Abstract The viscoelastic behavior of fabric under compaction is of crucial importance to the preforming process of fabric reinforced composites. Here, a viscoelastic model was originally proposed to characterize the compression and relaxation behavior for the 3D stitched carbon fabric with different stitching parameters. The compaction experiments were conducted to validate the proposed model. The established viscoelastic model agrees well with the experimental results and effectively captures the stress evolution. In the compression stage, the elastic modulus of the spring element is confirmed to play a dominating role in the rapid growth of compressive stress. The reduction of stitching space leads to the enhancement of the fiber volume fraction. Correspondingly, the elastic modulus of the spring element is remarkably enlarged. In the relaxation stage, the decreasing stitching space and the diagonal stitching pattern reduce the viscous stress in the fabric, resulting in the reduction the stress relaxation ratio of the first and second Maxwell elements. The enhanced elastic stress relaxation ratio indicates the weakened relaxation ability. As the restriction effect of the stitching thread primarily acts on the parallel fibers, the delay time of the second Maxwell element is much smaller than the delay time of the first Maxwell element. The viscoelastic model provides a significant insight into the viscoelastic behavior, especially the mechanism and influence of the stitching parameters on the 3D stitched carbon fabric.

中文翻译：

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模拟具有不同缝合参数的 3D 缝合碳纤维织物的粘弹性压实行为

摘要 织物在压实下的粘弹性行为对织物增强复合材料的预成型过程至关重要。在这里，最初提出了粘弹性模型来表征具有不同缝合参数的 3D 缝合碳织物的压缩和松弛行为。进行压实实验以验证所提出的模型。建立的粘弹性模型与实验结果吻合良好，有效地捕捉了应力演化。在压缩阶段，弹簧元件的弹性模量被证实在压缩应力的快速增长中起主导作用。缝合空间的减少导致纤维体积分数的增加。相应地，弹簧元件的弹性模量显着增大。在松弛阶段，缝合间距的减小和对角线缝合图案降低了织物中的粘性应力，从而降低了第一和第二麦克斯韦元件的应力松弛比。增强的弹性应力松弛比表明松弛能力减弱。由于缝合线的约束作用主要作用在平行纤维上，因此第二麦克斯韦元件的延迟时间远小于第一麦克斯韦元件的延迟时间。粘弹性模型提供了对粘弹性行为的重要洞察，尤其是缝合参数对 3D 缝合碳织物的机制和影响。导致第一和第二麦克斯韦单元的应力松弛比降低。增强的弹性应力松弛比表明松弛能力减弱。由于缝合线的约束作用主要作用在平行纤维上，因此第二麦克斯韦元件的延迟时间远小于第一麦克斯韦元件的延迟时间。粘弹性模型提供了对粘弹性行为的重要洞察，尤其是缝合参数对 3D 缝合碳织物的机制和影响。导致第一和第二麦克斯韦单元的应力松弛比降低。增强的弹性应力松弛比表明松弛能力减弱。由于缝合线的约束作用主要作用在平行纤维上，因此第二麦克斯韦元件的延迟时间远小于第一麦克斯韦元件的延迟时间。粘弹性模型提供了对粘弹性行为的重要洞察，尤其是缝合参数对 3D 缝合碳织物的机制和影响。第二个麦克斯韦元件的延迟时间远小于第一个麦克斯韦元件的延迟时间。粘弹性模型提供了对粘弹性行为的重要洞察，尤其是缝合参数对 3D 缝合碳织物的机制和影响。第二个麦克斯韦元件的延迟时间远小于第一个麦克斯韦元件的延迟时间。粘弹性模型提供了对粘弹性行为的重要洞察，尤其是缝合参数对 3D 缝合碳织物的机制和影响。