Glass/epoxy and graphite/epoxy (IM7/977-2) composites with stacking sequence [03]T,

[0/90/0]T and [90/0/90]T are chosen to verify the stress singularity of the transverse crack.

The ply thickness was taken as 2.2 mm. The length of the beam was 146 mm and the

width 18.7 mm. An initial crack normal to a ply-interface is placed at the center of the

beam subjected to tensile or bending loads (see Figure 3-3). The crack tip is located at the

interface of the top and mid layers. The region surrounding the crack-tip was refined

using 31,000 quadratic solid elements. The commercial finite element software

ABAQUS was used for this purpose.

 ,7.... .,... .. ..1 a.J I
 ? i T I rJ' T?^ T 1^Ti i n7Y{); i y"-r; ~ ..i\','}] rr iI tr T.' i. T':: i n1? ^ 1i l 'rt


 Undeformed Deformed
Figure 3-2. Deformed geometry in the vicinity of a crack and interfacial fracture finite
 element model.



 P P


 ---am





Figure 3-3. Contour plots of stress distribution for a [0/90/0]T composite model at a
 crack-tip under tensile and bending loads.

 The composite beam model is subjected to four-point bending and/or tensile

loading conditions as shown in Figure 3-3. For the tensile case, uniform displacement in

the x-direction is applied at the end of the beam. For bending cases, the beam is simply

supported at 63.7 mm away from the crack. The top load is located at 19.5 mm away