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Induction implant welding (IIW) of thermoplastic composites (TPC) is a new technology which uses the heat from the electromagnetic induction heating element implanted in the lap region of TPC laminate under the action of high-frequency alternating magnetic field to melt the thermoplastic resin in the interface area to achieve the connection of TPC structure. The technology has the advantages of simple operation, green efficiency, non-contact, etc., and has received extensive attention from the industrial sector in the past 30 years. Focusing on the IIW process of TPC, the influence of heat generation mechanism, heating effect, welding process parameters on the performance of welding joints was systematically introduced in this paper. Among them, the causes of uneven temperature in the welding area were explained, the method of regulating the temperature distribution in the welding area was presented, and the relationship between the uniformity of the temperature field and the quality of the welded joint was revealed. Finally, some problems faced by the APC structure IIW technology and its future development directions were also discussed.

In order to meet the high requirements of future high-speed and high acceleration tactical missiles for shell bearing capacity and heat protection function, the integrated structure-heat protection ϕ480 mm composite shell was prepared by dry winding process, in which the structure layer adopted T700 carbon fiber/cyanate ester composite, and the heat protection layer adopted composite heat protection structure. The internal pressure, acoustic emission and hydraulic burst tests had been done for integrated structure-heat protection ϕ480 mm shell. The strain variation law, the damage type and damage location of ϕ480 mm composite shell were researched. The structural integrity of external heat protection materials was evaluated. The capacity of bearing internal pressure load was also assessed for the integrated structure-heat protection ϕ480 mm composite shell. The results show that the strain of ϕ480 mm composite shell is linear with the pressure and increased with the raising pressure. The acoustic emission signals, such as resin cracking, monofilament fracture, fiber bundle fracture and delamination are distributed in the dome areas under the internal pressure. The Felicity ratio of ϕ480 mm composite shell is 0.96 after secondary loading. The bursting pressure of ϕ480 mm composite shell is 18.6 MPa, and the vessel characteristic coefficient reaches 42.1 km. The fiber fracture occurs in the dome areas. A small amount of fiber fuzzing, broken wire and whitening appear on the surface of the heat resistant layer material, and no delamination and shedding occur, maintaining good structural integrity.

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]

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]

To further improve the anti‐ablation property of boron phenolic resin (BPR), high‐temperature resistant reactive trisilanolheptaphenyl POSS (3OH‐POSS) was synthesized to modify BPR. The thermal stability of BPR was significantly improved. The initial decomposition temperature of the prepared 3OH‐POSS modified BPR (POSSBPR) was increased from 226.0 to 390.2°C and the chars at 800 and 1000°C was increased from 71.1 and 66.7% to 75.1 and 73.7%, respectively with 20% 3OH‐POSS addition. The prepared POSSBPR castings obtained linear ablation rate (LAR) and mass ablation rate (MAR) were as low as −0.122 mm/s and 0.0465 g/s. And the LAR and MAR of high silica fiber reinforced composites (HSC/POSSBPR) were 0.123 mm/s and 0.0602 g/s, respectively. Moreover, the mechanism of high‐temperature carbon microcrystalline and ceramic structure transformation, and ablation performance enhancement of POSSBPR were determined by X‐ray diffraction, X‐ray photoelectron spectroscopy, and Raman spectroscopy. Results indicated that the introduction of 3OH‐POSS promotes the formation of ordered graphite structure of BPR and forms high‐temperature species, such as SiC ceramic, on the ablated surface, which subsequently improves the ablation resistance of the material. [ABSTRACT FROM AUTHOR]

In this article, we proposed a new approach to design the winding patterns of filament-wound composite pressure vessel with unequal polar openings with non-geodesics. To ensure the continuity of winding angles between trajectories along the cylinder and the dome, the non-geodesics for cylindrical part were used. The developed winding patterns of the vessels were simulated using the MATLAB software to verify the feasibility of the acquired trajectories. To demonstrate the performance in designing the winding path for big polar ratios, we analyzed vessels with polar pole ratios of 1:2–1:4, respectively. The developed winding patterns have successfully achieved uniform fiber distributions along the mandrel without severe overlap, except for the polar pole regions. To avoid the severe overlap between filament bands, we further studied the relationship among the winding pattern, bandwidth, and the number of tangent points, and derived a suitable bandwidth based on the winding pattern. These simulated results proved the effectiveness of the developed method in design of winding pattern with unequal polar openings. [ABSTRACT FROM AUTHOR]