Concentration-Dependent Interlaminar Fracture Toughening in Carbon, Glass, and Hybrid Fiber-Reinforced Polymer Laminates via MWCNT Interlayers
- 1State Key Laboratory of Rail Transit Vehicle System, Southwest Jiaotong University, Chengdu 610031, China
- 2School of Automobile, Chang’an University, Xi’an 710064, China
- 3Chang’an Dublin International College of Transportation, Chang’an University, Xi’an 710018, China
Abstract
Fiber-reinforced polymer (FRP) laminates are prone to delamination because they lack continuous through-thickness reinforcement. Although multi-walled carbon nanotube (MWCNT) interlayers can improve interlaminar resistance, evidence has focused mainly on unidirectional carbon fiber-reinforced polymer (CFRP) and individual fracture modes. This study compared Mode I propagation and Mode II initiation toughness in CFRP, glass fiber-reinforced polymer (GFRP), and two carbon/glass hybrid laminates (HCRP and HGRP). Each system included unmodified (ORI), neat-epoxy interlayer (CON), and 0.1, 0.3, and 0.5 wt.% MWCNT conditions. The laminates were fabricated by N,N-dimethylformamide-assisted ultrasonication and hot pressing, and examined by ASTM D5528 double cantilever beam testing, ASTM D7905 end-notched flexure testing, and scanning electron microscopy. ORI and CON exhibited comparable toughness, indicating little contribution from the neat-epoxy interlayer alone. In all four systems, both toughness measures increased from 0.1 to 0.3 wt.% and decreased at 0.5 wt.%. At 0.3 wt.%, steady-state Mode I toughness increased by 31.2–51.2% and Mode II initiation toughness increased by 4.0–23.1% relative to CON. GFRP showed the highest absolute Mode I toughness, HCRP showed the largest Mode II improvement, and HGRP exhibited limited Mode II sensitivity. Matrix tearing, shear cusps, tortuous crack features, and distributed MWCNT pull-out at 0.3 wt.% contrasted with smoother regions, bundled or agglomerate-like structures, and cavities or pores at 0.5 wt.%. The effective MWCNT content therefore reflects a balance between nanotube-mediated energy dissipation and defect formation, modulated by fiber architecture and fracture mode.
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BibTeX
@article{zhang2026concentrationdependent,
title = {{Concentration-Dependent Interlaminar Fracture Toughening in Carbon, Glass, and Hybrid Fiber-Reinforced Polymer Laminates via MWCNT Interlayers}},
author = {Shile Zhang and Ju Yang and Xiang Peng and Lvze Dai and Dongdong Chen and Guohua Zhu and Zhen Wang},
journal = {Polymers},
year = {2026},
month = oct,
doi = {10.3390/polym18202515},
url = {https://www.mdpi.com/2073-4360/18/20/2515},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Concentration-Dependent Interlaminar Fracture Toughening in Carbon, Glass, and Hybrid Fiber-Reinforced Polymer Laminates via MWCNT Interlayers
AU - Shile Zhang
AU - Ju Yang
AU - Xiang Peng
AU - Lvze Dai
AU - Dongdong Chen
AU - Guohua Zhu
AU - Zhen Wang
PY - 2026
DA - 2026/10/14
JO - Polymers
DO - 10.3390/polym18202515
UR - https://www.mdpi.com/2073-4360/18/20/2515
AB - Fiber-reinforced polymer (FRP) laminates are prone to delamination because they lack continuous through-thickness reinforcement. Although multi-walled carbon nanotube (MWCNT) interlayers can improve interlaminar resistance, evidence has focused mainly on unidirectional carbon fiber-reinforced polymer (CFRP) and individual fracture modes. This study compared Mode I propagation and Mode II initiation toughness in CFRP, glass fiber-reinforced polymer (GFRP), and two carbon/glass hybrid laminates (HCRP and HGRP). Each system included unmodified (ORI), neat-epoxy interlayer (CON), and 0.1, 0.3, and 0.5 wt.% MWCNT conditions. The laminates were fabricated by N,N-dimethylformamide-assisted ultrasonication and hot pressing, and examined by ASTM D5528 double cantilever beam testing, ASTM D7905 end-notched flexure testing, and scanning electron microscopy. ORI and CON exhibited comparable toughness, indicating little contribution from the neat-epoxy interlayer alone. In all four systems, both toughness measures increased from 0.1 to 0.3 wt.% and decreased at 0.5 wt.%. At 0.3 wt.%, steady-state Mode I toughness increased by 31.2–51.2% and Mode II initiation toughness increased by 4.0–23.1% relative to CON. GFRP showed the highest absolute Mode I toughness, HCRP showed the largest Mode II improvement, and HGRP exhibited limited Mode II sensitivity. Matrix tearing, shear cusps, tortuous crack features, and distributed MWCNT pull-out at 0.3 wt.% contrasted with smoother regions, bundled or agglomerate-like structures, and cavities or pores at 0.5 wt.%. The effective MWCNT content therefore reflects a balance between nanotube-mediated energy dissipation and defect formation, modulated by fiber architecture and fracture mode.
SN - 2073-4360
ER -