Spread‐tow woven fabrics (STW) have attracted considerable attention because of their ultrathin structure and low porosity, which benefit the design and application of STW composites. Little is known about how the thickness relationship between the middle and surface layers affect the mechanical properties of sandwich structures. Therefore, this study developed an anti‐sandwich stitched composite with STW in the center and a nonwoven felt/STW hybrid on both sides. The interlayer shear behavior and damage mode transformation of STW composites with different middle‐layer thicknesses were studied using short‐beam shear tests, digital image correlation (DIC) full‐field strain nephograms and micro‐computed tomography (micro‐CT). The results showed that the anti‐sandwich structure improved the shear strength, particularly when the middle layer thickness was four times that of the surface layer. As the middle layer thickness ratio decreased, the synergistic effect of the anti‐sandwich structure was weakened, and the damage mode changed from ductile to brittle. Furthermore, the hybrid ratio of the STW/nonwoven fabric in the surface layer had little effect on the performance because of the good interfacial adhesion between the STW and nonwoven fabric. The anti‐sandwich structure that can improve the properties and stability of STW composites provides a reference for the structural design of STW composites in engineering applications.Highlights An anti‐sandwich composite was developed by spread tow woven fabrics. Nine types of anti‐sandwich composite were designed and fabricated. The thickness of the middle layer affected the synergistic mechanisms. The optimal anti‐sandwich structure has a 4.59% increase in shear strength. The specific shear strength is 14.86% higher over pure spread tow laminates.

中文翻译：

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反夹心结构展丝编织缝合复合材料的短梁剪切性能

丝束展布机织物（STW）因其超薄结构和低孔隙率而引起了广泛关注，这有利于 STW 复合材料的设计和应用。关于中层和表层之间的厚度关系如何影响夹层结构的力学性能知之甚少。因此，本研究开发了一种反夹心缝合复合材料，中间为 STW，两侧为非织造毡/STW 混合材料。利用短束剪切试验、数字图像相关（DIC）全场应变云图和微计算机断层扫描（micro-CT）研究了不同中层厚度的STW复合材料的层间剪切行为和损伤模式转变。结果表明，反夹心结构提高了剪切强度，特别是当中间层厚度是表层厚度的四倍时。随着中间层厚度比的减小，反夹层结构的协同作用减弱，损伤模式由塑性转变为脆性。此外，表层STW/无纺布的混合比例对性能影响很小，因为STW和无纺布之间具有良好的界面粘合力。能够提高STW复合材料性能和稳定性的反夹心结构，为STW复合材料在工程应用中的结构设计提供参考。 一种抗夹心复合材料是由展开丝束机织物开发的。 设计并制造了九种类型的反夹心复合材料。 中间层的厚度影响协同机制。 最佳反夹心结构的剪切强度提高了4.59%。 比剪切强度比纯丝束层压板高 14.86%。