活性炭纤维材料吸声性能分析

为研究活性炭纤维的吸声性能,在同一工艺条件下制备了不同规格粘胶基活性炭纤维毡,用传递函数法在250～1 600 Hz中低频率声波范围内采用阻抗管对活性炭纤维材料的吸声性能进行测试,分析材料比表面积、厚度、面密度、空腔厚度等参数对吸声性能的影响。结果表明:活性炭纤维毡多孔材料具有较好的吸声性能,其对声波中频段的吸声好于低频段,随材料的比表面积、厚度、面密度、空腔厚度的增加,其吸声性能越好,但平均吸声系数增幅不同。     

黄麻纤维对砂浆早期抗裂性能的试验研究

研究黄麻纤维在纤维掺量、纤维长度及混杂纤维配合比不同的情况下分别对砂浆早期抗裂性能的影响,并与聚丙烯腈纤维作对比研究。试验结果表明：黄麻纤维能有效地增强砂浆的早期抗裂性能,并随着纤维掺量的增加、纤维长度的减小以及混杂纤维中起主要作用的黄麻纤维含量的增加而增强;黄麻纤维对砂浆早期抗裂性能的增强效果不及聚丙烯腈纤维。     

车用PET/PP分散复合熔喷吸音材料的研究

本文采用分散复合融喷技术分别制得了PET/PP分散复合熔喷材料和羽毛/PP分散复合熔喷非织造材,研究了材料厚度、面密度、熔喷纤维平均直径对其吸引系数的影响,结果表明：吸声系数随着厚度的增加而增加;面密度对吸声系数影响较小,随着面密度的增加,样品的吸声系数也有所增加,但增幅较小;熔喷纤维平均直径在1.7~2.4μm内变化时对吸音系数无显著影响。另外,本文还进一步选用3M公司吸音产品和传统废纺毡吸引材料,对比分析了4种材料的吸音性能,结果表明：PET/PP分散复合熔喷吸音材料的吸音性能接近3M公司产品,而且其吸音性能优于传统车用废纺毡吸音材料及羽毛/PP分散复合熔喷非织造材料。     

棕榈纤维毡/聚(3-羟基丁酸酯-co-3-羟基戊酸酯)热压复合材料的吸声性能

为缓解当前我国汽车内饰用黄麻吸声复合材料产量缩减的现状,研究了棕榈纤维毡/聚(3-羟基丁酸酯-co-3-羟基戊酸酯)(PHBV)热压复合材料的吸声性能。在分析Johnson-Allard吸声模型后,研究了棕榈纤维毡与PHBV质量比、棕榈纤维毡面密度、棕榈纤维线密度、棕榈纤维毡梯度结构、多孔粉煤灰陶粒等对热压复合材料吸声系数的影响;探讨了优化工艺下棕榈纤维毡/PHBV热压复合材料的结构和性能。结果表明:当棕榈纤维毡与PHBV质量比为40∶60,棕榈纤维线密度为14.5 dtex,棕榈纤维毡梯度结构为143.3/102.5 g/m²时,制备的复合材料的平均吸声系数(200~1 600 Hz)最高,可达到0.53,添加质量分数为5%的多孔粉煤灰陶粒,可将复合材料的平均吸声系数提高到0.66,具有部分替代黄麻制备吸声复合材料的潜力。     

废弃羽毛的结构特征及其吸声性能

为对废弃羽毛资源进行合理化利用,借助多功能纤维投影仪、扫描电子显微镜、傅里叶变换红外光谱仪和X射线衍射仪分析了羽毛的大分子结构、聚集态结构及其形态结构,探究了羽毛结构与其吸声性能之间的关系。采用声阻抗传递函数法对羽毛及其他几种可用于吸声领域的纤维集合体进行吸声性能测试及对比。结果表明:几种纤维集合体吸声性能排序为废弃羽毛、木棉纤维、羊毛、大麻纤维、涤纶;在整个测试频率范围内废弃羽毛的吸声性能随纤维集合体密度的增加而提高,且纤维集合体最大吸声系数对应的吸声频率随纤维集合体密度的增加逐渐降低;废弃羽毛纤维具有优良的吸声性能,在吸声领域具有很高的应用价值。     

大豆蛋白纤维水刺非织造材料性能研究

分别采用大豆蛋白纤维和大豆蛋白/黏胶纤维制备水刺非织造材料,并对比了两种水刺非织造材料的基本性能。结果表明:在相同面密度下,大豆蛋白纤维水刺非织造材料比大豆蛋白/黏胶纤维水刺非织造材料的强力更高,柔软性更好,孔径更大,带液率更高;所有试样的横向强力均低于纵向强力,湿态强力均低于干态强力;试样的缠结系数和弯曲刚度随着面密度的增加而增加,孔径和带液率随着面密度增加而减小,弯曲刚度随着缠结系数的增加而增加,透湿量和带液率随着孔径的增加而增加;试样面密度越小,导湿性能越好。大豆蛋白纤维水刺材料可应用于医疗卫生领域。     

大麻纤维的吸声性能研究

为比较大麻纤维的吸声性能,采用驻波比法测试了大麻、羊毛和棉纤维在中、低频段下的吸声系数,研究了纤维层厚度、容重、后背空腔和孔隙率对吸声系数的影响。结果表明,增加大麻纤维层厚度、容重、后背空腔尺寸,均可提高大麻纤维在中、低频段的吸声系数。纤维层厚度增加,共振吸收频率向低频方向移动;容重增加,吸声系数开始时增加比较明显,随后增幅趋缓;孔隙率增加,大麻纤维吸声系数逐渐增大。当容重、厚度相同时,大麻纤维的吸声性能要比羊毛和棉纤维的吸声性能差。     

可降解黄麻/PBS复合材料的结构与力学性能

为解决当前环境污染和可持续发展问题,采用模压成型工艺制备可降解黄麻/PBS复合材料,通过拉伸、弯曲性能测试、红外分析和SEM观察,探讨纤维含量和碱处理对材料性能的影响。结果表明:随着纤维含量的增加,复合材料的拉伸强度先增大后减小,在纤维含量为10%时达到最大值,比纯PBS提高了30.1%;拉伸模量、弯曲强度和弯曲模量均随纤维含量的增大而提高,在纤维含量为30%时分别比纯PBS提高了24.2%、185.5%和107.7%。碱处理后黄麻纤维表面杂质被去除,表面部分刻蚀变粗糙,复合材料的综合力学性能得到提高,其中弯曲模量提高显著,比未处理的黄麻复合材料提高了58%。     

利用导电纤维生产抗静电混纺纱

介绍了利用有机导电纤维开发抗静电混纺纱的纺纱工艺和纱线电阻指标的测试方法。测试结果表明，只需混入少量的导电纤维，纱线的抗静电性能明显提高，而且纱线的导电性随着混入比例的增大而增加。     

麻纤维汽车内饰材料的吸声性能与针刺工艺的关系

本论文将黄麻纤维、苎麻纤维、大麻纤维分别针刺成毯,采用驻波管法测试其吸声系数,得出黄麻是很好的吸声材料。综合考虑原料来源及成本等因素,选取黄麻纤维为研究对象,利用单因素试验,分别探索针刺深度与针刺频率对黄麻针刺毯吸声性能的影响;以针刺深度、针刺频率、步进量为影响因素,设计3因素3水平正交试验,分别得出在200~500Hz的低频噪音范围内和630～2000Hz中频噪音范围内,使黄麻纤维针刺汽车内饰毯吸声系数最大时的最优工艺参数。     

羊毛及其混合纤维非织造材料的吸声性能

为优化羊毛非织造材料的吸声性能,以羊毛、毛/涤、毛/麻3种纤维制备非织造材料。通过阻抗管对3种非织造材料的吸声性能进行测试,分析了声波频率在250-6 300 Hz范围内,材料的纤维种类、厚度和空腔深度对其吸声性能的影响。结果表明,3种样品的平均吸声系数均大于0.2,纯毛非织造材料的吸声性能略好于毛/涤材料与毛/麻非织造材料;通过增加材料厚度或设置空腔的方式均可提高材料全频段（尤其中低频段）的吸声性能,其中厚度对材料吸声系数的影响程度更大;从环保、材料价格、便于施工等方面考虑,以厚度为6 mm的毛/麻非织造材料作为吸声材料,并设置6 mm的空腔, 即可达到较为优异的低频吸声性能。     

基于统计能量分析的簇绒地毯织机高频噪声抑制

为有效抑制簇绒地毯织机高频噪声,提出了基于统计能量分析(SEA)的簇绒地毯织机高频噪声降噪方法,并运用三聚氰胺多孔吸声材料实现了高频噪声的抑制。首先建立了包含13个结构子系统和10个声腔的簇绒地毯织机高频噪声SEA模型,随后采用理论计算方法确定了各子系统的模态密度、内损耗因子以及耦合损耗因子。实验测量了簇绒地毯织机工作时振动加速度信号从而获取SEA模型高频噪声声压级,并通过与簇绒地毯织机工作时实际声压级情况对比验证了SEA模型的有效性。最后在簇绒地毯织机表面粘附了不同厚度的三聚氰胺多孔吸声泡沫板实现降噪。结果表明:该方法能够满足工程上对簇绒地毯织机高频噪声抑制的要求,且噪声频率和三聚氰胺多孔吸声材料的厚度均对结果有影响。     

Sound absorption properties of acrylic carpets

Development of functional carpet structures is vital to improve sound quality of human life in transportation vehicles, residential and occupational environments. In this research, pile length and loop density parameters of acrylic carpets were studied to examine the effect on sound absorption properties. Carpet samples, with two different pile densities and four different pile lengths were produced for experimental purposes. Carpets with longer piles and dense loops result in the best sound absorption rates. Acrylic carpets produced with medium length piles and low density loops, yield better results at higher frequencies. Carpet samples with shorter piles and dense loops provide better sound absorption properties at low-to-mid frequencies. It has been observed that loop density and pile length parameters affect sound absorption properties at all frequency ranges. Anova analysis revealed that the combined effect of loop density and pile length parameters is evident in the mid and high frequency ranges.     

16—THE ACOUSTICAL PROPERTIES OF VARIOUS CARPET AND UNDERLAY COMBINATIONS

An account is given of measurements of the sound absorption and impact-insulation improvement for a range of carpets, underlays, and carpet–underlay combinations. It is shown that carpets, underlays, and woven carpet on underlay behave as simple porous absorbers. Tufted carpet on underlay behaves differently and exhibits a resonant peak in the absorption at 500–l000 Hz. The average absorption coefficient correlates well with the total thickness for all samples.

The average impact-insulation improvement of carpets, underlays, and combinations correlates reasonably well with the total thickness and with the maximum force measured during a simulated impact test involving the use of a single hammer containing an accelerometer. Either parameter would serve as an indicator of the impact performance of a carpet or carpet–underlay combination.     

车用废纺双密度毡吸声隔声性能研究

利用涤棉混纺纤维制得由一层紧密毡料和一层蓬松毡料构成的双密度毡,并测试了双密度毡的吸声和隔声性能.测试结果表明:双密度毡对高频噪声的吸收效果较好,而对低频噪声的吸收效果较盖;在一定范围内增加双密度毡的厚度,可以相应提高其吸声性能;材料的隔声性能与自身构件的振动频率有关,本试验样品的最高和最低隔声量分别出现在声波频率为3...     

Analysis of acoustic performance of glass fiber felts after water absorption and their estimation results by artificial neural network

Abstract

The acoustic performance of glass fiber felts after water absorption was researched in the paper. The effects of sound frequency and moisture content on the sound transmission loss (STL) and sound absorption coefficient (SAC) were analyzed. In addition, two types of artificial neural networks (ANN) were established to estimate the acoustic performance. In the first ANN model, the sound frequency and moisture content were chosen as input parameters to predict the STL and SAC values. In another model, the output parameters were replaced by the ratios of STL and SAC to areal density. In order to evaluate the accuracy of the two models, the mean relative error and correlation coefficient were calculated respectively. It has been proved that the predicted values resulted from ANN models fit well with the measured values.     

Analysis of the effect of fiber cross section and different bonding methods on sound absorption performance of PET fiber based nonwovens using Taguchi method

Abstract

In this study, sound absorption coefficients (SACs) of needle-punched and thermal-bonded nonwovens produced from polyester (PET) fibers with various cross sections, i.e., hollow, round and hexaflower, blended with a low melt PET, was reported. The acoustic performance of a hexaflower PET fiber was studied for the first time. Fibers were carded and then one set of samples was bonded by needle punching while the other set was air-through thermal bonded. A third set of samples was needled at various punch densities. Design of experiments was planned according to Taguchi method. Relationship between production parameters and SAC was analyzed using Minitab software. The most important independent variables affecting the sound absorption were areal density and web bonding method. The sample produced according to optimum production levels reached to a SAC value of 0.57 at 2000?Hz which could be a suitable choice for acoustic applications in the automotive industry.