P.E. Faria

Delamination in High Speed Drilling of Carbon Fiber Reinforced Plastic (CFRP)

When holes are produced on carbon fiber reinforced plastic (CFRP) laminates, in particular for the aerospace and automotive industries, special attention should be focused on as the machining parameters influencing the damage. In this study special drill bits and high-speed cutting (HSC) are used and compared with conventional cutting conditions. The digital image of the damage was conducted in order to analyze the delamination when two composite boards were drilled simultaneously. The experimental results indicated that the use of HSC in drilling is suitable to reduce the damages produced in CFRP with material removal rate increasing considerably.

Effects of high speed in the drilling of glass whisker-reinforced polyamide composites (PA66 GF30): statistical analysis of the roughness parameters

Glass fiber-reinforced polyamides are promising materials especially for automotive applications, exhibiting high mechanical strength and stiffness. In order to achieve the required tolerances and surface quality, these materials must be subjected to machining operations. Drilling is one of the machining processes most widely applied to composite materials and, for this reason, this article is focused on the machinability of polyamide reinforced with glass whiskers for high speed drilling operation. A full factorial experimental design was carried out in order to identify the main effects and interaction between the factors feed speed, spindle speed and drill point angle on surface roughness (R a) and normalized peak count (Pc) responses. The work material (PA66-GF30 polyamide reinforced with 30% glass whiskers) was drilled using tungsten carbide (ISO grade K10) drills. The results indicated that the interaction between feed speed, spindle speed, and drill point angle presented a significant effect on the Ra response. In addition to that, the factor feed speed and the interaction between spindle speed and drill point angle significantly affected the peak count response.

Dimensional and Geometric Deviations Induced by Drilling of Polymeric Composite

Tool material, tool wear, and machining parameters drastically affect the quality of holes produced in polymeric composites and, therefore, the performance of the finished component. This article investigates the influence of the above-mentioned factors on thrust force, diameter, and roundness deviations on holes generated after drilling glass fiber reinforced epoxy resin. High speed steel and cemented carbide drills were tested as tool materials and the results indicated that the high speed steel drill presented severe wear after drilling 1000 holes, thus promoting high thrust force and roundness deviation values, in addition to hole diameter figures considerably smaller than the nominal value. On the other hand, after drilling 10,000 holes the carbide drill presented lower wear land and, consequently, lower thrust force values, producing holes with superior dimensional and geometric quality.

The influence of tool wear on delamination when drilling glass fibre reinforced epoxy composite with high speed steel and cemented carbide tools

This work is concerned with the machinability of a glass fibre reinforced epoxy composite when subjected to drilling at distinct cutting speeds and feed rates using high speed steel and tungsten carbide drills with similar geometries. The influence of tool material and machining parameters on tool wear and delamination were the principal aspects investigated. The results indicated that the high speed steel drill presented severe wear rates, which resulted in larger delamination areas after drilling 1000 holes, whereas the wear observed on the cemented carbide tool was negligible. Furthermore, the combination of tool wear with high cutting speed and low feed rate values resulted in an increase in the damaged area.

Thrust Force and Wear Assessment When Drilling Glass Fiber-Reinforced Polymeric Composite

The principal aim of this article is to investigate the influence of the drilling parameters and tool material/coating (high speed steel and plain and coated carbide) on the thrust force and tool wear when drilling glass fiber reinforced epoxy composite. In order to predict the performance of the cutting tools in the industrial environment, extended drilling tests (up to 24000 holes) were conducted and the influence of changes in the geometry of the drills on the thrust force was assessed. The results indicated that the high speed steel tool presented remarkable wear rates, which drastically altered its edge preparation and resulted in a thrust force of 492 N after 1000 holes. In opposition to that, the cemented carbide drill presented superior wear resistance, with a thrust force of 147N after drilling 24000 holes. Finally, the use of the titanium nitride coated drill did not offer a significant contribution neither to the tool wear resistance nor to the machining thrust force.

Investigation on the Effect of Drill Geometry and Pilot Holes on Thrust Force and Burr Height When Drilling an Aluminium/PE Sandwich Material

Composite materials are widely employed in the naval, aerospace and transportation industries owing to the combination of being lightweight and having a high modulus of elasticity, strength and stiffness. Drilling is an operation generally used in composite materials to assemble the final product. Damages such as the burr at the drill entrance and exit, geometric deviations and delamination are typically found in composites subjected to drilling. Drills with special geometries and pilot holes are alternatives used to improve hole quality as well as to increase tool life. The present study is focused on the drilling of a sandwich composite material (two external aluminum plates bound to a polyethylene core). In order to minimize thrust force and burr height, the influence of drill geometry, the pilot hole and the cutting parameters was assessed. Thrust force and burr height values were collected and used to perform an analysis of variance. The results indicated that the tool and the cutting speed were the parameters with more weight on the thrust force and for burr height they were the tool and the interaction between tool and feed. The results indicated that drilling with a pilot hole of Ø4 mm exhibited the best performance with regard to thrust force but facilitated plastic deformation, thus leading to the elevation of burr height, while the lowest burr height was obtained using the Brad and Spur drill geometry.

Usinabilidade de materiais compósitos poliméricos para aplicações automotivas

Resumo: A cada dia o avanco tecnologico nos leva a encruzilhadas como a construcao de veiculos mais leves, com menor consumo de combustivel e mais seguros. Neste sentido, materiais compositos polimericos sao materiais usados atualmente em diferentes aplicacoes nas quais a leveza combinada com um alto modulo de elasticidade sao caracteristicas importantes. Poliamidas reforcadas com fibras de vidro se apresentam como materiais de grande futuro em aplicacoes automotivas. Desta forma, torna-se importante o estudo do comportamento deste tipo de material quando submetidos a processos de usinagem. Dentre os processos de usinagem o processo de furacao e um dos mais utilizados nos componentes de material composito. Neste trabalho sera analisada a influencia do avanco, da velocidade de corte e da geometria da ferramenta na forca de avanco, pressao especifica de corte e desvios dimensionais do furo realizado. Os testes foram realizados em poliamida sem reforco (PA6) e reforcada com 30% fibra de vidro (PA66-GF30) utilizando brocas de carbonetos sinterizados (K20) com ângulos de ponta diferente. Os resultados apontam claramente para a melhor usinabilidade do material reforcado em comparacao ao sem reforco. Palavras-chave: Compositos, polimeros reforcados, usinabilidade, furacao, danos. Machining Behavior of Polymer Composites Materials for Automotive Applications

Merchant Model Applied to Precision Orthogonal Cutting of Pa66 Polyamide with and without Glass Fiber Reinforcing

Polyamide composites are widely employed in various fields of engineering, such as aircraft, automotive, robots, and machinery owing to their remarkable properties. Precision machining aims the production of advanced components with high-dimensional accuracy and acceptable surface integrity. This work presents a preliminary experimental study based on Merchant theory applied to precision radial turning of PA 66 polyamide with and without 30% glass fiber reinforcing. Distinct feed rate values were tested using uncoated carbide tool (grade K15) without chip breaker. The aim of this study is to evaluate the chip compression ratio (Rc), chip deformation (ε), friction angle (ρ), shear angle (Φ), normal stress (σ), and shear stress (τ). In general, similar results were obtained when comparing the results obtained using Merchant model with the experimental findings.