Drilling Of Carbon Fiber Reinforced Plastics Research Articles

A study aimed at minimizing delamination during drilling of CFRP composites

The aim of this study is to present the methodology of Taguchi optimization technique for minimizing the delamination at the entrance of holes in high speed drilling of carbon fiber-reinforced plastics (CFRPs). The drilling process parameters evaluated are spindle speed, feed, and point angle. The experiments were performed as per Taguchi’s L27 orthogonal array using cemented carbide (K20) twist drills. The defects observed at the entrance of drilled holes of CFRP plates were measured and the delamination factor was computed for each trial of the orthogonal array. The analysis of means (ANOM) and analysis of variance (ANOVA) were employed to determine the optimal process parameter levels and to analyze the effect of parameters on delamination factor. The confirmation tests with the optimal levels of parameters were carried out to illustrate the effectiveness of Taguchi design. The optimization results indicate that point angle is the most significant factor followed by feed and spindle speed. The results also highlight the importance of employing the higher speeds to minimize the delamination defects.

Rotary ultrasonic machining of CFRP using cold air as coolant: feasible regions

Carbon fiber reinforced plastic (CFRP) composites are in demand for a variety of applications due to their superior properties. Drilling is involved in many CFRP applications. Experiments have been successfully conducted to use rotary ultrasonic machining (RUM) for CFRP drilling. These experiments were conducted using either cutting fluids or cold air as coolant. RUM of CFRP composites without cutting fluids can eliminate problems caused by cutting fluids, such as high cost of cutting fluids and their disposal, pollution to the environment, and harm to human health. However, dry machining (machining without cutting fluids) also has its limitations, such as burning of machined surface, more friction and adhesion between tool and workpiece, and reduction in tool life. This article presents an experimental study on feasible regions in rotary ultrasonic machining of CFRP using cold air as coolant. Three criteria (burning of machined surface, delamination, and tool blockage) were used to determine feasible regions. Each of four input variables (feedrate, tool rotation speed, ultrasonic power, and cold air pressure) was changed over a wide range so that its feasible region could be found.

Evaluation of Novel Approach on Delamination Factor after Drilling Composite Laminates

Drilling is the most economic and convenient operation of secondary machining for hole making of fiber-reinforced materials owing to the need for structure joining. Delamination is commonly recognized as a major defect after drilling composite materials. In general, the delamination is an irregular shape and size, containing long and fine breaks and cracks at the exit of the drilled hole, especially in the drilling of carbon fiber-reinforced plastic (CFRP). The conventional delamination factor ( ) is not appropriated to characterize the damage area because the shape of the delamination after drilled CFRP is not a regular representation of the damage magnitude. In this paper, a novel approach of the equivalent delamination factor ( ) is proposed and compared with the adjusted delamination factor ( ) and the conventional delamination factor ( ). The experimental results show the obtained is considered suitable for characterizing delamination at the exit of a hole after drilling composite materials.

Experimental Study on Drilling Process of CFRP Composite Laminate

This thesis deals with carbon fiber reinforced plastics (CFRP) composites, an advanced material which is widely used in manufacturing aircrafts because of their unique mechanical and physical properties. The research mainly involved drilling of CFRP. This study is focused on analyzing the thrust force and delamination against drilling parameters namely feed rate, spindle speed and type of tool materials. Also, the optimal parameters were chosen using an optimization method called D optimal. It was observed that the higher the feed rate and spindle speed employed, the higher the thrust force and delamination occur. The split point fibre (SPF) drill gave the lowest values of thrust force and delamination. Based on the optimal parameters, a verification test was conducted and the prediction error was 2.3% and 5.6% for thrust force and delamination respectively. This shows, that the optimal parameters obtained is reliable as it could improve the process considerably. The results of this study could be used as a reference for further research and studies on drilling of CFRP.

Study of drilling of composite material and aluminium stack

Abstract Drilling of CFRP/Al or CFRP/Ti, or Al/CFRP/Ti is a challenge to manufacturing engineers. Drilling of CFRP is manageable but the minute drill hits the Al or Ti, those hot and continuous chips destroy the hole. Few studies are carried out in this aspect; CFRP/Al is not reported till date. It is important to select right process parameters when drilling multimaterial stack since each material in the stack requires a different set of machining parameters. Hence, Drilling trials have been carried out in carbon-fibre reinforced plastics (CFRP)/aluminium (Grade 2024) stack without coolant, with plain carbide (K20) drills of various diameters to choose optimum process parameters. The parametric influences on thrust force, torque as well as surface finish were experimentally evaluated. The experimental results show that the quality of holes can be improved by proper selection of cutting parameters. This is substantiated by monitoring thrust force, torque, surface finish, circularity and hole diameter. For the CFRP, the circularity is found to be around 6 μm at low feed rates, when the feed is increased the circularity increases to 25 μm. The wear tests carried out show that, during first 30 holes, thrust force in CFRP undergoes a more important increase (90%) than thrust force of aluminium (6%).

Some experimental investigations in the drilling of carbon fiber-reinforced plastic (CFRP) composite laminates

In this paper, a concept of delamination factor F d (i.e. the ratio of the maximum diameter D max in the damage zone to the hole diameter D) is proposed to analyze and compare easily the delamination degree in the drilling of carbon fiber-reinforced plastic (CFRP) composite laminates. Experiments were performed to investigate the variations of cutting forces with or without onset of delamination during the drilling operations. The effects of tool geometry and drilling parameters on cutting force variations in CFRP composite materials drilling were also experimentally examined. The experimental results show that the delamination-free drilling processes may be obtained by the proper selections of tool geometry and drilling parameters. The effects of drilling parameters and tool wear on delamination factor are also presented and discussed. Cutting temperature has long been recognized as an important factor influencing the tool wear rate and tool life. An experimental investigation of flank surface temperatures is also presented in this paper. Experimental results indicated that the flank surface temperatures increase with increasing cutting speed but decreasing feed rate. Optimal cutting conditions are proposed to avoid damage from burning during the drilling processes.