Volume 25, Issue 1

A preliminary and groundbreaking study on the fiber orientation pattern in gas-powered projectile-assisted injection molding (G-PAIM) part of short-glass-fiber-reinforced polypropylene was reported, the results showed that the fiber orientation pattern across the thickness of G-PAIM part was remarkably different from that in the parts molded via gas-assisted injection molding (GAIM) and conventional injection molding (CIM) as reported earlier, and the difference of fiber orientation pattern between G-PAIM, GAIM, and CIM parts was mainly due to the unique flow fields generated by projectile penetration. Additionally, fiber orientation states within the G-PAIM part depended not only on their positions both across the part thickness and along the flow direction, but also on the processing parameters. Particularly along the thickness direction, fiber orientation states changed significantly. The results also showed that gas injection delay time was the main factor affecting the fiber orientation states within the G-PAIM part, and a shorter gas injection delay time could remarkably induce more ordered fiber orientation along the melt direction. Within the range of the investigated processing parameter values, a larger ordered region, where most fibers tended to be orderly oriented along the melt flow direction, could be obtained under a larger gas pressure (8 MPa), higher melt temperature (250°C), and shorter gas injection delay time (1 s). This work provides a comprehensive guidance for the fabrication practice of G-PAIM parts of short fiber-reinforced thermoplastics.

To enhance the long-term operational stability of transformers, this study focuses on silicone rubber composite insulation materials for dry-type distribution transformers (D-DTs). Based on obtaining the optimal initial performance of silicone rubber composite materials through response surface model, the thermal aging characteristics and long-term stability of intrinsic silicone rubber and silicone rubber composites are compared using molecular simulations, thermogravimetric analysis, and accelerated thermal aging tests. The results indicate that the addition of a small amount of h-boron nitride (BN) and Al 2 O 3 can improve the thermal stability of the composite materials, and the decline in elongation at break is the key factor determining the thermal lifetime of silicone rubber. The silicone rubber composite material doped with 21.42 phr h-BN, 1.58 phr carbon nanotubes, and 2.67 phr Al 2 O 3 , based on the optimal initial performance, is projected to have a lifetime of 3,128 h under accelerated thermal aging at 200°C and 27.40 years under stable operating conditions of D-DTs, making it suitable for widespread application.

Knowledge of the kinetics of polymerization plays a crucial role in the optimization of a synthesis process with appropriate polymerization rate and product quality. The polymerization of acryloyloxyethyl trimethyl ammonium chloride (DAC) was investigated using a dilatometer method in an aqueous solution. The impacts of temperature, monomer concentration, and initiator concentration on the polymerization rate were examined. The results showed that the polymerization rate increased with an increase in the temperature, monomer concentration, and initiator concentration. The activation energy of polymerization under the given conditions of 2.07 mol·L −1 DAC, 1.72 × 10 −3  mol·L −1 ammonium persulfate, and 1.05 × 10 −4  mol·L −1 Na 4 EDTA was E a = 85.25 kJ·mol −1 . The overall polymerization rate equation was R p = K [ M ] 1.69 [ I ] 0.53 . Based on the experimental results, the mechanism of polymerization was discussed in detail. The studies supplied the experimental basis for the industrial implementation of this reaction. Graphical abstract

Graphical abstract Poly(imide siloxane) exhibits good thermal and mechanical properties with enhanced flexibility and hydrophobicity. Abstract A series of poly(imide siloxane) (PIS) copolymers were synthesized using 1,3-bis(aminopropyl)tetradimethylsiloxane, naphthalene-1,4,5,8-tetracarboxylic dianhydride, and 4,4-oxydianiline as building blocks, with a siloxane content of 20–50 wt%, showing high solubility in organic solvents. Attenuated total reflectance-Fourier transform infrared and proton nuclear magnetic resonance spectroscopy were used to structurally characterize the polymers. The thermal properties of the copolymers were measured by thermogravimetric analysis and differential scanning calorimetry. Dynamic mechanical analysis measured the thermomechanical dynamics of polymers. The addition of siloxane boosted the material’s stretchability and water resistance but decreased its stiffness and pulling force resistance due to the plasticizing effect of the dimethylsiloxane moiety. Polymers with naphthalene moieties in the backbone also have different thermal and mechanical properties. PIS films were compared with the flexible bisphenol-A core having 30 wt% siloxane loading (PIS-BPADA-30). The morphological properties were examined using scanning electron microscopy and atomic force microscopy. The polymer backbone became more flexible and hydrophobic when siloxane was included. For hydrophobic and durable applications, siloxane-modified polyimides showed potential.

The recycling acrylonitrile–butadiene–styrene (ABS) copolymers from waste electrical and electronic equipment lightens the burden on landfills and enables us to reuse waste ABS (wABS), promoting environmental sustainability and resource conservation. In this work, the effect of electron beam irradiation on the properties of wABS by adding 1,3-bis(4,5-dihydro-2-oxazolyl)benzene (1,3-PBO) has been studied. Various characterization methods including gel permeation chromatography, Fourier-transform infrared spectroscopy, mechanical properties test, differential scanning calorimetry, and scanning electron microscopy were conducted to investigate the change of relative molecular weight, chemical structure, mechanical properties, glass transition temperature ( T g ), and fracture morphology, respectively. Results demonstrated that the incorporation of 1,3-PBO combined with electron beam irradiation led to significant improvements in molecular weight, tensile strength, impact strength, and T g . Irradiated wABS-PBO reached optimal comprehensive mechanical properties with the dose at 240 kGy. However, higher electron beam irradiation (>240 kGy) significantly reduced the tensile strength due to extensive chain scission. Besides, the fracture surface morphology became coarser with the reinforced intermolecular binding force of irradiated wABS. This study establishes electron beam irradiation as a promising and effective approach for wABS recycling and reuse.

Poly(ether ketone) (PEEK) is an engineering polymer that can be used as load-bearing structures in automotive and aerospace fields, and the systematic study of its properties at different environments is crucial for the design of PEEK-based materials. In this study, a meta-model of PEEK based on molecular dynamics (MD) theory has been built, and the relevant properties (i.e., density, Young’s modulus, and Poisson’s ratio) have been carefully studied. Specifically, Young’s modulus and Poisson’s ratio values of PEEK have been obtained through tensile simulation process, and the meta-model of PEEK sample has been creatively constructed over 100–500 K and 0.5–10 atm using the Gaussian regression process algorithm. The effects of different temperatures and pressures to the sample have then been carefully investigated based on the data of meta-models. Successfully combining the MD theory with the construction of high dimensional meta-model could provide a new strategy to design and study PEEK through modeling and optimization procedures, which leads to a brand-new method to study high-performance PEEK and PEEK-based materials. Graphical abstract

Bacterial keratitis is a common infectious eye disease. Conventional antibiotic eye drops are becoming less effective due to antibiotic resistance. Herein, we design an innovative transition metal ion-based nano-delivery system for the treatment of bacterial keratitis. Zinc (Zn 2+ )–gallic acid–poly- l -lysine nanocomplex (ZGNC) is designed by coordination interaction. ZGNC is stable in a physiological environment and can be dissociated in an acidic infected microenvironment. The positively charged ZGNC can be effectively adhered onto bacterial cells and subsequently realizes in situ release of Zn 2+ , leading to much better bactericidal effect than free Zn 2+ . Importantly, ZGNC maintains excellent bactericidal activity in a protein-rich environment, while free Zn 2+ is completely invalid to eradicate bacteria in a protein-rich environment. The in vivo bactericidal ability of ZGNC is further confirmed in a murine bacterial keratitis model. This research provides a promising method to treat bacterial keratitis by a transition metal ion-based nano-delivery system. Graphical abstract

Anticorrosive coatings are considered to be one of the most economical and effective means of protection. The adhesion of the coating is defined as the strength of the interfacial bond between the coating and the substrate, which directly determines the protective life of the coating. In this work, the epoxy–(5-{5-[2-(3,4,5-trihydroxyphenyl)-1 H -1,3-benzodiazol-6-yl]-1 H -1,3-benzodiazol-2-yl}benz-1,2,3-triol} (EP-BIB) composite coating was obtained by adding different mass fractions of BIB to the EP coating. The effect of mass fraction of BIB on the mechanical properties of composite coating were studied by Elongation at break, tensile shear strength, as well as Peel strength. The results showed that the mechanical properties of composite coating could be improved by adding an appropriate amount of BIB. The elongation at break, tensile shear strength, and peel strength of composite coating became better initially and then worse with the increase in BIB content in the composite coating. The composite coating with 0.9% (mass fraction) BIB had the elongation at break of 10.37 ± 0.53%, an optimal shear strength of 12.51 ± 0.48 MPa, and a maximum peel strength of 4.78 ± 0.54 N·mm −1 .

With the advancement of flexible electronic textiles, electronic braided cords have garnered significant attention in smart wearable fields by integrating electronic functionalities while preserving textile characteristics such as softness, breathability, and comfort. However, their electrical conductivity suffers varying degrees of degradation under mechanical conditions including friction, stretching, and flexure. This study employed polyester braided cord as a substrate and optimized the preparation of polypyrrole (PPy)-modified braided cord through in situ polymerization combined with orthogonal experimental design. The degradation mechanisms of conductivity under different mechanical conditions were systematically investigated. Experimental results demonstrate that the optimal conductivity (63 S·m −1 ) was achieved when the pyrrole monomer concentration, FeCl₃·6H₂O concentration, pre-immersion time, and polymerization time were set to 0.2, 0.2 mol·L −1 , 4 h, and 9 h, respectively. Although external forces can damage PPy conductive pathways on the cord surface, leading to conductivity loss, the modified cord exhibits excellent friction resistance, stretch tolerance, flexural durability, and stable conductivity under low-load conditions. This research provides critical scientific insights for prolonging the service life of electronic braided cords and their integrated smart textiles. Graphical abstract

With the depletion of energy and the increasing awareness of environmental protection, bio-polymer films will become a possible alternative to plastic packaging in the future. However, further improvement is needed in the mechanical, waterproof, anti-ultraviolet (UV), and antioxidant properties of bio-polymer films. In this work, a novel bio-polymer film consisting of gelatin, chitosan, and carnauba wax was developed by crosslinking reactions and exhibited excellent performance with appropriate mechanical strength (tensile strength 10 MPa, breaking elongation 38%), excellent water resistance properties (the contact angle reached 124°), and 2,2-diphenyl-1-picrylhydrazyl scavenging ability (69.1%) and can completely block UV rays. Consequently, carnauba wax/chitosan/gelatin film, as a new type of versatile film with excellent performance, will broaden the application of biobased polymer films in the packaging field.

Janus nanofiber membrane films (JNMF) are known for their asymmetric properties. This includes protecting the wound from external liquid contamination and efficiently soaking up excess fluids. The morphology of these membranes was meticulously analyzed using scanning electron microscopy, while their water absorption potential, water contact angle, and crucial mechanical properties were rigorously tested. With increasing calcium silicate (CS) concentration in JNMF, the tensile strain first increased and then decreased. When CS content was 15%, its peak value was 38.28%, indicating the best performance. In vitro tests confirmed that JNMF loaded with Si 4+ effectively promote cell adhesion, multiplication, and directional migration. In vivo studies have shown that JNMF possesses anti-inflammatory properties, promotes angiogenesis, and facilitates the regeneration of epidermal tissue. Immunohistochemical staining underscored the JNMF ability to accelerate wound healing by upregulating CD31 and α-SMA expression. As a result, JNMF presents itself as a promising material for the treatment of severe burn wounds.

In this article, a novel migration-resistant antioxidant (CGE-g-PPDA) was synthesized using cardanol glycidyl ether (CGE) and p -aminodiphenylamine (PPDA) and characterized by infrared spectroscopy, indicating that the antioxidant has been successfully synthesized. CGE-g-PPDA and other different types of antioxidants were added to natural rubber (NR) to make anti-aging NR composites, which were tested and characterized by processing properties, aging resistance, thermal stability, cross-linking density retention properties, and migration resistance. Comparative results showed that CGE-g-PPDA could reduce the Mooney viscosity of NR, improve its processing performance, prolong the oxidation induction time of materials, give long-term protection to the rubber, and improve the cross-linking retention rate of materials. In addition, the migration resistance and solvent extraction resistance of antioxidant CGE-g-PPDA were significantly better than that of antioxidant 4020, with higher stability. CGE-g-PPDA, as a new type of migration-resistant antioxidant, has a potential application value.

A numerical model for a polymer double-layer single lumen microtubes coextrusion flow was constructed and the finite element method was used for numerical solution. The distribution of the velocity, pressure, shear rate, etc., were analyzed, as well as the relationship between the normal stress difference, secondary flow, and die swell were explored. Then, the influence of the flow velocity difference on the die swell of the double-layer microtubes was revealed. The research results indicate that, in the traditional coextrusion process, the melts will undergo expansion and deformation after leaving the die. And the velocity difference caused by the increase in the outer layer melt velocity will cause the outer layer to squeeze the inner layer, resulting in an uneven wall thickness of the composite microtubes. In the gas-assisted coextrusion process, the distribution of the velocity, pressure, shear rate, etc., can be effectively improved. However, the extrusion deformation between the melt layers caused by the velocity difference cannot be eliminated. That is, the gas-assisted technology can effectively improve the overall shape and size accuracy of composite microtubes, but cannot solve the problem of uneven wall thickness caused by the velocity difference.

This study emphasizes on the production of nano-encapsulated phase change materials for the application of thermal energy storage (TES). The core is undecylenic acid (UA), a renewable latent heat storage material, which is encased inside the polyaniline (PANI) nanofibres (NFs) synthesized by interfacial polymerization technique. The morphological and structural features of the prepared NFs were examined by high-resolution transmission electron microscopy and Fourier transform infrared spectroscopy. According to differential scanning calorimetry analysis, the latent heat values were observed as 56 ± 1.4 and 57 ± 1.3 J·g −1 , while the melting and freezing temperatures were recorded as 18 ± 0.2°C and 14 ± 0.3°C, respectively. Thermogravimetric analysis revealed a multi-step deterioration pattern, demonstrating the developed nano-encapsulated-phase change material’s (PCMs’) exceptional thermal stability. In addition to exhibiting reliable thermal performance over numerous cycles, PANI/UA NFs showed excellent TES and release rates. This work addresses key challenges in TES applications by introducing a PCM based on renewable materials that offers enhanced thermal reliability and efficiency. The results contribute in the development of compact and environmentally friendly thermal management systems for utilizing in the applications of electronic device cooling, building energy systems, and renewable energy storage.

Sustainability is one of the main issues of today’s research and development. One aspect of sustainability is also the efficient treatment of waste. Fibrous-based wastes have quite different reasons. They are in different stages of degradation and are more or less chemically complex or contain nonfibrous materials (such as zippers, buttons, membranes, etc.). There are, therefore, plenty of various combinations of mechanical and chemical methods for processing them. The main aim of this work was to describe a proven practical strategy for depolymerization of mixed fibrous wastes to their submicron particles and monomeric components. High-pressure neutral and acid hydrolysis kinetics of cotton, wool, and polyester (PET) fibers and their 50/50 blends representing common components of textile wastes were investigated. High-pressure water-neutral hydrolysis and acid (strong and weak) hydrolysis were used for both pure-component and bicomponent fiber blends. Hydrolysis was conducted in a newly designed high-pressure reactor. Parameters of mechanistic models for the kinetics of heterogeneous solid–liquid degradation were evaluated by nonlinear least squares regression. Model characteristics were basic parameters for efficient selection of suitable decomposition of basic types of individual and mixture fibrous waste including time factor. Hydrolysis agents and conditions of decomposition were selected as optimal based on our previous experimental findings and modeling. Two pure, untreated raw materials were used for the experiments on the decomposition of natural fibers: raw cotton yarn and wool fibers. Two multicomponent mixtures, cotton and PET (weight ratio, 50:50) and wool and PET (weight ratio, 50:50), prepared from the materials described above, were selected.

The thermal mismatch between silicon chips, solder bumps, and substrates in electronic packaging raises reliability concerns, including solder joint failures and warping. To mitigate these issues, underfill materials with high thermal conductivity and a low coefficient of thermal expansion are essential. This study explores hexagonal boron nitride (h-BN) as a filler in epoxy composites, investigating both single and mixed filler systems. Epoxy resin and diethyltoluenediamine hardener were used, incorporating h-BN at 0–5 vol%. Optimal performance was achieved with 5 vol% of 70 nm h-BN, enhancing flexural strength (120 MPa) and thermal conductivity (0.17 W·m −1 ·K). Mixed filler systems with nano- and micron-sized h-BN at varying ratios showed that a 25:75 ratio of 70 nm to 5 µm h-BN improved fracture toughness (7.21 MPa·m¹/²) and thermal stability. These results highlight the role of particle size distribution in optimizing epoxy/h-BN composites for electronic packaging.

Integration of essential oils into nanofibers not only enhances the bioactivity of these substances but also offers greener solutions for many applications including protective textiles and coatings. Herein, citronella or thyme oil-loaded polyurethane nanofibers were fabricated via blend electrospinning, and their release behavior was evaluated. Initially, polyurethane nanofibers with different citronella or thyme oil concentrations (5%, 10%, and 15%) and spinning parameters (tip-to-collector distance: 15–20 cm, voltage: 15–20 kV) were fabricated. The nanofiber mats were characterized in terms of surface morphology, wettability, and porosity. Afterward, the release behaviors of the selected mats were examined. Depending on the oil concentration and spinning parameters, nanofibers with diameters in the range of 175–442 nm were produced. The incorporation of essential oil increased contact angles from 102° to 125°, while the bulk porosities were decreased from ⁓76% to ⁓58%, depending on the oil. Fourier-transform infrared spectroscopy analysis validated successful essential oil integration. The release studies revealed that thyme oil exhibited a release of ∼10% and citronella essential oil ∼5% over 18 h, indicating a controlled and sustained release. This study demonstrates the potential of essential oil-loaded polyurethane nanofibers as eco-friendly materials for protective textiles and coatings.

In this study, the efficiency of flexible composites consisting of viscous silicone rubber as matrix and micro- and nanoparticles of Bi 2 O 3 and SnO 2 as fillers was investigated. Four composites with a matrix/filler at 50:50 were prepared. The four samples are the liquid silicone rubber (LSR) materials with micro-Bi 2 O 3 , micro-Bi 2 O 3 , and nano-SnO, nano-Bi 2 O 3 , and nano-SnO, and both nano-Bi 2 O 3 and nano-SnO are labeled as LSR-Micro, LSR-Micro/Nano, LSR-Nano/Micro, and LSR-Nano/Nano, respectively. The morphologies and the homogeny of the nanoparticles and the prepared composites were checked by scanning electron microscopy. The efficiency of shielding characteristics was investigated experimentally by the narrow-beam technique using a lead collimator, different gamma-point sources, and a semiconductor detector. The results showed that at both energies, the composites that contain a combination of micro- and nanoparticles have higher linear attenuation coefficient (LAC) values than the composites with only micro- or nanoparticles. For example, at 0.060 MeV, the LACs are 5.592, 6.391, 6.412, and 6.202 cm −1 for LSR-Micro, LSR-Micro/Nano, LSR-Nano/Micro, and LSR-Nano/Nano, respectively, while at 0.662 MeV, they are, respectively, 0.185, 0.204, 0.210, and 0.199 cm −1 . The prepared composites were compared with commercial lead aprons of different thicknesses, and the results demonstrated the efficiency of the prepared flexible composites against gamma radiation, in addition to their lightweight and environmental safety.

Precise control of filament parameters, including material composition and printing orientation, enables the alignment of carbon fibres (CFs) in a single orientation in additive manufacturing processes. This study reveals that printing in 0° orientation enhances both tribological and mechanical properties in CF reinforced polylactic acid composites. By fabricating in-house filaments with CFs, superior flexural, impact, and tensile strength were achieved, with improvements of ∼75% compared to conventional filaments. Findings also reveal that 0° orientation improves the printed layups in terms of interfacial bonding and adhesion within the layup sequence. It highlights the precise adjustment parameter in polymer composite filament with fibre filler, opening possibilities for advanced structures with integrated programmable functionalities in 4D printing applications.

Electret technology is extensively utilized in fiber-based air filtration materials due to its ability to significantly enhance filtration efficiency (FE) without increasing the pressure drop. This improvement is attributed to the electrostatic attraction generated by the charges within the fibers. The stability of these electrostatic charges is critical for maintaining the long-term protective performance of air filtration materials. As a result, ongoing research into electrostatic technology, influencing factors, and charge storage mechanisms remains a highly active area of study. In this study, corona-charged melt-blown nonwoven (CMN) and hydro-charged melt-blown nonwoven (HMN) were fabricated using pure polypropylene (PP) and magnesium stearate-modified PP as raw materials. The filtration performance stability of CMN and HMN was systematically evaluated under three extreme environmental challenges: continuous salt aerosol loading, high-temperature heating, and organic solvent treatment. The results reveal that HMN consistently exhibits superior FE and greater stability under all tested conditions. For instance, after heating at 130°C for 30 min, the FE of HMN decreased slightly from 99.56% to 94.19%, whereas that of CMN dropped significantly from 91.84% to 82.41%. Similarly, after complete immersion in isopropanol for 24 h, the FE of CMN and HMN declined to 37.26% and 55.91%, respectively. These findings indicate that hydro charging technology not only generates a higher charge density but also enhances charge retention, thereby improving charge stability and enabling long-term filtration performance.

This investigation employs low-velocity impact (LVI) and quasi-static compression testing to evaluate failure modes in hot-pressed CFRP T-joints under corner-based out-of-plane impacts. Post-impact tensile testing quantifies LVI-induced strength reduction mechanisms. In order to improve the strength of CFRP T-joints, the effects of impact resistance and residual strength were studied by changing different suture methods and parameters. Experimental results demonstrate that the improved lock stitching significantly enhances the mechanical properties of T-joints. This improvement is attributed to the tighter interfacial connection between specimens and fibers achieved through the optimized stitching pattern. The ductile deformation of stitches enables effective energy absorption during impact loading, thereby reinforcing the structural integrity of the composite assembly. For instance, after the same LVI loading, the tensile strength of IS-20 J is more than 19.8% higher than that of US-20 J.

The use of adhesive joints in marine environments for extended periods and under adverse environmental conditions leads to accelerated adhesive degradation. Therefore, this study aims to perform a dual analysis, both experimental and FEM, based on steel–polyurethane–steel adhesive joints to evaluate their fracture behaviour in Mode I under degradation conditions caused by accelerated polymer aging, due to the combined effects of moisture (seawater immersion) and high temperature (50°C). Experimental tests provided insights into the moisture concentration profiles within polyurethane, determining its critical concentration (0.61%) and diffusion coefficient (5.105 × 10 −13  m 2 ·s −1 ). Additionally, the variation curve of fracture energy versus elongation and the cohesive behaviour law of polyurethane were obtained (maximum stress of 0.32 MPa with a deformation of 0.02 mm). These experimental results enabled the development of an FEM analysis of the polyurethane adhesive joint, allowing for the simulation of the polyurethane–steel interface behaviour under adverse environmental conditions and constant Mode I loading. This approach makes it possible to predict both the failure moment and failure mode of the joint.

Rapid plastic consumption has increased global plastic waste, with polyethylene terephthalate (PET) widely used in packaging. Recycling PET is challenging, as conventional methods often fail to manage the growing waste stream. Additive manufacturing (AM) offers a way to repurpose PET waste into useful products. Preserving the mechanical and physical properties of recycled PET (rPET) during printing is essential. This study used a design of experiments approach to optimize AM parameters, including nozzle temperature, bed temperature, and print speed. Mechanical tests evaluated tensile strength, Young’s modulus, and failure strength. Results revealed optimal conditions that improve part quality and performance. The study identified optimal printing parameters that significantly enhance both dimensional accuracy and mechanical properties of rPET parts, validating their suitability for functional AM applications and advancing circular economy efforts.

The fiber hybridization and stacking sequence of composite armors can significantly improve the ballistic performance and enhance the safety and survivability of military equipment. This article proposes a new structure (buffer/rigid/toughness/energy absorbing layers) of the carbon/aramid/ultra-high molecular weight polyethylene hybrid composite armor (K 3 C 6 K 12 U 6 ) based on multi-scale simulations, and the residual velocity decreased by 20 m·s −1 and ballistic protection index increased by 16%. The buffer layer at the facing surface disperses the stress concentration and increases the transverse strain and energy absorption. The rigid layer absorbs the kinetic energy through shear deformation. The toughness layer increases the stress area and friction effect through the stretching of aramid fibers. The energy absorbing layer on the rear surface decelerates delamination failure and enhances energy absorption and penetration resistance of the composite armor. This article provides a theoretical basis for the structural design and performance optimization of the composite armor, which is of great significance for modern warfare and national defense construction. Graphical abstract

Bending is a common mechanical load in carbon fiber resin matrix composites, often leading to brittle damage and various failure modes. This study explored the crack propagation and delamination in orthogonally laminated carbon fiber composites under positive and negative bending loads through staged unloading tests. The main failure modes included matrix cracking, fiber fracture, and interlaminar delamination. The study found that laminates with a 90° contact layer had higher bending strength than those with a 0° contact layer. However, the 90° laminate was more prone to delamination under positive bending loads, with both transverse and longitudinal cracks. The 0° laminate exhibited faster crack propagation than delamination under negative bending loads, with transverse cracks dominating, resulting in poorer flexural strength. The study emphasizes the importance of interlaminar bonding strength and the loaded contact layer in optimizing composite layer design for better practical engineering applications.

Here, we report a novel method for regulating the morphology of block copolymer assemblies through the use of reversible addition–fragmentation chain transfer dispersion polymerization in ethanol. In this method, poly( N , N -dimethylacrylamide) is used as a macromolecular chain transfer agent, and the side chain length of the ionic liquid monomer is modified. A notable change in the morphology of the alkyl-imidazole monomer (1-alkyl-3-(4-vinylbenzyl) imidazolium tetrafluoroborate) was observed when the side chain length was modified from methyl to butyl. This phenomenon can be attributed to a structural change in the alkyl imidazole monomers, which resulted in enhanced solvent-phobic properties. The polymerization kinetics and glass transition temperatures of the block polymers were investigated. These results demonstrated that the polymerization rate increased with increasing number of side chains, whereas the glass transition temperature of the block polymers decreased. It provides a novel approach for the synthesis and utilization of poly(ionic liquid) block polymers with higher-order morphologies. Graphical abstract Synthesis of the poly( N , N -dimethylacrylamide)- b -poly(1-alkyl-3-(4-vinylbenzyl)imidazolium tetrafluoroborate) (PDMA 43 - b -PIL x ) block copolymers prepared by RAFT ethanol dispersion polymerization at 70°C.