With increase in fiber content, the tensile strength of untreated and treated IDL fiber reinforced polyester (FRP) composites is increased. IDL CT FRP composites have shown 39.65 % more tensile strength than IDL FRP composites at maximum fiber volume fraction which is shown in Fig. 8.8. The specific tensile strength of the com­posites is also determined and is graphically represented in Fig. 8.9 against fiber volume fraction.

The IDL FRP composites under tensile load have exhibited relatively more elonga­tion than load at 12.08 % fiber volume fraction; thereby, tensile modulus is decreased (Fig. 8.10). An increase in trend of tensile modulus is observed at all volume fractions in case of IDL CT FRP composites. Chemical treatment to IDL fibers resulted in good locking between fibers and matrices, evidenced from the experimental results. Though IDL CT FRP composites have taken more load at all fiber volume fractions, they exhibited more elongation, thereby resulting in nearer tensile modulus of the IDL FRP composites. Similar trend was observed in the case of PALF FRP composites rein­forced with 2 % NaOH treated fibers for 1 h and has shown enhancement in tensile strength and modulus than untreated FRP composites, and its values are 55.4 MPa and 1.46 GPa, respectively (Uma Devi et al. 1997). The specific tensile modulus of IDL and IDL CT FRP composites is 906.44 and 871.72 (MPa/kg. m-3).10-3 respectively at maximum fiber volume fraction and is shown in Fig. 8.11.

The tensile strength and modulus of 22.5 MPa and 1,095-1,100 MPa, respec­tively, were observed in PALF fiber reinforced LDPE composites where the fibers were longitudinally oriented at 30 % fiber content (George et al. 1995). From the experimental results, it is obvious that the IDL CT FRP composites showed supe­rior performance than pineapple leaf fiber reinforced LDPE composites at maximum fiber content, and its value is 56.03 MPa, whereas tensile modulus of untreated and

treated IDL FRP composites exhibited similar trend to that of PALF-LDPE composites.

The influence of benzoylation treatment on tensile properties was reported in 1996. The bond between fiber and matrix was evidenced from the experimental results of the composites reinforced with treated fibers, in polystyrene matrix (Manikandan Nair et al. 1996). In the present work, NaOH-treated IDL FRP composites at 16.92 % fiber content exhibited 1.16 times more tensile strength than the composites (at 30 % fiber content) made of polystyrene matrix, benzoylate — treated sisal fiber.

PALF (30 mm fiber length) FRP composites have exhibited tensile strength of

63.3 MPa and are 1.13 times higher than IDL long FRP composites experimentally studied in this research (Uma Devi et al. 1997). Due to fiber entanglements that occurred above optimum size of the fibers, which was resulted in decrease in the tensile strength in PALF FRP composites when they were reinforced with 30 mm fiber length.