UUnniivveerrssiittyy ooff TTeennnneesssseeee,, KKnnooxxvviillllee TTRRAACCEE:: TTeennnneesssseeee RReesseeaarrcchh aanndd CCrreeaattiivvee EExxcchhaannggee Doctoral Dissertations Graduate School 5-2006 AAuuttoommoottiivvee CCrraasshhwwoorrtthhiinneessss ooff AAddhheessiivveellyy BBoonnddeedd CCaarrbboonn FFiibbeerr PPoollyymmeerr CCoommppoossiittee SSttrruuccttuurreess George Chennakattu Jacob University of Tennessee - Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Engineering Commons RReeccoommmmeennddeedd CCiittaattiioonn Jacob, George Chennakattu, "Automotive Crashworthiness of Adhesively Bonded Carbon Fiber Polymer Composite Structures. " PhD diss., University of Tennessee, 2006. https://trace.tennessee.edu/utk_graddiss/1723 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by George Chennakattu Jacob entitled "Automotive Crashworthiness of Adhesively Bonded Carbon Fiber Polymer Composite Structures." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, with a major in Polymer Engineering. John F. Fellers, Major Professor We have read this dissertation and recommend its acceptance: Gajanan S. Bhat, Madhu S. Madhukar, Roberto S. Benson Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official student records.) To the Graduate Council: I am submitting herewith a dissertation written by George Chennakattu Jacob entitled “Automotive Crashworthiness of Adhesively Bonded Carbon Fiber Polymer Composite Structures.” I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, with a major in Polymer Engineering. John F. Fellers Major Professor We have read this dissertation and recommend its acceptance: Gajanan S. Bhat Madhu S. Madhukar Roberto S. Benson Accepted for the Council: Anne Mayhew Vice Chancellor and Dean of Graduate Studies (Original signatures are on file with official student records.) Automotive Crashworthiness of Adhesively Bonded Carbon Fiber Polymer Composite Structures A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville George Chennakattu Jacob May 2006 Dedicated To My Mother & All Those Who Hope and Pray For My Well Being ii ACKNOWLEDGEMENTS First and foremost, I would like to thank my committee, Dr. John F. Fellers, Dr. Roberto S. Benson, Dr. Gajanan Bhat, and Dr. Madhu S. Madhukar for their interest in my research, as well as education. Dr. John F. Fellers who guided me in the capacity of a graduate advisor for both my Masters and Ph.D. has always been extremely supportive and encouraging to all my thoughts and actions during my entire stay at the University of Tennessee (UT). I would also like to express my deepest appreciation to Dr. J. Michael Starbuck from the Metals and Ceramics Division, Oak Ridge National Laboratory (ORNL), for guiding me through all my experimental work conducted at ORNL and the National Transportation Research Center (NTRC) under his supervision. I am indebted to Dr. Fellers and Dr. Starbuck for bringing this dissertation to fruition. My sincere gratitude to Dr. David A. Dillard, Professor from Virginia Tech, for his time, guidance, and help during the past one and half years of my doctoral research. Last but not the least, my special thanks to Dr. Raymond G. Boeman, Dr. Srdjan Simunovic, Robert Norris, and Dr. Thomas Zacharia from ORNL for their support during all my research activities at the lab. I owe all of the above-mentioned people my heartfelt appreciation and gratitude, for they are largely responsible for making my entire stay in Knoxville fruitful and rewarding. Finally, I would like to thank all the faculty and group members (especially Ronny D. Lomax, Rick Battiste, Dr. Donald L. Erdman, and Michael S. Davenport), staff, colleagues at both UT and ORNL for their assistance and support iii during these years. The financial support from the Department of Energy (DOE) is most greatly appreciated. iv ABSTRACT In passenger vehicles, the ability to absorb impact energy and be survivable for the occupant is called the “crashworthiness” of the structure. The ACC (Automotive Composite Consortium) has been and continues to be very interested in investigating the use of fiber-reinforced composites as crash energy absorbers. It would have been ideal if the composite structure to be used as a crash energy absorber were manufactured as an integral, monolithic component, but limitations in the present day manufacturing technology necessitate the presence of joints in composite structures. While many scientists have investigated the energy absorption characteristics in various fiber reinforced composite materials, there is no literature available on the energy absorption and crushing characteristics of these materials when they are used in a bonded structure. The influence of having a bonded joint within the crush zone of a composite structure has not been adequately characterized in the past. After reviewing the existing literature and based on our own work done in automotive crashworthiness studies it can be concluded that investigating the strain rate dependence of fiber reinforced polymer composites and bonded structures made from them are also very important since the amount of energy they absorb and their performance properties vary with loading rate. The above is the last stage in crashworthiness research, where in one would like to determine how best fiber composite structures can be bonded together in the pursuit of designing the most crashworthy adhesively bonded automotive composite structure. v Hence, a comprehensive experimental methodology to analyze and design adhesively bonded automotive composite structures made of carbon fiber polymer composites to sustain axial, off-axis and lateral crash/impact loads is developed and strain rate effects on the crashworthiness of these bonded carbon fiber composite structures are studied. The experimental results from this work are being used to provide the building blocks for model developments – first the coupon level, then progressing in complexity to component level. Correlation with experimental results will provide the basis for which the analytical developments including development of constitutive laws, materials models, damage algorithms and new finite elements, are made. vi TABLE OF CONTENTS Chapter 1 Introduction and Literature Review 1 1.1 Introduction 1 1.2 Literature Review on Strain Rate Dependence of Energy Absorption in Polymer Composite Materials for Automotive Crashworthiness 7 1.2.1 Abstract 7 1.2.2 Introduction 7 1.2.3 Test Methodologies 8 1.2.3.1 Quasi-static Testing 8 1.2.3.2 Impact Testing 9 1.2.4 Crushing Modes and Mechanisms 9 1.2.4.1 Catastrophic Failure Modes 9 1.2.4.2 Progressive Failure Modes 10 1.2.4.2.1 Transverse Shearing or Fragmentation Mode 11 1.2.4.2.2 Lamina Bending or Splaying Mode 11 1.2.4.2.3 Brittle Fracturing 14 1.2.4.2.4 Local Buckling or Progressive Folding 14 vii