rapid development of material combinations with properties superior to those of traditional, monolithic materials. The extension of the performance envelope by these materials is accompanied by a step change in the complexity of their stress/strain response. Finite element analysis (FEA), applied within an overall “design and build” strategy, offers the engineer an ideal practical alternative to replace the “make and test” strategy currently employed for the majority of components and structures constructed using continuous fibre reinforced composite materials, often referred to as “advanced composites.”

The purpose of this bookl is to present an overview of the current state-of-the-art for predictive analysis of structures comprising advanced composites and to provide a set of guidelines to promote best practice in the analysis of these materials using the finite element technique. A typical example of this type of advanced composite is carbon fibre reinforced epoxy, though there are many other types of composite material, for example, natural composites (wood), biological composites (bone) and macro composite (reinforced concrete). However, as the design requirements are often demanding for advanced composites (particularly for the analysis of linear structural response), the numerical and analysis tools and capabilities within commercial software are tailored to suit their requirements. Areas of analysis such as the use of explicit codes for crash simulations involving complex hyper-viscoelastic material models to simulate the time-dependent response of biological materials are not covered in this text.

The first sections of this book may be regarded as an introduction to the common features of advanced (rigid) composite materials, their typical constituent materials and the most common manufacturing techniques. These are followed by an overview of the classical closed form solutions used to investigate their performance as single layers and as consolidated laminated stacks.

This information is referenced by the later section, which illustrates the requirements specific to the analysis of composite laminates. A brief overview is given of the alterations to standard element formulations needed for analysing composites and the limitations this places on their use. This is followed by a discussion of the more advanced nonlinear analysis topics either currently available or under development in order to highlight the limitations of current commercial software.

Contents

1. INTRODUCTION

2. FUNDAMENTALS OF COMPOSITES

• 2.1 Introduction
• 2.2 Classification of Composite Materials
• 2.3 The nature of composite matrices and reinforcement
• 2.4 Generic manufacturing techniques
• 2.5 Stiffness and strength of laminated composites
  • 2.5.1 Lamina loaded in the principal directions
  • 2.5.2 Lamina mechanics
  • 2.5.3 Strength of a single lamina
  • 2.5.4 Laminate Mechanics

3. ELASTIC ANALYSIS OF COMPOSITES

• 3.1 Introduction
• 3.2 Laminate Homogenisation
• 3.3 Fibre orientation within laminated composites
  • 3.3.1 Laminated materials and directionality
  • 3.3.2 Fabric Draping
  • 3.3.3 Filament winding
• 3.4 Aspects of Layered Element Formulations
  • 3.4.1 Materials in laminated elements
  • 3.4.2 Some aspects of layered shell elements
  • 3.4.3 Some aspects of sandwich elements
  • 3.4.4 Some aspects of layered solid elements
• 3.5 Interlaminar stresses
• 3.6 Considerations for composite analysis

4. RESULTS INTERPRETATION

• 4.1 Introduction
• 4.2 General elastic stress distribution
• 4.3 First-ply failure

5. ADVANCED ANALYSIS TOPICS

• 5.1 Nonlinear damage material models
  • 5.1.1 Matrix cracking and fibre failure
  • 5.1.2 Delamination modelling
• 5.2 Analysis Methods
  • 5.2.1 Coupled thermo-mechanical analyses
  • 5.2.2 Superelements/Substructure modelling
  • 5.2.3 Structural Optimisation and Parametric studies
  • 5.2.4 Adaptive remeshing

6. CONCLUSIONS

7. GLOSSARY OF COMPOSITE TERMS

REFERENCES