Enhancing Strength and Toughness of Hierarchical Composites through Optimization of Position and Orientation of Nanotubes: A Computational Study

Abstract

Hierarchical composites that combine microscopic fibers and carbon nanotubes (CNTs) offer opportunities to further improve mechanical properties. Motivated by the experimental evidence that the spatial distribution of CNTs has a significant effect on the strength and toughness of these composites, we developed a novel modelling tool to help us explore mechanisms of strengthening and toughening in an efficient way. The spatial position and orientation of CNTs are chosen as design variables and their optimization is performed on the example of a unidirectional fiber-reinforced composite (FRC) subjected to transverse tensile loading. The model relies on the use of genetic algorithm and finite element method. Our modelling results show that the CNT network with an optimized morphology suppresses stress concentrations in the matrix near the fibers. The optimized morphology is shown to activate a new strengthening and toughening mechanism—diffusion of damage at micro-scale. It allows substantial increase in the consumption of the strain energy by matrix cracking, delocalization of damage, and with it, improvement of the strength and toughness. When the network morphology of 1.0 wt% of CNTs is optimized, the strength and toughness are increased by 49% and 65%, respectively, compared to the pristine FRC. The same amount of homogenously distributed CNTs in the composite leads to only 2% of the strength increase accompanied by a 13% decrease in toughness. The work emphasizes the importance of optimizing spatial position and orientation of CNTs for the strength and toughness improvements of composites.

Multi‐walled carbon nanotubes/carbon fiber fabric multiscale hybrid materials for improving the mechanical and tribological properties of phenolic resin composites

“…CFR‐C2 has the minimum wear rate among the four composites. The specific reason for the improvement in wear resistance can be attributed to three aspects: (i) MWCNT increase the mechanical interlocking between fiber and matrix, enhancing the wear resistance; (ii) MWCNT/carbon fabric multi‐scale hybrid materials play synergistic effects between nano‐scale MWCNT and micro‐scale carbon fiber reinforcements 30 ; (iii) friction film could be formed during the friction process, providing wear protection and increasing the surface lubrication 31 . Besides, the wear rate of CFR‐C3 slightly increase compared with that of CFR‐C2.…”

Impact of Carbon Nanotubes on the Mechanical and Electrical Properties of Silicone

“…By filling epoxy resins with carbon nanotubes, the strength properties of the resulting nanocomposite can be modifieddepending on the resin and nanotubes used. According to Ciecierska et al (2015), Ganesh et al (2017), andLiu et al (2020), the highest strength of the obtained nanocomposite is observed at a content of 0.1%-0.5% by weight of nanotubes, and according to the work (Smoleń et al, 2021) at a content of 1.5%. Increasing the amount of nanofiller added results in a decrease in the strength of the material.…”

Enhancing the Mechanical Performance of Fiber‐Reinforced Polymer Composites Using Carbon Nanotubes as an Effective Nano‐Phase Reinforcement

“…Other finite element modeling [ 143 ] at dual‐scales demonstrated four failure types in CNT‐grafted FRPs using the CNT tensile strength and CNT/matrix interfacial strength as a means of comparison. The four failure modes are listed as follows: (I) denoted low CNT‐matrix interfacial strength that led to excessive CNT debonding from the fiber and fiber debonding; (II) CNTs partially debonding and matrix cracking, (III) CNT debonding, fiber debonding, and CNT detachment simultaneously, and (IV) fiber debonding and then CNT debonding.…”

“…These events can significantly enhance the toughness of FRPs. [ 99,143 ] In particular, analytical research has revealed that crack bridging by CNTs and their subsequent fracture can contribute considerably to increases in the interlaminar fracture toughness of the CNT‐FRPs. [ 152 ] CNT bridging can also induce crack deflection [ 146 ] and prevent delamination, [ 153 ] which provides significant energy absorption during the fracture of FRPs.…”