Table 8 SEM fractographic features identified at marked regions for composites.
ID | Key SEM features | Dominant fracture/interface characteristics |
|---|---|---|
S1 | (1) Long, clean fiber pull-out (2) Smooth fiber surfaces (3) Clear gaps between fiber and matrix (4) Relatively flat matrix regions | Weak fiber–matrix adhesion leading to interfacial debonding and extensive fiber pull-out |
S2 | (1) Roughened fiber surfaces (2) Partial matrix adhesion on fibers (3) Shorter pull-out lengths (4) Fibrillation of fiber walls | Improved interfacial bonding due to alkali treatment, but still governed by mixed pull-out and partial debonding |
S3 | (1) Strongest fibrillation (2) Fibers often fractured rather than pulled out (3) Matrix tightly wrapped around fibers | Highly efficient load transfer with fiber fracture dominated failure indicating optimal interface strength |
S4 | (1) Slight matrix roughening (2) CNT -rich regions (3) Interface improved (4) But still some pull-out (5) Crack deflection limited | Initial matrix toughening due to CNT addition with moderate crack deflection and improved interface continuity |
S5 | (1) Highly cohesive fracture surface (2) Matrix uniformly rough (fine granular texture) (3) Fibers almost fully embedded (4) Minimal voids Crack bridging and deflection evident | Optimal CNT dispersion leading to maximum energy absorption, effective crack bridging, and highest tensile strength |
S6 | (1) Presence of larger agglomerates (2) Voids around clusters (3) Local debonding despite overall good interface (4) Some cracks emanating from cluster regions | Over-reinforcement effects where CNT agglomeration induces stress concentration and premature local failure |
