// Pb. 2.10 Glass fibers
mode(0)
d = 400; // mm
p = 20; // MPa
R = 2; // safety factor applied to the load (pressure)
Ff = [3.45, 4.8, 4.4, 3.31, 2.5]*1E3; // MPa, Glass fibers
rhof = [2.59, 2.49, 2.55, 2.56, 2.14]; // g/cc, Glass fibers
max(Ff)
tf = R*p*d/2*Ff.^-1;
min(tf)
WL = %pi*d^2*R/10*p/2.*rhof.*Ff.^-1 
min(WL)
