A slender composite beam of width w and length L is subjected to an external bending moment M13 as shown. The outer layers are made of a material A which always deforms at a constant stress oo (i.e., a rigid plastic material). The inner core is made of an elastic material B which has a stress-strain relationship given by where p is the radius of curvature, and E is the time-independent elastic modulus. Determine 1) the location of the neutral axis and 2) the equilibrium conditions by relating M13 to the stress distribution in the beam. If the modulus of the inner core is time dependent [i.e., viscoelastic where E = Er(t)], does the neutral axis remain at the same location? State all assumptions M13 X2 h h E 011 = E 11 = = x h3 A B A L W M13 X1