Vacuum infusion experiments were conducted to characterize the elastic recovery and thickness effect in the vacuum infusion molding process (VIMP). The results indicate that both the local fluid pressure and the part thickness increment increase with flow propagation until filling completion, and subsequently decrease during the post-filling stage. The maximum thickness increment increases with the number of reinforcement layers, while the thickness-increment rate decreases due to the enhanced compliance of the reinforcement. Specifically, for reinforcements with 10, 20, and 30 layers under in-plane 1D (One-Dimensional) flow, the thickness-increment rates are 4.97%, 4.74%, and 3.86%, respectively. In out-plane 1D flow, a distinct progressive three-stage thickness growth is observed, with corresponding increment rates of 43.7%, 23.0%, and 15.8% for 10, 20, and 30 layers, highlighting a significantly more pronounced effect. In contrast, for both coupled seepage-flow configurations (A and B), the thickness-increment rate shows no significant variation with layer number and remains consistently around 6%. This suggests that the thickness effect is offset by the coupled seepage-flow interaction of in-plane, out-plane, and distribution medium (DM) flows. It can be concluded that elastic recovery decreases with increasing part thickness. The thickness effect exerts a positive influence on the vacuum infusion molding of large-scale (thick-section) composite structures. Both elastic recovery and thickness effect are closely related to the injection mode (process strategy), with the effect in out-plane 1D flow being significantly greater than that in in-plane flow and coupled seepage flow.

With the advancement of aerospace technology, spacecraft impose increasingly stringent requirements on polymer composites. Polyimide (PI) composites have emerged as critical materials for extreme environments such as aerospace applications due to their exceptional thermal stability, mechanical properties, and molecular and structural design flexibility. This paper systematically reviews research progress in multifunctional polyimide composites for extreme environment applications, covering molecular and structural design, fabrication processes, and resin formulation strategies. First, from a molecular engineering perspective, it explores the influence of molecular structure, chemical bonds, and reinforcements on performance. Second, it systematically analyzes the applicability, advantages, and challenges of 3D printing technology in PI forming. Subsequently, it reviews the evolution of PI resin formulation design from empirical trial-and-error, theoretical models, and computational simulations to data-driven and AI-assisted methods, emphasizing the potential of machine learning to accelerate high-performance PI development. This shift aims to propel future PI re-search from traditional empirical optimization toward a paradigm shift toward systematic material discovery. This review seeks to provide a systematic reference for the rational design and engineering transformation of high-performance, multifunctional polyimide composites for extreme environments.

Perforation is generally considered a worst-case failure mode for radar-absorbing structures because it removes lossy volume and amplifies edge-induced specular echoes. Here we show that, with phase-gradient scattering engineering, perforation can instead be leveraged as a controllable scattering-redistribution-and-loss element. A laminated metastructure that integrates a magnetic impedance-matching layer with a carbon-based multiple-reflection layer achieves broadband absorption (2–18 GHz) in the pristine state. Remarkably, although perforation increases the reflection amplitude locally, the phase gradient between adjacent subcells is largely preserved, which steers backward scattering away from the specular direction and stabilizes the global absorption/backscattering signature. The metastructure maintains effective absorption over 3–18 GHz under both periodic-array and randomly distributed perforation modes up to a 40% perforated area fraction. An inverted trend further emerges for a single central perforation: within a moderate damage window (hole radius ∼ 10 mm), the monostatic RCS is reduced relative to the pristine state, whereas larger holes eventually degrade as expected. Full-wave analyses indicate that pore-induced multiple scattering and edge-localized power dissipation compensate for missing absorber volume, explaining the counterintuitive damage-enhanced response. These results reframe perforation from an unavoidable liability into a practical design knob for damage-aware absorbing skins.

Understanding the thermal decomposition of Phthalonitrile (PN) resin is essential for improving its heat resistance and flame retardancy. Nevertheless, most studies in this field have so far been limited to experimental investigations. This study established a cross-linking model for PN resin and systematically investigated the thermal decomposition behavior of PN resin using reactive force field molecular dynamics (ReaxFF-MD) simulations, combined with thermogravimetry-infrared-mass spectrometry (TG-IR-MS) experiments to validate the simulation results. The results show that the initial thermal decomposition temperature of the PN resin is approximately 400 degrees C, and it still maintains a high char residue rate of 73% at 1000 degrees C in N2 atmosphere. The volatile products of its pyrolysis are mainly composed of non-flammable gases such as H2O, NH3, HCN, and CO2. A notable finding is that the stable cross-linked network and rigid structure of the PN resin facilitate the rapid formation of a dense carbonized layer at elevated temperatures. Under simulated thermal decomposition conditions at 3000 K, the system transitions into the condensation-carbonization stage within just 10 ps. This property enables the prompt formation of a surface carbon layer during service, creating a protective barrier that effectively isolates the material from heat and oxygen.Meanwhile, ReaxFF-MD simulations elucidated the evolution pathway of N2 formation during the high-temperature pyrolysis of PN resin, thus providing critical insights for further enhancing its flame retardancy. This study reveals the atomic-level pyrolysis mechanisms of PN resins at high temperatures, providing a theoretical basis for designing higher-performance resins.

Mesophase pitch-based carbon fibers (MPCF) are ideal reinforcements for composite materials used in space craft due to their extraordinary thermal conductivity and high stiffness. However, their practical applications are severely limited by a lack of understanding of fiber-matrix interfacial interactions. Here, through a joint study of fiber push-out testing and molecular dynamics simulations, we investigated the effect of fiber microstruc ture on the interfacial shear strength of MPCF-reinforced epoxy composites with the microstructure of MPCF being tailored by different spinneret geometries. Our results showed that the surface roughness and interfacial contact mode are two predominant factors determining the interfacial shear strength (IFSS), which contradicts the common intuition that carbon fibers with a higher degree of graphitization generally lead to worse inter facial properties. Owing to the enhanced surface roughness and full edge-plane contact mode, the skin-core structured MPCFs exhibit an IFSS of 17.83 MPa, which is nearly 3 times that of the split-radial structured MPCFs (5.14 MPa). The distinct interface behavior between epoxy and MPCFs with different microstructures, as revealed by molecular dynamics (MD) simulations, stems from more pronounced mechanical interlocking and enhanced intermolecular attraction at the interface. These findings offer significant guidelines for fabricating MPCFs with high thermal conductivity without sacrificing the interfacial load transfer ability through the modulation of surface roughness and interface contact modes.

Phthalonitrile (PN) resins are promising for extreme environments, yet their complex multi-pathway curing mechanism has long hindered rational property design. The study establishes a DFT-experimental framework to decouple the competitive polymerization kinetics and networks topological evolution of PN. A concentration-dependent transition state switching is revealed: a high barrier four membered pathway at low curing-agent concentration shifts to a low barrier six membered cooperative pathway at high concentration. Notably, intermolecular cyclization to triazine consistently exhibits thermodynamic and kinetic dominance, whereas intramolecular cyclizations to isoindoline and phthalocyanine require overcoming higher barriers but are selectively promoted at elevated amine concentrations—validated by Boltzmann distribution and FTIR. By varying the curing agent concentration, the product distribution is systematically tuned, governing macroscopic properties: triazine and phthalocyanine confer superior thermal stability (Tg > 400°C) and flexural strength (91.7 MPa), while isoindoline enhances crosslinking density. This work deciphers the complex curing mechanism and provides a strategy for tailoring properties of PN resin.

Superhydrophobic surfaces have emerged as a promising and energy-efficient solution for ice accretion. However, their practical implementation is hindered by the vulnerability of the Cassie-Baxter state under realistic icing conditions, where multi-scale water environments exposure leads to rapid wetting transition and ice adhesion. This review provides a novel and comprehensive perspective on the design of robust superhydrophobic anti-icing surfaces (SAISs), highlighting the key role of anti-wetting/dewetting performances at both macroscopic and microscopic scales. We begin by revisiting fundamental wetting theories from static to dynamic wetting models. Special emphasis is placed on the roles of micro/nano-textures in stabilizing the non-wetting state and facilitating spontaneous dewetting during condensation, icing, and melting. Furthermore, we systematically categorize recent advances in current state-of-the-art SAISs, including all-nanostructured, periodic hierarchical, and random hierarchical architectures, and evaluate their anti-wetting robustness, condensation tolerance, and deicing performance. The integration of superhydrophobicity with photothermal or electrothermal functionalities is also discussed as an emerging strategy to achieve low-energy and high-durability anti-icing systems. Finally, we outline key challenges and future directions for the rational design of SAISs. This review shifts the focus from the often-discussed mechanical and chemical durability to the more pressing issue of wetting stability under water environment exposure, aiming to inspire further innovation in materials engineering for aerospace, energy, and transportation applications in cold climates.

Bismaleimide (BMI) resins are widely used in aerospace and electronics industries owing to their excellent heat resistance and mechanical properties. However, conventional toughening approaches often degrade the heat resistance of BMI resins, and further improvement in their dielectric properties is required. Benzoxazine (BOZ) is a promising modifier for BMI resins, and the introduction of fluorine-containing groups can further enhance the resin's dielectric properties. Herein, a series of modified resins (BDF) were prepared by introducing fluorinated allyl benzoxazine (BOZ-F) into a BMI/DABPA system (BD). The effect of BOZ-F content on the properties of BDF resins was studied, and the evolution of the interpenetrating polymer network (IPN) structure was investigated. Results show that the introduction of BOZ-F considerably changes the curing pathway of the resin. Differential scanning calorimetry curves exhibit a double-peak characteristic, confirming the formation of a bicontinuous IPN structure. At the optimal BOZ-F content, the impact toughness increases by 33.9%, while the glass transition temperature (Tg) increases by 10.2 degrees C, reaching 304.0 degrees C. With increasing BOZ-F content, the dielectric constant decreases from 3.09 to 3.01, and the dielectric loss decreases from 0.0119 to 0.0091 at 15.4 GHz. The IPN structure exhibits a staged evolution with increasing BOZ-F content: a DABPA-dominated locally entangled IPN at low contents, a bicontinuous-phase IPN at the critical content and a BOZ-F-dominated reverse IPN at high contents.

The pursuit of higher performance in the aerospace industry is pushing the limits of resin-based wave-transparent composites, demanding superior thermal resistance and lower dielectric constants. However, simultaneously optimizing thermal and dielectric performance in polymer matrices remains challenging due to their inherent trade-off. In this study, a novel polyhedral oligomeric silsesquioxane (POSS) monomer end-capped with phthalonitrile groups, TtSPPN, was synthesized and employed as an organic-inorganic copolymerization modifier to a baseline phthalonitrile resin (BPh). Results indicate that TtSPPN exhibited superior thermal stability, with a 5% thermal decomposition temperature (Td5%) exceeding 500 degrees C. Owing to its terminal phthalonitrile groups, the modifier enables molecular-level dispersion and participates in copolymerization cross-linking. The copolymers demonstrated exceptional thermal properties, with a Td5% reaching 584 degrees C and a glass transition temperature above 500 degrees C. Additionally, the incorporation of 5 wt% TtSPPN significantly reduced the dielectric constant and dielectric loss of the composite to 3.28 and 0.007 at 12 GHz, respectively, compared to 3.54 and 0.013 for pure BPh resin. Notably, the addition of TtSPPN into the cured samples significantly decreased water absorption. This study presents a novel design strategy for PN resins specifically engineered for extreme environments, demonstrating transformative potential for applications in high-performance composite materials.

The effectiveness of superhydrophobic anti/deicing surfaces hinges on the intervening air layer between water/ice and substrate. However, the evolution and binding state of this buried interface during the freezing-melting cycle remain notoriously difficult to characterize. Herein, we introduce a simple and intuitive method based on conventional differential scanning calorimetry (DSC) to probe this buried interface and the corresponding thermal resistance. By analyzing the ice melting processes on surfaces with identical topography but opposite wettability (Wenzel vs. Cassie-Baxter states), we demonstrated that the slope of the DSC endotherm peak quantitatively reflects the interfacial thermal resistance from the trapped air. This DSC-derived metric is robust against thermal history and clearly distinguishes hierarchical structures from single-scale analogues, correlating with their ice-delaying performance. Crucially, we demonstrate that the benefit of this air layer in reducing ice adhesion dominates its thermal insulation effect in electrothermal deicing, enabling faster and more energy-efficient ice removal. This work establishes DSC as a universal thermal analysis tool for evaluating icephobic surfaces and provides key insights for their rational design.

Next-generation aerospace platforms demand lightweight sandwich-core foams that withstand extreme temperatures (200-400 degrees C) while maintaining structural integrity. However, conventional polymer foam degrades above 200 degrees C. Phthalonitrile (PN) resins offer exceptional thermal stability but are hindered by high melting points, narrow processing windows, and curing challenges. Here, we present a melt-prepolymerization-foaming (MPF) strategy that overcomes the incompatibility between the high melting point and high curing temperature of PN and the relatively low decomposition temperature of conventional chemical foaming agents, which otherwise leads to pore coarsening or even foaming failure. We successfully fabricate tailorable cellular Phthalonitrile foams (PNF) with ultralow density (0.056 g & centerdot;cm-3) and a high expansion ratio (up to 22.82). By decoupling prepolymerization from gas release, we achieve precise control over rheology and pore morphology, enabling closed-cell structures with uniform pore size (200-800 mu m) and superior thermal stability (5% weight loss temperature up to 527 degrees C) and up to 15.309 MPa & centerdot;cm3 & centerdot;g-1 specific strength. The resulting foams outperform existing high-temperature foams in density-normalized strength and thermal resistance, offering a scalable solution for extreme-environment applications in aerospace and beyond.

Superhydrophobic surfaces offer a promising passive anti-icing alternative, yet they frequently fail to sustain the non-wetting Cassie-Baxter state under dynamic icing conditions. Conventional approaches for robust superhydrophobic anti-icing coatings rely on high nanoparticle loadings (>50 wt%) to achieve the desired nanoporous roughness, often compromising cost efficiency and interfacial robustness. Herein, we proposed a novel and practical substrate-driven spraying strategy to construct fine nanoporous structures, allowing superhydrophobicity at a substantially reduced nanoparticle content of 2.5 wt%. The optimized nanoporous superhydrophobic films exhibited excellent dynamic anti-icing performance, effectively repelling impacting droplets at -141 °C and suppressing long-term condensation for over 3 h. Furthermore, the dynamic deicing behaviors are confirmed by the high slipperiness of melted ice and coalescence-induced wriggling of melting ice/frost. When integrated into composite airfoils, the film surface exhibits outstanding practical efficacy in icing wind tunnel tests. A power density of only 0.4 W cm-2 was required to suppress icing at both the leading edge and runback zone. This work offers a promising pathway for implementing high-performance anti-icing solutions in advanced resin-based composite materials in wind turbine blades, aircraft, and cryogenic fuel storage tanks.

To address the issues of complex ply angles and unclear curing deformation mechanisms in carbon fiber/epoxy resin (CF/EP) multi-coupled laminates, this study carried out optimal design and curing deformation verification. By introducing geometric factors of composites and based on hygrothermal stability conditions, the necessary and sufficient conditions for achieving hygrothermal stability in such multi-coupled laminates were derived. A criterion for measuring curing deformation was proposed. Using a genetic algorithm (GA), asymmetric multi-coupled laminates with extension-shearing coupling were optimized, resulting in a ply scheme based on common engineering angles (0 degrees, +/- 45 degrees, 90 degrees). Corresponding composite laminates were fabricated via compression molding, and their curing deformation was measured by laser scanning. Experimental and simulation results show that the curing warpage of the multi-coupled laminates can be controlled within 0.5% of the side length, and the simulation error of curing deformation can be kept within 20%.

Fiber hybridization offers a useful way to achieve an optimal combination of stiffness and toughness via developing pseudo-ductile behavior. As for intralayer hybrid composites, the dispersion of carbon fiber bundle is crucial to their mechanical properties and damage modes. In this work, intralayer hybrid composites with different fiber bundle dispersion were designed and manufactured. Then, the tensile behaviors of these hybrids were tested experimentally and simulated via FEM. The results indicated that the carbon fiber bundles were more prone to fragmentation with higher dispersion ratio, which could be increased via reducing the fiber bundle size or altering the fiber bundle shape. As a result, the intralayer hybrid composite with dispersed carbon fiber bundles tended to exhibit pseudo-ductility. With the carbon fiber bundle dispersion ratio increasing, the carbon fiber bundle volume fraction (VCFB), at which the pseudo-ductile behavior was demonstrated, could be improved from 10 % to 18.3 %. Furthermore, the tensile strength was increased by 15.5 % for the dispersed hybrid composite with VCFB=10 % and 6.1 % for that with VCFB=13.3 % compared to their counterparts with centralized carbon fiber bundles.

In the aerospace industry, adhesively bonded external patch repair has become a prevalent method due to its simplicity and efficiency. However, the conventional patch repair technique under tensile load frequently exhibits a failure mode characterized by top-layer tearing of the parent plate. This results in the adhesive’s inability to fully exert its intended performance, leading to a reduction in repair efficiency. This paper presents a systematic study on adhesively bonded external patch repair for top-layer tearing in parent plate and its underlying causes. Concurrently, a novel method of toughness-layer-enhanced patch repair has been developed for the effective protection of the parent plate’s top layer. The findings indicate that top-layer tearing of the parent plate in patch repair is extremely associated with stress concentration in the top layer near the longitudinal edge of the patch, and the sandpaper grinding treatment of the top layer also contributes to this failure. Moreover, the integration of the toughness layer effectively protects the parent plate’s top layer, preventing the occurrence of that undesirable failure mode and enhancing the repair efficiency from 76.31% to 86.12%. This approach has been shown to enhance the strength restoration capability of patch repairs, reducing the requirements for sanding operations on the surface of the parent plate.

The temporary fixation of precision devices during manufacturing demands adhesives capable of high efficiency and controlled debonding, while existing thermosetting adhesives face challenges in on-demand debonding due to irreversible covalent crosslinking. To address this dilemma, UV-curable polyurethane acrylate adhesive (DSPUA) integrating dual-dynamic networks of hydrogen bonds and disulfide bonds was developed. This synergy between dynamic networks effectively resolved the trade-off between adhesive strength and on-demand debonding capability. The dual-dynamic network provided strong and tough adhesive strength (5.88 MPa and 8.99 kN/m), surpasing that of existing UV-curable adhesives featuring controlled debonding. The disulfide bonds enabled rapid debonding at medium temperatures (complete detachment within 4 min at 90 degrees C). In addition, the DSPUA-2 adhesive also experienced a significant reduction in adhesive strength when exposed to ultraviolet light or in the presence of chemical reducing agents. This work paves the way for the design of high-performance and debondable adhesives, with significant implications for temporary fixation of precision components and material recycling.

Due to its great mechanical properties and high-temperature resistance, bismaleimide (BMI) has important applications in the aerospace field. The incorporation of thermoplastic polyimide (PI) into thermosetting resins is an effective strategy for enhancing toughness. The phase separation mechanisms of PI within the resin matrix have been extensively studied. However, the majority of studies have concentrated on epoxy, and research on BMI is limited. Moreover, compared with factors such as the content and structural composition of the modifier PI, the molecular weight is often overlooked. In this work, a tailored series of fluorine polyetherimides (abbreviated as PI-X) with weight-average molecular weights (Mw) ranging from 1.5 to 3.6 × 104 were synthesized using an in situ prepolymerization method. In this method, the basic modifier of BMI, ortho-diallyl bisphenol A (DABPA) was used as a solvent to synthesize a PI-X solution; here, the process was simplified and met the requirement of green chemistry with no pollutant emissions. The novel PI-X contains fluorine elements, ether bonds and asymmetric structures; these bonds and structures are beneficial for synergistically improving toughness and high-temperature resistance. By maintaining a constant concentration of 4 wt