Effect of Nano-Reinforcement Topologies on the Viscoelastic Performance of Carbon Nanotube/Carbon Fiber Hybrid Composites.

Suma Ayyagari,Marwan Al-Haik,Yixin Ren,Dhriti Nepal

doi:10.3390/nano10061213

Abstract

In this investigation, multi-walled carbon nanotubes (MWCNTs) were grown over carbon fiber fabrics via a relatively nondestructive synthesis technique. The MWCNTs patches were grown into three different topologies: uniform, fine patterned and coarse patterned. Hybrid carbon fiber-reinforced polymer composites (CFRPs) were fabricated based on the patterned reinforcements. Tensile tests, dynamic mechanical thermal analyses (DMTA) and flexure load relaxation tests were carried out to investigate the effect of the patterned nano-reinforcement on the static, dynamic, glass transition, and viscoelastic performance of the hybrid composites. Results revealed that the hybrid composite based on fine-patterned topology achieved better performance over all other configurations as it exhibited about 19% improvement in both the strength and modulus over the reference composite with no MWCNTs. Additionally, the increase in glass transition for this composite was as high as 13%. The damping parameter (tan δ) was improved by 46%. The stress relaxation results underlined the importance of patterned MWCNTs in minimizing the stress decay at elevated temperatures and loading conditions. Utilizing patterned MWCNTs topology significantly reduced the stress decay percentage at the thermomechanical conditions 60 MPa and 75 °C from 16.7% to 7.8%. These improvements are attributed to both the enhanced adhesion and large interface area by placing MWCNTs and by inducing an interlocking mechanism that allows the interaction of the three constituents in load transfer, crack deflection and hindering undesired viscoelastic deformations under different thermomechanical loadings.

Highlights

Fiber-reinforced plastics (FRPs), composites based on high strength and stiffness fibers, have long been utilized for structural applications due to their outstanding mechanical properties [1]
While there are several techniques to evaluate the thermal stability of polymers and their composites, such as differential scanning calorimetry (DSC), thermo-mechanical analysis (TMA), thermogravimetric (TGA) and dynamic mechanical thermal (DMTA) analyses, DMTA is most suitable for FRPs as it is sensitive enough to capture the macro and microscale processes and molecular relaxations of the polymeric matrices [2,3]
In several of our pervious investigations, we have shown that growing carbon nanotubes (CNTs) using a nondestructive technique; graphitic structures by design (GSD) can improve the strength, damping parameter, fatigue resistance and interlaminar fracture toughness of Nanomaterials 2020, 10, 1213

Summary

Introduction

Fiber-reinforced plastics (FRPs), composites based on high strength and stiffness fibers (e.g., glass and carbon), have long been utilized for structural applications due to their outstanding mechanical properties [1]. Polymer matrix composites are prone to growing deformation under constant loads (creep) and tend to carry less load under constant displacement (stress relaxation) in relatively long time periods These behaviors are accelerated under elevated temperatures environments. Like many other mechanical properties, the creep compliance and stress relaxation modulus (as two governing material parameters for viscoelasticity) are much weaker along the transverse directions to the fiber orientation [16] This heightens the importance of studying the flexural viscoelastic properties in FRPs where the axial direction is designated as the fiber direction which exhibits the least deformation imposed by time or temperature variations. Most of the previous work focused on functionalizing the fiber or the matrix via chemical means The goal of this investigation is to probe the effects of growing CNTs into different topological patterns on the composites’ rheological properties including the Tg and damping. The investigation characterizes the elastic (tensile) and viscoelastic (load relaxation) performances of composites with different CNTs topologies

Synthesis of Hybrid Reinforcements

Composites Fabrication

Mechanical Testing

Hz 10Hz

Conclusions