Protocol for preparation of highly durable superhydrophobic bulks with hierarchical porous structures.

Superhydrophobic surfaces face challenges in comprehensive durability when used in extreme outdoor environments. Here, we present a protocol for preparing nanocomposite bulks with hierarchical structures using the template technique. We describe steps for using hybrid nanoparticles of polytetrafluoroethylene and multi-walled carbon nanotube to fill inside and dip on the polyurethane (PU) foam. We then detail procedures for its removal by sintering treatment. The extra accretion layer on the PU foam surface was highlighted to construct hierarchical porous structures. For complete details on the use and execution of this protocol, please refer to Wu et al.1.

Super tough and high adhesive eutectic ionogels enabled by high-density hydrogen bond network.

Ionogels have attracted tremendous interest for flexible electronics due to their excellent deformability, conductivity, and environmental stability. However, most ionogels suffer from low strength and poor toughness, which limit their practical applications. This article presents a strategy for fabricating ionogels with high toughness by constructing high-density hydrogen bonds within their microstructure. The ionogels exhibit a maximum fracture strength of 11.44 MPa, and can sustain a fracture strain of 506%. They also demonstrate a fracture energy of 27.29 MJ m-3 and offer a wide range of mechanical property adjustments (fracture stress from 0.3 to 11.44 MPa, fracture strain from 506% to 1050%). Strain sensors assembled with ionogels demonstrate exceptional sensing performance and enable motion detection of human joints. This study provides a new approach for achieving strong and tough ionogel design used for high-performance flexible electronic applications.

Stitching Repair for Delaminated Carbon Fiber/Bismaleimide Composite Laminates.

Due to the excellent mechanical properties and heat resistance, bismaleimide matrix composite materials have been widely used in aircraft. However, they are susceptible to low-energy impacts, such as bird hits, gravel, tools falling, etc., which can easily result in delamination. The delamination can significantly reduce the compression performance of composites and become a potential hazard for aircraft in service. In this paper, a stitching method developed from the Z-pin manufacturing process was proposed to repair delaminated laminates. Firstly, the delaminated area was stitched by fiber bundles that were pre-impregnated with glue. Then, the fiber bundles threading through the laminate become the pins after the curing process, thus producing the bridging effect between delaminated layers. As a result, the in-plane compressive properties of the laminate are enhanced. The parameters, including the size, number, and position of the stitching hole, for the stitching repair were optimized, and the factors affecting the repair effect were discussed through both finite element analysis and experiments. The results showed that for a carbon fiber/bismaleimide composite plate with a circular delamination roughly 30 mm in diameter, the in-plane compressive strength can be recovered from 54.45% to 84.23% of the pristine plate, and the modulus was fully recovered.

Molding processed multi-layered and multi-functional nanocomposites with high structural ability, electrical conductivity and durable superhydrophobicity.

Bioinspired superhydrophobic surfaces are mainly attributed to nano/micro textures and low surface energy materials, and have exciting potential for use in fields such as self-cleaning, water-proofing, anti-icing, anti-fouling, and so forth. However, the natural weakness of such delicate hierarchical surface structures pose great challenges to using artificial superhydrophobic surfaces under harsh mechanical conditions. Completely transforming multi-layered composite materials with good structural ability into superhydrophobic surfaces would greatly extend their durability under continuous mechanical abrasion. Endowing these composites with electrical conductivity could further expand their scope of application, especially in anti-static environments. Here we employ a facile molding process to fabricate a new type of multi-layered and multi-functional nanocomposite (MMNC), with a tensile strength up to ∼226.4 MPa, a modulus of up to ∼24.8 GPa, a surface electric conductivity of ∼1.2 S cm-1, a water contact angle of ∼155.4° and a water sliding angle of ∼2.0°. These multi-layered and multi-functional nanocomposites (MMNCs) demonstrate robust water-repellency under harsh mechanical abrasion (tested using a high tack sticky tape peel, cyclic sand paper abrasion and even file abrasion) and strong chemical corrosion (tested by using hydrochloric acid, sulfuric acid and sodium hydroxide solutions). Additionally, our MMNCs are highly resistant to water impalement (tested by turbulent water jet impact with a velocity of up to ∼29.5 m s-1 and a corresponding Weber number of ∼32 000). The robustness of the superhydrophobicity is multifaceted, and owing to the excellent structural performance and conductivity, these MMNCs could find potential uses in vehicles, containers, wind blades, infrastructures, electronics and so forth, which usually experience comprehensively harsh conditions such as rainfall, abrasion, static electricity, high loads and so forth.

Interface conjugation enhances the interface adhesion performance of carbon fiber-reinforced phthalonitrile composites by π-π stacking.

There has been little research focus on the interface problems of phthalonitrile (PN) resin and carbon fiber. However, interface performance is related to the overall mechanical properties of composites and is very important. This study focused on the interfacial performance and adhesion mechanism of a carbon fiber Cf/PN composite. Micro-composites of Cf/PN and Cf/epoxy resins were prepared, and their interfacial shear strengths (IFSS) were tested by micro-droplet testing. The result showed that the IFSS of Cf/PN was higher than that of Cf/epoxy resin, indicating that the interfacial adhesion of the PN matrix composite must be more effective. To explain the obtained results, a number of tests, including SEM, SEM-EDS, FTIR, and TGA, were carried out. From the SEM analyses, cured PN polymer films were found on the surface of de-bonded carbon fibers. With the aid of SEM-EDS, the elements on the de-bonded carbon fiber surface of the Cf/PN composite were detected in situ. An interesting synchronous relationship was observed in the IFSS and SEM-EDS results. Through the FTIR spectra, the chemical structures of the PN polymers were identified. From the detailed analyses and discussion in this work, the effective interfacial bond function in the Cf/PN composite appears to be a complex result for all relative functions. The functional advantage of the PN composite may be the interface conjugation between the PN polymers and the graphene layer on the surface of the carbon fiber.