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Comprehensive Multi-Scale Progressive Failure Analysis for Damage Arresting Advanced Aerospace Hybrid Structures

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Comprehensive Multi-Scale Progressive Failure Analysis for Damage Arresting Advanced Aerospace Hybrid Structures Comprehensive Multi-Scale Progressive Failure Analysis for Damage Arresting Advanced Aerospace Hybrid Structures Brandon Horton Dissertation submitted to the Faculty of Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy In Mechanical Engineering Javid Bayandor, Chair Francine Battaglia Fayette S. Collier Dawn C. Jegley Walter F. O’Brien Wayne A. Scales July 18th, 2017 Blacksburg, Virginia Keywords: PRSEUS, stitched composites, finite element, composite failure, progressive damage Copyright 2017, Brandon Horton Comprehensive Multi-Scale Progressive Failure Analysis for Damage Arresting Advanced Aerospace Hybrid Structures Brandon Horton ACADEMIC ABSTRACT In recent years, the prevalence and application of composite materials has exploded. Due to the demands of commercial transportation, the aviation industry has taken a leading role in the integration of composite structures. Among the leading concepts to develop lighter, more fuel- efficient commercial transport is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. The highly integrated structure of PRSEUS allows pressurized, non-circular fuselage designs to be implemented, enabling the feasibility of Hybrid Wing Body (HWB) aircraft. In addition to its unique fabrication process, the through-thickness stitching utilized by PRSEUS overcomes the low post-damage strength present in typical composites. Although many proof-of- concept tests have been performed that demonstrate the potential for PRSEUS, efficient computational tools must be developed before the concept can be commercially certified and implemented. In an attempt to address this need, a comprehensive modeling approach is developed that investigates PRSEUS at multiple scales. The majority of available experiments for comparison have been conducted at the coupon level. Therefore, a computational methodology is progressively developed based on physically realistic concepts without the use of tuning parameters. A thorough verification study is performed to identify the most effective approach to model PRSEUS, including the effect of element type, boundary conditions, bonding properties, and model fidelity. Using the results of this baseline study, a high fidelity stringer model is created at the component scale and validated against the existing experiments. Finally, the validated model is extended to larger scales to compare PRSEUS to the current state-of-the-art. Throughout the current work, the developed methodology is demonstrated to make accurate predictions that are well beyond the capability of existing predictive models. While using commercially available predictive tools, the methodology developed herein can accurately predict local behavior up to and beyond failure for stitched structures such as PRSEUS for the first time. Additionally, by extending the methodology to a large scale fuselage section drop scenario, the dynamic behavior of PRSEUS was investigated for the first time. With the predictive capabilities and unique insight provided, the work herein may serve to benefit future iteration of PRSEUS as well as certification by analysis efforts for future airframe development. Comprehensive Multi-Scale Progressive Failure Analysis for Damage Arresting Advanced Aerospace Hybrid Structures Brandon Horton GENERAL AUDIENCE ABSTRACT In recent years, the prevalence and application of composite materials has exploded. Due to the demands of commercial transportation, the aviation industry has taken a leading role in the integration of composite structures. Among the leading concepts to develop lighter, more fuel- efficient commercial transport is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. The highly integrated structure of PRSEUS allows a new type of fuselage design to be implemented, known as Hybrid Wing Body (HWB) aircraft. PRSEUS unique fabrication process, the through-thickness stitching utilized by PRSEUS overcomes the low post-damage strength present in typical composites. Although many proof-of-concept tests have been performed that demonstrate the potential for PRSEUS, efficient computational tools must be developed before the concept can be commercially certified and implemented. In an attempt to address this need, a comprehensive modeling approach is developed that investigates PRSEUS at multiple scales. The majority of available experiments for comparison have been conducted for small specimens. Therefore, a computational predictive methodology is developed to accurately model the response of PRSEUS. A thorough analysis is performed to identify what needs to be considered in the model to predict an accurate result while remaining computationally efficient. From the baseline analysis, realistic models of the PRSEUS structure are created numerically and validated against the existing experiments. Finally, the validated approach is extended to panel and a fuselage section to compare PRSEUS to the current state-of-the-art. Throughout the current work, the developed methodology is shown to make accurate predictions that are well beyond the capability of existing predictive models. While using commercially available softwares, the methodology developed herein can accurately predict local behavior up to and beyond failure for structures such as PRSEUS for the first time. Additionally, by applying the methodology to a fuselage section drop scenario, the dynamic behavior of PRSEUS was investigated for the first time. With the predictive capabilities and unique insight provided, the work herein may serve to benefit future iteration of PRSEUS as well as certification by analysis efforts for future airframe development. Acknowledgements I wish to acknowledge my gratitude to my advisor, Dr. Javid Bayandor for his guidance and the many opportunities he has provided throughout my graduate studies. I would also like to acknowledge my Ph.D committee members, Dr. Francine Battaglia, Dr. Fay Collier (Program Manager), Ms. Dawn Jegley (Program Manager), Dr. Walter O’Brien, and Dr. Wayne Scales. Their involvement in my thesis work and the critiques they have provided has improved my dissertation. This research was supported by the “Multiscale Modeling of Advanced Aerospace PRSEUS Structures” grant from the National Aeronautics and Space Administration (NASA), for which I am very grateful. It has provided me with the opportunity to collaborate with many technical experts and exposed me to much of the cutting edge research performed at NASA. In particular, the guidance and insights of the Program Manager, Ms. Dawn Jegley, has had a significant impact on the success of this work. I also greatly appreciate the collaboration with the Marion branch of General Dynamics to conduct non-destructive imaging for this project, particularly with Joseph Butler and Kurt Ruoff. I wish to thank my colleagues and friends in the CRASH Lab for their endless advice and support throughout the many long nights of research. In particular, the mentoring and collaboration with the recent Dr. Yangkun Song has made a huge impact on my technical abilities in finite element analysis. I wish to thank my parents and my sister for their love and emotional support that has carried me through my graduate work. Without them, I wouldn’t be where I am today. Finally, I wish to thank Joyci for her endless patience, care, and understanding, especially during the final stages of my dissertation. iv | P a g e Table of Contents 1 Introduction ......................................................................................................................... 1 2 Element Formulation Theory ............................................................................................... 6 2.1 Beam Element Formulation ...................................................................................... 7 2.2 Shell Element Formulation ....................................................................................... 8 2.3 Hourglass Control .................................................................................................... 9 2.4 Solid Element Formulation ..................................................................................... 13 2.5 Continuum (Thick) Shell Element Formulation ...................................................... 15 2.6 Contact in Finite Element Analysis......................................................................... 16 3 Material Theories .............................................................................................................. 19 3.1 Composite Material Model ..................................................................................... 19 3.2 Cohesive Zone Modeling ....................................................................................... 23 3.3 Metal Material Model ............................................................................................ 25 3.3.1 Isotropic Model .......................................................................................... 25 3.3.2 Johnson-Cook Model .................................................................................. 27 3.3.3 Equation of State ........................................................................................ 29 4 Preliminary Element Study ................................................................................................ 31 4.1 Cantilever Beam Analysis .....................................................................................
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