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Large tow carbon fiber (LTCF) has excellent performance and low cost. However, there are still many difficulties in the application of LTCFs, among which the problem of interfacial penetration is mainly solved. Building interfaces with sizing structures of fiber composites is an effective approach to achieve high performance. In this article, a water-based epoxy sizing agent suitable for LTCF fiber thermoset composites was studied. A comparison of the five LTCFs in this study shows that the wettability and contact angle of the sized LTCFs are significantly improved. In addition, the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) increased from 52.3 to 71.0 MPa (35%) and 36.4 to 54.6 MPa (50%), respectively. Compared with other imported LTCFs, domestic large-size LTCFs have a wide variety and a large number of surface functional groups, thereby improving their wettability and covalent bonding with the resin matrix. This work has reference significance for the practical application and industrial production of LTCFRP. [ABSTRACT FROM AUTHOR]

In this work, a dicyclopentadiene monomer/Grubbs 2 catalyst was added to a mixture of epoxy oligomers and methyl nadic anhydride to obtain a poly‐dicyclopentadiene (DCPD) modified epoxy cross‐linked network via sequential curing. The hybrid resin was used as a matrix for preparing carbon fiber composites. The results indicated that the addition of DCPD monomers significantly reduced the viscosity of the epoxy resin. The toughness and heat resistance of the co‐cured resin was improved without significant loss of strength, which was attributed to the high compatibility between epoxy and the modifier polymer. Regarding the composites, the flexural strength of the hybrid resin‐derived composite first increased and then diminished slightly. Meanwhile, the mode‐I interlaminar fracture toughness continued to increase with the increase of PDCPD content compared to the non‐modified composites. Generally, the change trend of the above properties in the composites was consistent with the change trend of the strength and toughness exhibited in the bulk resin with increasing PDCPD contents, while the change extent was inconsistent due to factors such as fiber volume content and interfacial bonding. Highlights: The epoxy/PDCPD hybrid resin system was obtained via sequential curing.The PDCPD as modifier can reduce the viscosity of the epoxy curing system.The toughness and heat resistance of the PDCPD modified epoxy resin was improved.The loss in flexural strength of the hybrid resin system was insignificant.The GIC of the epoxy composites modified with PDCPD improved appreciably. [ABSTRACT FROM AUTHOR]

Weak interfacial bonding properties between thermoplastic liners and carbon fiber‐reinforced composites (CFRP) can easily lead to debonding failure, which is a major challenge in development of type IV composite hydrogen storage vessels. We optimized Box–Behnken design atmospheric‐pressure plasma process parameters for maximizing interfacial bonding properties between thermoplastic liner (PA11 liner) and CFRP using Design‐Expert software. From various designs, plasma process parameters, including time (t), nozzle‐to‐specimen distance (d) and gas flow rate (r) of treatment were selected for optimization to assess the effects of their interactions on climbing drum peel (CDP), flatwise tensile (FWT) and asymmetric double cantilever beams (ADCB). The CDP strength, FWT strength and strain energy release rate (GADCB) of untreated samples were 4.2 N·mm/mm, 0.26 MPa and 87.2 J/m2, respectively. After the plasma treatment, optimum process parameters of t = 200 s, d = 12.5 mm, and r = 700 L/h were used to achieve 33.8 N·mm/mm, 2.97 MPa and 1008.4 J/m2, respectively, which were 8.0, 11.4 and 11.6 times that of untreated PA11 surface, respectively. This method has the potential for guiding thermoplastic liner surface treatment of type IV hydrogen storage vessels before winding. [ABSTRACT FROM AUTHOR]

In this work, the tackified PDCPD (PDCPD-T) specialized for vacuum assistant resin infusion process (VARI) was developed. The epoxy resin and methyl nadic anhydride (NMA) was subsequently added to the PDCPD-T to improve the interfacial bonding with the carbon fibres. The results showed that the introduction of NMA-cured epoxy undermined the mechanical properties of the PDCPD-T owing to the agglomeration of the tackifier particles. Nonetheless, the mechanical properties of the CFRCs based on the co-cured blends of the PDCPD-T and the NMA-cured epoxy were comprehensively improved compared to the composites based on the PDCPD-T. The improvement was that a part of NMA-cured epoxy in the co-cured blends would phase separate on the surface of the carbon fibre, which formed the "bridge" connecting the matrix and the carbon fibre. In addition, the degree of the tackifier agglomeration would also decrease due to the decrease in the surrounding epoxy concentration. [Display omitted] • The continuous carbon fiber reinforced polydicyclopentadiene (PDCPD) composites based on the vacuum-assisted resin infusion process are realized by tackifying the dicyclopentadiene (DCPD) monomer. • The further addition of anhydride-cured epoxy resin to the tackified DCPD monomer solves the problem of poor interfacial bonding between the PDCPD resin and the carbon fiber. • The carbon fiber composites based on the modified PDCPD matrix are proved to be far superior in interlaminar fracture toughness and impact resistance than the epoxy-based composites. [ABSTRACT FROM AUTHOR]

The fiber-reinforced composite (FRP) shaft need to consider vibration performance of the transmission system to improve work efficiency, comfort, service life and safety. The fiber materials and tubes containing metal connectors are important parts of the FRP shaft so that the study on the vibration performance of these two key components is of great significance for an in-depth understanding of the vibration performance of shafts. The finite element analysis (FEA), pulse vibration excitation technique (PVET) and formula computing were used to study the effect of the vibration characteristics of shafts. This study revealed that increasing the modulus of the fiber is one of the effective methods to increase the natural frequency of the FRP tube and the damping ratio of the carbon FRP tubes were slightly smaller compared with basalt and glass fiber. The FEA of FRP tube results were not distinct from the measured and calculated results so that these FEA results were relatively reliable. The damping of the tube with metal flanges at both ends were weaken compared the FRP tube. This work will be of great significance to the optimization design of the vibration performance of FRP shafts. [ABSTRACT FROM AUTHOR]