# Compression or Tensile on Fiberglass

1. May 20, 2010

### n707jt

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. May 21, 2010

### PhanthomJay

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.

3. May 23, 2010

### n707jt

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. :(

4. May 23, 2010

### n707jt

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.

Thanks!