纺粘非织造聚合物拉伸模型初探

为探究纺粘非织造工艺中工艺参数对纤维最终直径的影响,文章基于纺粘非织造聚合物拉伸过程,构建了纺粘非织造聚合物拉伸理论模型,并应用MATLAB对模型进行数值计算。同时,选取纺粘工艺参数中的气流初始速度、聚合物初始温度、聚合物质量流量3个因素,通过控制变量法比较观察不同方案下经过数值求解后得到的纤维直径,得出3个因素分别对纤维最终直径的影响。结果表明,气流初始速度越大,聚合物初始温度越高,聚合物质量流量越小,最终形成的纤维直径越细。     

超高分子量聚乙烯纤维增强中空蜂窝模压复合材料性能研究

为研制车船等壳体所用的轻质、高强复合板材,选用超高分子量聚乙烯(UHMWPE)短纤维纱,制备成单层经纬为120根/(10 cm)的平纹组织,采用多组经纱持续更替交织层的方法制成2L(1+0)型、4L(2+1)型、6L(3+2)型3种多层角联锁结构织物,采用扦插芯棒、模压成型方法制成菱形蜂窝状的热固性环氧树脂基中空板,并与2块真空吸液法制成的面板组成“三合一”复合板,同时测定了复合板材的结构特征及其平拉、平压和弯曲性能。结果表明:3种类型复合板的密度均远小于水的密度,其中6L(3+2)型最小,为0.48 g/cm³;复合板层数越多,环氧树脂越难渗透尤其是在中空板菱形交叉点处,复合板平拉、平压、抗弯曲强度则呈现递增,制成的6L(3+2)型复合板试样平压强度可达到1.03 MPa。     

冷拌冷铺超粘纤维磨耗层研究与应用

冷拌冷铺超粘纤维磨耗层作为一种新型技术,结合了微表处的材料特点和Novachip的施工工艺,具有优异的粘结性、防裂性、防水性、耐久性、环保性和经济性。本文从该项技术原理及性能要求、施工工艺及经济和社会效益进行了阐述。     

基于翻领松量结构模型的翻折领结构设计方法

为解决翻领松量计算精准性及翻折领通用结构设计方法的问题,提出了一种基于翻领松量结构模型的翻折领结构设计方法。通过构建翻领松量结构模型确定了翻领松量计算系数,对6种不同状态下的翻领间隙量变化进行数据统计分析,依据翻领间隙回归系数模型确定了翻领松量计算给定常数,运用SPSS统计软件对实验数据进行了相关性分析、回归分析、配对样本T检验,并推导出翻领松量计算公式。实验结果表明:使用该公式计算的翻领松量提高了翻折领结构造型的准确性,基于翻领松量结构模型的翻折领结构设计方法可以满足不同翻折领领型结构设计要求。     

PVA纤维对纳米水泥基复合材料单轴拉伸性能的影响

为研究PVA纤维掺量对掺纳米SiO_2水泥基复合材料抗拉性能的影响,通过单轴拉伸试验测得了试件的极限拉伸应变和极限拉伸应力,并得到了试件应力—应变关系曲线。纳米SiO_2的质量掺量为2%,PVA纤维采用五种体积掺量(0.3%、0.6%、0.9%、1.2%、1.5%)。结果表明,PVA纤维的掺加增大了纳米水泥基复合材料单轴拉伸试件的极限拉应变和极限拉应力。当PVA纤维体积掺量不大于1.5%时,随PVA纤维掺量的增大,试件极限拉应变逐渐增大,极限拉应力先增大后减小。当PVA纤维体积掺量分别为1.5%、1.2%时,试件极限拉应变和极限拉应力分别达到最大值;PVA纤维水泥基复合材料中掺加2%纳米SiO_2后,整体上提高了试件的极限拉应力,但试件极限拉应变变化不明显,纳米SiO_2使PVA纤维增强水泥基复合材料的抗拉伸性能得到了进一步提高。研究成果可为工程应用提供指导。     

液滴撞击细纤维的研究进展

液滴撞击细纤维现象在空气过滤、淡水收集及纤维涂层等工程领域很常见,研究该过程的动力学行为及捕集机理,对提高纤维过滤器效率、优化捕获液滴数量具有重要意义。简要分析了液滴碰撞动力学;综述了国内外学者对液滴撞击细纤维动力学过程进行的可视化及数值研究,讨论了撞击速度与丝径、偏心距和纤维表面温度、纤维弹性等参数对碰撞后流动状态及液膜厚度的影响,以及液滴在细纤维上的形状和临界体积等问题。结合电场作用下液滴的动力学特性,耦合电场和重力场是未来研究液滴碰撞动力学的重要方向。     

Technical note: Evaluation of a novel enzymatic method to predict in situ undigested neutral detergent fiber of forages and nonforage fibrous feeds

The purpose of this study was to optimize the conditions of a previously proposed enzymatic method used to estimate in situ undigested neutral detergent fiber (uNDF). We used a multi-step enzymatic approach, in which samples were first solubilized in NaOH solutions as a preincubation (PreInc) phase. After rinsing, samples were incubated (24 h at 39°C) in a buffered solution (pH 6) containing hemicellulase, cellulase, and Viscozyme L enzymes (Sigma-Aldrich s.r.l., Milan, Italy), followed by incubation (24 h at 39°C) in a buffered solution (pH 5) containing xylanase. Two sets of experiments were performed: a calibration trial (that tested different PreInc conditions on 9 selected forages) and a validation trial (that verified the results by testing multiple samples of 6 different forage types and a group of fibrous by-products). In the calibration trial, samples (300 mg in Ankom F57 filter bags; Ankom Technology Corp., Fairport, NY) were preincubated at 39°C in a 0.1 M NaOH solution for 90, 180, or 240 min, or in 0.2, 0.5, 1.0, or 2.0 M NaOH solution for 90 min. The results indicated that the best PreInc method, in terms of intra-laboratory repeatability and estimation of reference in situ values, was 90 min in a 0.2 M NaOH solution. Thus, we used this PreInc condition to determine enzymatic uNDF of 257 samples in the validation trial. Although the selected method generally had good accuracy in predicting in situ uNDF, inconsistencies were noted for certain forage types. Overall, when enzymatic uNDF was used to predict the in situ uNDF of all samples, the regression was satisfactory (intercept = 7.098, slope = 0.920, R² = 0.73). The regression models developed for alfalfa hays, corn silages, and small grain silages had also acceptable regression performances and mean square error of prediction (MSEP) values, and the main sources of MSEP variation were error due to incomplete (co)variation and random error. Even when R² values were >0.70, the MSEP value of the regression model for grass hays was 149.55, and that for nonforage fibrous feeds was 155.16. Although enzymatic uNDF partially overestimated the in situ uNDF, particularly in grass silages, the proposed procedure seems to be promising for accurately predicting in situ uNDF, because it generally had good repeatability and provided satisfactory estimates of in situ uNDF.