| Warp-knitted spacer fabric is a three-dimensional knitted fabric of sandwich structure, which is composed of an upper layer, a lower layer and a middle layer connecting the two surface layers. Spacer fabric is gradually becoming the preferred structural material in the field of cushion material under dynamic conditions for good vibration-absorption performance. The paper focuses on the vibration transfer properties of warp-knitted spacer fabric, and explore the relationship between structure and vibration performance. So, it can provide optimization guidance for the design and application of cushion material. The main research contents include:(a)Effect of structural parameters on compression behavior. Plate compression test is conducted to analyze the effect of different structure parameters of spacer fabric on compression performance.(b)Effect of structural parameters on vibration damping behavior. Theoretical model of damping coefficient is established and the knocking test is conducted to analyze the effect of different structure parameters of spacer fabric on vibration damping performance.(c)Effect of structural parameters on vibration transfer behavior. Theoretical model of vibration transfer coefficient is established and the sine excitation vibration test is conducted to analyze the effect of different structure parameters of spacer fabric on vibration transfer coefficient. Conclusions can be drawn as follows:(1)Based on the plate compression test, effect of different structure parameters of spacer fabric on compression performance is concluded as follows:(1)The thickness of spacer fabrics increases from 5.96 mm to 13.23 mm. The compression work increases from 0.433 J to 1.076 J, but the initial stiffness is from 59.0Kpa to 68.7Kpa to 30.5Kpa,and the recovery rate is from 0.67 to 0.59 to 0.74.It indicates that the larger the thickness of spacer fabric, the greater the compression work; while there is an optimal range for the initial stiffness and recovery rate.(2)The diameter of spacer yarn of three sets of spacer fabric increases from 132.6μm to 192.7μm, from 178.0μm to 228.1μm, from 169.7μm to 204.3μm, respectively. The compression work increases from 0.213 J to 0.433 J, from 0.265 J to 0.501 J,from 0.528 J to 0.814 J, respectively, and the initial stiffness increases from 37.4Kpa to 59.0Kpa, from 29.4Kpa to 39.1Kpa, from 46.8Kpa to 68.7Kpa, respectively, and the recovery rate increases from 0.61 to 0.67,0.59 to 0.64,0.69 to 0.74. It demonstrates that the greater the diameter of spacer yarn, the greater the compression work and the initial stiffness, and the compression elasticity is better and it is more difficult to be compressed.(3)The areal density increases from 439.5g/m2 to 616.3g/m2, and the compression work increases from 0.425 J to 0.481 J, and the initial stiffness increases from 53.3Kpa to 64.1Kpa,but the and the recovery rate is from 0.76 to 0.79. It manifests that the greater the areal density, the greater the compression work and the initial stiffness, and the better the compression elasticity and it is more difficult to be compressed.(4)The angle of spacer yarn of two sets of spacer fabric increases from 19.7° to 38.6°, from 18.9° to 31.5°, respectively. The compression work increases from 0.325 J to 0.425 J, from 0.345 J to 0.466 J, respectively; and the initial stiffness increases from 45.4Kpa to 53.3Kpa, 42.7Kpa to 51.2Kpa, respectively, and the recovery rate increases from 0.71 to 0.76,0.62 to 0.69. It displays that the larger the angle of spacer yarn, the greater the compression work and the initial stiffness, and the better the compression elasticity.(5)Comparing X–shaped with V–shaped of the arrangement of spacer yarn, the compression work increases from 0.433 J to 0.315 J, and the initial stiffness increases from 59.0Kpa to 32.4Kpa, and the recovery rate increases from 0.63 to 0.67, which shows that compression elasticity is better, and it is more difficult to compress the spacer fabric in initial phase for the X-shaped arrangement of spacer yarn.(2)Theoretical model of damping coefficient is established based on a single-degree-of-freedom system composed of mass, spacer fabric and vibration platform. The knocking test is conducted to acquire the acceleration & time curve. Then, the damping ratio, logarithmic decay rate, free vibration period are acquired further. The conclusions are drawn as follows: The experimental and theoretical attenuation curves of displacement and time are almost identical, and errors between the theoretical and experimental damping ratio, logarithmic decay rate, free vibration period are all very small. The maximum errors of the experimental and theoretical logarithmic decay rates and free vibration periods are 4.30% and 15.86%, respectively. It exhibits that the theory curves are almost identical to the testing curves. So the theoretical formulas can be used to express the decaying-degree of the spacer fabric.Effect of different structure parameters of spacer fabric on damping property is concluded as follows:(1)The thickness of spacer fabrics increases from 5.96 mm to 13.23 mm.The damping ratio increases from 0.092 to 0.145,which indicates that the thicker the spacer fabric thickness, the greater the damping ratio.(2)The diameter of spacer yarn of three sets of spacer fabric increases from 132.6μm to 192.7μm, from 178.0μm to 228.1μm, from 169.7μm to 204.3μm, respectively. The damping ratio increases from 0.078 to 0.092, 0.079 to 0.114, 0.081 to 0.105, respectively, which shows that the greater the diameter of spacer filament, the larger the damping ratio.(3)The areal density increases from 439.5g/m2 to 616.3g/m2. The damping ratio increases from 0.132 to 0.161. It manifests that the greater the areal density, the greater the damping ratio.(4)The angle of spacer yarn of two sets of spacer fabric increases from 19.7° to 38.6°, from 18.9° to 31.5°, respectively. The damping ratio increases from 0.089 to 0.132, 0.134 to 0.172. It draws conclusions that the greater the angle of spacer yarn, the greater the damping ratio.(5)Comparing X–shaped with V–shaped of the arrangement of spacer yarn, the damping ratio increases from 0.081 to 0.092, which explains that the damping ratio of the X-shaped arrangement of spacer yarn is better.(3)Based on the theoretical model of vibration transfer coefficient under sine excitation, the single-degree-of-freedom vibration system consisting of mass, spacer fabric and vibration platform is established. The sine excitation test is conducted to obtain vibration transfer coefficient and frequency curve. Then, the natural frequency and the maximum transfer coefficient are calculated. The theoretical and experimental results are compared, and the conclusions are drawn as follows: The maximum errors of the experimental and theoretical results for natural frequency and transfer coefficient are 14.64% and 2.13%, respectively. It demonstrates that the theory curves are almost identical to the experimental result. So, the theoretical formulas can be used to express the vibration transfer performance of the spacer fabric.Effect of different structure parameters of spacer fabric on vibration transfer performance is concluded as follows:(1)The thickness of spacer fabrics increases from 5.96 mm to 13.23 mm.The natural frequency is from 49.75 Hz to 52.29 Hz to 39.48 Hz, and the maximum transfer coefficient increases from 4.81 to 4.05. It shows that the thicker the spacer fabric thickness, the smaller the maximum transfer coefficient, while there is an optimal range of the natural frequency.(2)The diameter of spacer yarn of three sets of spacer fabric increases from 132.6μm to 192.7μm, from 178.0μm to 228.1μm, from 169.7μm to 204.3μm, respectively. The natural frequency increases from 44.84 Hz to 49.75 Hz, from 40.06 Hz to 43.55 Hz, from 42.48 Hz to 52.29 Hz, respectively; and the maximum transfer coefficient increases from 5.06 to 4.81, from 5.98 to 5.48, from 5.03 to 4.31, respectively. It indicates that the greater the diameter of spacer filament, the smaller the maximum transfer coefficient and the greater the natural frequency;(3)The areal density increases from 439.5g/m2 to 616.3g/m2. The natural frequency increases from 51.53 Hz to 54.16 Hz, and the maximum transfer coefficient increases from 3.82 to 3.44. It exhibits that the greater the areal density, the smaller the maximum transfer coefficient and the greater the natural frequency.(4)The angle of spacer yarn of two sets of spacer fabric increases from 19.7° to 38.6°, from 18.9° to 31.5°, respectively. The natural frequency increases from 45.71 to 51.53 Hz, from 49.25 Hz to 52.99 Hz, respectively, and the maximum transfer coefficient increases from 4.26 to 3.82, 4.68 to 3.56, respectively. It shows that the greater the angle of spacer yarn, the smaller the maximum transfer coefficient and the greater the natural frequency.(5)Comparing X –shaped with V –shaped of the arrangement of spacer yarn, the natural frequency increases from 49.75 Hz to 43.61 Hz, and the maximum transfer coefficient increases from 4.81 to 5.52, which indicates that the natural frequency is greater, while the maximum transfer coefficient is smaller when the arrangement of spacer yarn is X –shaped. |
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