that the absolute values of interfacial normal and shear stresses are lower for the
hexagonal unit cell.
y, 3, v
x, 2, u
z, 1, w
I Cn s Cy
Figure 2-9. Normal and shear stresses at the fiber-matrix interface in square and
hexagonal unit cells.
It explains that the interfacial fracture between fiber and matrix is less likely to
occur in a hexagonal unit cell than in a square unit cell. In real composite, fiber
distribution are in hexagonal patterns, the interfacial stresses can be reduced.
1E+07
- Hexagonal Cell
5E+06 Square Cell
0 /I
-5E+06
F -1E+07 -
E
-1 5E+07
-2E+07
25E+07
90 135 180 225 270
Angle (Deg)
Figure 2-10. Interfacial normal stresses in uniaxial graphite/epoxy laminate system
at AT = -405 K.