Структура сварных соединений наноструктурированного титана, полученных методом контактной сварки

The paper presents the research of the weld structure of two Ti specimens of the type VT6 having nano- and submicrocrystalline structures. Electrical contact welding is used to obtain welds. The acicular structure is formed in the weld area. Two types of defects are detected, namely micropores and microcracks

Electromagnetic shielding behaviour of conductive filler composites and conductive fabrics – A review

In this study, theory of EMI shielding and research conducted on textile fabrics to impart conductivity for attenuating the electromagnetic (EM) radiation by means of different techniques have been reviewed in detail. Shielding of the EM waves can be done by means of reflection, multiple reflection and absorption by the shield. Different metals with their alloys and polymeric materials are initially used as shielding materials with some limitations. However, the recent developments in conductive fabrics and composites replace the conventional shielding materials. The composites with better conductivity and light weight could be a promising barrier material for protecting electronic circuits from the EM radiation and mechanical damage. Materials with high absorption co-efficient could impart shielding effectiveness of 80 dB for the frequency of 18 GHz. This paper mainly focuses on the necessity of conductive textile fabric and composites used as hybrid electromagnetic shields

Electromagnetic shielding behaviour of conductive filler composites and conductive fabrics – A review

329-342In this study, theory of EMI shielding and research conducted on textile fabrics to impart conductivity for attenuating the electromagnetic (EM) radiation by means of different techniques have been reviewed in detail. Shielding of the EM waves can be done by means of reflection, multiple reflection and absorption by the shield. Different metals with their alloys and polymeric materials are initially used as shielding materials with some limitations. However, the recent developments in conductive fabrics and composites replace the conventional shielding materials. The composites with better conductivity and light weight could be a promising barrier material for protecting electronic circuits from the EM radiation and mechanical damage. Materials with high absorption co-efficient could impart shielding effectiveness of 80 dB for the frequency of 18 GHz. This paper mainly focuses on the necessity of conductive textile fabric and composites used as hybrid electromagnetic shields

Investigation of the mechanical performance of carbon/polypropylene 2D and 3D woven composites manufactured through multi-step impregnation processes

In this work, pre-impregnation techniques including Dr. Ernst Fehrer (DREF) spinning and electrostatic powder coating were used to negate the poor impregnation of highly viscous thermoplastics. The DREF spun hybrid yarns and electrostatic spray coated towpregs were woven into 2D and 3D fabrics and subsequently consolidated to yield two variations of 2D and four variations of 3D composites including 3D angle inter-lock and 3D orthogonal weave. The 2D composites possessed higher tensile and flexural strength than the 3D composites. However, better notch impact properties were observed for 3D orthogonal weave. The closer wrapping in 3D orthogonal slightly improves the shock absorption capability of the composite than the angle interlock composite. Composites made from powder coated towpregs performed better than composites made from DREF spun hybrid yarns, minimizing the effect of the weave pattern. Porosity was a common feature of composites manufactured from DREF spun yarns as observed from micro-CT images

Mechanical Properties of Flax-Polypropylene Composites from Dry Flexible Towpregs: Influence of Radial Position of Flax Fibers in the Towpreg

The radial position of the flax fibers as reinforcement and polypropylene (pp) fibers as matrix was altered using friction spinning in three distinctive sequences from core to sheath, namely, (a) pp-flax-flax-pp (PFFP), (b) flax-pp-flax-pp (FPFP), and (c) flax-flax-pp-pp (FFPP). Interestingly, at the towpregs stage, PFFP demonstrated higher tensile characteristics than FPFP and FFPP. The towpregs were consolidated to yield three unidirectional composites (UDCs), namely, UDC-PFFP, UDC-FPFP, and UDC-FFPP, using compression molding. The tensile strength of the composites ($${{\rm{\sigma}}_{{\rm{UDC}} - {\rm{FFPP}}}} \gt {\rm{}}{{\rm{\sigma}}_{{\rm{UDC}} - {\rm{FPFP}}}} \gt {\rm{}}{{\rm{\sigma}}_{{\rm{UDC}} - {\rm{PFFP}}}}$$) was contrary to the breaking load (f) of the corresponding towpregs ($${f_{{\rm{FFPP}}}} \lt {\rm{}}{f_{{\rm{FPFP}}}} \lt {\rm{}}{f_{{\rm{PFFP}}}}$$) which necessitated the current investigation. Remarkably, the UDC with the lowest tensile as well as interlaminar shear strength i.e. UDC-PFFP, yielded the maximum energy absorption in Charpy and Notch impact tests. In the towpreg, the flax fibers when placed at the core position, slid over each other resulting in poor strength in FFPP while post-curing the pp matrix impregnated the core flax fibers in UDC-FFPP, resulting in the highest strength amongst the three UDCs in tensile and flexural modes. Micro-computed tomography (µCT) was carried out to confirm the same. Thus, the user can select the requisite fiber-matrix radial positions within towpreg to suit the ultimate applications

Influence of composite architecture and interfacial bonding on their impact properties

Resistance to impact thrust is one of the most important requirement along with many others for defining suitable applications of any composite materials. In this present work, the influence of composite architecture and composite interfacial bonding strength on the impact performance of flax reinforced PP composites have been investigated. In this regard two different composite architecture through conventional film stacking method and through DREF (DR. E. Fehrer open-end friction spinning process) yarn consolidation method have been produced and to alter the fibre–matrix interfacial bonding the flax fibres are treated with MAgPP (Maleic Anhydride grafted Polypropylene). Finally, the notch Izod impact behaviour of all composite samples are evaluated and compare

Mathematical modelling and experimental validation of thermal conductivity of outer layer of fire protective clothing

Motivation for development of this mathematical model is the difficulties related to the experimental measurement of the thermal conductivity like frequent sample preparation, experimental setup availability and lack of easier methods for quick estimation of thermal conductivity of outer layer of fire protective clothing. Considering this, various studies were devoted in the past to determine the thermal conductivity of fabrics. Two mathematical approaches for prediction of thermal conductivity of woven outer layer have been presented in the present study. Series-parallel thermal resistance configuration has been used for prediction of effective thermal conductivity of the fabric. First approach uses input values of structural parameters and can be useful in the development of new woven fabrics for outer layer of fire protective clothing. Second approach uses fibre volume fraction and thermal conductivity of fibre and air. It is suitable for predicting thermal conductivity of finished fabrics. The values obtained from mathematical model were validated with experimental values.</p