Modelling of the bonding process for a non-woven fabric: analysis and numerics

The main two directives of the European Commission (EC) has been regulating the automotive industry. The aforementioned directives and education of residents on environmental issues has created the need for new materials that have been produced from renewable resources and should be recycled at the end of product life cycle. The objective of this project is to develop a nonwoven materials (NWM) that would incorporate fibers of plants, which could be grown in Latvia because of suitable local climate conditions, for the use in automotive industry. Furthermore, inclusion of polymer fibers in the NWM will expand the areas of use of such material – the NWM can be transformed into a composite material by means of a thermal press. Manufacturing process of NWM consist of structure modelling and material samples manufacturing. NWM samples production process to be carried out by fibers preparation, fibers mixing, formation by airlaid method, preparation of fiber webs for fixation with a mechanical needle punching method, mechanical fixation of fiber webs, preparation of fixed fiber webs for NWM manufacturing and manufacturing of NWM by mechanical needle punching method. This article reflects the comparison of two compositions NMW (Polylactid (PLA) (60 wt%) and long flax fibres (40 wt%), and PLA (60 wt%) and technical hemp fibres (40 wt%)) with the same structure by visual appearance, geometrical parameters and tensile strength. The average surface density of hemp NWM varies in the range of 792.09 to 958,71 g•m−2 , thickness varies from 6.91 to 9.23 mm. Flax NWM average surface density is higher than hemp NWM and varies in range of 1,064 to 1,260 g•m−2, thickness of the material varies from 12.62 to 15.54 mm. For comparison, the surface density of NWM currently used in automotive industry, depending on the use of the material, varies from 100 to 1,400 g•m−2.

Roller drafting air-laid web formation is a new method that can be used to produce metal fiber webs, conventional textile fiber webs, and blended fiber webs. The configuration of inner-fiber arrangements in the web is researched in this study. A roller drafting air-laid web is processed by opening sliver into individual fibers with conventional 3/3 drafting rollers. The fibers are then collected lay by lay to form a web on a stainless mesh conveyer belt with suction air. The process uses drafting roller opening as a way to replace the opening saw rollers of a conventional dry web machine. Therefore, researching the configuration of fiber arrangement in the web and its effect on the strength and elongation of the nonwoven fabric are necessary. In this study, we prepare a series of pet webs with basis weights of 40, 80, and 100 g/m2, respectively. After the webs are needle punched, we examine the strength and elongation of the nonwoven fabrics in the machine direction (MD) and cross direction (CD), respectively. We compare the results with other conventional dry forming webs. Our results show that the strength of the nonwoven fabrics is similar in both MD and CD, and their elongation has the same trend. The strength ratio of the nonwovens in the MD/CD ranges from 1:1.2 to 1:1.4 and the elongation ratio from 1.2:1 to 1.3:1. Contrary to other dry forming webs, the strength of nonwoven fabrics in the MD is lower than that in the CD. The mechanical properties of this new web formation process are quite similar to existing air-laid webs, since the strength of nonwoven fabrics in the MD is nearly equal to that of the CD. This new web formation possesses the advantages of fiber disorder arrangement and even mechanical properties in both MD and CD.

PurposeThree-dimensional computer-aided design (CAD) assembly model has become important resource for design reuse in enterprises, which implicates plenty of design intent, assembly intent, design experience knowledge and functional structures. To acquire quickly CAD assembly models associated with specific functions by using product function requirement information in the product conceptual design phase for model reuse, this paper aims to find an approach for structure-function correlations analysis and functional semantic annotation of mechanical CAD assembly model before functional semantic-based assembly retrieval.Design/methodology/approachAn approach for structure-function correlations analysis and functional semantic annotation of CAD assembly model is proposed. First, the product knowledge model is constructed based on ontology including design knowledge and function knowledge. Then, CAD assembly model is represented by part attributed adjacency graph and partitioned into multiple functional regions. Assembly region and flow-activity region are defined for structure-function correlations analysis of CAD assembly model. Meanwhile, the extraction process of assembly region and flow-activity region is given in detail. Furthermore, structure-function correlations analysis and functional semantic annotation are achieved by considering comprehensively assembly structure and assembled part shape structure in CAD assembly model. After that, a structure-function relation model is established based on polychromatic sets for expressing explicitly and formally relationships between functional structures, assembled parts and functional semantics.FindingsThe correlation between structure and function is analyzed effectively, and functional semantics corresponding to structures in CAD assembly model are labeled. Additionally, the relationships between functional structures, assembled parts and functional semantics can be described explicitly and formally.Practical implicationsThe approach can be used to help designers accomplish functional semantic annotation of CAD assembly models in model repository, which provides support for functional semantic-based CAD assembly retrieval in the product conceptual design phase. These assembly models can be reused for product structure design and assembly process design.Originality/valueThe paper proposes a novel approach for structure-function correlations analysis and functional semantic annotation of mechanical CAD assembly model. Functional structures in assembly model are extracted and analyzed from the point of view of assembly structure and function part structure. Furthermore, the correlation relation between structures, assembled parts and functional semantics is expressed explicitly and formally based on polychromatic sets.

Thermal, Microstructural and Mechanical Coupling Analysis Model for Flatness Change Prediction During Run-Out Table Cooling in Hot Strip Rolling

Summary Nonwovens are polymer-based engineered textiles having randomly distributed fibres bonded together with mechanical, thermal or chemical techniques. This paper focuses on thermally bonded nonwoven fabrics manufactured with bicomponent fibres. Such fibres have a core/sheath structure, with a material of the inner region core - having a higher melting temperature than that of the surface region (sheath). During the bonding of these fibres, a hot calender with an engraved pattern contacts a fibre web causing the sheath part of fibres to melt; the latter acts as an adhesive while the fibres’ core part remains fully intact. As a result of the bonding process, two distinct regions, namely bond points and the fibre matrix, possessing different characteristics, form the nonwoven fabric. The structure of the resulting thermally bonded bi-component fibre nonwoven is shown in Fig. 1 obtained with scanning electron microscopy (SEM). In this paper a dynamic response of core/sheath type thermally bonded bicomponent fibre nonwoven textiles is simulated in finite element (FE) environment. The simulated nonwoven fabric is treated as an assembly of two regions with distinct mechanical properties. One region - the fibre matrix - is composed of randomly oriented core/sheath fibres acting as link between bond points. Random orientation of individual fibres is introduced into the model in terms of the orientation distribution function in order to calculate the structure’s anisotropy. A code based on digital image processing techniques is developed to analyse the ODF of fibres and the mechanical anisotropy of the fabric using micro-scale images of fibre matrix obtained with SEM or X-ray micro computed tomography. Another region - bond points - is treated as a deformable bicomponent composite material composed of the sheath material as its matrix and the core material as reinforcing fibres with random orientations. A second code is developed to assess the time-dependent anisotropic mechanical properties of these regions based on fibre characteristics and manufacturing parameters such as the planar density, core/sheath ratio, fibre diameter etc. Having distinct anisotropic mechanical properties for two regions, the fabric is modelled with shell elements with thicknesses identical to those of the bond points and fibre matrix. The developed model is used to simulate a dynamic interaction of a falling ball with the nonwoven fabric, resulting in several rebounds. Finally, results of the FE

6 - Nonwoven natural fiber preforms

Characteristic analysis of mechanical thermal coupling model for bearing rotor system of high-speed train

In the study, electromagnetic shielding efficiency (EMSE) absorption and reflectivity properties of fabric produced from staple stainless-steel fibres and recycled staple polyester fibres by carding and needling technologies were investigated. The bi-component core/sheath polyester fibres at a fixed ratio of 20% in producing all nonwoven fabrics were used. The staple stainless-steel fibres and recycled staple polyester fibres were blended at 13 different ratios such as 1%, 2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 22.5%, 25%, 27.5%, 30%. The fibre webs were formed at wool type carding machine and then the folded webs were bonded mechanically with needle punching machines. Half of the produced nonwoven composite fabrics were bonded by thermal bonding technology with oven and calender machines. As the conductive fibres were costly, the study aimed to obtain optimum shielding effectiveness with the usage of minimum conductive fibres. Electromagnetic shielding properties, absorption and reflection characteristics of needle-punched nonwoven fabrics with calendered or un-calendered were performed by coaxial transmission line method according to ASTM-D4935-10 in the frequency range of 15 MHz to 3000 MHz. It is a known fact that electromagnetic shielding effectiveness increases with the increase in the amount of conductive fibre. It was found that nonwoven fabric produced with a usage of 17.5% stainless steel fibre has at least 90% electromagnetic shielding percentage in general use with 15 dB at a frequency of 1800 MHz. Increased stainless steel fibre content in nonwoven fabrics resulted in decreased nonwoven fabric thickness and tensile strength. Such a nonwoven composite material with electromagnetic shielding property could be used for construction and building applications.

Highly selective and lightweight protective suits featuring excellent breathability, mechanical robustness, and catalytic degradation performance toward chemical warfare agents (CWAs) are highly desirable for first responders and the military. However, current multilayered state-of-the-art chemical/biological (CB) protective textiles containing activated carbon and separate aerosol-protective layers exhibit several drawbacks including high thermal burden and secondary contamination. Herein, we present for the first time, a highly sorptive, breathable, and mechanically strong aerosol-protective layered fabric with prominent catalytic degradation capability of CWA simulant, through novel material selection and engineering design. The electrospun polymer of intrinsic microporosity (PIM-1) fiber web with hierarchical porosity is used as a matrix material, preventing toxic gas penetration while providing pathways for air and water vapor molecules. Polyacrylonitrile (PAN) nanofibers assembled with PIM-1 fibers via a layer-by-layer electrospun-deposition approach are shown to achieve significantly enhanced mechanical integrity and filtration efficiency, due to the high polar chemical structure and small fiber diameter of PAN. The subsequent incorporation of UiO-66-NH2 particles, a Zr-based metal-organic framework (MOF), further enhances the sorption capacity while maintaining excellent filtration efficiency, mechanical strength, and breathability, and also endows the fiber web with remarkable catalytic degradation towards CWA simulants. The resulting PIM/PAN/MOF composite fiber mat demonstrates unprecedented integrated properties with water vapor transmission rate of 1,013 g/m2·24 h, surface area of 574 m2/g, increased tensile strength (more than 70 times compared to neat PIM-1 fiber web), and PM2.5 and PM10 filtration efficiency of 99.88% and 99.94%, respectively, comparable to commercial polypropylene (PP) non-woven textile. This facile and effective fabrication of such a multifunctional composite fiber mat is valuable for the design of protective garments in health care, personal protective gear, and law enforcement and military uniforms.

With highly deviated wells and horizontal wells are widely used in the oil industry. The large slope well sections and long horizontal well sections will lead to a sharp increase of the drill string torque and friction, which may reduce the drilling efficiency, and even lead to accidents. Therefore, real-time and accurate analysis of drill string’s torque and friction is an urgent problem facing by the modern drilling technology. The paper established a real-time friction prediction model that combines machine learning methods with drill string mechanical mechanism analysis model. Based on 84000 sets of field monitoring data obtained on-site, a regular data training set for weight on bit (WOB) and torque prediction was constructed with 23 types of time-series related parameters and 10 types of timing independent parameters. Relationships between time-series related parameters and timing independent parameters with the weight on bit and torque were trained to utilize long and short-term memory (LSTM) neural network and muti-layer back propagation (BP) network respectively. The new developed LSTM-BP neural network achieves high-precision prediction results of WOB and torque with a relative error of less than 14%. Based on derived WOB and torque prediction results, a theoretical mechanical analysis model of the entire drill string was adopted in this paper to develop the quantitative relation between WOB and torque with the friction coefficient of the drill string and oil casing. Suitable friction coefficients along the drill string can be finally obtained by solving the equilibrium function between predicted WOB, torque and measured hook load, rotary-table torque via an iteration algorithm. A case study was performed finally using the proposed intelligent analysis method to calculate the friction coefficients. This proposed methodology can be referenced to decrease the sticking risks and improve the drilling efficiency, which can finally increase the extension limit of horizontal wells in complex strata.

Minimum ground pre-freezing time before excavation of Guangzhou subway tunnel

Preparation of hydroentangled CMC composite nonwoven fabrics as high performance separator for nickel metal hydride battery

Conductive needle punched nonwoven fabrics are developed from staple polypropylene (PP) and varying weight fractions (10, 20 and 30 wt.%) of staple carbon fibres. A fibrous webs of staple PP and carbon fibres were formed at a wool-type carding machine, and these webs subsequently bonded on needle punching machine with 132 punches/cm2 and 13.5 mm needle penetration depth. The electromagnetic shielding effectiveness (EMSE), absorption and reflection characteristics of as-produced needle punched nonwoven fabrics were determined using a network analyser as specified in ASTM D4935-10 in the frequency range 15–3000 MHz. The surface resistivity measurements were carried out in accordance with ASTM D 257-07 standard. These results indicate that the EMSE values increase incrementally with frequency in the 15–3000 MHz range. The nonwoven sample with 30 wt.% carbon fibre showed the lowest surface resistivity of 3.348 kΩ and corresponding highest EMSE of ~42.1 dB in the 3000 MHz frequency range. In comparison, the highest EMSE values from 10 to 20 wt.% staple carbon fibre were found to be 15.6 and 32.2 dB in the 3000 MHz frequency, respectively. It was observed that the absorbance and reflectance curves of each nonwoven fabric move at opposite directions to each other. It was found that as the amount of carbon fibre in the nonwoven fabric increases, absorbance values decrease, but reflectance values increase. The resultant nonwoven fabric samples are expected to be used as garment interlining after thermal bonding and wall interlayer in the future.

A hydraulic model of the hemodynamics of the arterial part of the myocardium is considered, and a numerical analysis of the model is conducted. Computer experiments are used to investigate the dependence of blood flows on parametric and structural changes in the system.

Numerical analysis of continuous models of structures in non-linear wind flow using the time-marching approach