Abrasive water jet drilling of advanced sustainable bio-fibre-reinforced polymer/hybrid composites : a comprehensive analysis of machining-induced damage responses

This paper aims at investigating the effects of variable traverse speeds on machining-induced damage of fibre-reinforced composites, using the abrasive water jet (AWJ) drilling. Three different types of epoxy-based composites laminates fabricated by vacuum bagging technique containing unidirectional (UD) flax, hybrid carbon-flax and carbon fibre-reinforced composite were used. The drilling parameters used were traverse speeds of 20, 40, 60 and 80 mm/min, constant water jet pressure of 300 MPa and a hole diameter of 10 mm. The results obtained depict that the traverse speed had a significant effect with respect to both surface roughness and delamination drilling-induced damage responses. Evidently, an increase in water jet traverse speed caused an increase in both damage responses of the three samples. Significantly, the CFRP composite sample recorded the lowest surface roughness damage response, followed by C-FFRP, while FFRP exhibited the highest. However, samples of FFRP and hybrid C-FFRP recorded lowest and highest delamination damage responses, respectively. The discrepancy in both damage responses, as further validated with micrographs of colour video microscopy (CVM), scanning electron microscopy (SEM) and X-ray micro-computed tomography (X-ray μCT), is attributed to the different mechanical properties of the reinforced fibres, fibre orientation/ply stacking and hybridisation of the samples.Peer reviewe

Drilling characteristics and properties analysis of fiber reinforced polymer composites: A comprehensive review

Fiber-reinforced polymer (FRP) composites play a vital role in the production of structural and semi-structural components for engineering applications. The drilling process is a commonly employed machining process for FRP composites to join the FRP structural elements. Usually, the FRP composites possess a heterogeneous nature because of their multi-layered structure, hybridization, and the presence of multi-phase materials. Hence, common problems like delaminations, fuzzing, buckling, cracking, matrix and fiber burning occur during the drilling operations. These problems cause dimensional inaccuracy, poor surface finish, and tool wear and reduce the mechanical strength of the composites. The optimum drilling parameters (drill geometry, speed, feed, and depth of cut) selection for the specific materials is good to achieve effective drilling performance and better surface quality of the holes. Yet, little study has been done on how all of these factors affect the size of the drilled hole. The majority of drilling studies on FRPCs in the past have focused on how to improve the hole quality by maximizing processing conditions, and there has been little discussion on the correlation between drilling conditions, physical properties, and production techniques. This is what motivated to review the characteristics and properties analysis of FRP composites. As a consequence of this research, it is anticipated that scientists and researchers would place a greater emphasis on the drilling characteristic of the workpieces made from FRPCs than on other attributes. This review clearly presents an overview of FRP composites drilling that had progressed from 2000 to 2021. The analysis of different drilling conditions and parameters like thrust force, drill geometry, temperature, speed, and feed also includes the post-drilling analysis through delaminations, thermal damage, and surface roughness. Furthermore, the recent developments in carbon, glass, and natural fiber reinforced polymer composites are studied with both conventional and nonconventional drilling techniques. Based on the above studies, some future challenges and conclusions are drawn from this review

Manufacturing, characterization and modelling of biodegradable composite materials

In the recent decades, there has been a high rise in the development of renewable materials due to awareness in environmental care. Part of the research in such materials has focused on the development of biodegradable composites using natural fibres as reinforcement of 'green' plastics. The use of biocomposites means a major reduction in the environmental impact of industrial components after their life cycle, thus, the development of tools for design with biocomposites could mean a breakthrough for its implementation in the industry. In this thesis, the basis for the development of tools for modelling the mechanical behavior of biocomposites have been arise for first time through the development of a constitutive model based on the simulation of the mechanical behaviour through rheological elements. The seven model parameters have been adjusted by quasi-static tensile tests, while the model has been successfully validated by tensile tests at different strain rates. The constitutive model has proved to be valid for composites reinforced with cotton, flax and jute, allowing a greater understanding of the behaviour of those biocomposites, as the fact that the viscoplastic behaviour is mainly produced by fibres behaviour. The existence of a constitutive model for biocomposites opens the doors to its application in structural components of responsibility greatly reducing design costs. Four different biocomposites were chosen to test the versatility of the constitutive model. Biodegradable PLA composites were manufactured by compression moulding combining two types of PLA as matrix and three natural fibres (flax, cotton and jute) as reinforcement. Moreover, the ACC’s were manufactured by solving the surface cellulose of the fibres, which after a regeneration process forms the composite matrix. Thus, four different biocomposites were successfully manufactured in this thesis. The parameters influencing the PLA based biocomposites manufacturing process (temperature, pressure, number of layers, type of fibre and matrix type) have been optimized to obtain a material with a strength greater than 100 MPa, indicating their potential application for replacing traditional composites, especially glass fibre composites. This could mean a large increase in the use of biocomposites in industrial applications such as automotive or aviation. However, it has been observed that biocomposites presents a viscoplastic behaviour with permanent deformations, which is far from the linear elastic behaviour until failure of traditional composites. This has motivated the development of computational tools for biocomposites to predict their behaviour under dynamic conditions such as impacts or machining. Impact test in drop tower were conducted in flax/PLA biocomposites, revealing a high energy absorption, above the absorbed by carbon fibre composites in the range of energies analysed. The main failure mode was fibre failure, while delaminations were not found. Due to this differences in failure modes, the normalized residual strength observed in biocomposites was higher than that reported in carbon fibre reinforced composites. Two different Finite Element Models were developed. First, a linear elastic model was used to reproduce the impact behaviour of ACC plates. Second, a model considering the influence of strain rate on the plastic behaviour of biocomposites was implemented to reproduce the impact behaviour of flax/PLA biodegradable composites. Finally, the different mechanisms of damage induced in drilling had been studied. For this, the damage induced under different cutting speeds, advances and drill geometries was analysed, noting that in this case delaminations were neither found as failure mode, revealing a good cohesion between fibre and matrix. Is also detachable the damage reduction with increasing drill feed rate, which is a novelty that can reduce the processing times of these materials in the industry. These machining tests are the basis for the application of a numerical model based on the constitutive model defined in this work.En las últimas décadas se ha producido un gran auge en el desarrollo de materiales renovables debido a la concienciación en el cuidado del medio ambiente. Parte de la investigación en dichos materiales se ha focalizado en el desarrollo de materiales compuestos biodegradables, empleando fibras naturales como refuerzo de plásticos ‘verdes’. El uso de los biocomposites puede suponer una gran reducción en el impacto ambiental de componentes industriales tras su ciclo de vida, por lo que el desarrollo de herramientas para el diseño con biocomposites significaría un gran avance para su implementación en la industria. En el presente trabajo se han planteado por primera vez las bases para el desarrollo de herramientas para el modelizado de los biocomposites desarrollando un modelo constitutivo que los defina, basándose dicho modelo en la simulación de su comportamiento mecánico por medio de elementos reológicos. Los siete parámetros del modelo han sido ajustados mediante ensayos a tracción cuasi-estáticos, mientras que la validación de los mismos se ha realizado con éxito por medio de ensayos de tracción a distintas velocidades de deformación. El modelo constitutivo ha demostrado ser válido para biocomposites reforzados con algodón, lino y yute, permitiendo una mayor comprensión del comportamiento de los biocomposites, tal como el hecho de que los comportamientos viscoplásticos tienen origen en las fibras y no en la matriz. La existencia de un modelo constitutivo para biocomposites abre las puertas a su aplicación en componentes de responsabilidad estructural reduciendo enormemente los costes de diseño. Se han fabricado distintos materiales para comprobar la versatilidad del modelo constitutivo. Los materiales compuestos biodegradables de PLA se han fabricado mediante modelizado por compresión en caliente, empleando dos tipos de PLA y tres fibras naturales (lino, algodón y yute). Por otro lado, los ACC han sido fabricados mediante la disolución de la celulosa superficial de las fibras, que tras una regeneración conforma la matriz del compuesto. Por lo tanto, se han fabricado con éxito cuatro biocomposites diferentes en el marco de la tesis. Los parámetros que influyen en el proceso de fabricación de los compuestos de PLA (temperatura, presión, número de capas, tipo de fibra y tipo de matriz) han sido optimizados para la obtención de un material con una resistencia superior a los 100 MPa, lo que revela su potencial aplicación para la sustitución de los materiales compuestos tradicionales, especialmente los compuestos de fibra de vidrio. Esto hace prever un gran incremento en su uso en aplicaciones industriales tales como la automoción o la aviación. Sin embargo, también se ha podido observar que los biocomposites presentan un comportamiento viscoso con deformaciones permanentes, lo que dista del comportamiento elástico lineal hasta rotura de los materiales compuestos tradicionales. Esto ha motivado el desarrollo de herramientas de cálculo para los biocomposites para la predicción de su comportamiento en condiciones dinámicas tales como impactos o mecanizados. Se han realizado ensayos de impactos en torre de caída en compuestos de lino/PLA, lo que ha revelado una gran absorción de energía de los mismos, superior a la absorbida por compuestos de fibra de carbono en el rango de energías analizado. El principal modo de fallo localizado en los biocomposites es la rotura de fibras, mientras que no se han encontrado delaminaciones. Debido a esta diferencia en los modos de fallo la resistencia residual normalizada es mayor en biocomposites que en compuestos de fibra de carbono estudiados. Se han desarrollado dos modelos de elementos finitos. En primer lugar, se han reproducido impactos en placas de ACC por medio de un modelo elástico lineal. En segundo lugar, se ha desarrollado un modelo que tiene en cuenta la influencia de la velocidad de deformación en el comportamiento plástico de los biocomposites, el cual fue implementado para reproducir el comportamiento ante impactos de compuestos de lino/PLA. Por último, se han estudiado los distintos mecanismos de daño inducidos en el taladrado de compuestos de PLA. Para ello, se ha estudiado el daño ante distintas velocidades de corte, avances y geometrías de broca, destacando que en este caso tampoco se han localizado delaminaciones como modo de fallo, revelando una buena cohesión entre fibra y matriz. También cabe destacar que se ha determinado una reducción del daño con el incremento de la velocidad de avance, lo que supone una novedad que puede reducir los tiempos de procesado de estos materiales en la industria. Estos ensayos son la base para la aplicación de un modelo numérico basado en el modelo constitutivo definido en este trabajo.Author gratefully acknowledge the support of Spanish Ministry of Economy under the project DPI2013-43994-R and the Carlos III of Madrid University for the financial support during the last three years.Programa Oficial de Doctorado en Ingeniería Mecánica y de Organización IndustrialPresidente: José Fernández Sáez.- Secretario: Eugenio Giner Maravilla.- Vocal: Samuel Charca Maman

Microstructural investigation and hole quality evaluation in S2/FM94 glass-fibre composites under dry and cryogenic conditions

International audienceS2/FM94 glass fibre reinforced epoxy is an aerospace-grade composite currently bonded with aluminium alloys and installed in parts of the Airbus A380 fuselage. In addition to its abrasive and hard nature, S2/FM94 glass fibre is sensitive to thermal effects developed during the drilling process, and therefore using coolants becomes necessary. However, conventional oil and water-based coolants are not suitable for drilling of composites. Cryogenic coolants on the other hand are an attractive choice for machining composites and are environmentally friendly. In this study, a new environmentally friendly cryogenic cooling technique in a liquid nitrogen bath was used for the drilling of S2/FM94 glass fibre reinforced epoxy composite. The aim was to investigate the effect of drilling parameters and cryogenic cooling on cutting forces, surface roughness, hardness and delamination factor at hole entry and exit sides. The workpiece was drilled within a cryogenic bath. In this way, both cryogenic workpiece cooling and tool cooling were obtained. In addition, the drill geometry is fixed and only the cutting parameters (i.e. spindle speed and the feed rate) are varied under dry and cryogenic conditions. The results indicate that the spindle speed and cryogenic cooling had the most significant influence on the cutting forces and surface roughness parameters (R a and R z ), while the use of cryogenic cooling had the most significant influence on increasing the hardness and size of delamination at entry and exit sides of the holes

Recent advances in drilling of carbon fiber–reinforced polymers for aerospace applications: a review

Drilling is considered as one of the most challenging problems in aerospace structures where stringent tolerances are required for fasteners such as rivets and bolts to join the mating parts for final assembly. Fiber-reinforced polymers are widely used in aeronautical applications due to their superior properties. One of the major challenges in machining such polymers is the poor drilled-hole quality which reduces the strength of the composite and leads to part rejection at the assembly stage. In addition, rapid tool wear due to the abrasive nature of composites requires frequent tool change which results in high tooling and machining costs. This review intended to give in-depth details on the progress of drilling of fiber-reinforced polymers with special attention given to carbon fiber–reinforced polymers. The objective is to give a comprehensive understanding of the role of drilling parameters and composite properties on the drilling-induced damage in machined holes. Additionally, the review examines the drilling process parameters and its optimization techniques, and the effects of dust particles on human health during the machining process. This review will provide scientific and industrial communities with advantages and disadvantages through better drilled-hole quality inspection

Quantification of drilling quality and mechanisms in CFRP composites

Drilling on fibre reinforced composites is a crucial process in fabrication of airframes in aircraft industry. In this research, an extensive experimental investigation on drilling and machining CFRP laminates using different tools is carried out to analyse effects of processing parameters on drilling performance. Drilling performance and quality of circular holes on a commercial aircraft CFRP laminate are investigated, using drill bit with three different configurations made of solid carbide, namely GT50 dagger drill, GT15 reamer drill, and twist drill. Back support of different geometry, as full support, partial support and no support, is employed during drilling at spindle speeds of 500, 1000, and 2000 rpm, and feed rate of 50 mm/min. Thrust force and torque, are measured. Quantification of the quality and holes integrity is accomplished by evaluating surface roughness, heat distribution, drilled hole roundness or circularity, chip size, and damage factor. The second major study is an energy-based analysis based on the energy balance model established by William’s on cutting polymers is presented by addressing Mode I fracture as a key mechanism in different cutting directions in a unidirectional CFRP laminate, induced by orthogonal cutting. Then, tool wear and tool life of dagger and reamer drill bits are investigated, evaluating blunting and wear of the tools. With that, assessment on tool wear and tool life are made by addressing their significant influence on thrust force and torque during drilling, delamination factor in the CFRP laminates, fibre peel-up and push-down mechanisms, surface roughness and temperature increase. Lastly, finite element analysis is added to explore and predict the drilling mechanism and chip removal mechanism as a function of failure criteria. With all that has been addressed above, this study plays a critical role for selection of the optimal drilling conditions for minimising production cost and maximising productivity

Multiscale modelling and experimental analysis of ultrasonic-assisted drilling of GLARE fibre metal laminates

This study aims to evaluate the effectiveness of Ultrasonic-assisted drilling (UAD) of Glass laminate aluminium reinforced epoxy (GLARE) at high cutting speeds (Spindle speeds: 3000–7500 rpm; feed rates 300–750 mm/min) by analysing the thrust force and hole quality metrics (surface roughness, hole size, and burr formations. The research also presents numerical modelling of FMLs under conventional and UAD regimes to predict thrust force using ABAQUS/SIMULIA. The thrust force and exit burrs were reduced by up to 40.83 % and 80 %, respectively. The surface roughness metrics (Ra and Rz) were slightly higher using UAD but remained within the desirable limits of surface roughness for machined aeronautical structures. The discrepancy between the simulation and experimental results was adequate and did not exceed 15 %. The current study shows that it is feasible to drill holes in GLARE using higher cutting parameters and maintain excellent hole quality, which means increased productivity and reduced costs

Mechanical Properties of Drilling Defect Induced Glass Fiber Epoxy Composites Developed By Resin Infusion Technique

Composite laminates such as Glass Fiber Reinforced Epoxy (GFRE), Carbon Fiber Reinforced Epoxy (CFRE) and other fiber metal composite laminates have been widely used in industries which include aerospace, aircraft structural components and oil and gas fields due to their superior mechanical properties. Drilling can be considered as an important machining operation for the assembling of laminates. By reason of hard-to-machine characteristics of the components, the drilling operation induced defects. This paper studies the mechanical properties that are affected from the induced defect. In this research, GFRE composite were used and fabricated using the vacuum assisted resin infusion method. The results of the drilled samples were tested for its tensile strength and structural analysis. This research is intended to help readers obtain a comprehensive view on mechanical properties of glass fiber reinforced epoxy

Multi-Response Optimization in Drilling of MWCNTs Reinforced GFRP Using Grey Relational Analysis

The present work concentrates on the use of Grey Relational Analysis for optimizing the drilling parameters like weight percentage of multi-wall carbon-nanotube (MWCNTs), cutting speed and feed rate on the thrust force and the delamination factor in the drilling of GFRP composites. Full factorial design is utilized for the trial. Analysis of variance (ANOVA) is applied to determine the significance of drilling parameters on multi-response. Considering the multi-response optimization results, which are acquired from the largest Grey Relational Grade (GRG), it is determined that optimal parameters are 1 wt. % MWCNTs, cutting speed 25 m/min, and feed rate 0.10 mm/rev to minimize concurrently thrust force and delamination factor. It is provided that the percentage development in GRG with the multi-response optimization is 50.53%. It is clearly indicated that the quality characteristics are crucially developed using this approach in the drilling of GFRP. According to the results of ANOVA of the GRG, the crucial factor is feed rate. Validation experiment was confirmed by computing the confidence level within the interval width. Eventually, results of validation experiment with the optimum drilling conditions settings have indicated that the proposed model develops overall performance of drilling process