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Over the course of many years of use, impingement wear from dust, sand, and other materials can damage wind turbine blades, necessitating repairs and other maintenance work. Recently, wind turbine operators are turning to protective films, which allow such work to be completed more efficiently, as an alternative to the conventional approach of using paint to repair wind turbine blades. However, the erosion resistance characteristics of repaired blades remain unclear. In this study, we create paint- and protective film-coated samples to reproduce repairs, measure their erosion resistance, and study underlying factors in an effort to verify the erosion resistance of repaired materials and associated mechanisms. The low erosion resistance of GFRP can be significantly improved by applying a protective film made of a ductile material. Such material effectively protects the surface of the GFRP. Moreover, the erosion resistance of protective films made from polyurethane material is superior to that of paint. We recommend use of protective film with wind turbine blades when manufacturing blades and regular maintenance. [ABSTRACT FROM AUTHOR]

In this study, impact-resistant polypropylene (MPP), thermoplastic polyurethane (TPU) and polypropylene-grafted maleic anhydride (MA) are made into MPP/TPU/MA blends using melt-compounding and injection methods. The blending morphology, crystallization behavior, and melting and thermal behaviors of the blends are evaluated in terms of the content of TPU and MA, examining the influences of the parameters. The scanning electron microscope (SEM) observation shows that 1 wt% of MA can effectively enhance the interfacial adhesion and compatibility between MPP and TPU. The differential scanning calorimetry (DSC) results show that the crystallization temperature and melting temperature of the blends are not dependent on the content of TPU or MA. However, using TPU and MA adversely affect the crystalline and melting enthalpy of the blends. The thermogravimetric analysis (TGA) and derivative thermogravimetry (DTG) curve both show that the higher the MPP, the greater the thermal stability of TPU. Likewise, using MA as compatibilizer also has a positive influence on the thermal stability of the blends. The X-ray diffraction (XRD) analyses confirm that the addition of TPU decreases the diffraction intensity of MPP, but does not harm the crystalline structure of MPP. Moreover, the addition of MA improves the compatibility between MPP and TPU. MA marginally decreases the peak value and does not influence the crystallinity degree of MPP. It is expected that the results of SEM, DSC, TGA, DTG, and XRD can serve as a valuable reference for the design of composites with improved thermal and crystallization behaviors. Keywords: Impact-resistant polypropylene, Thermoplastic polyurethane, Maleic anhydride, Thermogravimetric analysis, Derivative thermogravimetry, Blends, Crystallization

With high specific strength, carbon fiber reinforced plastic (CFRP) is used in many fields. Repair is necessary when the strength of the leading edges of aircraft wings (CFRP) and wind power turbine blades (CFRP) are damaged by lightning strikes or collisions with birds. Some studies have been conducted on the mechanical properties of repair methods, but they do not address erosion characteristics. In order to develop a high quality repair method, this study examined the repair patch and fabricating samples that reproduces the conditions associated with the current repair method, the erosion characteristics of the sample were investigated using the erosion test. Differences in the adhesive used to affix the repair patch to the base plate have little effect on the erosion resistance of repaired areas, but deteriorations in adhesion between the repair patch and base plate result in degraded erosion resistance in the repaired area. With regard to the mechanism by which post-repair erosion resistance characteristics changed, our tests revealed that adhesive irregularities between the repair patch and base plate allowed impact energy from particle collisions to cause the repair patch to vibrate, and the resulting fatigue breakdown caused resin and fiber fragments to more readily separate, accelerating erosion. [ABSTRACT FROM AUTHOR]

Extrusion is employed to combine carbon fiber tows and thermoplastic polyurethane (TPU) blend. TPU‐cladded carbon fibers undergo knitting to form carbon fiber knitted composites. Microscopic observation proves that the compound carbon fibers are composed of a double‐layered structure with interfacial bonding and fiber axial alignment. In addition, the TPU coating can reduce friction during knitting, which provides the carbon fiber knitted composites with flexibility and resilience. Regarding the mechanical properties, the tensile strength is in direct proportion to the number of lamination layers. In particular, six‐layered knitted composites exhibit an optimal tensile strength of 43.72 MPa, whereas four‐layered knitted composites exhibit optimal tensile elongation. Through the manufacturing and evaluations in this study, continuous carbon fibers can be fabricated via extrusion, thereby obtaining a knitted structure that can be laminated to strengthen the mechanical properties and electromagnetic interference shielding efficacy of the laminated composites. Large composites can also be achieved, which overcomes the limits of continuous carbon fibers in subsequent production. © 2021 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

Christian ideas are having some influence on public discussions of changing paradigms in China. As the Maoist paradigm is waning, reformers are conducting a critical evaluation of the old paradigm and seeking a new paradigm that will solve problems of modernization and morality that China is experiencing. Some intellectuals, influenced by postmodernism and deconstruction, do not support any new value paradigm. The idealists adhere to either Neo-Confucianism-Neo Marxism, liberalism or Christianity.

Sandwich‐structure materials consist of a high‐strength skin material and a lightweight core material. The advantages of sandwich structures are known to include excellent mechanical properties and low weight, the latter of which is the result of a lightweight core. However, soft‐core members such as plastic foam materials have low rigidity and therefore may not exhibit adequate functionality when used in sandwich structures. This research sought to reduce environmental impact and to facilitate sustainable development by developing a method for fabricating high‐strength carbon foam using alkali lignin for use as an FRP sandwich core and enhancing the mechanical properties of the carbon foam with short glass fiber. PMMA particles decomposed at high temperatures to leave gaps, creating carbon foam with a closed structure. The relationship between PMMA particle size and foam pore size was investigated by observing cross‐sections of the foam. [ABSTRACT FROM AUTHOR]

In this study, three differently composed polyurethane (PU) composites are developed and then compared with the pure PU foam in terms of combustion resistance and mechanical properties using the compression test, the drop-weight impact test, the horizontal burning test, and the sound absorption test. Flame-retardant fabric (FRF)-PU is composed of PU foam that is enclosed with two cover sheets of FRFs. FR-PU10 is composed of PU foam that contains 10 wt% of flame-retardant agents. FRF-PU10 is composed of PU foam containing 10 wt% of flame-retardant agents and enclosed by two covers sheets of FRFs. Based on the test results, both FR-PU10 and FRF-PU10 are structurally stabilized and have good combustion resistance. The sample using FRFs as cover sheet had the same combustion resistance property and better compression resistance as the sample using flame-retardant agent. The carbonized layer extinguishes the alighted samples and stops the fire spread right after they are out of the source of fire, suggesting the FRF-PU10 is flame retardant. In addition, FRF-PU10 is easier to process and healthier because of the low use of flame retardants. Therefore, in this study, we proposed PU foam composites have good mechanical and flame-retardant properties and are a suitable candidate for productions of vehicles, plants, construction, and staple merchandises. [ABSTRACT FROM AUTHOR]