THE EFFECT OF LOADING FREQUENCY AND LOADING LEVEL ON THE FATIGUE BEHAVIOR OF ANGLE-PLY CARBON/PEEK THERMOPLASTIC COMPOSITES. A Thesis in The Department of Mechanical Engineering. Presented in Partial hifiilment of the Requirements for the Degee of Master of Applied Science at Concordia University Montreal, Quebec, Cana& OImad A. Al-Hmouz, 19 National Library Bibliothèque nationale du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395, rue Wellington Ottawa ON KIA ON4 Ottawa ON K1A ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Libmy of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microfonn, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/^ de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantid extracts fiom it Ni la thése ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. THE EFFECT OF LOADING FREQUENCY AND LOADING LEVEL ON THE FATIGUE BEEAVIOR OF ANGLE-PLY CARBON/IPEEK TRERMOPLASTIC COMPOSITES. Imad A. AI-Hmouz The effect of loading frequency and loading level on the fatigue behavior of [+45j4, carbonlPEEK composite was investigated. Tention-tention load controlled fatigue tests were performed on straight sided samples using a 100-KN MTS l o b ) machine. Three loading frequencies (le5,E z, and and three load levels (60%odL, 70%oir, and 8 0 % ~w~er~e 3use d, with a load ratio of R=0.13. During each fatigue test, the cyclic load, axial strain, and the sample's surface temperature were recorded through a data acquisition system. It was found that the fatigue He of this materid decreases as loading frequency increases. At the same frequency, the fatigue life decreases as the !oading level increases, with more decline at higher frequencies. Eligh levels of temperature rise were obtained during fatigue tests at high frequencies, which increase as loading level increases. Consequently, it cm be said that the major effect of loading frequency on the fatigue üfe is the temperature rise and the consequent thermal degradation. High levels of creep deformation were obsewed throughout the tests. At high frequencies, the high levels of temperature rise accelerate the creep deformation rates. A mode1 for the effect of loading frequency on the fatigue iife was suggested, based on the general degradation of the material's strength under fatigue loading. Also, the variation in viscoelastic properties during fatigue were investigated, and the thermal behavior was anlyzed. iii The author wishes to express his gratitude and deep appreciation to his supervisor Dr. X.R. Xiao who provided guidance and encouragement throughout this research project. Special th& to the Natural Science and Engineering Research Council (NSERC) for providing the funds in making this research project possible. The author gratehilly acknowledges the cooperation and help from Mr. Paul Ouellette r€ om Concordia Center for Composites. He also deeply expresses his appreciation to Mr. Jacques Dufault from the National Research Center (NRC) for his help and cooperation in manufachiring the composite plates. The author also wishes to express his acknowledgment to Mr. Motaz El- Karmalawi, a Ph.D. student from Concordia University for his assistance. TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES CHAPTER 1 Itroduction 1.1 GENERAL 1.2 The fatigue Problem in Composites 1 -2 Carbon fiberlPEEK composites (APC-VAS-4) 1 -4 Problem definition 1.5 Scope of the study 1.6 Selection of the study parameten 1.7 Study outline Effect of loading frequency on the fatigue behavior of composite laminates; a review. 2.1 General 2.2 Viscoelasticity and hysteretic heating 2.3 Effect of loading frequency 2.3 1 Effect of fiber 2.3.2 Effect of matrix Description of the material and experimental procedure 3.1 Material description 3.2 Manufacturing of composite laminates 3.3 Preparation of samples 3.4 Experimental set-up 3 -5 DMA tests 3.6 Measurernent of fibers reorientation CHAPTER 4 Experimental results 4.1 S tatic tests 4.2 Fatigue tests 4.3 Fibers reorientation after fatigue 4.4 Results and observations of fatigue tests 4.4.1 Fatigue tests at 1 Hz 4.4.1.1 6 0 % ~ ~ ~ ~ 4.4.1.2 7 0 % ~ ~ ~ ~ 4.4.1.3 8 0 % ~ ~ ~ ~ 4.4.2 Fatigue tests at 5Hz 4.4.2.1 6 0 % ~ ~ ~ ~ 4.4.2.2 7 0 % ~ ~ ~ ~ 4.4.2.3 8 0 % ~ ~ ~ 4.4.3 fatigue tests at lOHz 4.5 DMA tests CE?APTER 5 ANALYSIS 5.1 Hysteretic energy dissipation 5.2 Thermal analysis 5.3 Modeling the frequency effect on fatigue life 5.4 Viscoelastic properties CaAPTER 6 DISCUSSION 6.1 Generd fatigue behavior 6.2 Fatigue damage mechanisrn 6.3 Thenna1 effect 6.4 Creep and viscoelastic effects CRAPTER 7 CONCLUSION References LIST OF FIGURES Figure 3.1 A schematic drawing for the picture frarne mold used in manufacturing the composite plates 3.2 Manufachiring set-up for composite plates by hot-press molding 3.3 A typical manufachiring cycle for APC-UAS-4 composite plates by hot-press molding 3.4 A schematic diagrarn of the experimentai set-up for fatigue tests 4.1 Stress-strain behavior of angle-pIy APC-ZAS-4 under static loading 4.2 S-Nd iagrarn for angle-ply APC-2/AS-4 samples after tention-tention load-controlled fatigue 4.3 Typicai fatigue samples cycled at 1H z and the three loading Ievels 4.4 Variation in hysteresis loops during fatigue at 1Hz and 60Yca,, 4.5 Strain variation during fatigue at 1Hz and60%aul, 4.6 Temperature variation dunng fatigue at IHz and 60Vmui, 4.7 Variation in hysteresis loops durhg fatigue at 1Hz and 709%'oo,1t 4.8 Strain variation dunng fatigue at IHz and 70%ouit 4.9 Temperature variation dunng fatigue at 1Hz and 7 0 % ~ ~ ~ ~ 4.10 Variation in hysteresis loops during fatigue at 1H z and 8OYmU1, 4.1 1 Strain variation during fatigue at 1Hz and 8 0 % ~ ~ ~ ~ 4.12 Temperature variation during fatigue at 1Hz and 8 0 % ~ ~ ~ ~ viii 4.13 Typical fatigue samples cycled at 5Hz and the three loading levels 4.14 Variation in hysteresis loops during fatigue at 5Hz and 6OYmuI, 4.15 Strain variation during fatigue at 5% and 6 0 % ~ ~ ~ ~ 4.16 Temperature variation during fatigue at 5Hz and 60Ymd, 4.17 Variation in hysteresis loops during fatigue at 5Hz and 70b/ikruit 4.18 Strain variation dunng fatigue at 5Hz and 7 0 % ~ ~ ~ ~ ~ - 4.19 Temperature variation during fatigue at 5Hz and 700/00.1L 4.20 Variation in hysteresis loops during fatigue at 5Hz and 800/co.i, 4.21 Strain variation during fatigue at 5Hz and 8 0 % ~ ~ ~ 4.22 Temperature variation dunng fatigue at 5Hz and 8 0 % ~ ~ 4.23 Typical fatigue sarnples cycled at lOHz and the three loading levels 4.24 Variation in hysteresis loops dunng fatigue at lOHz and 6O%oUi, 4.25 Strain variation during fatigue at lOHz and 6 0 % ~ ~ ~ ~ 4.26 Temperature variation during fatigue at 1O Hz and 600hou1, 4.27 Variation in hysteresis loops duhg fatigue at lOHz and 700/mUl, 4.28 Strain variation dunng fatigue at 1O Hz and 70%crUI, 4.29 Temperature variation dunng fatigue at lOHz and 7 0 % ~ ~ ~ ~ 4.30 Variation in hysteresis loops during fatigue at lOHz and 80%nU1, 4.31 S train variation during fatigue at 1 OHz and 80%crult- 4.32 Temperature variation during fatigue at 1OHz and 804muiL 5.1 Hysteresis loop area vs. Normalïzed fatigue life at 1H z, 5Hz, and 1O Hz. 5.2 Estimation of the heat transfer coefficient from the loop area vs. equilibriurn temperature at 1H z 5.3 Experimental and predicted temperature variation at IHz 5.4 Experimental and predicted temperature variation at 5Hz 5.5 Experimental and predicted temperature variation at 1OHz 5.6 Experimental and predicted S-N curves for AS-WEEK angle-ply composite larninates 5.7 Typical sinusoidal stress-strain signais during fatigue loading 101 5.8 Variation in the dynarnic viscoelastic properties dunng fatigue at 1Hz and the three 10' loading conditions 5.9 Variation in the dynamic viscoelastic properties during fatigue at 5Hz and the three loading conditions 5.10 Variation in the dynamic viscoeiastic properties during fatigue at lOHz and the three loading conditions