Effect of Plasma-Treatment of Interleaved Thermoplastic Films on Delamination in Interlayer Fibre Hybrid Composite Laminates

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.

Plasma and Polymers: Recent Progress and Trends

Plasma-enhanced synthesis and modification of polymers is a field that continues to expand and become increasingly more sophisticated. The highly reactive processing environments afforded by the inherently dynamic nature of plasma media are often superior to ambient or thermal environments, offering substantial advantages over other processing methods. The fluxes of energy and matter toward the surface enable rapid and efficient processing, whereas the charged nature of plasma-generated particles provides a means for their control. The range of materials that can be treated by plasmas is incredibly broad, spanning pure polymers, polymer-metal, polymer-wood, polymer-nanocarbon composites, and others. In this review, we briefly outline some of the recent examples of the state-of-the-art in the plasma-based polymer treatment and functionalization techniques.

Preparation of multilayer electrospun nanofibrous scaffolds containing soluble eggshell membrane as potential dermal substitute

Electrospinning of natural and synthetic polymers has shown to be a great candidate for the fabrication of tissue engineering scaffolds due to their similarity to the nanofibrous structure of natural extracellular matrix (ECM). Moreover, the addition of ECM-like proteins could enhance the biocompatibility of these scaffolds. In this study, soluble eggshell protein (SEP) was first extracted and synthesized from the raw eggshell membrane. The characteristics and biocompatibility of the extracted SEP were evaluated using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) analysis and 3-(4,5- dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide) (MTT) assay. For scaffolds fabrication, a three-layer nanofibrous composite structure was produced using the electrospinning technique. The outer layers composed of polyvinyl alcohol, chitosan, and extracted SEP while the middle layer composed of polyethylene oxide, gelatin, and zinc oxide nanoparticles (ZnO-NPs). For each layer, the electrospinning parameters were adjusted to form bead-free fibers. To improve fibers' stability against body fluids, the produced fibers were crosslinked using glutaraldehyde vapor. Several techniques such as scanning electron microscopy (SEM), energy dispersive X-ray, ATR-FTIR, swelling, tensile test, in vitro biodegradation, and MTT assay were implemented to evaluate the physical, chemical, and biological characterization of the fabricated fibers. The results showed that crosslinked fibers have adequate stability in water, suitable mechanical properties, and promising water uptake capacity. The MTT results also revealed that SEP and ZnO-NPs could increase scaffolds biocompatibility. Moreover, SEM photographs of cultured fibroblasts cells on the scaffolds showed that cells were well attached on the scaffolds and preserve their natural spindle shapes. Altogether, our findings demonstrated that the produced three-layer composite scaffolds are potential candidates for skin tissue engineering.