The IDL FRP composites under flexural loading beyond 15.55 % fiber volume fraction exhibited decreasing trend of flexural strength due to the lack of bond between the fibers and matrices. Figure 8.12 represents flexural strength against fiber volume fraction, where IDL CT FRP composite flexural strength is increasing with increase in volume fraction of the fiber. All the IDL CT FRP composites failed due to bend­ing only at the outer surface of the specimen. Though the IDL CT fiber volume fraction is 8.48 % less when compared with IDL fiber, the flexural strength of IDL CT FRP composites is 17.38 % more when compared with untreated fiber reinforced composites at maximum fiber volume fraction. From the Fig. 8.13, it is observed that the specific flexural strength of IDL CT FRP composites is 13.41 times higher than IDL FRP composites at maximum fiber volume fraction.

The flexural modulus of IDL CT FRP composites crossed its value after 15.5 % fiber volume fraction when compared with IDL fiber reinforced composites, as

ОЛ

40 20 0

0 5 10 15 20 25 30 35

Volume fraction (%)

evidenced from Fig. 8.14. The determined flexural properties from the experimental results show the flexural modulus of treated and untreated FRP composites is increas­ing with increasing fiber content. In PALF fiber reinforced composites, the flexural properties at 30 % fiber content are very good, and its specific stiffness is 0.25 m x 106

(Uma Devi et al. 1997). The specific flexural modulus of IDL CT FRP composites have shown very good performance when compared with the composites reinforced with untreated IDL fibers, which is evident from Fig. 8.15.