关键词: 氧化铝涂层织物, 氧化铝缝纫线, 缝合结构, 接缝强度, 接缝效率

Abstract: Facing the needs of planetary exploration and landing, flexible inflatable vehicle technology has become one of the most potential key technologies. Flexible inflatable aircraft require high temperature resistance and large size, and it is usually stitched by high-performance and high-temperature resistant fiber fabrics to form complex curved surface structures. Alumina fibers, with the characteristics of high modulus and good high temperature resistance, have become one of the most potential materials for thermal protection materials of flexible inflatable aircraft. After the alumina fibers are made into a fabric, the bending resistance is poor, and the surface coating treatment makes the fabric have better flexibility, gas barrier and heat insulation properties and mechanical properties. However, there is a lack of knowledge about the seaming method, seam performance, and seam failure mechanism of alumina-coated fabrics.
In order to explore the seaming performance and seam efficiency of alumina-coated fabrics, alumina-coated fabrics were sewn with alumina sewing threads. The effects of the stitch structure on the mechanical properties of the seam were explored by adjusting the number of strands, stripes, spacing and needle spacing of the sewing threads, and the changing rule of the seam efficiency was analyzed. The results show that the tensile breaking strengths of the alumina fabric before and after coating finishing are 586.5 and 638.7 N/cm, respectively. The coating improves the mechanical properties of the alumina-coated fabric, and the mechanical failure of the alumina-coated fabric shows brittle fracture. When the number of stitching strands is one and two, the seam strength of coated alumina fabric is 37.1 and 47.0 N/cm, respectively, and the seam strength of double strand stitching is 27% higher than that of the single strand. Double strand sewing can increase non-simultaneity of yarn breakage at seams. When the sewing spacing is 5 and 10mm, the difference in seam strength is small. As the sewing pitch gradually increases to 20mm, the seam strength improves significantly and the breaking strain of the fabric gradually decreases. When the number of sewing lines is 1, 2, and 3, the seam strengths of the fabrics are 35.0, 47.0, and 99.5 N/cm, respectively. With the increase of the number of seams lines, the seam strength of the alumina-coated fabrics increases significantly, indicating that the number of seams has great influence on the seam strength. With the increase in the number of sewing lines, the failure mode of the seam changes from collapse failure to slow oscillation failure, the load-bearing yarns increase, and the non-simultaneity of yarn breakage increases significantly. The seam strengths of the fabrics are 73.3, 47.0, and 26.6 N/cm when the stitching lengths of the thread are 3, 5, and 10 mm, respectively. The smaller the stitching length, the greater the stitching density, and the greater the resistance to slipping is between yarns during stretching. The seam efficiency of coated alumina fabric ranges from 4.2% to 15.6%. Based on the above results, it can be seen that in order to optimize the seam strength of coated alumina fabrics, double strands, multiple threads, and large spacing should be selected, and the stitching spacing should be reduced as many as possible within the allowable range of working conditions and production efficiency.

Key words: coated alumina fabrics, alumina stitching thread, stitching structure, seam strength, seam efficiency