Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Compression or Tensile on Fiberglass

  1. May 20, 2010 #1
    1. The problem statement, all variables and given/known data

    A piece of aluminum as shown in the picture is applying a compressive force on the fiberglass material. I need to know if the loading material will exceed the specification of the fiberglass material.


    2. Relevant equations

    Properties of fiberglass
    Tensile strength Monolayer (Warp): 380 MPa
    Tensile strength Monolayer (Weft): 300 MPa

    Fiber Volume: 50%

    Properties of resin
    Tensile strength: 30 MPa

    Volume: 50%

    3. The attempt at a solution

    My question is, since the loading structure is pressing against the fiberglass, the load will cause the fiberglass to be stretched inwards thus resulting in tension. Is this deduction reasonable?
  2. jcsd
  3. May 21, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Is that an aluminum frame of sorts breing pressed upward against a fiberglass panel which is supported along its edges only? If so, the fiberglass bending streses are tensile on the outside fibers and compressive on the inside fibers, just like any plate subject to bending loads. Calculating those streses is quite difficult without a copy of Roarke's 'Stress and Strain' or computer finite element software.
  4. May 23, 2010 #3
    Hi there,

    I do have Roark's. But I am not so sure if it possible to apply those formulas meant for metal plates to my composite? I am quite lost actually. :(
  5. May 23, 2010 #4
    Hi there,

    I've included a picture of my loading condition. Ive realized Roark does not provide any flat plate condition similar to that of my problem but I was wondering if it is possible to use Case no 8 in page 508 of Roark's?

    I plan to take the outer dimension minus the inner dimension. Please advise as I am extremely new to structural engineering and I would gladly appreciate if someone could help me.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook