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Dhakal H.N.,University of Portsmouth | Zhang Z.Y.,University of Portsmouth | Bennett N.,University of Portsmouth | Lopez-Arraiza A.,University of the Basque Country | Vallejo F.J.,IDEKO IK4 Research Alliance
Journal of Composite Materials | Year: 2014

Flax and jute fibres are inexpensive and easily available bast fibres and they are extensively used as reinforcement in polymer matrix composites. However, due to their susceptibility to moisture absorption, their application is restricted to non-structural interior products. In this study, flax- and jute fibre-reinforced bioresin-based epoxy biocomposites were fabricated using hand lay-up method and their nanoindentation and flexural properties were investigated. In order to study the effects of water absorption on the nanoindentation and flexural properties, the biocomposites were subjected to water immersion tests by immersing specimens in a de-ionised water bath at 25 for a period of 961h. The nanoindentation behaviour and flexural properties of water-immersed specimens were evaluated and compared alongside with dry specimens. The percentage of moisture uptake and diffusion coefficient (D) was recorded higher for jute-reinforced specimens compared with flax. The flexural properties for both types of specimens were found to decrease with increase in percentage moisture uptake. Comparison of flexural strength and flexural modulus between flax dry and flax wet biocomposites showed that wet samples lost almost 40% of strength and 69% of modulus compared with dry flax samples. The jute wet samples lost 60% of strength and 80% of modulus compared with dry samples. The nanohardness value decreased from 0.207 to 0.135GPa for dry flax sample after immersion in water. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav. Source


Lopez-Arraiza A.,University of the Basque Country | Castillo G.,University of Malaga | Dhakal H.N.,University of Portsmouth | Alberdi R.,IDEKO IK4 Research Alliance
Composites Part B: Engineering | Year: 2013

Although grinding is one of the most versatile machining operations that can be used to produce surface finish up to the micrometer level; it often induces thermal damage to a ground surface and higher power consumption if careful selection of grinding parameters are not made. The main aim of this study is to investigate the effect of a newly developed composite structure with enhanced coolant delivery system for optimizing grinding processes in comparison to the nozzles commercially available. The current investigation further aims to correlate the effect of tool geometry developed on grinding process conditions through experiment and modeling by means of Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA). The results show that with the use of the newly developed composite nozzle, a 30% decrease in coolant waste was achieved. Besides, it was found that the new nozzle yielded approximately 60-80% percentage pump pressure and power reduction compared to commercially available nozzles. © 2013 Elsevier Ltd. All rights reserved. Source


De Lacalle L.N.L.,University of the Basque Country | Rodriguez A.,University of the Basque Country | Lamikiz A.,University of the Basque Country | Celaya A.,University of the Basque Country | Alberdi R.,IDEKO IK4 Research Alliance
Materials and Manufacturing Processes | Year: 2011

In this article, the ball burnishing is applied on sculptured surfaces, aiming at enhance surface roughness. Different strategies are possible for burnishing, the continuous burnishing (CB) which uses a five-axis interpolation of the machine tool, and the patch burnishing (PB) using a more simple 3+2 axis interpolation. Using both techniques complex parts are burnished and a big improvement in surface roughness achieved, but some differences between both approaches appear. Two parts have been previously machined in a five-axis milling center and finished using the ball burnishing approaches. The first one is a steel AISI 1045 with a hemisphere shape, whose geometry is simple. The second one is a steel DIN 1.2379 part (64 HRC), with more complex features. Surface quality was evaluated for both burnishing approaches, obtaining significant improvements on surface roughness and hardness. The main general conclusion is that ball burnishing reduces roughness without penalizing the manufacturing time or surface integrity and, therefore, is suitable for complex surfaces. © 2011 Taylor & Francis Group, LLC. Source


Lopez-Arraiza A.,IDEKO IK4 Research Alliance | Amenabar I.,IDEKO IK4 Research Alliance | Agirregomezkorta A.,University of Mondragon | Sarrionandia M.,University of Mondragon | Aurrekoetxea J.,University of Mondragon
Journal of Composite Materials | Year: 2012

The emergence of new high-performance thermoplastics to replace thermosets in fiber-reinforced polymers puts up a new challenge: their machining. In this study, carbon fiber-reinforced poly-cyclic butylene terephthalate laminates were manufactured, drilled, and inspected. Different commercial drill geometries and machining conditions were compared. Roughness, microscopy, and non-destructive tests allowed us to determine the hole quality as well as delamination. The surface tests showed better results after working at the most common cutting speed (3000rpm) than at high speed (15,000rpm) with a constant feed rate. This fact can be explained based on the viscoelastic properties of the matrix that becomes fragile at high cutting speeds. The Delamination factor obtained by means of Ultrasonics and X-ray Computed Tomography also confirmed that the best results are achieved with a Twist drill bit at 3000rpm. In contrast to carbon fiber-reinforced thermosets, the detected delamination at high cutting speeds is not as remarkable as expected. These results allow us to conclude that this new composite will certainly increase production rate without delamination damage. Chip formation takes also a special role. It can be recovered to be used as reinforcement in manufacturing processes due to the recyclability of the thermoplastic matrix. © The Author(s) 2011. Source

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