linear and nonlinear progressive failure analysis of laminated composite aerospace structures a

144 Pages·2012·3.31 MB·English

LINEAR AND NONLINEAR PROGRESSIVE FAILURE ANALYSIS OF
LAMINATED COMPOSITE AEROSPACE STRUCTURES

A THESIS SUBMITTED TO
THE GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES
OF
MIDDLE EAST TECHNICAL UNIVERSITY

BY

MURAT GÜNEL

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR
THE DEGREE OF MASTER OF SCIENCE
IN
AEROSPACE ENGINEERING

JANUARY 2012
Approval of the thesis:

LINEAR AND NONLINEAR PROGRESSIVE FAILURE ANALYSIS OF
LAMINATED COMPOSITE AEROSPACE STRUCTURES

submitted by MURAT GÜNEL in partial fulfillment of the requirements for the degree
of Master of Science in Aerospace Engineering Department, Middle East Technical
University by,

Prof. Dr. Canan Özgen ________________
Dean, Graduate School of Natural and Applied Sciences

Prof. Dr. Ozan Tekinalp ________________
Head of Department, Aerospace Engineering

Prof. Dr. Altan Kayran ________________
Supervisor, Aerospace Engineering Department, METU

Examining Committee Members:

Asst. Prof. Dr. Melin ġahin ________________
Aerospace Engineering Department, METU

Prof. Dr. Altan Kayran ________________
Aerospace Engineering Department, METU

Asst. Prof. Dr. Demirkan Çöker ________________
Aerospace Engineering Department, METU

Asst. Prof. Dr. Ercan Gürses ________________
Aerospace Engineering Department, METU

Dr. Muvaffak Hasan ________________
Chief Engineer, TAI

Date: 19.01.2012
I hereby declare that all information in this document has been obtained and
presented in accordance with academic rules and ethical conduct. I also declare
that, as required by these rules and conduct, I have fully cited and referenced all
material and results that are not original to this work.

Name, Last name: Murat GÜNEL
Signature:

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ABSTRACT

LINEAR AND NONLINEAR PROGRESSIVE FAILURE ANALYSIS OF
LAMINATED COMPOSITE AEROSPACE STRUCTURES

Günel, Murat
M.Sc., Department of Aerospace Engineering
Supervisor: Prof. Dr. Altan Kayran

January 2012, 129 pages

This thesis presents a finite element method based comparative study of linear and
geometrically non-linear progressive failure analysis of thin walled composite aerospace
structures, which are typically subjected to combined in-plane and out-of-plane loadings.
Different ply and constituent based failure criteria and material property degradation
schemes have been included in a PCL code to be executed in MSC Nastran. As case
studies, progressive failure analyses of sample composite laminates with cut-outs under
combined loading are executed to study the effect of geometric non-linearity on the first
ply failure and progression of failure. Ply and constituent based failure criteria and
different material property degradation schemes are also compared in terms of predicting
the first ply failure and failure progression. For mode independent failure criteria, a
method is proposed for the determination of separate material property degradation
factors for fiber and matrix failures which are assumed to occur simultaneously. The
results of the present study show that under combined out-of-plane and in-plane loading,
linear analysis can significantly underestimate or overestimate the failure progression
compared to geometrically non-linear analysis even at low levels of out-of-plane
loading.

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Keywords: Progressive Failure Analysis, Composite Aerospace Structures, Non-linear
Deformation, Material Property Degradation, Nastran PCL Code

v
ÖZ

LAMĠNAT KOMPOZĠT HAVACILIK YAPILARINDA DOĞRUSAL VE
DOĞRUSAL OLMAYAN ĠLERLEYEN HATA ANALĠZĠ

Günel, Murat
Yüksek Lisans, Havacılık ve Uzay Mühendisliği Bölümü
Tez Yöneticisi: Prof. Dr. Altan Kayran

Ocak 2012, 129 sayfa

Bu tez ince cidarlı havacılık yapılarında genel olarak maruz kalınan düzlem içi ve
düzlem dıĢı kombine yüklemeler için, sonlu eleman metodu kullanılarak yapılan bir
doğrusal ve geometrik olarak doğrusal olmayan hata analizi karĢılaĢtırmasını
sunmaktadır. Farklı katman ve bileĢen temelli hata kriterleri ve hasara bağlı olarak
malzeme özelliklerini indirme metodları MSC Nastran‟da çalıĢtırmak üzere bir PCL
koduna dahil edilmiĢtir. Örnek çalıĢmalar olarak, geometrik olarak doğrusal olmayan
hasar analizinin ilk katman hasarında ve hasar ilerlemesindeki etkilerini inceleme amaçlı
delikli kompozit laminatların kombine yükler altında ilerleyen hasar analizleri
yapılmıĢtır. Katman ve bileĢen temelli hasar kriterleri ve malzeme özelliklerini indirme
metodları ilk katman hasarı ve hasar ilerleyiĢini tahmin etmeleri açısından
kıyaslanmıĢtır. BileĢenden bağımsız hasar kriteri olarak, eĢ zamanlı gerçekleĢen lif ve
matris hasarları için ayrı malzeme özelliği indrime faktörleri elde etmeye yarayan bir
method önerilmiĢtir. Sunulan çalıĢmanın sonuçları göstermektedir ki, kombine düzlem
içi ve düzlem dıĢı yükler altında doğrusal analiz düzlem dıĢı yüklemenin çok alt
seviyelerinde bile hata ilerlemesini geometrik olarak doğrusal olmayan analizin tahmin
ettiğinin önemli ölçüde altında veya üzerinde tahmin edebilmektedir.

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Anahtar Kelimeler: Hata Ġlerleme Analizi, Kompozit Havacılık Yapıları, Doğrusal
Olmayan Deformasyon, Malzeme Özelliği DüĢürme, Nastran PCL Kodu.

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ACKNOWLEDGMENTS

The author would like to express sincere appreciation to his supervisor Prof. Dr. Altan
KAYRAN; for his guidance, advice, motivation, continuous support and
encouragements throughout this study.

The author also wishes to express his love and gratitude to his wife Elvan ZEYBEK
GÜNEL; for her understanding and endless love through the duration of his studies.

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TABLE OF CONTENT

ABSTRACT ................................................................................................................. iv
ÖZ ................................................................................................................................ vi
ACKNOWLEDGMENTS ........................................................................................... viii
TABLE OF CONTENT ................................................................................................ ix
LIST OF TABLES ........................................................................................................ xi
LIST OF FIGURES ..................................................................................................... xii
CHAPTERS
1. INTRODUCTION ................................................................................................. 1
2. FAILURE THEORIES .......................................................................................... 5
2.2 Mode-Dependent Failure Theory...................................................................... 8
2.1 Mode-Independent Failure Theory ................................................................... 9
3. DESCRIPTION OF PCL ..................................................................................... 12
4. PROGRESSIVE FAILURE ANALYSIS ............................................................. 15
4.1 Methodology .................................................................................................. 15
4.2 Material Degradation ..................................................................................... 18
4.2.1 Material Property Degradation Method for Mode Dependent Failure
Theory............................................................................................................ 24
4.2.2 Material Property Degradation Method for Mode Independent Failure
Theory............................................................................................................ 26
4.3 Linear and Nonlinear Analysis ...................................................................... 31

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5. RESULTS AND DISCUSSIONS ........................................................................ 37
5.1 Verification of PCL Code by Hand Calculation .............................................. 37
5.2 Verification of PCL Code by Test Results ...................................................... 44
5.3 Description of the Model and Laminate Definition ......................................... 52
5.4 Mesh Sensitivity Study .................................................................................. 54
5.5 Pure Tensile Loading (Load Case 1)............................................................... 58
5.6 Pure Pressure Loading (Load Case 2) ............................................................. 59
5.7 Gradual Tensile Loading under Constant Pressure (Load Case 3) ................... 62
5.8 Gradual Compressive Loading under Constant Pressure (Load Case 4) .......... 68
5.9 Effect of Degradation Factor on the Failure Progression ................................. 74
6. CONCLUSIONS AND FUTURE WORKS ......................................................... 80
REFERENCES ............................................................................................................ 85
APPENDICES
A. PCL CODE ..................................................................................................... 88
B. NONLINEAR SOLUTION PARAMETERS ................................................. 116
C. MESH SENSITIVITY STUDY ..................................................................... 126
CURRICULUM VITAE ............................................................................................ 128

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