EFFECT OF CARBON NANO TUBES ON EROSION WEAR OF CARBON FIBER, GLASS FIBER & KEVLAR FIBER REINFORCED UNSATURATED POLYESTER COMPOSITES

In the present study, nano composites were prepared by Hand lay-up molding. The nano composites component of the unsaturated polyester resin (UP) as a matrix, 3% volume fractions of Carbon Fiber (C.F), Glass Fibers (G.F), Kevlar Fiber (K.F) as reinforcement and (0.5%,1%, 1.5% and 2%) volume fractions of Carbon Nanotubes (CNTs) as filler. The erosion wear behavior of this nano composite at four different impingement angles 30°, 45°, 60° and 90° and four angular silica sand abrasive particle sizes 400, 500 , 600 and 800 μm and density were studied. The results showed that the specimens (UP + 3% (GF, CF, KF) +2% CNTs) have the maximum density when compared with the other volume fractions. The non – reinforced unsaturated polyester have lower erosion resistance than nano composites and the specimen (polyester +3% carbon fiber + 0.5% CNTs) has higher erosion resistance than other nano composites at 15cm, angle 30°, grin size of sand 400μm and 15 hour. Application of this work in protection of aircraft structure, turbine blades and pipes from erosion. The Taguchi experimental design ANOVA shows that the filler content factor has great effect on erosion rate of CNTs filled carbon, glass and Kevlar fibers reinforced unsaturated polyester resin. Keyword: Nano Composites, Carbon Nanotubes, Erosion wear, Carbon Fiber, Glass fiber, Kevlar Fiber. رتسا يلوبلا تابكارتمل ةيرعتلا يلب يلع ةيونانلا نوبراكلا بيبانا ريثات عبشم ريغلا رلفكلا فايلا و جاجزلا فايلاو نوبراكلا فايلاب ىوقملا ةصلاخلا : ةبكارتم داوم ريضحت ثحبلا اذه يف مت ةيونان بكارتملا نوكتت .ةيوديلا ةبلوقلا ةقيرط ةطساوب ةيونانلا تا جنتار نم يلوبلا عبشملا ريغرتسا فايلاو ساسا هدامك و نوبراكلا جاجزلا رلفكلاو يمجح رسكب ةيوقت ةدامك 3 % و ةيونانلا نوبراكلا بيبانا يمجح رسكب ( 0.5%, 1%, 1.5%, 2% ) . ةوشحك كولس ىلب ةيرعتلا ةعبراب ةيونانلا تابكارتملل ةفلتخم اياوز 30 ،ةجرد 45 و ةجرد 60 ةجرد و 90 ةجرد اكيليسلا لمر نم ماجحا ثلاثو 400 و 500 و 600 و 800 و نوركيم ةفاثكلا اهتسارد تمت دق . ناب جئاتنلا ترهظا ةنيعلا ] + رتسا يلوب 3 فايلاو نوبراكلا فايلا( % + رلفكلا فايلا و جاجزلا 2 % )ةيونانلا نوبراكلا بيبانا [ عم نراقت امدنع ةفاثك ىلعا كلتمت ريغلا رتسا يلوبلا . ىرخلاا ةيمجحلا روسكلا ةيرعتلل ةمواقم كلتمي ىوقم لقا نم + رتسا يلوب( ةنيعلا و ةيونانلا تابكارتملا 3 فايلا % + نوبراكلا 0.5 )ةيونانلا نوبراكلا بيبانا % لتمت ىرخلاا ةيونانلا تابكارتملا نم ةيرعتلل ةمواقم ىلعا ك دنع 15 ةيواز ، مس 30 o مجح ، ةيرعت قئاقد 400 نوركيام و 15 ذه قيبطت . ةعاس ه ةيامح وه ةساردلا يبروتلا شيرلا و تارئاطلا لكايه و ةين ةيرعتلا نم بيبانلاا . * dr.material @yahoo.com Vol. 22, No. 4, July 2018 ISSN 2520-0917 https://doi.org/10.31272/jeasd.2018.4.6 Journal of Engineering and Sustainable Development Vol. 22, No. 4, July 2018 www.jeasd.org (ISSN 2520-0917)


Introduction
Polymer composite materials have generated wide interest in various engineering fields, particularly in aerospace applications, because they exhibit, high specific strength and stiffness as compared to monolithic metal alloys. Polymer composite materials are therefore, finding increased application under conditions in which they may be subjected to solid particle erosion. Examples of such applications are pipe line carrying sand slurries in petroleum refining, helicopter rotor blades [1&2], pump impeller blades, high speed vehicles and aircraft operating in desert environments, water turbines, aircraft engine blades [3].
However, polymer composite materials exhibit poor erosion resistance as compared to metallic materials [4]. It is also known that the erosive wear of polymer composites is usually higher than that of the unreinforced polymer matrix [5]. Erosion is an important wear mode which involves the removal of material from a surface as a result of the impingement of solid particles or liquid droplets. Erosion caused by solid and sharp airborne particles is an especially severe problem in the operation of aircraft structures and of turbine blades over dusty terrains [6]. Erosion rate of the volume loss (v) is defined by the following equation [7]: ( ) Where ε: erosion rate of weight loss. W L : weight loss of the specimen (gm). Ws: total weight (gm).
: density of the testing material (g/cm 3 ) . There are many studies about composite materials. Mohammed Ismail et. al., (2012) fabricated epoxy resin reinforced with 20% weight fraction carbon fiber and (0, 2, 4) % weight fraction of fly ash cenosphere (CSP) having particle size 25 to 50 µm by hand lay-up technique followed by compression molding. The solid particle erosion characteristics of the (CSP) filled (C-E) composites were studied and the experimental results were compared with those of unfilled (C-E) composites.
For this, an air jet type erosion test and Taguchi orthogonal arrays (L27) were used. The result showed that the tensile modulus and flexural modulus of fly ash cenosphere filled (C-E) composites are high compared with that of the unfilled (C-E) composites, this enhance is due to higher silica content (60%), therefore a good interfacial adhesion between the cenospheres particles and the matrix occurs. The samples of composite materials (epoxy resincarbon fiber) and (epoxy resin + carbon fiber+ CSP) shown ductile erosion behavior and the peak erosion rate was found at 30° impingement angle. The erosion rate increased when the impact velocity increased. Also, the filler content had the greater effect factor than impact velocity, particle size impingement angle, and time of erosion during the erosive wear process [8].
Shakuntala Ojha. et.al. (2013) have studied solid particle erosion wear behavior of epoxy resin reinforced by jute-glass fiber and (2%, 4%, 6%) volume fraction of nano alumina .The flexural strength of nano composite is investigated, also the parameter used in the erosion wear test were impact velocity (72 m/s), impact angle (30 °, 45°, 60°, 90°) and silica sand with particle size (200 µm) .The results showed that the flexural strength of epoxy resin is lower than jute and glass fiber. After addition of nano alumina, there is an increase in the strength of jute and glass fiber composites. The erosion wear rate of the specimen GF+EP is less than of the net epoxy specimen and also depicted that as the volume fraction of nano alumina increases the erosion resistance increases. The maximum erosion occurs at 90° angle so the material behaves as brittle due to increase in alumina content [9]. Sridhar R. et. al (2014) have studied the effect of adding nano clay in percentages (2, 3,and 4)%wt. on erosion wear of vinyl esterglass fiber composites material by using Taguchi orthogonal array method. Erosion test were perform by used silica sand particle with size 177 to 595 nm. The parameter used in the erosion wear test were impact velocity (33, 45, 66 m/sec), impingement angle (30 • , 60 • , 90 • ), stand -off distance (120, 180, 240 mm) and erodent size (177, 420, 595 µm). The results showed that the addition of nano clay up to 3% weight fraction decrease the erosion rate of the composite material under the factors (66 m/s velocity, 240mm stand-off distance, 30 • impingement angle and 595 µm erodent size ) [10].

Objectives of the research
1. Prepare nano composites of unsaturated polyester resin reinforced with carbon fiber, glass fiber, and Kevlar fiber and carbon nanotube. 2. Study The erosion wear behavior of this nano composite at four different factors. 3. Study the Taguchi and analysis the result of ANOVA in other to find the most effecting factor on erosion rate.

Experimental Work
The materials that used in the manufacturing of specimens consisting of carbon fibers (Carbon UD Stockinette) from Tenax Company, glass fibers (Woven E-Glass Fiber) from the Tenax company, Kevlar fiber (fabric 49) and unsaturated polyester resin base as the matrix from the (faralop0115 company) in the form of transparent viscous liquid at room temperature which is a thermally hardened polymers (Thermosets) with a density of (1.11gm / cm 3 ). Multi-walled carbon nanotube (Intelligent Materials Pvt. Ltd, NANOSHEL LLC) [11].
All the required moulds for preparing the specimens were made from glass with dimensions of (120×120×5) mm.
The inner face of the mould was covered with a thin layer of (thermal paper) made from polyvinyl alcohol (PVA) to remove easily from the mould after molding. The mean grain size of carbon nanotube was (48) nm, as shown in figure (1).

Raw Materials
The properties of materials used in preparation of nano composite materials as shown in table (1):  (2) shows that x-ray diffraction pattern confirmed for (CNT) powder. From the results of x-ray diffraction indicating a high crystalline in the synthesized powder. All peaks could be indexed to a hexagonal structure [17].

Preparation of Nano Composites
Nano composites specimens were prepared from unsaturated polyester reinforced with 3% volume fraction of (Carbon fiber, Glass fiber, Kevlar fiber) and carbon nanotube with volume fraction of (0.5 %, 1%, 1.5%, and 2%). The method used in the preparation of the specimens in this research is the (Hand lay-Up Molding). The nano composites were prepared by cutting fibers into dimensions (120 × 120) mm, according to the dimensions of the mould.
The volume fractions of (C.F, G.F, and K.F) were (3%).Then weighing the reinforcing carbon nanotube to specify volume fraction of (0.5%, 1%, 1.5%, and 2%). Weighing the unsaturated polyester depending on the volume fraction of reinforcement materials (fibers and powder), with taking into consideration the weight of hardener. The unsaturated polyester was mixed with the hardener slowly and continuously by using a glass rod in order to avoid bubbles and then the powder was adding gradually into the mixture and stirring it to obtain homogeneity for a period of (10-15) minutes. While Pouring the mixture into the mould, fibers putting the mat into the mould and continuing of mixture pouring until it covers the entire mat then Pressing the mixture with an appropriate load.
Finally leaving the specimens in the mould for a period of (24) hour at room temperature. Specimens are then extracted from the mould and then heat treated in an oven at (60Ċ) for a period of (60) minutes. This process is very important for the purpose of obtaining the best cross linking between polymeric chains, and to remove the stresses generated from the preparation process and complete the full hardening of the specimens [18].

True Density Test
This test is done according to (ASTM D792) standard at the room temperature [19]. The specimens were cut into a thickness of 5 mm and a diameter of 40 mm that shown in figure (3).

Erosion Wear Test
This test is performed according to (ASTM G76) at room temperature [20,21]. Specimens have been cut into disk shape of a diameter of (40mm) and a thickness of (5mm) [22] as represented in figure (3). .The used device for erosion is locally 5 mm d = 40 mm manufactured; the principal scheme is shown in figure (4) show an illustration of erosion wear device sketch a plastic (Perspex) tank is used as a chamber. The Perspex tank has dimensions of (40) cm in length, (20) cm in height, and (20) cm in width. The pump joints and valves connected to the chamber are made from steel and slurry as well as jet nozzle.

True Density
Figure (5) shows the true density for the specimens unsaturated polyester+3% carbon fiber + (0.5%, 1%, 1.5%, 2%) carbon nanotube, unsaturated polyester+3% glass fiber + (0.5%, 1%, 1.5%, 2%) carbon nanotube and unsaturated polyester +3% Kevlar fiber + (0.5%, 1%, 1.5%, 2%) carbon nanotube. From the figure (5) it may be noted in all values of the nano composites density increased with increasing the volume fraction due the more voids are found with the addition of fiber and filler in the nano composites material [24]. In figure (5) can be seen that the specimens UP+ 3%C.F+0.5%-2% CNTs, UP+3% GF+0.5%-2% CNTs,UP+ 3%K.F+0.5-2% CNTs) have density higher than specimen UP, This is due to the fact that these fibers have a high density compared with the density of UP, also can be observed that the higher density has been found for the specimen (UP+ 3% G.F + 2% CNTs) than other specimens at same volume fraction because these CNTs are made to diminish or fill the voids and spaces which were inside the UP matrix. While the lower true density has been found for the specimen (UP + 3% K.F +2% CNTs) than other specimens. The preparation of composites with more than two materials is difficult, and increasing the volume fraction of any constituent can increase the difficulty and defect directly on the shrinkage of the matrix, and may create more voids-preferred sites. Also, the overall density will depend on the good distribution and bonding of all constituent [25].

Erosion Wear Test
The solid particle erosion wear rates of CNTs filled unsaturated polyester composites under various test conditions are studied. The weight of the Nano composite is taken before the erosion test, later after the erosion test again the weight of the Nano composite under study is taken and the difference in their weight is calculated. The weight of the Nano composite after erosion is always less than that of before erosion. The difference in their weight is called mass or weight loss of the specimen due to solid particle impact. The ratio of this mass loss to the mass of the eroding particles causing the loss is then computed as the erosion rate. The erosion rate is thus defined as the mass loss of the specimen due to erosion divided by total weight of the specimen multi by true density of the testing materials. Erosion wear rate include many mechanisms which are largely controlled by different factors such as impingement angle, particle size of silica sand, stand -off distance and filler content.

Effect of impingement angle on erosion rate
The impingement angle can be defined as the angle between the trajectory of the particle immediately before impact and the eroded surface. In cases when erosion shows a maximum at low impingement angles, it is concluded that the "ductile mode of erosion wear" prevails [26]. Conversely, if the maximum erosion rate is found at high impingement angles, then the "brittle mode" is assumed [27]. It is evident from figure (6) that impingement angle has significant influence on erosion rate and the maximum erosion is occurring at an impingement angle of 90° for all specimens and the minimum at (30°-60°). So the mode of erosion wear is neither a ductile erosion mode nor brittle erosion wear mode, it is behaving like semi ductile modes of erosion wear.

Effect of particle size of silica sand on erosion rate
The erosion rate of nano filler reinforced the unsaturated polyester resin has been studied by different size of silica sand (400, 500, 600, and 800) μm at constant flow rate (35 L∕min) as shown in figure (7). It is observed, that with the increase in erodent size from (400 μm to 800 μm) the erosion rate increase.

Effect of stand-off distance on erosion rate
The stand-off is the distance between the eroded surface and the nozzle. The figure (8) shows the erosion rate of nano composites have been studied by different stand-off distance (15,20,25, and 30) cm. it is observed, that with the decrease in distance from (30 cm to 15 cm) the erosion rate increase.

Taguchi Analysis
Tables (3) to (6) show the erosion rate of nano composites type for all 16 test runs and their corresponding S/N ratios.
The analysis is performed using the common software specially used for design of experiment MINITAB 17. The effect of the four factors on erosion rate for different nano composites are shown in figure (10 a, b, c, d).

Analysis of ANOVA
Analysis of ANOVA has been carried out from the experimental data for nano composites on erosion rate. Tables (7) to (10) shows the ANOVA result for the erosion rate of nano composites under solid particle erosion. This analysis is undertaken for a level of confidence of significance of 5%. The laste column of the  The ANOVA analysis can be performed from the experimental data for composites materials on erosion rate. "Table (7,8)" Results are appears of ANOVA for composites materials specimens. This analysis is pledge for a level of confidence importance 5%. The last column of the table appears that the essential influences are very highly significant (all have very small P-values).
3. From the Taguchi experimental design (ANOVA) filler content factor has great effect on erosion rate of CNTs filled carbon, glass and Kevlar fibers reinforced unsaturated polyester resin. The response for all nano composites is found semi-ductile and the maximum erosion rate takes place at the impingement of 90º.