AS2070: Aerospace Structural Mechanics
Jan-May, 2025

• Dr. Nidish Narayanaa Balaji
  • nidish@iitm.ac.in, Room 139 AE building
• TA: Priyanka Samal, Senthil Balamurugan.
• Textbook References
  1. Module 1
     • Buckling of Bars, Plates and Shells (1975) by Brush and Almroth [1]
     • Theory of Elastic Stability (2009) by Stephen P. Timoshenko [2]
     • Aircraft Structures for Engineering Students (2013) by T. H. G. Megson [3]
  2. Module 2
     • Mechanics of Composite Structures (2003) by Kollar and Springer [4]
     • Principles of Composite Material Mechanics (2012) by Ronald F. Gibson [5]
  3. Module 3
     • Fracture Mechanics: An introduction (2005) by Gdoutos [6]
     • Elements of Fracture Mechanics (2009) by Kumar [7]

• The lectures will be split into three modules:

  Sno.	Topic	Lectures	Assignments
  1	Elastic Stability	11	1-2
  2	Laminated Composites	11	1-2
  3	Introduction to Failure	11	1-2
  	Total	33	3-6

  • The weekly split-up (nominally) is
    • 3 Lectures
    • 1 Tutorial

• The End Semester Examination will carry 40% weightage for the overall.
• The quizzes (together) will carry 30% weightage.
• The assignments (together) will carry 15% weightage.
• A Course Project will carry 15% weightage.

Upon my honor I state that I have received no unauthorized support and can attest that the submission reflects my understanding of the subject matter.

• The honor code may be signed either by hand or just initials (in case of typed submission), but the key is that you should mean it.
• Honor code violations will not be taken lightly.

• Each module will have at least one assignment and at most 2.
• Late submissions will be accepted till the closest subsequent weekend with a linear penalty accrued.
  • For example, if an assignment is due on a Tuesday, late submissions will be accepted till Sunday night.
  • The obtained grade will be scaled by a factor of \(\frac{1-x}{5\times24\times60\times60}\) where \(x\) is the number of seconds elapsed since midnight Tuesday.

• The first week of classes will provide an executive overview of the three modules to be taught in the class.
• You will be given 2 weeks' time to decide which module you want to work on for your project.

• The problem statement for the project is:

  Develop an experimental demonstration of pedagogical value that highlights some of the concepts covered in class.

• I will group you in teams of 5-6 based on your preferences.
• The deliverables are:
  • a demonstration of the experiment.
  • a 15 minute presentation to class.
  • a 1-2 page summary (keep this very brief).

• I will be using an Attendance App on a tablet to record attendance.
• The app logs the time of press also, so attendance will be computed as the ratio of the number of seconds spent in class and the total number of class hours.
• Please be aware of institute policy regarding attendance matters, I can not provide any flexibility here.

• Semester Calendar
• https://archive.nptel.ac.in/content/storage2/courses/101104010/
• https://fracturemechanics.com/
• Video on Fatigue testing
• Attendance App

• What is stability?
• Buckling of columns
• Energy Perspectives to Stability
• Snap-Through Buckling
• Flat Plates

• Classification of composite materials
  1. Continuous fiber composite laminate
     • Interlaminar strength is matrix dominated.
  2. Woven fiber composites
     • Strength compromized but no risk of delamination.
  3. Chopped fiber composites
     • Poorer strength but cheaper.
  4. Hybrid composites
  5. Sandwich structure
     • High strength faces bonded through a lightweight foam/honeycomb core.
     • High flexural stiffness-to-weight ratios.
• Materials in Composites
  1. Fibers
     • Fiberglass-Reinforced Plastics (FRPs)
       • Low cost, "basic" composites
     • "Advanced" composites: Carbon, SiC, aramid polymer, etc.
       • Higher modulus, strength; lower density.
     • Carbon Nanotubes, Nanofibres.
  2. Matrix, Filler
     • Polymers
       • Thermosets: Epoxy, Polyester, etc.
         • Highly cross-linked 3D molecular network which doesn't melt again.
       • Thermoplastics: Polyetherketone (PPEK), PolyPhenyl Sulphide (PPS), etc.
         • Polymer chains that do not cross-link. Will melt, can be reshaped.
     • Metal, ceramic, or carbon matrix for higher temperature applications.
• Effective Moduli, Effective Strength.
• Constitutive relationships.
• Classical Laminate Theory (Subject to Time)

• Structure of Materials
  • Lattice, Defects
• Introduction to Fatigue
  • S-N Curve
  • Miner's Rule
  • Stress Concentration
• Introduction to Fracture Mechanics
  • Modes of Fracture
  • Crack Growth

• Link to pdf

1. Indicate project preferences:
   • Moodle Link: https://courses.iitm.ac.in/mod/assign/view.php?id=52699
   • Deadline: 11.59pm, <2025-02-03 Mon>