direction, FIGURE 7.5 多 static equilibrium of the element with respect to the forces along the x must act at the inner edge of the kth ply,as shown in figure 7.5.From under these normal stresses alone,the interlaminar shear stress, as shown in figure 7.5.Since the element cannot be in static equilibrium on the two faces of the jth ply in a differential element must be different, too,must the normal stress,o.This means that the normal stresses acting (7.13),we see that if the bending moment changes with respect to x,so, must change along the length of the beam(the x direction).From equation Thus,the presence of the shear force implies that the bending moment M,is related to the transverse shear force,V,by the equation Recall from the mechanics of materials [2]that the bending moment, stresses,as summarized here. 兵 a mechanics of materials approach for estimating these interlaminar shear for static equilibrium when the bending moment varies along the length. Differential element of a laminated beam showing interlaminar shear stress that is necessary ↓4 ↓@ +t号 Principles of Composite Material Mechanics 160 where which is where for a laminated beam Thus,the transverse shear stress is given by for a homogeneous isotropic beam equation for transverse shear stress in a homogeneous isotropic beam, Equation (7.20)is seen to be similar to the "mechanics of materials" for a rectangular beam having an even number of plies of uniform thick- ness,zj=jh/N,and equation (7.19)reduces to integrating,we find that the interlaminar stress at the inner edge of the Substituting equation (7.13)and equation(7.16)in equation(7.18)and Analysis of Laminates d(odz G23 G22 G211 (7.20) G13 多