Experimental Investigation of Slurry Erosion Wear Analysis of Epoxy Resin Reinforced with Aramid Woven Fabric with Taguchi Experimental Design

Abstract

Fibre reinforced polymer composites as hybrid composites are commonly used for certain applications in which erosion wear and fracture are serious issues. These composites have engineering/structural applications in which they are subjected to sand slurries and dusty environment. Composites with different fibre loading are used to evaluate steady state erosion behavior for different operating conditions on slurry jet erosion testing machine. In this chapter Slurry jet erosion test rig is used for experimental investigation of steady state erosion rate of aramid composite samples as per ASTM standards. Steady state erosion test is conducted by defining certain control factors and fixed parameters. Test is conducted in two cases. In first case by varying impact angle and keeping impact velocity and discharge rate constant and in second case by varying impact velocity and keeping impact angle and discharge rate constant. Steady state erosion rate is calculated for both the cases. The Taguchi experimental design (orthogonal array) is used to optimize the design parameters and used to analyse the effect of control factors on output parameters, which reduces overall testing time and cost. To understand the effect of control factors and their iterations ANOVA (analysis of variance) is used. Results of steady state erosion rate and Taguchi experimental design are analysed to selection best suitable material for turbine blade application based on minimum erosion rate

Introduction

I. INTRODUCTION

Solid particle erosion can be of two types one is constructive and second one is destructive. Constructive erosion is desired loss material whereas destructive erosion is undesired loss of material. Sand blasting, high-speed water-jet cutting, erosive drilling of hard materials are some recent applications of constructive erosion whereas erosion of machine parts, erosion of pipelines carrying slurries, surface degradation of steam turbine blades are some industrial applications of destructive type. Polymers and their composites are widely used in structural as well as some engineering applications have to come in contact with erosive environment [16] [17]. These composites have further applications such as in petroleum refining pipe line carrying sand slurries, pump impeller blades, high speed vehicles, aircraft operating in desert environment, helicopter rotor blades, aircraft engine blades, water turbines subjected to solid particle erosion [1] [2]. Patnaik and Satapathy investigated the solid particle erosion of fly ash filled glass fibre reinforced polyester composites using Taguchi experimental design, in which factors like fly ash content, impingement angle, erodent size and impact velocity in order of priority are significant to minimize the erosion rate [3][10]. Filler loading, grit size and filler type are the most significant factors in controlling the specific wear rate of the carbon-epoxy composite as investigated by Ramesh and Suresh [4] [11]. Erosion wear rate of glass fibre reinforced vinylester composites increased (up to 6 times higher weight loss) as the erodent concentration of the slurry and total kinetic energy of the erodent particle is increased [5]. In one of the recent paper M.J. Pawar and Patnaik have evaluated slurry jet erosion wear behaviour of unfilled and granite powder filled jute epoxy composite and have investigated that with the addition of granite powder (0 to 8 wt%) as filler, slurry erosion rate is reduces by 32%. But this reduction% is decreases to 20% as the filler content increases from 8 to 16 wt% and again increases to 25% reduction in erosion rate when filler content is in between 16        to 24 wt % [6] [12].

Against this background, the present research work has been undertaken to investigate the new class of synthetic organic (aramid) fibre reinforced polymer composite. The main emphasis has been on the fabrication of a number of aramid fibre reinforced epoxy composites, assessment of their erosion behavior using steady state erosion wear.

II. EXPERIMENTAL DETAILS

A. Slurry Jet Erosion Test of Composite

As per ASTM standard -73, slurry jet erosion test is conducted using slurry jet erosion tribometer as shown in Fig.  1. The test setup is consisting of a mixing chamber to make homogeneous mixture of water and sand particles, a nozzle valve of 3 mm inner diameter, a specimen holder plate to maintain different angles between samples and slurry jet direction. The velocity of jet changes from 10 m/s to 50 m/s. The test setup is having a 50 mm stand-off distance (SOD) between sample and nozzle tip. The impingement angles are marked over the sample plate starting from 30° to 90° with an interval of 15°. Weights of the samples prepared are taken using an analytical weighing machine with least count of 0.01 mg. For erosion test samples are prepared of dimensions 25 mm×25 mm from composite plate. The slurry jet erosion rate is obtained by calculating total mass loss of the sample. Total mass loss is the difference of weight taken before and after erosion test. In this study silica sand is taken as erodent of size 300 µm.

The slurry erosion rate is influenced by the number of control factors like impact velocity, impingement angle, fibre loading, erodent size, slurry concentration, stand-off distance, flow rate respectively [7][13].

Table 1. Operating conditions for slurry erosion test

Table 2. Control factors and levels

B. Experimental Design using Taguchi Method

The Taguchi experimental design (orthogonal array) is used to optimize the design parameters and used to analyse the effect of control factors on output parameters, which reduces overall testing time and cost. It is a simple, systematic and efficient technique for optimization of control factors. Taguchi defines two types of variables; one is controlled variables known as signal or control factors and variables that are not under control known as noise. The objective of this experiment is to determine highest possible value of signal to noise ratio (S/N), that implies that signal is higher than effect of noise factors.

The slurry erosion rate is influenced by the number of control factors like impact velocity, impingement angle, fibre loading, erodent size, slurry concentration, stand-off distance, flow rate respectively [8][14].

Table 2 shows the levels for various control factors for slurry erosion test. In this study the design of experiments is planned for 4 levels and 4 factors, so the orthogonal array selected is L16 (44). Table 3 shows the orthogonal array design as per L16 for unfilled and marble dust powder filled aramid epoxy composites respectively.

Table 3. Orthogonal array for l16 (44) taguchi design

The major tool for Taguchi experimental design is S/N ratio, and is termed as the ratio of mean to standard deviation or the ratio of signal to noise. For minimum erosion rate, the S/N ratio is determined as logarithmic transformation by considering ‘smaller-is-the-better’ characteristic.

1. Comparison of S/N ratios of unfilled aramid Reinforced Epoxy Composites

Experimental design of unfilled aramid reinforced epoxy composites using orthogonal array (L16) is shown in Table 4. The mean S/N ratio of erosion rate is calculated is 50.29db. S/N ratios are calculated by considering smaller-is-the-better characteristic for minimization of slurry erosion rate.

TABLE 4. COMPARISON OF S/N RATIOS OF UNFILLED ARAMID REINFORCED EPOXY COMPOSITES

2.  ANOVA and the Effect of Factors

It is required to develop analysis of variance (ANOVA) to understand effect of control factors and their interactions. Table 5 shows the results of the ANOVA with the erosion rate. This analysis was undertaken for a level of confidence of significance of 95%. The last column of the table indicates that the main effects are highly significant (all have very small p-values).

Table 5. Anova table for erosion rate of unfilled aramid epoxy composites

DF: degree of freedom; Seq. SS: sequential sum of squares; Adj SS: extra sum of squares; Adj MS: extra mean squares; p: level of significance; F: variance ration.

III. RESULTS AND DISCUSSION

A. Effect of Impact Angle on Erosion Rate of Composites

The erosion wear behavior of composites loaded with different fibre loading (20wt% - 50 wt%) are plotted with change in impingement angle and by keeping all other parameters constant (impact velocity = 37 m/s, stand-off distance = 50mm and erodent size = 300 µm). It can be noted form Fig. 2. that irrespective of fibre content (20wt% - 50wt %) of all the samples at an angle of 45° peaks of erosion rates are located. This type of behaviour of composite is called semi-ductile erosion behaviour. The erosion rate in increasing order can be written as EA20?EA30?EA40?EA50 respectively. The slurry jet erosion behaviour of composites is dependent upon the working condition. The erosion can be of ductile or brittle nature depending upon certain parameters such as change in impingement angle, fibre content, and properties of erodent material. Erosion rate decreases as the fibre content increases from (20wt% - 50wt %), this is due to the decrease in the void fraction from (20wt% - 40wt %). But due to again increase in void fraction for fibre loading of 50wt%, there is marginal decrease in the erosion rate for fibre loading of (40wt% - 50wt %). Therefore, it is clear that erosion resistance increases with increase in fibre loading.

B. Effect of Impact Velocity on Erosion Rate of Composite

Erosion tests are conducted to study the influence of impact velocity on erosion rate by altering the impact velocity from 27 m/s to 42 m/s while other parameters like impingement angle (60°), stand-off distance (50 mm) and erodent size (300µm) were retained constant.

The change in erosion rate was recorded with change in impact velocity as shown in Fig. 3. With increase in impact velocity a systematic increase in the steady state erosion rate is observed. As the impact velocity of the sand particles increases, leads to increase in the kinetic energy, which further increases erosion wear [9][15].

C. Comparison of Taguchi experimental results of erosion rate of unfilled and marble dust filled aramid reinforced epoxy composites

The mean S/N ratio of erosion rate is 50.29 db. Fig. 4. is the graphical representation of the  effect of four control factors on erosion rate of composites. MINITAB 16 based on design of experiment is used for analysis. Possible interactions between the control factors are determined. From this analysis it is concluded that to get minimum erosion rate A4, B4, C2 and D1 are significant factor levels. The average S/N ratios of the marble dust filled composites are recorded as 53.37 db.

Conclusion

In this present analysis a series of aramid fibre reinforced epoxy matrix composites have been fabricated successfully. The experimental evolution erosive characteristics of composites of different fibre loading 20wt% - 50wt% is done. The study of impact velocity, impingement angle and erodent discharge rate on erosion rate of unfilled and marble dust filled composites shows semi-ductile behaviour of the material with respect to erosion wear. Irrespective of fibre content (20wt% - 50wt %) and filler content (5wt% - 15wt %) of all the samples the peak erosion rates are located at an angle of 45°. The erosion rate is also influenced by the impact velocity and erodent discharge rate. Result shows that fibre/filler content, impact velocity, slurry concentration, and impingement angle are the significant factors in decreasing order i.e., impingement angle is least significant factor. Therefore, it is clear that erosion resistance increases with increase in fibre loading. With increase in impact velocity a systematic increase in the steady state erosion rate is observed.

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Copyright

Copyright © 2023 Namita Soni, Nitin Goyal, Monu Gupta, Monika Khurana, Sumita . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.