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Composite materials are widely used in aerospace, automotive industry and medical equipment, where most of the structural parts are made of fiber laminates. Rotary braiding is one of the most important methods to prepare composite preforms. The ordinary rotary braided preforms have low porosity and dense yarns, but are single-layer structures after molding, which do not meet the needs of most applications. To solve the problem that traditional laminates are prone to delamination, this paper designs a flat cross-linked braiding process for the preparation of multilayer-interlocking composite panels. The carrier trajectory is analyzed, and the spatial coordinate system of the braided chassis is established by combining the effect of the end traction system on the morphology of the preform yarns. The numerical model of the preform is initially obtained by using cubic B-spline curve fitting, and an algorithm for gathering yarns towards the fabric center is proposed to optimize the numerical model. Experimental samples of flat cross-linked preforms are prepared according to the braiding process, and the reliability of the optimization algorithm is verified by comparing the yarn coordinates of the experimental samples with those of the optimized numerical model. [ABSTRACT FROM AUTHOR]

Poly(p-phenylenetere phthamide) fiber is a high-performance synthetic fiber whose reinforced composites are widely used for their advantages of high strength and lightweight. However, the further potential usage of poly(p-phenylenetere phthamide) and its reinforced composites is limited in areas such as antistatic materials, conducting materials, and electromagnetic shielding materials due to their high electrical insulation. To improve the electrical conductivity, an online polymerization coating technology was used to manufacture conductive poly(p-phenylenetere phthamide)/polyaniline composite yarns continuously. The conductive poly(p-phenylenetere phthamide)/polyaniline composite yarns' structure and properties such as surface morphology, electrical conductivity, Fourier-transform infrared spectroscopy spectra, thermogravimetric performance, and mechanical properties were studied in details. Then, three kinds of multiaxial composites were prepared by using the conductive poly(p-phenylenetere phthamide)/polyaniline composite yarn as the reinforcement and unsaturated polyester resin as a matrix, and the electromagnetic shielding performance of the composites was measured. The results indicated that the conductivity of conductive poly(p-phenylenetere phthamide)/polyaniline composite yarn can reach to ∼160 S/m. The thermogravimetric performance of poly(p-phenylenetere phthamide) was reduced after conductive treatment. The mechanical properties of the composite yarns, such as the breaking strength and elongation, remained unchanged when the oxidant concentration was lower than 0.6 mol/L and decreased with the increase in the oxidant concentration. The electromagnetic shielding composites show a certain anti-electromagnetic radiation capability, and the shielding effectiveness value increased with the axial number and density of the conductive poly(p-phenylenetere phthamide)/polyaniline composite yarns. For the tetra-axial composite with a conductive yarn density of 37 yarns per inch, the average shielding effectiveness value in the frequency range of 100 MHz to 1500 MHz can exceed 22 dB. [ABSTRACT FROM AUTHOR]

Novel biodegradable blend fibers based on the biomaterials poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P3HB4HB) and poly(lacticacid) (PLA) were successfully prepared by combining melt spinning and hot drawing. The results showed that the commixture could continuous and stable spin for a P3HB4HB ratio of 30–35 wt% and winding speed of 20–30 m/min. The thermal stability of the P3HB4HB/PLA blend fiber was increased, as determined by thermogravimetric analysis. The crystallinity degree of the P3HB4HB/PLA blend fibers increased with increasing the P3HB4HB content. The addition of PLA resulted in a low cold crystallization temperature and diminutive size of the lamellar stacks, which would be favorable for the enhancement of the mechanical properties of the blend fiber, when the P3HB4HB content was 30–35 wt%. The P3HB4HB/PLA composite fiber was one type of high‐strength and high‐toughness fiber, with 1 GPa breaking stress and over 80% strain at break. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48956. [ABSTRACT FROM AUTHOR]

Multi-needle water bath electrospinning is one of the most efficient methods used to prepare micro/nanofiber composite yarns. The nanofiber structure can be targeted and regulated to obtain high-performance composite yarns. To explore the effect of the receiving distance on the structure and properties of micro/nanofiber composite yarns, polyacrylonitrile nanofibers were uniformly coated on silver-coated nylon yarn via a four-needle continuous water bath electrospinning method. The electric field distribution at different receiving distances was simulated by ANSYS finite element analysis software, and the effects of electric field distribution on the structure and properties of the micro/nanofiber composite yarns were studied. The results indicated that the peak electric field intensity appeared at the tip of the needles and decreased with the increase in the receiving distance. The receiving distance was constant, and the field intensity was lower when the direction of the centerline of the needle tip was farther away from the tip; however, the field intensity at the conductive core yarn was higher than that in the surrounding area (small spikes). The average field intensity of the small spikes at 180 mm was only 1/4 of that at 80 mm. When the receiving distance increased within a certain range (100∼140 mm), the nanofibers had a smooth surface and good separation, their diameters decreased continuously and the porosity changed inversely. With a further increase in the receiving distance, the nanofibers gradually bonded, their diameter increased and the porosity showed the opposite trend. The coating rate of the nanofibers showed a decreasing trend, and the mechanical properties of the micro/nano composite yarns were improved. When the receiving distance was 100 mm, the porosity reached 38.94%, and the breaking force, breaking elongation and breaking strength were 13.71 ± 1.36 cN, 22.76 ± 6.62% and 0.15 ± 0.02 cN·dtex -1 , respectively. Upon consideration of all the above factors, the receiving distance of 100 mm is appropriate., (© 2023 IOP Publishing Ltd.)