Page 288 - Engineered Interfaces in Fiber Reinforced Composites

Chapter 6. Interface mechanics and fracture toughness theories 269

Crack extension (mm)

for
Fig. 6.23. R-curve prediction ( - and experimental data (0) a carbon fiber-epoxy matrix quasi-
)
isotropic [O"/ f 45"/90"], laminate. After Wells and Beaumont (1987).
curve (Fig. 6.23) and composite notch strength (Fig. 6.24). They noted that the crack
resistance increases even at large crack extensions, particularly for laminates
containing symmetric [*45"] plies (Fig. 6.23). This is attributed to the large scale
damage zone ahead of the fracture path where the energy is absorbed mainly by
delamination. This observation rather contradicts the earlier finding by Ochiai and

5 0,5- HM
f m ':<L 08
c
a
-
0
r
U
4- - HS
0
z -
-
0 I I l I l I l

Fig. 6.24. Comparison of notched strength of carbon fiber-epoxy matrix quasi-isotropic [o"/ & 45"/90"],
HM
laminate between predictions (- ) and experimental data (0): = high modulus carbon fiber; HS =
high strength carbon fiber. After Wells and Beaumont (1987).