Studies on acoustic properties of non-woven fabrics

This study is divided in to two main parts. The first part deals with the optimization of process parameters of needle-punched non-woven fabrics for achieving maximum sound absorption by employing a Box-Behnken factorial design. The influence of fibre type, depth of needle penetration and stroke frequency on sound absorption properties were studied. These parameters were varied at three levels during experimental trials. From multiple regression analysis, it was observed that the depth of needle penetration alone was the most dominant factor among the selected parameters, which was followed by the interaction between depth of needle penetration and stroke frequency. Fibre type was the least dominant parameter affecting sound absorption. A maximum sound absorption coefficient of 47% (0.47) was obtained from the selected parameters. The results showed that for a process such as needle-punching, which is influenced by multiple variables, it is important to also study the interactive effects of process parameters for achieving optimum sound absorption. The second part of the study deals with the effect of type of natural fibre (fineness), and the blending ratio (with PET fibres) on the air permeability of the needle-punched non-woven fabrics and then it proceeds to study the effect of the air-gap, type of natural fibre (fineness) and blending ratio (with PET fibres) on sound absorption of needle-punched non-woven fabrics. These parameters are tested individually and their two way interaction (synergy) effect using ANOVA. The air-gap was varied from 0mm to 25mm with 5mm increments, three natural fibre types were used and all were blended with polyester fibres at three blending ratios for each natural fibre type. The Univariate Tests of Significance shows that all three parameters have a significant effect on sound absorption together with two two-way interactions, with the exception of the Blend Ratio × Air Gap two-way interaction which was not significant. It was found that the sound absorption improves with the increase in the air-gap size up to 15mm after which sound absorption decreased slightly with the further increase in the air-gap up to 25mm

Characterization of Yarn Diameter Measured by Different Systems

katedra: KTT; přílohy: 1 CD; rozsah: 88 s.This thesis work tries to establish ways of comparing yarn diameter measurement values obtained from different measuring systems particularly Uster Tester 4 and QQM 3 as attempts have been made in the past to try and correlate the results from these two instruments. The work will also try and further investigate the versatility of the D-Yarn program in analyzing yarn diameter (and its variations) data compared to other similar analyzing systems. Yarn diameter and its variations together with hairiness were measured and compared accordingly, using various instruments and systems and from there, conclusions were drawn as to the comparability (correlation) of the results from these instruments.This thesis work tries to establish ways of comparing yarn diameter measurement values obtained from different measuring systems particularly Uster Tester 4 and QQM 3 as attempts have been made in the past to try and correlate the results from these two instruments. The work will also try and further investigate the versatility of the D-Yarn program in analyzing yarn diameter (and its variations) data compared to other similar analyzing systems. Yarn diameter and its variations together with hairiness were measured and compared accordingly, using various instruments and systems and from there, conclusions were drawn as to the comparability (correlation) of the results from these instruments