The module descriptors for this programme can be found below.

Composites 4

Module aims

Stress Analysis

To introduce a series of significant aspects in the stress analysis of laminated composite components: analysis of laminated beams, free edge stresses in laminates, effect of holes on the strength of laminates and the buckling of laminated plates.

Fracture

The lectures are designed to provide the students with a general background in fracture mechanics with particular reference to the concept of energy release. This basis is then used to examine the various standard test methods for delamination of composite laminates. Some discussion of the application of these data to design will be included. 

Fatigue
The overall aim of this course is to produce graduates with state of the art knowledge in the field of fatigue of composite materials and thus help them to gain employment where they will be able to utilise and apply the knowledge they have gained.  They should become adept in both practical and theoretical aspects of the subject and have the confidence to be able to use their knowledge for the good of themselves and their country.  

Environmental Effects

The overall aim of this course is to produce graduates with state of the art knowledge in the field of environmental behavior of composite materials and thus help them to gain employment where they will be able to utilise and apply the knowledge they have gained. They should become adept in both practical and theoretical aspects of the subject and have the confidence to be able to use their knowledge for the good of themselves and their country. 

Impact

To describe the types of damage that can occur in laminated composites as a result of transverse impact.  To distinguish between small and large mass impact responses. To estimate the peak impact forces and delamination damage thresholds, and the properties affecting these parameters.  To review the local and overall structural response mechanisms of composite laminates after impact loading.  To identify failure mechanisms in impact damaged composites and to model their response under tensile and compressive loading. 
 

Learning outcomes

Stress Analysis

Knowledge and understanding
On successfully completing this course unit, students will be able to:

Analyse the stresses in a thin-walled beam section manufactured from laminated plates. This will include:

  • an introduction to engineers theory of bending for bending stresses in a beam section of single material;
  • extension of engineers theory of bending to a thin-walled beam section manufactured from laminates;
  • calculation of shear flows in laminated beams.

Understand the effect of a free edge on the stress distribution in a laminate. This will include:

  • the failure of classical lamination theory to satisfy the free edge condition;
  • qualitative assessment of the interlaminar stress distribution in a uniaxially loaded laminate specimen and comparison with numerical solutions;
  • simple assumed stress distribution models and their application;
  • significance of the interlaminar stresses to the failure of a laminate and the inadequacy of the assumed stress distribution models.

Use simple techniques for predicting the strength degradation of a laminate due to the presence of a hole. This will include:

  • a discussion of the inadequacy of the stress concentration factor approach for laminate;
  • an introduction to three prediction methods: the point stress criterion, the average stress criterion and the damage zone criterion;
  • evaluation of these prediction methods using experimental data.

Examine buckling problems associated with laminates. This will include:

  • an introduction to the phenomena of buckling through the analysis of a simple strut;
  • the development of the plate buckling equations and simplification for uniaxially loaded, simply supported, specially orthotropic plates;
  • a comparison of predicted buckling loads with experiment and the significance of bend-twist coupling.

Skills and other attributes
On successfully completing this course unit, students will have had practice in the following skills:
Intellectual skills
Engineering analysis
Transferable skills
Number skills

Fracture 

Knowledge and understanding 

On successfully completing this course unit, students will be able to: 

  • Discuss, using appropriate technical vocabulary, the principles of fracture mechanics and the differences between the fracture modes; 
  • Recall the principal standard test methods used to measure the toughness of composites; 
  • Recall the toughening mechanisms for particulate and short-fibre composites; 
  • Explain the effects of rate and temperature on fracture, and discuss the use of time/temperature superposition. 


Skills and other attributes 

On successfully completing this course unit, students will be able to: 

  • Analyse typical fracture test data and calculate the fracture energy;  
  • Propose a suitable failure envelope to characterise pure- and mixed-mode fracture data;  
  • Propose a suitable test method for measuring the toughness of a composite material.  

Fatigue

The course will give students an appreciation of the problem of fatigue loading as applied to composite materials. It will deal with the full range of topics required to give students a thorough basic understanding of the subject with they can call upon in the future.  On the completion of the course, students will have developed a sound knowledge of the subject and have the confidence to apply that knowledge. 

Environmental Effects

The course will give students an appreciation of the problem of environmental exposure as applied to composite materials. It will deal with the full range of topics required to give students a thorough basic understanding of the subject which they can call upon in the future. 

Impact

To understand the development of damage in laminated composites subjected to transverse impact loading.  To recognise the effects of impact damage upon the residual performance of composite structures, and how these can be mitigated.  To be able estimate the peak impact forces and delamination damage thresholds and the properties that affect these parameters. 

Module syllabus

Stress Analysis

Analysis of laminated beams: calculation of shear force and bending moment diagrams for statically determinate beams; engineers theory of bending for beam sections of a single material; analysis of bending stress distribution in beam sections consisting of two or more materials and application to thin-walled laminated beams; analysis of shear flow distribution in thin-walled laminated beams.
Free edge stresses in laminates: failure of classical lamination theory to satisfy the free edge condition; typical interlaminar stress distributions; approximate analysis of edge stresses using assumed stress distribution models; failure of the assumed stress distribution models; effective ply thickness concept.
Effect of holes on the strength of laminates: failure of the stress concentration factor approach for fibre reinforced laminates; point stress criterion; average stress criterion; damage zone criterion; application of these criteria and comparison with experimental results.
Buckling of laminated plates: pin-ended strut and the Euler buckling load; buckling of laminated plates; simplification for a rectangular, simply supported, uniaxially loaded, specially orthotropic laminated plate; effect of bend-twist coupling on buckling loads; influence of stacking sequence on shear buckling.

Fracture 

Fundamentals of Fracture Mechanics:  Typical fracture processes. Fracture mechanics. Energy balance. Energy release rate G, area method, general forms in terms of load, displacement and energy. Stress intensity factor K and relationship to G. 
Application of Fracture Mechanics to Delamination in Composites:  Definition of fracture modes. Derivation of G for beam specimens. Mode I delamination tests, analysis and experimental details. Standards. Mode II test, analysis and test details. Mixed mode testing. Failure envelopes. Mode III tests. 
Further Applications of Fracture Mechanics to Composites:  Effect of rate & temperature. Multi-directional composites. Use of fracture mechanics for short fibre & particulate composites. Toughening mechanisms. 

Fatigue

Behaviour of notched and unnotched specimens. Tension-tension, compression-compression and tension-compression testing. Residual strengths and influence of fatigue damage. Effect of matrix and fibre properties. Implications for component design 

  • Introduction 
  • Test Methods 
  • Fatigue Behaviour and Damage 
  • Variables in Fatigue Performance 
  • Consequences of Fatigue Damage 
  • Conclusions 

Environmental Effects

Influence of moisture and other contaminants on fibre, matrix and interface. Effect on mechanical and other properties. stress corrosion cracking. Influence of high and low temperatures. Prediction of long-term behaviour. 
 

  • Introduction 
  • Effect of Temperature 
  • Effect of Moisture 
  • Other Environmental Effects 
  • Conclusions 

Impact

Typical impact damage; role of fibre, matrix and interface. Small and large mass impacts. Peak impact forces. Test methods and effect of specimen size. Delamination damage thresholds. Residual strengths. Energy absorbing mechanisms. 

Pre-requisites

Stress Analysis

AERO97036 Revision Stress Analysis
AERO97048 Analysis of Laminated Composites

Fatigue

A basic knowledge of what a composite material comprises. 

Environmental Effects

A basic knowledge of what a composite material comprises. 

Impact

AERO97046 Introduction to Composites (FRP). 

Teaching methods

Stress Analysis

Skeleton lecture course notes will be issued. These are incomplete in the sense that they contain gaps which need to be filled in during the lectures. There is sufficient space for students to add extra notes. The lectures will cover all the material in the course notes – not just the gaps. The aim of using skeleton notes is to help students gain an understanding of the material during the lecture period rather than simply taking notes.

Tutorial sheets containing a number of problems are issued at the end of each double lecture period (except the final double lecture) and are intended to enable students to consolidate their understanding of the relevant material as soon as possible after the lecture. The sheets will be discussed with the class and/or individuals during a 10/15 minute break at the mid-point of the following double lecture. Students are invited to make an appointment with the course lecturer in the case of special difficulties with the tutorial sheets.

Fracture 

Three lectures. Printed handouts of the slides used in the lectures are given out. One tutorial sheet covering all the topics is given out, which has numerical answers given. Model solutions are made available.  

Fatigue

The course is presented using a combination of the whiteboard, Powerpoint presentation and pre-printed notes. 

Environmental Effects

The course is presented using a combination of the whiteboard, Powerpoint presentation and pre-printed notes. 

Impact

The course is presented using a combination of the whiteboard, Powerpoint presentation and pre-printed notes. 

Assessments

This course is assessed by a written examination.Full marks may be obtained by correctly answering FOUR questions. You may answer more than four questions, but only the best four answers will count

Stress Analysis

There will be two questions in the exam paper on this course. .
 

Fracture

This course is assessed by one exam question in Paper 4.  

Fatigue

There is 1 question in Paper 4 on this lecture topic. 

Environmental Effects

There is 1 question in Paper 4 on this lecture topic. 

Impact

This course is assessed by one examination question in Paper 4.