Comparative analysis of drills for composite laminates (original) (raw)
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Materials Science Forum, 2010
The distinguishing characteristics of carbon fibre reinforced laminates, like low weight, high strength or stiffness, had resulted in an increase of their use during the last decades. Although parts are normally produced to "near-net" shape, machining operations like drilling are still needed. In result of composites non-homogeneity, this operation can lead to delamination, considered the most serious kind of damage as it can reduce the load carrying capacity of the joint. A proper choice of tool and cutting parameters can reduce delamination substantially. In this work the results obtained with five different tool geometries are compared. Conclusions show that the choice of adequate drill geometry can reduce thrust forces, thus delamination damage.
Journal of Materials Processing Technology, 2010
Composites use in the aerospace industry is expanding, in particular carbon fibre reinforced plastics (CFRP) for structural components. Machinability can however be problematic especially when drilling, due to CFRP's inherent anisotropy/in-homogeneity, limited plastic deformation and abrasive characteristics. Following a brief review on composites development and associated machining, the paper outlines experimental results when twist drilling 1.5 mm diameter holes in 3 mm thick CFRP laminate using tungsten carbide (WC) stepped drills. The control variables considered were prepreg type (3 types) and form (unidirectional (UD) and woven), together with drill feed rate (0.2 and 0.4 mm/rev). A full factorial experimental design was used involving 12 tests. Response variables included the number of drilled holes (wear criterion VB B max ≤ 100 m), thrust force and torque, together with entry and exit delamination (conventional and adjusted delamination factor values calculated) and hole diameter. Best results were obtained with woven MTM44-1/HTS oven cured material (3750 holes) while the effect of prepreg form on tool life was evident only when operating at the higher level of feed rate. Thrust forces were typically under 125 N with torque values generally below 65 Nmm over the range of operating parameters employed. Finally, the delamination factor (F d) measured at hole entry and exit ranged between ∼1.2-1.8 and 1.0-2.1 respectively.
Composite materials have become valuable construction materials in aerospace, defense and in recent years in automotive industry. The advantage of composite materials over conventional materials stems largely from their higher specific strength, stiffness and fatigue characteristics. Composite components are joined by mechanical fasteners, accurate, precise high quality holes need to be drilled to ensure proper and durable assemblies. Drilling of composite materials causes several damages, such us: delamination, fibre-pull out, edge chipping, uncut fibers and others. Delamination is a major problem associated with drilling fiber reinforced composite materials. It causes poor assembly tolerance, reduces structural integrity of material and the potential for long term performance deterioration. The thrust force has been cited as main cause of delamination. In this paper the objective was to establish correlation between cutting parameters and thrust force, drilling torque and delamination. Drilling tests were carried out on carbon epoxy composite material using three different drills, HSS-Co twist drill, Multi Constructional twist drill and "Brad & Spur" drill. The data have been processed by the "DesignExpert" software package which generated the mathematical models.
Experimental Study on Drilling Process of CFRP Composite Laminate
Materials Science Forum, 2010
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...
The major objective of this work was to investigate a statistical model, based on Taguchi technique and to estimate the quality of drill in CFRP composite material prepared by hand layup technique. The design of experiments were made to investigate the influence of drill parameters such as cutting speed, feed rate and drill diameter on thrust force and delamination factor in drilling of CFRP laminates. Analysis of variance (ANOVA) was used to analyze the significance level of every drill parameters. The statistical model yields the results showing that the speed and feed rate were the major parameters affecting significantly the drilling process. Delamination due to drilling was analyzed by the stereomicroscope.
2017
Delamination is one of the most common defects occur during drilling of carbon fiber reinforced polymer composites. It is an inter-ply failure phenomenon and it has to be minimized to have better quality of drilled holes for structural applications. The current study is conducted to investigate the effect of machining parameters (spindle speed, drill diameter, feed rate and point angle) on delamination while drilling of 60-40 weight % and 55-45 weight % of bi-directional carbon fiber reinforced polymer (BD CFRP) composites with titanium nitride (TiN) coated solid carbide drills. Taguchi L27 orthogonal array is used for determining the experimental results of delamination and the Taguchi methodology is also employed for determining the predicted results of delamination of both BD CFRP composite laminates. The investigation reveals that there is a good concurrence between the experimental and the predicted results of delamination. The main effect plot shows that the drill diameter has...
Drilling is the most frequently used machining process for carbon fiber reinforced polymer (CFRP) composite laminates owing to the need for structural joining. Delamination is a major problem associated with drilling of CFRP composites. Therefore, it is important to investigate and minimize the drilling induced delamination that can affect structural integrity of materials, assembly tolerance, mechanical properties of produced parts, and the quality of drilled holes. Thrust force has been cited as the main cause of delamination. The damage caused at the entrance and the exit of the drilled hole is characterized by delamination factor. In this paper, the drilling tests are carried on bi-directional carbon fiber reinforced epoxy composite (BCFREC) laminate by using high speed steel drill at different feed rate and spindle speed. The study reveals that delamination tendency, thrust force and torque increase with the increase in feed rate and spindle speed. The drilling-induced delamination is visualized and measured by using high resolution scanner.
The International Journal of Advanced Manufacturing Technology, 2017
Delamination is one of the major damages associated with drilling carbon fiber-reinforced plastics (CFRP), Peel-up and Push-out are two recognizable delamination mechanisms, while drilling without using a backup plate under the workpiece complicates the delamination mechanism even more. Minimizing delamination is dependent on many factors such as cutting parameters, geometry and type of drill bits used. The objective of this study is to present a new approach to measure the equivalent adjusted delamination factor (F eda) when drilling unidirectional CFRP laminates without using a backup plate and comparing it experimentally and numerically with conventional delamination factor (F d) and adjusted delamination factor (F da). A polycrystalline diamond (PCD) twist drill and a special diamond coated double point angle drill was used for drilling in this study. The 3D finite element model was developed in ANSYS-Explicit to simulate the drilling process using the ply-based modeling method instead of a conventional zone-based concept. Experimental drilling validation process was implemented by utilizing a CNC machining center. Results show that the F eda obtained is suitable to estimate the drilling induced damages, damage analysis shows that good agreements were obtained from the experiments and finite element method (FEM) simulation, while the special diamond coated double point angle drill seemed to provide a better hole quality, and drilling induced damage is highly affected by feed rate which is considered one of the important parameter.
Study of delamination in drilling carbon fiber reinforced plastics (CFRP) using design experiments
Composite Structures, 2003
In this paper is presented a new comprehensive approach to select cutting parameters for damage-free drilling in carbon fiber reinforced epoxy composite material. The approach is based on a combination of Taguchi’s techniques and on the analysis of variance (ANOVA). A plan of experiments, based on the techniques of Taguchi, was performed drilling with cutting parameters prefixed in an autoclave carbon fiber reinforced plastic (CFRP) laminate. The ANOVA is employed to investigate the cutting characteristics of CFRP’s using high speed steel (HSS) and Cemented Carbide (K10) drills. The objective was to establish a correlation between cutting velocity and feed rate with the delamination in a CFRP laminate. The correlation was obtained by multiple linear regression. Finally, confirmation tests were performed to make a comparison between the results foreseen from the mentioned correlation.