Effect of carbon nanofiber z-threads on mode-I delamination toughness of carbon fiber reinforced plastic laminates

Abstract

Delamination is a major drawback of carbon fiber reinforced plastics (CFRPs). Studies have reported that carbon nanofibers (CNFs) can improve the delamination toughness of various FRPs. However, lack of CNF alignment control caused substantial uncertainty in the improvements. In this study, a novel CNFs z-threaded CFRP (ZT-CFRP), which utilized z-aligned CNFs as long-range reinforcement threading through the packed carbon fiber bed, was manufactured. The mode-I delamination toughness (G IC) of the ZT-CFRPs was tested against both control CFRPs and unaligned CNF-modified CFRPs (UA-CFRPs). Through statistical comparison against control CFRPs, UA-CFRPs exhibited a relative change in mean G IC and coefficient of variation of +13.99% and +116.35%, respectively, whereas the ZT-CFRPs of equivalent CNF concentration exhibited a relative change in mean G IC and coefficient of variation of +28.93% and-12.33%, respectively. Accordingly, the CNF z-threads were found to play a positive role in toughening CFRPs, as supported by delamination experiments and microscopy analysis.

Loading rate effects on mode-I delamination in glass/epoxy and glass/CNF/epoxy laminated composites

“…Additionally, another research gap that needs to be more explored is the rate dependency study of delamination in hybrid reinforced composites. In order to address the delamination susceptibility of fiber-reinforced plastics (FRPs), different methods have been studied, including matrix modification by nano-reinforcements [20][21][22][23][24]. It has been frequently reported that the quasi-static G IC of fiber-reinforced epoxies can be increased by adding nanofillers without compromising their outstanding in-plane mechanical characteristics.…”

“…It has been frequently reported that the quasi-static G IC of fiber-reinforced epoxies can be increased by adding nanofillers without compromising their outstanding in-plane mechanical characteristics. Due to their high aspect ratio and superior mechanical properties, Carbon nanofibers (CNFs), as a promising candidate material have been utilized in numerous studies [22][23][24][25][26][27][28]. This extensive research background reveals a good potential for adding CNFs to the pure resin in laminated FRPs as a beneficial and low-cost reinforcing method to improve G IC .…”

Enhancement of Through-Thickness Thermal Transport in Unidirectional Carbon Fiber Reinforced Plastic Laminates due to the Synergetic Role of Carbon Nanofiber Z-Threads

“…The CFRP prepregs used in this study were fabricated using the methods described in Figure 1; note that these steps are described in further detail by the authors in a previous study [16]. The prepreg manufacturing processes used in this study, including both the hand wet lay-up process (used for the control CFRPs and the UA-CFRPs) and the sponge transfer process (used for the ZT-CFRPs), were performed on single plies of carbon fabric to minimize any potential particle filtering effect.…”

“…Previously reported CFRP and CNF zthreaded CFRP composite prepreg manufacturing process data were used to support this study and are available at [doi:10.1016/j.compositesa.2016.10.022]. These prior studies (and datasets) are cited at relevant places within the text as references [16].…”

“…The necessity for multiscale reinforcements in CFRPs that utilize high aspect ratio nanoparticles led to the recent development of CNF z-threaded CFRPs (ZT-CFRPs) [16], which utilize the desirable length of CNFs (approximately 10-100 times longer than the carbon fiber diameter) to achieve a long-range threading effect in the carbon fiber array. The z-threaded CNF network within ZT-CFRPs has been shown to increase both interlaminar fracture toughness [16] and through-thickness electrical conductivity [17,18]; however, no previous studies have characterized the contribution of these CNF z-threads on thermal transport in the z-direction. This paper experimentally and analytically investigates the effect and role of CNF z-threads regarding through-thickness thermal conductivity enhancement of unidirectional CFRPs.…”