I created a composite using natural fiber and polyester resin, natural fiber +epoxy resin.
I got stress-strain curve from tensile test.
what is the strain range for composite material finding the young modulus of the curve?
Epoxy ?
Polyester?
If you have a stress-strain curve for your samples, calculating the young modulus is simple. Identify the linear region of the curve that corresponds with Hooke's law. Then, determine the slope of the linear part of the curve, which represents the young modulus. ( E = stress/strain )
Unlike metallic materials, composite materials like GFRP & CFRP have low strain to failure. Even the initial stress/strain graph is not likely to be linear. The Young's modulus will be different for different range of strains.
ASTM D3039 is the standard for tensile strength & tensile modulus of composite materials. It stipulates 0.1% to 0.3% strain range for the computation of E.
In textbook Autar Kaw it is mentioned that "Young’s modulus of an elastic material is the initial slope of the stress–strain curve."
In William D callister text book it is mentioned " tangent modulus , secant modulus"- I have attached image for your reference.
For my composite specimen, how do I find Young's modulus?
Which method I have to follow to find Young's modulus?
suppose I am looking for a strain range 0.1 to 0.3% I am getting a slope is 112.27 MPa. Which method is correct for composite material
theoretical calc:
ultimate tensile strength = 130 MPa
strain range: 1.6%
E=stress/strain = 130/0.016= 8125 MPa = 8.125 GPa
Rajamohan Ayiravalli Mohammad Razmara
Dear Suganth,
The composite products are designed generally to work in the strain range of 0.1% to 0.3%. Hence the young's modulus is the difference in stress in the 0.1% to 0.3% strain range divided by 0.002 strain.
What are the fibre and the matrix in your composite specimen?
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