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In this study, halloysite nanotubes (HNTs) were heat-treated at various temperatures in order to minimize particle aggregation, and the mechanical properties in the humid environment was compared and analyzed to prevent the pore formation and achieve an optimal bonding with epoxy resin. As a result, the glass fiber-reinforced plastic (GFRP), with 0.5 wt.% heat-treated HNT at 700${}^{\circ }$C, showed the highest moisture absorption resistance, tensile strength and interlaminar shear strength.

In the nanocomposite, the dispersion and bonding properties of the nanoparticles at the interfaces were major factors that were related to the physical properties of the final product. Nanoparticle aggregation mainly occurs in the dispersion process between nanoparticles and a polymer. In addition, re-aggregation phenomenon generates by large amounts of pores during curing process. In this case, it was necessary to break the physical bonds, such as the attraction between the initial nanoparticles, and achieve a smooth chemical bonding with the polymer. In this study, the effect of halloysite nanotube (HNT) dispersion on the interfacial bonding was compared and analyzed in $70^{\circ }\mathrm{\text{C}}$ high temperature water environment over 30 days by adding 0.5 wt.% HNT to glass fiber reinforced plastic (GFRP) and basalt fiber reinforced plastic (BFRP). As a result, the HNT contributed to disturbing the moisture absorption rate. It has great effect on thinner lamination part. Moreover, the thicker the lamination, the less the HNT re-aggregation occurred on the curing process. This phenomenon showed a uniform dispersion in the entire laminate area. The weight recovery rate by moisture absorption was high in the HNT-glass fiber (GF), because structural relationship between HNT and GF are larger than in epoxy resin.

In this study, halloysite nanotubes (HNTs), an environmentally friendly inorganic nanomaterial, was added to epoxy matrix glass and basalt fiber reinforced plastics (GFRP and BFRP) by heat treatment of HNTs with crystalline and amorphous structure at $700^{\circ }\mathrm{\text{C}}$ and $1000^{\circ }\mathrm{\text{C}}$. Their interfacial bonding strength and effect of HNTs before and after carbonization by flame were analyzed. We found that the HNT/epoxy formed a physical barrier on the surface because of the char generated by carbonization. The barrier showed excellent thermal stability and limiting oxygen index in BFRP. The flexural strength after carbonization was low in the amorphous 1000HTHNT-BFRP with strong interfacial bonding. In other words, the morphological structure of the HNTs helped the improvement of the interfacial bonding strength; hence, the reinforcing effect of the HNTs on the thermal stability and mechanical strength before and after carbonization can be controlled.

Glass fiber–halloysite nanotube (GF/HNT) nanocomposites were fabricated with different numbers of fiber layers and were exposed to a high-temperature water environment to analyze the role of the HNTs regarding the relationship of interface between the fibers and the moisture absorption behavior. The sections of the GF/HNT nanocomposite plates were divided, and the change in the moisture absorption rate was measured. As a result, the ratio of the HNT to epoxy resin was not related to the water deterioration phenomenon according to the fiber-laminated thickness. However, in the curing process after the vacuum bag molding, the external pressure that was applied to each interface influences the flow characteristics and promotes the occurrence of HNT agglomeration, which interferes with interfacial crosslinking.

This paper presents an investigation into the effect of particle accumulation on an amorphous halloysite nanotube (A-HNT)/Carbon fiber reinforced plastic (CFRP) laminate, fabricated through Vacuum-assisted Resin Transfer Molding (VaRTM). Resin blending and Electrophoretic deposition (EPD) methods were impeded to incorporate the A-HNTs. Bending, short beam shear (SBS), and end-notched flexure (ENF) tests were individually conducted on three sections, which were divided from an integral CFRP laminate. The anchoring effect of the carbon fibers and the scouring effect of the resin flow together lead to the different A-HNT accumulation patterns in both incorporation methods, and thus caused the observed distinctions in the properties of each separated section. Extensively incorporated A-HNTs showed a tendency to aggregate, resulting in the degradation of the material’s properties.

There are numerous methods for reinforcing laminate composites using nanoadditives. However, the random dispersion of nanoparticles in polymer resins leads to critical defects owing to excessive dispersion. This study investigated a method of depositing halloysite nanotubes (HNTs) on a carbon fabric surface via electrophoresis deposition (EPD) for reinforcing the through-thickness strength of carbon fiber-reinforced plastic (CFRP) composites. The voltage during the EPD process was set as 6–12 V, which is the working range for nanoparticles during EPD. In addition, CFRPs were fabricated from modified carbon fabrics using vacuum-assisted resin transfer molding. The optimum voltage was determined as 6 V. At higher voltages, the mechanical properties deteriorated owing to the distribution of HNTs and damage to the fibers. The performance of the EPD-modified CFRPs was better than that of neat CFRPs. The highest strength was observed at 0.7 wt.% HNTs and 6 V, which indicated the feasibility of the EPD process and a well-dispersed morphology. The strong interaction of HNTs with carbon fabric influences the through-thickness mechanical properties of CFRP composites.