Interfacial Adhesion Characteristics of Kenaf Fibres Subjected to Different Polymer Matrices and Fibre Treatments

Table 5

Main fibre pullout mechanisms and their brief remarks for the different types of fibre treatments used subjected to epoxy matrix at dry loading conditions.

Epoxy
Corresponding SEM figure	Fibre treatment	Brief remark/explanation	Main fibre pullout mechanism
Figure 7(a)	Untreated	High amount of impurities observed on the fibre surfaces which significantly lowered the IAS of the fibre and matrix	Fibre breakage associated with mild torn fibre
Figure 7(b)	4% HCl	(i) Fibre stripes were easily detached from the core main fibre because of the hollow spots on fibre surfaces which contributed to stress concentrations during SFPT causing severe micro cracks on fibre surface; (ii) Relatively smooth fibre surfaces after the treatment which did not contribute to any improvement in IAS of the fibre against the matrix	Brittle-like fracture at end of fibre was observed because of the acidic treatment
Figure 7(c)	6% HCl	(i) Massive debonding of fibre associated with macro crack at the resinous region indicating that fibre could not even withstand the low pullout force (less than 0.8 N); (ii) Fibre easily ruptured because of high acidic treatment	Deteriorated fibre at the end of fibre breakage
Figure 7(d)	4% NaOH	(i) Slight debonding of fibre was observed associated with some loose fibre detached from the main core fibre indicating that the fibre could withstand the high pullout force; (ii) Rough fibre surfaces	Ductile-like breakage was observed at the end of the fibre
Figure 7(e)	6% NaOH	Slight debonding of fibre associated with severe signs of fibre contractions which denotes that the fibre could withstand the increment in pullout force (more than 2 N) during SFPT	Ductile-like breakage was observed at the end of the fibre