Thermoreversible Bonds and Graphene Oxide Additives Enhance the Flexural and Interlaminar Shear Strength of Self-Healing Epoxy/Carbon Fiber Laminates

Abstract

In the current era of high-strength, lightweight, and durable aircraft components, the need for carbon fiber-reinforced epoxy (CFRP) laminates is highly desired owing to their high specific strength and modulus, low coefficient of thermal expansion, and tunable properties that are unmatched by other materials. However, such components’ catastrophic failure occurs due to the interfacial defects and debonding, thereby reducing service life and economic viability. Therefore, there is a pressing need to enhance the mechanical properties of CFRPs through matrix and fiber modifications and introduce the components’ self-healing ability under a natural trigger. This study assessed the crucial role of “thermoreversible bonds” and graphene oxide (GO) “interconnects”, which worked in tandem toward significantly improving the mechanical properties and imparting self-healing properties in CFRP laminates. The laminates were fabricated with varying percentages of GO-modified epoxy matrix via vacuum-assisted resin transfer molding (VARTM) method. The carbon fibers were covalently modified with bis-maleimide (BMI) to establish a thermoreversible bond with GO at the fiber matrix interface to make interconnects. Flexural strength and interlaminar shear strength (ILSS) values for the optimized GO-modified epoxy laminates with BMI-deposited carbon fibers exhibited a significant increase of 30 and 47%, respectively. After a self-healing cycle triggered at 60 °C, they exhibited a recovery in their ILSS values up to 70%. These improvements are particularly useful for aircraft wings made up of CFRP laminates.

Graphene oxide-mediated thermo-reversible bonds and in situ grown nano-rods trigger ‘self-healable’ interfaces in carbon fiber laminates

“…BMI was deposited over neat CFs in a covalent functionalization route following the protocol established in our previous work. 44 De-sized CF was first subjected to OH treatment, followed by APTES treatment, and was finally immersed in BMI (DMF) solution to complete the functionalization process.…”

“…A self-healing efficiency of 70% in terms of ILSS, with an improvement in mechanical properties was reported. 44…”

“…A self-healing efficiency of 70% in terms of ILSS, with an improvement in mechanical properties was reported. 44 In this work, we have provided a detailed chemical analysis of the synthesis and growth of uniform ZnO nano-rods on the surface of CFs using the successive ionic layer adsorption and reaction (SILAR) technique. We have studied the chemistry behind the interaction of such rods with both the fiber and the matrix.…”

Tuneable chemistry at the interface and self-healing towards improving structural properties of carbon fiber laminates: a critical review

“…Recent work by Banerjee et al 131 focused on designing a protocol for modified CFRP laminates with improved mechanical strength properties as well as self-healing behavior through modifications on both the bulk epoxy matrix and carbon fiber surface. A Diels'–Alder (D–A) reaction with GO dispersed in epoxy and BMI covalently coated over the carbon fiber surface led to increased flexural strength and ILSS by 30% and 47%, respectively.…”

Interfacial reinforced carbon fiber composites inspired by biological interlocking structure

“…The main purpose of these strategies is to improve the interfacial bonding strength between fibers and the matrix by providing more physical contact for mechanical interlocking, thereby creating rich active groups or good wettability for chemical bonding ( Karnati et al., 2020 ; Raphael et al., 2018 ; Sharma et al., 2014 ). Many methods for surface modification of CFs were proved to be effective, including sizing, coating ( Sepe et al., 2018 ; Nie et al., 2017 ; Su et al., 2021 ; Acar et al., 2020 ), chemical grafting ( Cheng et al., 2018a , 2018b ; Nasser et al., 2019 ; Banerjee et al., 2021 ; Krushnamurty et al., 2016 ; Jia et al., 2021 ), oxidation treatment ( Prakash and Rajadurai, 2017 ; Dai et al., 2011 ; Andideh and Esfandeh, 2016 ; Wang et al., 2019 ; Chukov et al., 2019 ; Sun et al., 2020 ), adding nanoparticles ( Lau et al., 2013 ; Yao et al., 2021 ; Liu et al., 2021 ; Kurtulus et al., 2021 ), etc. Unfortunately, strong acid or toxic polar organic reagent treatments are easy to cause defects on the fragile surface of CFs, sacrificing the inherent tensile strength of the CFs in some degree.…”