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Xiaozhi Hu – 1st expert on this subject based on the ideXlab platform
flexure and flexure after impact properties of carbon Fibre composites interleaved with ultra thin non woven Aramid Fibre veilsComposites Part A-applied Science and Manufacturing, 2020Co-Authors: Bingyan Yuan, Mingxin Ye, Yunsen Hu, Fei Cheng, Xiaozhi HuAbstract:
Abstract Laminar carbon Fibre reinforced polymer (CFRP) composites contain inherent weak ply interfaces due to the lack of through-thickness Fibre reinforcement. In this study, all ply interfaces were interleaved with ultra-thin (13 μm) non-woven short Aramid Fibre (SAF) veils to generate across ply Fibre bridging, formed in-situ by movements of free Fibre ends during the composite forming process. The toughening effect of ultra-thin SAF veils (13 μm and 29 μm in thickness) before and after impact was measured and compared. It was found that the 13 μm SAF veils increased the bulk flexural strength and modulus of CFRP by 16.9% and 19.8% prior to impact, challenging the common belief that interleaving with micro-length or short Fibres is only beneficial to post-impact properties. X-ray micro-computed tomography and cross-section microscopy examinations were used to explain the mechanisms for improved flexural properties before and after low-velocity impact.
improving impact resistance and residual compressive strength of carbon Fibre composites using un bonded non woven short Aramid Fibre veilComposites Part A-applied Science and Manufacturing, 2019Co-Authors: Bingyan Yuan, Yunsen Hu, Jeremy Shaw, Xiaozhi HuAbstract:
Abstract Laminar carbon Fibre composites with weak ply interfaces were toughened with ultra-thin (less than 20 μm) un-bonded non-woven Short Aramid Fibre (SAF) veils in the form of home-made pre-pregs. The effects of SAF veil on impact behaviour and compressive strength after impact of Carbon Fibre Reinforced Polymer laminates with multiple ultra-thin SAF interfacial layers were investigated. Optical observation and X-ray micro-computed tomography were employed for intact inspection of external and internal damage after high energy penetration impact. 50.8% decrease in back-face deflection and inhibited in-plane delamination growth were seen when compared with unmodified laminates. Compression after impact tests were performed after low energy impact to assess damage tolerance. SAF veils increased the residual compressive strength by 38.6% and changed the damage mode from delamination dominated fracture to shear failure.
Effects of Aramid–Fibre toughening on interfacial fracture toughness of epoxy adhesive joint between carbon-Fibre face sheet and aluminium substrateInternational Journal of Adhesion and Adhesives, 2014Co-Authors: Zhi Sun, Xiaozhi Hu, Haoran ChenAbstract:
Brittle epoxy adhesive joints, between the carbon-Fibre/epoxy face sheets and aluminium substrate, were toughened using randomly-distributed short Aramid Fibres. In this study, effects of the epoxy adhesive thickness on interfacial fracture toughness of the adhesive joints, with and without short Aramid–Fibre toughening, were investigated. Short Aramid Fibres of 6 or 14 mm in length with an area density of 12 g/m2 were inserted between the carbon-Fibre face sheet and aluminium substrate during the laminating process. Two and six layers of aluminium foils were inserted at the interface to form the controlled thin and thick adhesive joints, which are around 20 and 70 ??m in thickness. The two “composite adhesive joints”, with different volume densities of short Aramid Fibres, reversed the adhesive-thickness influence on the interfacial toughness in comparison to that of the plain epoxy adhesive joints. However, both “composite adhesive joints” with low and high Aramid–Fibre densities resulted in significant improvement in the interfacial toughness. Analytical models, together with optical and scanning electron microscopy observations, were used to explain the experimental findings, and relevant toughening mechanisms. ?? 2013 Elsevier Ltd.
Hiromi Kitano – 2nd expert on this subject based on the ideXlab platform
effect of water absorption and desorption on the interfacial degradation in a model composite of an Aramid Fibre and unsaturated polyester evaluated by raman and ft infra red microspectroscopyJournal of Raman Spectroscopy, 1999Co-Authors: M Kawagoe, S Hashimoto, M Nomiya, Mikio Morita, W Mizuno, Hiromi KitanoAbstract:
The interfacial degradation in a model composite of an Aramid Fibre (Kevlar 49) and unsaturated polyester (UP) followed by absorption and desorption of hot water at 90 °C was monitored by measuring the variations in residual stress in the embedded Fibre by means of the micro-Raman technique. The Fourier transform infra-red (FTIR) microspectroscopic analyses were also conducted to study the structure and the quantity of absorbed water causing interfacial degradation. Copyright © 1999 John Wiley & Sons, Ltd.
microspectroscopic evaluations of the interfacial degradation by absorbed water in a model composite of an Aramid Fibre and unsaturated polyesterPolymer, 1999Co-Authors: M Kawagoe, M Nomiya, Mikio Morita, W Mizuno, M Takeshima, Hiromi KitanoAbstract:
Abstract The laser Raman and the Fourier transform infra-red ( FT i.r.) microspectroscopic analyses were conducted to monitor the interfacial degradation process in a model composite of an Aramid Fibre (Kevlar 49) and unsaturated polyester (UP) exposed to water at 30 and 90°C. For micro-laser Raman spectroscopy, a single long Fibre was embedded in the UP resin being subjected to static tension. Removing the applied tension after curing the film specimen introduced the residual tensile stress into the Fibre. The progress of degradation by water in a region of interface was monitored by measuring the peak shift of the Raman spectrum varying proportionally to the stress generated in the Fibre. The micro- FT i.r. measurements were done to examine the quantity and the state of absorbed water in the UP resin very near the interface. The thin film specimen, in which the long Fibre was not subjected to pre-tension during the cure, was analysed under transmission mode. The residual tensile stress in the Fibre was monotonously decreased in hot water at 90°C, and completely released for about 150 h, although the stress reduction for early period of 24 h was mainly caused by the relaxation of elastic modulus of the UP matrix. In water at 30°C, on the contrary, the residual stress remained the initial value for a long time above 1000 h. The micro- FT i.r. analyses revealed that at an early stage the isolated water is mainly observed, and then larger amount of clustered water is absorbed with increasing soaking time, particularly at 90°C. At present, however, it is not clear which type of water more strongly participates in the interfacial degradation.
Bhabani K. Satapathy – 3rd expert on this subject based on the ideXlab platform
viscoelastic interpretations of erosion performance of short Aramid Fibre reinforced vinyl ester resin compositesJournal of Materials Science, 2011Co-Authors: Sandeep Kumar, Bhabani K. Satapathy, Amar PatnaikAbstract:
Short Aramid Fibre reinforced vinyl ester resin based isotropic composites are fabricated with varying Fibre weight fractions (20–50 wt%). The composites were evaluated for their erosion performance under a dynamic set of variables such as impingement angle (30°–90°), impact velocity (43–76 m/s), erodent size (250–600 μm) and stand-off distance (55–85 mm) following design of experiments (DOE) based on Taguchi analysis approach. The thermo-mechanical attributes such as storage modulus, loss modulus and damping properties as viscoelastic responses of the composites were investigated in the temperature range of 0–180 °C for their possible interpretations regarding reinforcement efficiency and energy dissipation aspects relevant to erosion process. An interrelation between the full-width half-maxima (FWHM) of loss modulus peak and erosion rate has emerged indicating the erosion to be mainly controlled by the Fibre–matrix interfacial characteristics. The eroded surface morphology investigation by scanning electron microscopy (SEM) revealed the nature of wear-craters, material damage mode and other qualitative attributes responsible in facilitating erosion of the composites.
hybrid composite friction materials reinforced with combination of potassium titanate whiskers and Aramid Fibre assessment of fade and recovery performanceTribology International, 2011Co-Authors: Mukesh Kumar, Amar Patnaik, Bhabani K. Satapathy, D K Kolluri, Bharat S TomarAbstract:
Abstract Composite friction materials based on synergistic ternary combination of potassium titanate whiskers, Aramid Fibre and graphite have been characterized for friction braking performance on Krauss friction tester. The dynamics of friction build-up and friction-decay as a function of number of braking instances and modes of braking cycles have been found to be more consistent in the composites with ≥7.5 wt% of Aramid Fibres whereas the absolute friction effectiveness remained higher in the composites with ≥25 wt% of potassium titanate whiskers. Wear surface morphology has revealed topographical variations and their underlying role in controlling the friction and wear performance.
performance sensitivity of hybrid phenolic composites in friction braking effect of ceramic and Aramid Fibre combinationWear, 2010Co-Authors: Amar Patnaik, Bhabani K. Satapathy, Mukesh Kumar, Bharat S TomarAbstract:
Abstract Hybrid phenolic composites based on combination of ceramic (alumino silicate based Fibres) Fibre and Aramid Fibre were fabricated followed by their characterization and tribo-evaluation in friction braking mode. The tribo-performance in terms of their friction-fade and friction-recovery behaviour has been rigorously evaluated while synchronously taking into account of the in situ braking induced temperature rise in the disc at the braking interface on a Krauss friction testing machine following ECE regulations. The friction-fade behaviour has been observed to be highly dependent on the Fibre combination ratio i.e. fade followed a consistent decrease with the decrease in the ceramic Fibre content, whereas the frictional fluctuations in terms of μ max – μ min has been observed to decrease with the increase in Aramid Fibre content. A higher recovery response is registered when the ceramic Fibre concentration is adequately balanced with Aramid Fibre content. The analysis of friction performance has revealed that the fade and static friction response are the major determinants of overall frictional response whereas contributions from recovery and frictional fluctuations have been counterbalancing. The interdependence of fade–recovery-disc temperature rise-wear characteristics have been intensively analyzed and a semi-empirical “ composition domain-performance attribute ” thematic correlation is established. Worn surface morphology investigation using scanning electron microscopy (SEM) has been carried out which has revealed that the dynamics of formation–destruction of contact patches (friction-layers) and topographical attributes largely influence the friction and wear performance of such composite brake-pads.