Effect of Dispersing Multiwalled Carbon Nanotubes and Graphene Nanoplatelets Hybrids in the Matrix on the Flexural Fatigue Properties of Carbon/Epoxy Composites

Yi-Ming Jen,Wei-Lun Ni

doi:10.3390/polym14050918

Abstract

The synergistic effect of applying hybrid nanoparticles in improving the fatigue property of fiber reinforced polymer composites has rarely been explored before. Hence the monotonic and fatigue flexure properties of the carbon fiber reinforced epoxy laminates with matrix modified by multiwalled carbon nanotubes and graphene nanoplatelets were experimentally studied herein. The nanofiller ratio applied in the matrix modification was considered as a variable in the experimental program to investigate the effect of nanofiller ratio on the studied mechanical properties. A synergistic index has been employed to evaluate the synergistic effect of hybrid nanoparticles on the studied properties successfully. Experimental results show that the laminates with matrix modified under a nanofiller ratio (multiwalled carbon nanotube: graphene nanoplatelet) of 9:1 have the higher monotonic and fatigue strengths than those modified under other nanofiller ratios. The monotonic flexural strength and fatigue limit of the specimens modified under a nanofiller ratio of 9:1 are higher than the neat laminate specimens by 9.3 and 11.0%, respectively. The fatigue limits of the studied nano-modified laminates increase with the static strengths. Adding hybrid nanoparticles under proper nanofiller ratios in the matrix can suppress the degradation of the stiffness, further increase the resistance to fatigue damage. Examining the fracture surfaces of fatigued specimens reveals that the pullout/bridging effects of carbon nanotubes and the crack deflection effect of graphene nanoplatelets are the main reinforcement mechanisms in enhancing the fatigue strength of the composites.

Highlights

Owing to the characteristics of light weight, high specific strength, specific stiffness, and corrosion resistance, etc., fiber reinforced polymer (FRP) laminates have been widely applied in the aerospace, automobiles, shipbuilding, and construction industries
Understanding the mechanical properties of the FRP composites subjected to various types of loading are critical to the application of these composite materials
It is found that for all carbon fiber reinforced epoxy (Cf/Ep) composite specimens with matrix modified under different nanofiller ratios, the load–displacement curves present linear behavior from the beginning of the monotonic tests till the applied loads reach the peak values

Summary

Introduction

Owing to the characteristics of light weight, high specific strength, specific stiffness, and corrosion resistance, etc., fiber reinforced polymer (FRP) laminates have been widely applied in the aerospace, automobiles, shipbuilding, and construction industries. The FRP laminates with appropriately designed ply-sequences have excellent in-plane properties. The poor out-of-plane properties due to the fabrication of building-up laminates reduce the structural applicability of FRP composites significantly. Many efforts, such as three-dimensional weaving, embroidery, stitching and braiding [1–4], have been made to improve the interlaminar properties of the FRP laminates. Some in-plane strengths or properties may be lost due to the misalignment of fibers or ununiform distribution of resins when applying these techniques

Methods

Results

Conclusion