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P3.2: The material of a tension link is changed from a Ti-6A1-4V (aged) titanium

ID: 1862229 • Letter: P

Question

P3.2: The material of a tension link is changed from a Ti-6A1-4V (aged) titanium alloy to a uniderectional continuous Gy-70 carbon fiber-expoxy.  The stress-strain curve of the epoxy resin is shown below.  Calculate the volume fraction of GY-70 fibers required in the composite link to match the modulus of the titanium alloy.


HInts: Find the modulus of Ti and carbon fiber from table

Get Em from graph

Solve E(L) = EfVf+Em(1-Vf) for Vf

.  Calculate the volume fraction of GY-70 fibers rerquired in the composite link to match the modulus of the titanium alloy.

Also, estimate the tensile strength of the composite link and compare its strength-weight ratio with that of the titanium alloy. Consider a unidirectional continuous fiber lamina containing brittle, clastic fibers in a elastic, perfectly plastic matrix. The stress-strain diagrams for the fibers and the matrix are shown on

Explanation / Answer

modulus of carbon fibre is 138 Gpa.

for the given titanium alloy is 113.8 Gpa

from the graph, the slope is the youngs modulus .
= 9/.02=450 ksi=3.1 GPa

From formula
E(Ti alloy)=E(fibre)(Vf)+E(epoxy)(1-Vf)
113.8=138(Vf)+3.1(1-Vf)
113.8=Vf*134.9 +3.1

=>110.7/134.9=.82
i.e    82% is the required volume fraction