Experimental and theoretical investigations of stiffened and unstiffened composite panels under uniform transversal loading

Diploma Thesis , 2003 , 102 Pages , Grade: 1,0

Engineering - Mechanical Engineering

With the increased use of composite materials in various structural applications, the subject of analysing the properties of composite unstiffened and stiffened panels has received widespread attention. Laminated panels are considered as the basic modules of high performance boats, aircraft and many other complex structures, which require less specific weight, better durability, and excellent damage tolerance and are often subject to air-blast loading or under water shock. The failure mode of fibre reinforced composite materials is rather more complex than that of isotropic material. This is because of the different properties of fibres and matrix the composite is made of. There has been a number of failure theories developed since the first industrial usage of composites in the early 1980s. Those theories are based on different failure criteria and often just cover some special set up. In the last years computer simulations based on FEA were set up to predict the failure of composites. Because there is only few experimental data available for comparison, the need for experimental investigations of composites is big.
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Inhaltsverzeichnis (Table of Contents)

• INTRODUCTION
• BASICS OF COMPOSITE STRUCTURES
  • COMMON FIBRES
  • GLASS FIBRE
  • COMMON MATRICES
  • EPOXY MATRIX
  • FIBRE - MATRIX INTERACTION
  • FAILURE TYPES OF COMPOSIte Materials
    • Micro Failure Mechanism
    • Macro Failure Mechanism
• EXPERIMENTAL INVESTIGATION OF A CANTILEVER BEAM
  • SETUP AND PROCEDURE
  • RESULTS AND DISCUSSION
  • E-MODULUS
  • CONCLUSION
• EXPERIMENTAL INVESTIGATION OF COMPOSITE PANELS
  • PROBLEM STATEMENT
    • Commonly Used Methods and Former Experiments
    • Method Adopted
  • SPECIMEN PROPERTIES
    • Sample Preparation
    • Stiffeners
    • Sensor Setup
  • EXPERIMENTAL PROGRAM AND INSTRUMENTATION
  • Test ResulTS AND ANALYSIS
    • Panel-1, no Stiffener
    • Panel-2, one Stiffener
    • Panel-3, two Stiffeners
  • DISCUSSION
    • Panel-1, no Stiffener
    • Panel-2, one Stiffener
    • Panel-3, two Stiffeners
  • DISCUSSION AND ERRORS
• LAMINATE THEORY FOR THE UNSTIFFENED PANEL
  • ELASTIC PROPERTIES
  • ANALYTIC APPROACH WITH KNOWN FORMULAS
  • LAMINA STRENGTH AND Failure TheorIES
    • Lamina Strength and Failure Mechanism
    • Failure Theories
  • LAMINATE STRENGTH AND FAILURE
    • First Ply Failure
    • Ultimate Laminate Failure
• FINITE ELEMENT ANALYSIS
  • SETUP
  • RESULTS
    • Panel-1, no Stiffener
    • Panel-2, one Stiffener
    • Panel-3, two Stiffeners
  • DISCUSSION AND ERRORS
• COMPARISON
  • DEFLECTIONS
  • STRAINS
  • FAILURES AND STRESSES
• CONCLUSION
• REFERENCES
• APPENDIX A: NOMENCLATURE
• APPENDIX B: CALCULATIONS

Zielsetzung und Themenschwerpunkte (Objectives and Key Themes)

This diploma thesis aims to investigate the behavior of stiffened and unstiffened composite panels under uniform transversal loading through both experimental and theoretical approaches. The study focuses on understanding the mechanical properties, failure mechanisms, and load-carrying capacity of these panels.

• Experimental investigation of the mechanical behavior of stiffened and unstiffened composite panels under uniform transversal loading.
• Analysis of failure mechanisms and load-carrying capacity of the panels.
• Comparison of experimental results with theoretical predictions based on laminate theory and finite element analysis.
• Evaluation of the effectiveness of stiffeners in enhancing the structural performance of composite panels.
• Assessment of the accuracy and limitations of different analytical and numerical methods in predicting the behavior of composite panels.

Zusammenfassung der Kapitel (Chapter Summaries)

The thesis begins with an introduction to the basics of composite structures, covering common fibers, matrices, and failure mechanisms. Chapter 3 presents an experimental investigation of a cantilever beam made of composite material, focusing on the determination of the E-modulus and failure analysis. Chapter 4 delves into the experimental investigation of composite panels with varying stiffener configurations, including detailed descriptions of the specimen properties, experimental setup, and analysis of test results. Chapter 5 explores the laminate theory for the unstiffened panel, covering elastic properties, analytical approaches, and failure theories. Chapter 6 presents the finite element analysis of the panels, including the setup, results, and discussion of errors. Chapter 7 compares the experimental, theoretical, and numerical results, focusing on deflections, strains, and failures. Finally, the thesis concludes with a summary of the findings and recommendations for future research.

Schlüsselwörter (Keywords)

The keywords and focus themes of the text include composite panels, stiffened structures, uniform transversal loading, experimental investigation, laminate theory, finite element analysis, failure mechanisms, load-carrying capacity, E-modulus, and structural performance.

• Grade: 1,0
• Author: Dr.-Ing. Jan Brökel (Author)
• Publication Year: 2003
• Pages: 102
• Catalog Number: V114919
• ISBN (eBook): 9783640150984
• ISBN (Book): 9783640151073
• Language: English
• Tags: Experimental