The Thickness Effect of PSF Nanofibrous Mat on Fracture Toughness of Carbon/Epoxy Laminates

Carbon nanotube (CNT)‐polyetherimide (PEI) hybrid nanofibrous veils were prepared through the electrospinning process to function as an interlayer in carbon fiber reinforced polymer composites (CFRP), and the effects of the addition of the hybrid fiber veils on the interlaminar fracture properties and flexural properties of CFRP were investigated. The results showed that interleaving CNT/PEI hybrid veils can effectively avoid long‐troubled trade‐off between mode‐I interlaminar fracture toughness and in‐plane properties when using thermoplastic toughening materials. Specifically, the GIc value and flexural strength of the laminates were increased by as much as 86.2% and 14.3%, respectively when CNT content was reached up to 0.7 wt% in CNT/PEI hybrid veil. This method adopts ultra‐low PEI and CNT additions, and the limited quantity of these additives demonstrates a notably high interlaminar toughening efficiency while concurrently enhancing the strength, rendering it a promising strategy for both toughening and strengthening.Highlights PEI is used as a carrier to transport CNT to the CFRP interlaminar layers. PEI‐CNT hybrid fiber veils improve GIC and flexural strength of CFRP. PEI‐CNT hybrid fiber veils impede crack expansion through various mechanisms. This method adopts ultra‐low PEI and CNT additions.

Towards developing advanced CFRP with simultaneously enhanced fracture toughness and in‐plane properties via interleaving CNT/PEI hybrid veils

Weng,

Liu,

et al. 2024

Interlaminar toughening of carbon fiber/epoxy composites via interleaving co‐polyamide (Co‐PA) veils

Alshrif,

Peng,

Yang

et al. 2024

Thermoplastic veil interlayers offer a promising approach to improve interlaminar reinforcement in composite materials. This study investigates co‐polyamide (Co‐PA) interleaved veils, fabricated through the hot melt adhesive (HMA) technique. These veils are then applied with varying areal weight densities as interleaves to simultaneously toughen and strengthen carbon fiber/epoxy (CF/EP) composites, utilizing the vacuum‐assisted resin infusion (VARI) method. Integrating Co‐PA veils with a low melting point in the interlaminar of CF/EP composites improves compatibility and promotes strong adhesion between thermoplastics and epoxy resins. As result, The Co‐PA laminates exhibited significant improvements compared with the untoughened composites, with a maximum enhancement of 148.1% and 67.8% for Mode‐I (GIC) and Mode‐II (GIIC), respectively. Moreover, ILSS, tensile strength, and flexural strength improvements were also 20.9%, 34.9%, and 14.5%, respectively. The fracture surface analysis via scanning electron microscopy directly revealed the crack propagation on the fracture surfaces of Mode‐I and Mode‐II specimens. This analysis revealed that Co‐PA demonstrated excellent compatibility with epoxy resin, melts during the stage of epoxy curing, and undergoes phase separation in the later stage, resulting in the formation of “bead‐like” structures within the fibrous network. Remarkably, this structure significantly enhanced the toughness of the CF/EP composites. The Co‐PA veils can improve the interlaminar toughness of CF/EP composites due to their compatibility with the epoxy matrix and high inherent toughness and strength. This method is straightforward to manage and can be utilized for manufacturing large‐scale composite materials incorporating CF fabrics, demonstrating promise for industrial applications.Highlights With its low melting point, co‐polyamide helps prevent structural failure or excessive damage and is proposed to be utilized in composites to enhance the interlaminar fracture toughness properties. The effects of Co‐PA veils of different areal densities on the mechanical characteristics of interlaminar composites were examined. Co‐polyamide particles with fiber‐carbon laminates offer superior fatigue properties and an optimum carbon fiber‐bridging mechanism. Co‐polyamide veils with CF/EP laminates are feasible for structural use in high‐tech automotive applications.

Investigating the effect of Nylon 6.6 electrospun nanofiber mats and punch—Die clearance on the damaged area and residual strength of punched glass/epoxy composite laminates

Gholizadeh,

Nikbakht,

Mollaei Dariani

2024

In this study, interleaving electrospun Nylon 6.6 nanofibers in the laminate was utilized to improve interlaminar properties of glass/epoxy composite during punching and as a solution to this issue. In order to do so, virgin and nano modified samples are produced and punched and the results are compared to determine the effect of nanofibers on the damaged area as well as the three‐point bending residual strength (carried out on both penetration and exit sides) of the punched laminate. Furthermore, punch—die clearance was also varied to investigate the range in which the nano modification improves the outcome of the process on the laminated composite. According to results of this study, using of Nylon 6.6 nanofibers between composite layers causes significant decrease in the damaged area up to 50%. Also, in both virgin and nano modified laminates, increasing the punch—die clearance increases the damaged area up to 50% and reduces the residual strength of the laminates up to 17%. In addition, nano modified laminates, the residual strength increased up to 28% and 22% for three‐point bending tests carried out on both punch penetration‐ and exit‐side samples, respectively. This is due to the fact that the punch exit‐side contains more damage compared to the penetration‐side.Highlights Toughening glass/epoxy laminates using electrospoon Nylon 6.6 nanofibers. Decreasing the damage area occur in the punching of composite laminates. Decreasing the damage area in punching by decreasing the punch‐die clearance. Increasing the strength of punched laminates by applying nanofibers.