Physics and Mechanics of New Materials and their Application

The following sections are included:

• Foreword
• Contents

This paper discusses the influence of Vietnam rare earth (RE) with the composition of 69.4% Ce and 30.5% La (modification content of 4% and 6%) on the microstructure and mechanical properties of Al–5Zn–3.5Mg–1.2Cu alloy when the temperature modification is changed at 750^°C in 150, 200, 250 s. By optical microscopy, the results showed that the microstructure of the modified sample is finer than the nonmodified sample. By the SEM and EDS analysis, at the grain boundaries of this alloy, MgZn₂ and/or Mg₃Zn₃Al₂ intermetallic phases appeared. The modified elements (La, Ce) in RE and aluminum were formed in the intermetallic Al₁₁RE₃ and Al₂RE phases, which prevents the development of the dendritic α phase. The result showed Al–5Zn–3.5Mg–1.2Cu alloy modified with 4% RE in 150 s which is the most optimal result, the grain size is 6.67 μm and the hardness is 107 HB.

Core–shell structure Fe@TiO₂ was synthesized by sol–gel method. The photocatalytic degradation of methylene blue over the Fe@TiO₂ reached 98% under UV light irradiation within 5 h. The band gap of the core–shell Fe@TiO₂ was found to have a redshift through a sintering treatment. The redshifted Fe@TiO₂ had a good performance of methylene-blue degradation (reaching 85%) under visible light irradiation for 5 h.

In this paper, the Photoplethysmography (PPG) signal response of humans under different perceptual stimuli was mainly discussed. The autonomic nervous system (ANS) regulates the functioning of organs or tissues in the body to make the body adapt to the environment. When the human body is stimulated, it can obtain information about ANS from the analysis results of heart rate variability (HRV). The proposed method is used with PPG signals for time domain and frequency domain analysis to obtain HRV parameters and short-time Fourier transform (STFT) output heat map, respectively. Different environmental stimuli were given during the experiment and changes in PPG signals were observed. There were eight males and eight females with a total of 16 subjects with an average age of 24 years. Heart rate was observed to vary with stimulation in 16 subjects. The heat map clearly distinguishes whether the subject is affected by the stimulus and causes the ANS to regulate the human body. The data obtained under various stimuli are directly compared and measured from physiological signals. It can establish an objective patient’s current emotional judgment and can be used to explore the patient’s diagnosis status during the diagnosis process.

Slag fiber has economic and environmental advantages in that it converts a low-value-added material to a high-value-added material. However, although the slag fiber has a chemical composition similar to basalt fiber, its competitiveness in the fiber industry is significantly lower. Moreover, the slag fiber remains in the pre-commercial stage due to the uncertainty and instability of the basic properties. Therefore, in this study, the slag fiber customized through the fiberization process was compared with the existing basalt fiber to analyze the effect of the similarity of chemical composition on the environmental degradation characteristics and mechanical properties under tensile loading. As a result, the slag filament composites showed lower tensile strength due to the weaker interfacial bonding strength with the epoxy matrix than the basalt filament composites, but the difference in decreased tensile strength rate was not significant. In addition, long-term moisture absorption in fresh water and seawater demonstrated excellent moisture absorption resistance.

In this paper, selective laser sintering (SLS) was applied to join two materials by printing Ti–6Al–4V powder on a Ti substrate without any support parts. The characteristics of the interface between the as-built Ti–6Al–4V sample and the substrate were investigated. The analysis indicates that a heat-affected zone (HAZ) and the fish-scale type were formed at the joining area. The combination of smaller grains, acicular α′ martensite, and lamellar (α + β) structures was observed inside the interface zone. The hardness value at the interface area was measured by about 320 HV which is higher than 280 HV of the substrate and smaller than 369 HV of the as-built sample. The results predict that the SLS process is a promising method for manufacturing of hybrid materials.

Mantispids are small brown bugs about 1.5 cm in length. Mantispid eggs are produced in large quantities, with about 1000 eggs per spawning, and are tiny and densely packed. Traditionally, mantispid eggs are counted manually. However, counting such a large quantity of eggs is difficult. To provide accurate data for researchers, we detail methods to accurately detect and count the number of mantispid eggs using image processing. The following methods were used to count the mantispid eggs: background estimation, morphological image processing, background subtraction, stretching, image thresholding, gray-level transformation, labeling and counting. The results of automated counting were compared with the results of manual counting. The segmentation results were verified, and the accuracy of the mantispid egg counts was determined to be 100%. This provides a useful resource for mantispid egg counting. The automatic counting system cannot only count mantispid eggs, it can also be used to count other similar insect eggs.

The vacuum pump usually used traditional curves such as the circular, cycloidal curves and their combinations to construct tooth profile. However, to increase efficiency and design flexibility for the vacuum pump, a novel rotor tooth profile for Roots rotor of vacuum pumps is proposed. Which is named “CEIEC” tooth profile and orderly composed of five significant segments, a circular arc for tooth tip, an epicycloid curve with variable extension, an involute, an enveloped epicycloid curve and a conjugated circular arc for tooth root. A numerical example is presented to evaluate the performance indices for proposed vacuum pump, including the hermeticity coefficients of the rotor mesh gap and tip gap.

This study deals about the influence of vibrations incorporated into a workpiece during powder-mixed electrical discharge machining (PMEDM) on quality measures such as material removal rate (MRR), surface roughness (R_a) and microhardness. It has been found that the low-frequency vibration incorporated into the workpiece positively affects the processing efficiency of electrical discharge machining (EDM) and PMEDM. However, the effect of low-frequency vibration in PMEDM has been better than EDM. The higher vibration frequency significantly improves the MRR and R_a in PMEDM. The MRR has been improved by 95.89% and with lower R_a of 63.2% in PMEDM. The hardness of the machined surface after PMEDM using titanium powder mixed in dielectric liquid was increased approximately two times as compared with conventional EDM.

3D printing technology has emerged as a high value-added industry with high efficiency that has dramatically broken away from the existing material and manufacturing industry’s human-based production system. These technologies, ranging from small parts to large structures, are rapidly developing due to the challenge of various filament materials, whereas there are significant concerns about waste filler materials, and complimentary research is needed to improve them. Polylactic acid (PLA), the representative polymer of 3D printing, contributes to minimizing environmental risks. However, although thermoplastic PLA has excellent reversible properties for heat in terms of sustainable resources, it is degraded as a low value-added material afterward. Therefore, in this study, the effect of repetitive recycling on the mechanical and thermal properties of PLA filaments was analyzed to verify and re-evaluate PLA as a renewable resource. As a result, recycled PLA has decreased tensile and flexural strength by up to 69% and 53%, respectively, compared to initial neat PLA with the increase of the number of repetitive recycling, and this demonstrates the change in the thermal properties of recycled PLA.

In this study, we investigate the effect of fluorine (F₂) flow rate on the crystal characteristics and chemical bonds of Al-Doped ZnO (AFZO) Films. At first, 1 wt% Al₂O₃ was mixed with 99 wt% ZnO to form the Al-doped ZnO ceramic target, the radio frequency (RF) magnetron sputtering method was used to deposit the AFZO films by introducing different flow rates of F₂ gas using F₂/(Ar + F₂) mixing atmosphere during the deposition process. F₂ flow rates (F₂/(Ar + F₂)) were changed in the range of 0 ∼ 0.25%, and F₂ ratio was controlled using the mixing gases of (F₂(5%) + 95% Ar) and pure Ar. AFZO films were deposited on the EagleXG glass and the films’ thickness was about 330 nm by controlling the deposition time. After AFZO films were deposited, their crystalline structure and electrical characteristics were well investigated. Finally, a comparative study of surfaces of AFZO films was investigated using X-ray photoelectron spectroscopy (XPS) to find the variations of the chemical bonds as the deposition temperature and F₂ flow rate were changed.

The classical molecular dynamics (MD) technique was used to investigate the atomistic structure of amorphous hafnium oxide (HfO₂) under pressure. The local atomic structure and the liquid-solid transition of HfO₂ were analyzed for the pair radical distribution functions, bond angle distributions and coordination number. The simulation reveals that although the fractions of structural units HfO_x and OHf_y strongly change with the density, the partial bond angle distributions of these structural units are almost identical for all constructed models. This result has enabled us to establish a relationship between the bond angle distributions and the fractions of structural units.

This paper presents a method for estimating vehicle speed using two roadside passive infrared (PIR) sensors whose optical axes are parallel to each other and perpendicular to the moving direction of vehicles. The vehicle speed was calculated based on the time lag between the two signals received by the PIR sensors, which was evaluated by using cross-correlation analysis. The experiments show that the method has an error of less than 5 km/h over a speed range of 20−60 km/h.

We had successfully synthesized green-emitting phosphors based on Li₂BaSiO₄ material activated by bivalent europium ions (Eu²⁺) using a solid-state reaction method in a reducing gas environment and investigated their luminescence properties. The Li₂BaSiO₄:0.003Eu²⁺ (LSB-Eu) phosphors were synthesized at 850^°C for 1 h, and the reduction gas was removed at 500^°C, 600^°C, 700^°C and 800^°C, respectively. XRD pattern showed that the Li₂BaSiO₄, Ba₂SiO₄ and Li₄SiO₄ phases were observed in the synthesized Li₂BaSiO₄ composition. As the reduction gas was removed at 800^°C, the LSB-Eu phosphor emitted a weak red light rather than a green light. Two weak emission peaks were found at about 588 nm and 613 nm corresponding to ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions. As temperature to remove the reduction gas was lower than 800^°C, the emission spectra of LSB-Eu phosphors reveled a broad peak centered at 501 nm, which emitted a green color. The intensity of photoluminescence excitation (PLE) photoluminescence emission (PL) spectra increased as the removing temperature was decreased from 700^°C to 500^°C and saturated at 500^°C. These results show that LSB-Eu can be a noteworthy candidate of green-emitting phosphor for the investigation of white light-emitting diodes (WLEDs).

The failure mechanism of composites dominates the matrix, fiber and interface, and in general, the matrix corresponds to the definitive cause of damage. A filament–wound composite structure involves a notable bridging effect owing to the matrix between the layers, and particle additives are generally adopted to strengthen the matrix. However, particle additives exhibit a low performance when applied to structures, owing to the dispersibility and particle agglomeration. In this study, the strengthening performance of carbon nanotube (CNT)/epoxy interleaves was experimentally verified to facilitate their implementation in the structural design of a filament–wound cylinder structure. The burst pressure, compression, bending and interfacial bonding strength of the cylinder improved by approximately 20%, 161%, 16% and 36%, respectively, and the positioning of CNT/epoxy interleaves was a more notable influencing factor compared to the proportion of CNTs in the entire winding layer. The number of macro voids decreased inside the epoxy modified CNT. The findings demonstrated that the incorporation of CNTs through CNT/epoxy interleaves could facilitate the matrix strengthening and enhance the interfacial bonding.

This study used rubber fruit shells (RFS) as raw material for making carbon nanotubes (CNTs). The CNTs were carried out by hydrothermal process at low-temperature after carbonization and chemical activation was done. This experiment succeeded in obtaining a bundle of MWCNT (Multi-Wall Nanotube) from the raw material of RFS. The results of characterization using SEM and TEM showed that the resulting CNTs were not homogeneous in diameter, ranging from 13 to 455 nm, with an average diameter of about 179 nm. XRD was used to identify crystallographic structure; it has two peaks 2θ at around 26.0 and 44.0, index to 002 and 101 reflections hexagonal graphite diffraction of the MWCNTs. This study can provide an alternative inexpensive raw material and a simple method to obtain carbon nanotubes.

The production of long cellulose macrofibers starting from nanofibers is still complex and expensive. This study proposes a method of manufacturing long macrofibers from plant fiber bundles by chemically extracting non-cellulosic substances but preserving the original shape of the fibers. Once the cellulosic fiber bundles are dried, the original cellulose nanofibers are bridged to neighboring nanofibers by the formation of hydrogen bonds, giving shape stability and enhanced mechanical properties. By the process, the tensile strength was increased by about 50% and the modulus doubled from the original plant fiber bundles.

In this study, a laser cleaning method was developed in order to replace the existing manual work-based technologies. The experimental investigation analyzed the cleaning properties of the paint and the oxide layer on the steel surface according to the laser beam scanning method. Experiments showed that in the cleaning process, the line beam patterns with a moving stage showed differences in heat input depending on the area, and the square area beam patterns obtained with control of a Galvano scanner showed uniform cleaning performance. The results of this study demonstrated that through the prosed laser cleaning technique, oxide layers as well as paint on steel surfaces can be removed with excellent precision, which is expected to be useful in the development of eco-friendly surface cleaning techniques.

Two dimensional (2D) materials are widely attracting the interest of researchers due to their unique crystal structure and diverse properties. In the present work, tungsten disulfide (WS₂) nanorods were synthesized by a simple method of pulsed laser ablation in liquid (PLAL) environment. The prepared WS₂ are analyzed by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV-visible spectroscopy (UV-vis) and Raman spectroscopy to confirm the surface morphology, phase and structure. A possible growth mechanism of WS₂ is proposed. This study indicates new door for the preparation of 2D materials with specific morphology.

In recent years, the sewer system in Japan is becoming obsolete. It is, therefore, necessary to reinforce or repair without stopping sewer functions by applying a suitable water stopping method. In this study, a multi-layered sewer pipe plug consisting of a protective sheet and inner and outer rubber balls is focused since it can be installed and removed at the construction site in a short time conveniently. This sewer pipe plug has several advantages dealing with various diameters compared to the conventional type. In this study, the rupture test is conducted to improve the water stopping performance. The fractured position of the protective sheet of the sewer pipe plug is investigated experimentally. It is clarified that the maximum stress around the flange portion can be reduced by decreasing the flange inner diameter.

Since Japanese sewer system is becoming obsolete, it is necessary to reinforce and repair the system without stopping sewer functions. In this study, a multilayered sewer pipe plug consisting of a protective sheet and inner and outer rubber balls is focused to be installed and removed conveniently at the construction site. In this paper, a suitable testing method and the strength of the protective sheet are discussed experimentally by changing the specimen geometry providing slit and seams. It is found that the slit specimen is most desirable to obtain the standard tensile strength of UHMWPE cloth named Izanas cloth. It is found that the seamed strength is σ_B = 34 MPa, which is about 17% of the standard tensile strength σ_B0 = 200 MPa.

In this study, the parameters for underwater laser cutting of 50-mm thick stainless steel, which is typically used in nuclear power structures, are investigated. The focal position of laser beam significantly affects the cutting quality. In particular, in the cutting of the thick sample, change in the focal position determines the kerf width and the roughness of the cut surface. Moreover, the effects of the variation of kerf width and the cut surface characteristics on the focal position of the laser beam are investigated. As the focal position moved to the inside of the material, the upper kerf width increased, but the quality of the cut surface was improved.

The rolls are classified into two types; one is a single-solid type, and the other is a shrink-fitted construction type consisting of a sleeve and a shaft. The bimetallic work rolls are widely used in the roughing stands of hot rolling stand mills. Regarding a shrink-fitted construction type, the interfacial slip sometimes appears between the shaft and the shrink-fitted sleeve. This interfacial slip can be regarded as the relative displacement between the sleeve and the shaft. In this paper, the stress due to the interfacial slip is studied because the stress may cause the sleeve fracture. It is found that the stress in the shrink-fitted surface is slightly decreased with increasing number of rotations n. Therefore, the stress obtained by the simulation at n = 2 can be used to estimate the fatigue strength.

This study analyzed the relationship between the defect area identified through a C-scan and the void volume in CF-PEKK composite materials through the water absorption behavior to predict the void volume. The water absorption content varies with the defect area; however, the defect area identified through a C-scan and the water absorption content did not show a proportional relationship. This is because voids are distributed in the through-thickness. The results indicated that the absorption behavior could be used to predict the void volume. Irreversible absorption was found to be independent of the void volume. Further, no matrix degradation was seen with water immersion at 70^°C; however, some local swelling was seen.

Radiation therapy is an essential part of the comprehensive breast cancer treatment strategy, and radiation dermatitis is the inevitable side-effect. According to either patient-related or treatment-related factors, patients will experience different degrees of acute radiation dermatitis. This study proposes a machine learning architecture based on image and time series features. Using the skin image of the irradiated part during radiotherapy, the image feature is extracted with a gray-level co-occurrence matrix (GLCM) and color space, combined with the time series feature with gradient boosting decision trees (GBDT) to predict the severity of dermatitis after seven days of treatment. The results show that, through the combination of image and time series features, the predicted accuracy (ACC) and area under the curve (AUC) can be effectively improved to 0.8 and 0.85 respectively. The results of GBDT show higher prediction accuracy and robustness than AdaBoost algorithm. This framework can be used as an auxiliary diagnostic tool to assist doctors in making appropriate treatments before severe dermatitis occurs, in order to reduce the radiotoxicity caused by radiotherapy of patients.

The purpose of this study is to determine the correct estimation of the concept design and laminating pattern for composites. In this study, the effect of carbon tow prepreg on the composite structure has been investigated. Also, this work evaluated the structural safety according to the laminating pattern and process technique by computer simulation. The laminating pattern of three kinds was designed through the normal shape. Also, process technique of two kinds were carried out in dry and wet method to produce composites structure. The result of FEA showed that the structural safety of carbon tow prepreg is not significantly superior to that of the structure with wet method material. How-ever, considering the benefits of working environment and the reduction of the number of process, the possibility of replacing materials and process technique will be sufficient for composite structure.

When wood materials are used for a mechanical structure, the fatigue strength should be estimated due to repeated loads they receive. This paper reveals that the methods to calculate allowable stresses along with American Society for Testing and Materials (ASTM) and Architectural Institute of Japan (AIJ) can take the strength reduction due to fatigue into account because the ASTM/AIJ allowable stresses against the static strength closely resemble the fatigue limit against the wood static strength.

In this study, a DLC pattern was fabricated through a photolithography process that constitutes a part of the semiconductor process, to investigate the frictional wear characteristics. The photolithography was used to produce negative patterns with a pattern width of 10 µm or 20 µm and a pattern depth of 500 nm on the DLC surface. The change in the coefficient of friction of the surface was investigated through a ball-on-disk tribology test on the fabricated micro/nano-sized DLC pattern. The DLC pattern fabricated by the photolithography process showed a superior coefficient of friction to that of the general DLC sample. These results show that the decrease in the surface friction coefficient of the patterned DLC thin film is due to the reduction in the surface contact area owing to the modification of the micro/nano-texture of the surface as well as the low friction characteristics of the DLC.

In this study, the stress intensity factor (SIF) of an interface kinked crack is analyzed by the singular integral equation of the body force method. The problem can be expressed by distributing the body force doublets of the tension and shear types along all the boundaries of the kinked and interface crack parts. The SIFs can be obtained directly from the densities of the body force doublets at the crack tips. Although the problem has already been calculated using the crack connection model, the accuracy of the analysis has not been clarified. From the analysis results in this study, it can be seen that the SIFs calculated by the crack connection model have a nonnegligible error, and the present method gives more accurate results. The advantage of the present method is that the SIFs of the kinked and the interface crack tips can be obtained at the same time with high accuracy.

The alloy aluminum of 5000 series will have relatively high strength through solid solution strengthening of Mg. However, when laser welding the 5000 series aluminum alloys, the Mg is selectively evaporated by welding heat due to its low melting and vaporization points, resulting in a reduction in the strength of welds. Therefore, laser welding application is difficult because of such a reduction in strength [M. Peel, A. Steuwer, M. Preuss and P. J. Withers, Acta Mater. 51, 4791 (2003); A. Haboudou, P. Peyre, A. B. Vannes and G. Peix, Mater. Sci. Eng. A 363, 40 (2003)]. In this paper, welding experiments were carried out using laser and laser–arc hybrids on aluminum alloy 5083 with 8-mm thickness. Tensile testing, scanning electron microscopy (SEM) analysis and electron probe microanalyzer (EPMA) analysis were carried out on specimens on which the laser and laser–arc hybrid weldings were performed. According to the tensile test results, the tensile strength during laser–arc hybrid welding was greater than 85% of the parent metal. In addition, EPMA analysis showed that the strength of the laser–arc hybrid welds was maintained by supplementing the optional evaporating Mg element, since they use the filler wire.

In this work, we synthesized well-grown cadmium sulfoselenide (CdSSe) microflowers on gold-coated silicon substrate using a simple and low-cost chemical bath deposition technique. The deposited CdSSe film was annealed in a furnace for 30 min at 250°C. Subsequently, the annealed CdSSe film was further characterized using structural, morphological and field-emission analyses. The CdSSe microflowers show photosensitive field-emission behavior. In the photosensitive field emission, the emission current rises by nearly 2−3 times of its primary preset current value of ∼1 μA.

The purpose of this study is to develop a lightweight design model for an 18ft leisure boat. The existing leisure boat is manufactured using glass fiber-reinforced plastics (GFRP) material and the hand lay-up process. Carbon fiber-reinforced plastics (CFRP) was applied to the new design to reduce the boat’s weight, while an automated tape laying machine was applied to the lightweight boat’s manufacturing process to increase boat manufacturing productivity. The newly designed CFRP model is 25% lighter than the existing GFRP model. It was confirmed that the newly designed lightweight hull has sufficient structural integrity compared to the existing hull through the structural integrity evaluation by the FEA.

The purpose of this study is to determine the correct estimation of laminated design for composite materials applied to a ship radar mast. Recently, as the IMO’s environmental regulations have been strengthened to increase the energy efficiency of ships, the IMO has also begun to consider operational economics such as energy reduction through lightening the hull. Demand for lighter weight technology using composite materials is increasing. Examples would include lightweight large structures using composite materials, composite materials replacing metal design parts, and polymer composite materials applicable to marine environments. Therefore, in this study, the properties of the material were analyzed using a simulation program to verify the applicability of the composite material for ship radar mast. In addition, the reliability of the simulation result was secured through Fiber/Matrix/Ply correction and the calculation of the laminate dynamics. The results provide basic properties (E33, G23, G13, ν23, ν13, S13, S23) for computer analysis other than mechanical properties derived experimentally.

In this study, we focused on the molten salt method and attempted a simple synthesis of SrTi_0.8Co_0.2O₃. It was clarified that SrTi_0.8Co_0.2O₃ can be obtained under relatively mild conditions by using the molten salt. In all samples, the electrical conductivity increased with increasing temperature. Compared with the sample without the molten salt, the electric conductivity of the samples with the molten salt was greatly improved. The sample using the KCl-NaCl mixed salt showed the highest electrical conductivity of 83 S/cm at 973 K. The relative densities of all the samples using the molten salt were above 85%. It is considered that the improvement in the electrical conductivity is partly due to the increase in the relative density.

This study utilized a new type of detector, the CROSS II (Liverage Biomedical Inc., Taiwan), to perform a beam quality assurance (QA) procedure on a Sumitomo (Sumitomo Heavy Industries, Inc., Japan) pencil beam linear scanning proton therapy machine. The Cross II can monitor proton Pristine Bragg peak range, beam width, beam size, beam position, and scanning speed. All the data presented here were collected during a time span of over one year. The accuracy of the QA program could be verified if all the QA items were tested stably and within the programmed tolerances. Our results showed that the proton range remained within the ±2 mm tolerance, with the majority of measurements within ±0.5 mm, ±2 mm for spot size, 1.5 mm for spot position, and ±2% for scanning speed. We found that the CROSS II detector is in high precise and steady state with highly efficient. Our proton therapy system was also proven to be in an accurate and reliable condition according to our QA results.

In this study, we developed a nanoscale emitter having a multi-layer thin-film nanostructure in an effort to maximize the field-emission effect with a low voltage difference. The emitter was a sapphire board on which tungsten– DLC multi-player thin film was deposited using PVD and CVD processes. This multi-layer thin-film emitter was examined in a high-vacuum X-ray tube system. Its field-emission efficiency according to the applied voltage was then analyzed.

MIM devices fabricated with 10-nm thickness of Al₂O₃ high-k thin film deposited using plasma-enhanced atomic layer deposition (PEALD) system on Al-coated Si substrate were investigated. The structural, morphological and electrical properties of Ti/Al₂O₃/Al/Si MIM capacitors as-deposited and post-deposition annealed (PDA) at different temperatures were studied and compared. Al₂O₃ thin films were investigated using atomic force microscopy (AFM) and X-ray diffraction (XRD) and Ti/Al₂O₃/Al/Si MIM capacitors were characterized by current–voltage (I–V) and capacitance–voltage (C–V) measurements. The stable phase formation of Ti/Al₂O₃/Al/Si MIM capacitor provides the lowest leakage current density in the range of nA/cm² for as-deposited and annealed films.

This research aims to study the effects of water pH and immersion time on water absorption and mechanical properties of carbon fiber-reinforced bioplastic composites. The composite samples were exposed to three different water conditions of normal water, distilled water and saltwater. The composites were immersed for a maximum of 40 days. After immersing for 40 days, the highest moisture absorption was found for the composites immersed in distilled water. Young’s modulus and tensile strength decreased with increasing the immersion time for the composite immersed in normal water. Moreover, the effect of the moisture absorption on the mechanical properties and the fracture surface was discussed by the glass transition temperature’s thermal behavior.

This study achieved a homogeneous hierarchical distribution of non-conductive halloysite nanotubes (HNTs) on unidirectional glass fabrics using electrophoretic deposition (EPD). Silane modification was successfully applied to HNTs and glass fabrics. The HNTs and glass fabrics were covalently bonded by condensation polymerization between the carboxyl and amino groups during the EPD process. The HNT-grafted glass fabrics were fabricated into glass fiber-reinforced polymers (GFRPs) using vacuum-assisted resin transfer molding. These results demonstrate an effective enhancement in the through-thickness of HNT-grafted GFRPs. The enhanced mechanical properties of the hierarchically and covalently distributed HNTs were attributed to the excellent interfacial bonding and nanobridging of the HNTs.