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The primary objective of the paper is the numerical and experimental investigation related to the damage recognition effects for CFRP tubes of four dynamic parameters. Four damage identification indexes consisting of natural frequency‐based index, Mode Shape‐based index (MS), Mode Shape Curvature‐based index (MSC), and Modal Flexibility Curvature‐based index (MFC) are established by analyzing the dynamic parameter data obtained before and after damage occurs. The performances of dynamic parameters are thoroughly discussed in the context of numerical simulations and experiment. The results indicate that the effect of natural frequency is not as significant as that of mode shape. MFC has the most notable effectiveness out of the four indexes. The simulation peak index pair is predicted to rise from 0.3 to 0.6 as the damage in the simulation model increases by 25% from 12.5%, indicating that MFC can feedback the damage degree. Moreover, the circumferential curvature index exhibits superior performance compared to the axial curvature index. To enhance the accuracy of the axial curvature index, it is proposed to increase the number of measuring sites along the tube's long direction. Highlights: Damage identification indexes of four dynamic parameters are established.Discuss the identification ability of dynamic parameters by simulation and test.Two numerical models of CFRP tube with delamination damage are established.Impact and modal tests are executed to study the ability of four indexes. [ABSTRACT FROM AUTHOR]

A new solution method to synthesize NaTiO with titanium powder is presented, and the C/NaTiO nanocomposite with high specific surface area and tunnel structure as the electrode material has excellent electrochemical performance. The single electrode composed of the C/NaTiO nanocomposite based on carbon fiber fabric (CFF) has the highest area capacitance of 1066 mF cm at a current density of 2 mA cm, which is superior to other titanates and Na-ion materials for supercapacitors (SCs). By scan-rate dependence cyclic voltammetry analysis, the capacity value shows both capacitive and faradaic intercalation processes, and the intercalation process contributed 81.7% of the total charge storage at the scan rate of 5 mV s. The flexible symmetric solid-state SCs (C/NaTiO/CFF//C/NaTiO/CFF) based on different C/NaTiO mass were fabricated, and 7 mg SCs show the best supercapacitive characteristics with an area capacitance of 309 mF cm and a specific capacitance of 441 F g, it has a maximum energy density of 22 Wh kg and power density of 1286 W kg. As for practical application, three SCs in series can power 100 green light-emitting diodes (LEDs) to light up for 18 min, which is much longer than our previous work by Wang et al. lighting 100 LEDs for 8 min. Thus, the C/NaTiO nanocomposite has promising potential application in energy storage devices. [ABSTRACT FROM AUTHOR]

The K 2 Ti 6 O 13 nanobeams (K-TNBs) with tunnel structure have been prepared by simple hydrothermal method. To attain the flexible property and the high cycle stability, the carbon absorbed on K-TNBs (C@K-TNBs) supercapacitor (SC) has been encapsulated by the flexible PDMS (polydimethylsiloxane). The solid SC device shows excellent rate capability, high cycle stability and high flexibility at any degrees. The capacitance of the device can attain 301 F g −1 at current of 3 mA, energy density of 26.8 Wh kg −1 at power density 400 W kg −1 and power density of 1.47 kW kg −1 at energy density 16.3 Wh kg −1 . The retention of specific capacitance remains 82.7% after 10000 cycles at high current value of 21 mA. Three supercapacitors in series can light 100 green color commercial light emitting diodes (LEDs) for about 16 minutes. All these results indicate that the C@K-TNBs nanomaterial could provide the potential application in high performance supercapacitor. [ABSTRACT FROM AUTHOR]

Highlights: [•] Atmospheric air plasma treatment introduced some polar groups to PBO fiber surfaces. [•] Surface morphologies of PBO fibers were etched drastically by the plasma treatment. [•] The interfacial adhesion of PBO/epoxy composites were improved significantly. [•] The plasma treatment has little effect on tensile properties of PBO multifilament. [ABSTRACT FROM AUTHOR]

Owing to their excellent physical and chemical properties, the carbon fibre reinforced poly(ether‐ether‐ketone) composites (CF/PEEK) are widely used in aerospace applications such as rockets, missiles, and high‐speed vehicles. However, both carbon fibre (CF) and poly(ether‐ether‐ketone) (PEEK) have inert molecular chain structures, which seriously affect the interfacial properties of CF/PEEK composites. In this study, to improve the properties of CF/PEEK composites, carboxylated PEEK (PEEK‐COOH) with different carboxylation degrees is synthesized as the sizing agent by a "two‐step" method. Then, the activated CF surface is coated by PEEK‐COOH sizing layers with different functionalization degrees to prepare the CF/PEEK composites. The results show that the interfacial properties of CF/PEEK composites are improved after applying the sizing agent. When the carboxylation degree of PEEK‐COOH is 19.61%, the flexural strength, flexural modulus, and interlaminar shear strength (ILSS) of CF/PEEK composites reach 489.34 MPa, 25.387 GPa, and 81.3 MPa, respectively. In addition, the use of PEEK‐COOH sizing agents can form an excellent transition layer between CF and PEEK, creating an efficient stress transfer system and facilitating an even stress distribution between CF and PEEK. Furthermore, the main mechanism of material fracture changes from CF debonding to CF and resin fracture. [ABSTRACT FROM AUTHOR]

Abstract: The effects of oxygen plasma treatment power on surface properties of poly(p-phenylene benzobisoxazole) (PBO) fibers were investigated. Surface chemical composition, surface roughness and surface morphologies of PBO fibers were analyzed by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. Surface free energy of the fibers was characterized by dynamic contact angle analysis (DCAA). The results indicated that the oxygen plasma treatment introduced some polar groups to PBO fiber surfaces, enhanced surface roughness and changed surface morphologies of PBO fibers by plasma etching and oxidative reactions. The polar groups and surface free energy of PBO fibers were significantly improved by the oxygen plasma treatment when the plasma treatment power was lower than 200W. However, these two parameters degraded as the plasma treatment power went up to 300 and 400W. PBO fibers were notably roughened by the oxygen plasma treatment. Surface morphologies of the fibers became more complicated, and surface roughness of the fibers enhanced almost linearly with the plasma treatment power increasing. [Copyright &y& Elsevier]

Abstract: The influence of oxygen plasma treatment on surface properties of poly(p-phenylene benzobisoxazole) (PBO) fibers and aging effect of the oxygen plasma modified PBO fiber surfaces were investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and dynamic contact angle analysis (DCAA), respectively. The results indicated that the oxygen plasma treatment introduced some polar groups to PBO fiber surfaces, enhanced surface roughness and changed surface morphologies of PBO fibers by plasma etching and oxidative reactions. Surface wettability of PBO fibers may be significantly improved by increasing surface free energy of the fibers via oxygen plasma treatment. Aging effect of the oxygen plasma treated PBO fibers showed that the fiber surface wettability degraded in the first several days after the plasma treatment, and it was found to be changeless as the aging time continued as long as 30 days. [Copyright &y& Elsevier]

The resin matrix and CF fibers itself of CF/PEEK composites exhibit surface inertness, resulting in poor interface bonding between CF and PEEK matrix. This phenomenon seriously affects the mechanical properties of CF/PEEK composites especially the interlaminar shear strength (ILSS). In order to improve the interfacial properties of CF/PEEK composites, a novel sizing agent of CF fibers namely PPS‐NH2 was synthesized, and its influence on the fibers–matrix interface interaction and properties of CF/PEEK composites was investigated by using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, atomic force microscopy. The results showed that the interface of CF/PEEK composite was improved by coating PPS‐NH2 sizing agent on the surface of CF. When the amination degree of PPS‐NH2 reaches 31.25%, the ILSS, flexural strength and modulus of CF/PEEK Composites reach 73.9 MPa (119%), 671.4 MPa (63%) and 32.8GPa (51%) and, respectively. At the same time, the main failure mechanism of CF/PEEK composites changes from fibers–matrix debonding into interface layer deformation and resin fracture. This method can effectively improve the interface defects between CF/PEEK composites. [ABSTRACT FROM AUTHOR]

Highlights: The homogeneous hybridization of organic–inorganic-metal elements in 3D aerogel was achieved by an expeditious method. The aerogel tightly integrates excellent thermal insulation (49.6 mW m−1 K−1), ablative resistance, mechanical strength, and superhydrophobic properties. The ablated carbon aerogel combines notable electromagnetic interference shielding properties (31.6 dB) and load-carrying properties (272.8 kN·m kg−1). Vehicles operating in space need to withstand extreme thermal and electromagnetic environments in light of the burgeoning of space science and technology. It is imperatively desired to high insulation materials with lightweight and extensive mechanical properties. Herein, a boron–silica–tantalum ternary hybrid phenolic aerogel (BSiTa-PA) with exceptional thermal stability, extensive mechanical strength, low thermal conductivity (49.6 mW m−1 K−1), and heightened ablative resistance is prepared by an expeditious method. After extremely thermal erosion, the obtained carbon aerogel demonstrates noteworthy electromagnetic interference (EMI) shielding performance with an efficiency of 31.6 dB, accompanied by notable loading property with specific modulus of 272.8 kN·m kg−1. This novel design concept has laid the foundation for the development of insulation materials in more complex extreme environments. [ABSTRACT FROM AUTHOR]

A novel B–Si–Zr hybridized ceramicizable resin(BSZ-PR) was fabricated by chemical reaction of boric acid, zirconium hydroxyl-containing polyhedral oligomeric silsesquioxane(Zr-POSS) and phenolic. The incorporation of boric acid and Zr-POSS improved the thermal stability of the resin effectively, and the residual carbon rate increased to 72.63% at 800 °C under nitrogen atmosphere. The flexural strength of carbon fiber/BSZ-PR and high silica fiber/BSZ-PR composites were increased by 25.7% and 175.5%, and linear ablation rates were reduced by 37% and 44.75%, respectively. It was discovered that the ceramic structures such as SiO 2 , ZrO 2 and SiC can be formed at high temperatures as well as under extreme ablative conditions from both BSZ-PR and its fiber-reinforced composites, which may be the key to the improved thermal, ablative properties. [ABSTRACT FROM AUTHOR]

The utilization of advanced propellants leads to unbearable temperature and pressure in propellent ramjet engines, paving the way for the enhancement of thermal insulation materials. High temperature vulcanized polydimethylsiloxane composites have been adopted due to the satisfactory ablation resistance at the expense of complicated industrial costs. For the purpose of simplifying the processes and enhancing the ablation resistance of polymer matrices, room temperature vulcanized hydroxyl-terminated polydimethylsiloxane (HPDMS) crosslinked with multi-ethoxy POSS (EOPS) coatings (EOPS@ HPDMS) were prepared through capping crosslink. Comparative analyses of different EOPS loadings of EOPS@HPDMS revealed the chemical bonding of EOPS ameliorated the effects about crosslinking properties, mechanical strengths, thermal performance and ablation resistance of HPDMS. This work could provide an optional method for developing advisable ablation resistance composites in aerospace applications. Image 1 [ABSTRACT FROM AUTHOR]

• The aryl-boron phenolic resins (ABPRs) suitable for RTM processes were synthesized. • The inclusion of PBA improved the thermal and oxidation resistance of ABPRs. • 3D woven composite was prepared by RTM process reinforced with 3D carbon-fibre fabric. • The 3D woven composites exhibited excellent mechanical and ablative properties. Boron phenolic resin (BPR) is one of the most extensively utilized matrix resins in ablative field due to its outstanding heat resistance and ablation performance. However, the existing BPR applications are severely limited since they are unsuited for the resin-transfer molding (RTM) process. This research created and manufactured arylboronic acid (PBA) modified phenolic resins (ABPRs) for RTM techniques. Since ABPRs maintain a low viscosity (0.8 Pa·s) throughout a wide temperature range (65–80°C), they can meet the essential criteria of co-injection RTM techniques. The inclusion of PBA significantly improved the heat and oxidation resistance of ABPRs. The char yield of PR and ABPR-d are 64.5% and 70.4%, respectively (800°C, N 2 atmosphere). Three-dimensional woven carbon fiber textiles strengthen the CF/ABPR composites, which possess excellent mechanical and ablation properties. The oxygen-acetylene test revealed the mass ablation rates of CF/PR and CF/ABPR-d were 0.052 and 0.049 mm/s, respectively. Since the ABPRs for RTM developed for this work have excellent processability, thermal characteristics, mechanical properties and ablation capabilities, the resin matrix can offer excellent comprehensive attributes for the nozzle-expanding section of solid rocket motors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergistically crosslinked phenolic resin (HPNR) networks are constructed. • The HPNR exhibits excellent thermal stability and controlled plasticity. • The HPNR matrix composites show the healing capability and superior ablation resistance. • This paper provides a new strategy for developing sustainable aerospace materials. Due to the excellent processability and high char yield, phenolic resin plays a pivotal role in ablative thermal protection systems for the aerospace industry. However, internal defects in conventional phenolic resin matrix composites could potentially scrap the entire thermal protection system and cause devastating safety hazards to the spacecraft. Herein, hexamethylenetetramine (HMTA) and phenylboronic acid are applied as the co-curing agents of novolac resin. With the HMTA amount below 2.5 phr, a series of synergistically crosslinked phenolic resin (HPNR), which consist of both traditional methylene linkages and dynamic boronic ester linkages, are successfully synthesized. By tuning the ratio of the traditional/dynamic bonds, the HPNR demonstrates high char yield and controlled plasticity. Compared with its conventional counterparts, the carbon fabric reinforced HPNR matrix composites show healing capability and superior mechanical properties and ablation resistance, with an interlayer shear strength and mass ablation rate of 37.0 MPa and 0.055 g/s, respectively. The synergistic crosslinking strategy provides a promising pathway for designing and preparing healable ablative thermal protection system materials. [ABSTRACT FROM AUTHOR]

Abstract: The effects of oxygen plasma treatment on both the fiber surface and interfacial adhesion of Armos fiber reinforced PPESK composites were investigated in this paper. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to analyze fiber surface chemical composition and surface roughness, respectively. The results indicated that oxygen plasma treatment had introduced a large amount of reactive functional groups onto the fiber surface and the fiber surface roughness was increased largely. The interlaminar shear strength (ILSS) of the untreated and oxygen plasma-treated composites was measured to evaluate the interfacial adhesion. The values of ILSS were enhanced dramatically; the water molecule diffusion into composite along interface was prevented effectively. The composite fracture mode was observed by scanning electron microscopy (SEM), which showed that the primary failure mode varied from interface failure to matrix failure after oxygen plasma treatment. Results indicated that oxygen plasma treatment was an effective method to improve the interfacial adhesion properties of Armos fiber reinforced PPESK composites by both chemical bonding and physical effects. [Copyright &y& Elsevier]