STUDY AND MOLDING CYCLE OPTIMIZATION PART WITH POLYPROPYLENE COMPOSITES/SHORT HEMP FIBERS

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 8, August 2017, pp , Article ID: IJMET_08_08_008 Available online at me.com/ijmet/issues.asp?jtype=ijmet&vtype=8&i IType=8 ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed STUDY AND MOLDING CYCLE OPTIMIZATION OF INJECTED AUTOMOTIVE PART WITH POLYPROPYLENE COMPOSITES/SHORT HEMP FIBERS Hamid Bakhtari, BasmaBenhadou, Mariam Benhadou, AbdellahHaddout, Laboratory of industrial management and energyand technology of plastics and composites - ENSEM Casablanca University Hassan II- Casablanca Morocco ABSTRACT We present in this paper the study the effect of injection parameters on polypropylene composites reinforced with short hemp fibers in order to define the optimums cycle production parameters and their influence on the morphological and mechanical properties and appearance and odor of the manufactured parts. We studied the distribution and orientation of fibers during the injection molding process in order to obtain better performance of composite materials made with polypropylene reinforced with short hemp fibers. The parameters chosen and which require good control are the transformation temperature, the screw rotation speed, the counter pressure and the holding pressure. We defined the optimum parameters and determined a molding plug for each material formulation. We used the molding parameters established to inject an automotive part with complex geometry. We have shown that molding complex parts is possible with a stable and capable process. Keywords: Injection molding, Processing parameters, Molding cycle optimization, Hemp fibers, Thermoplastics composites. Cite this Article: Hamid Bakhtari, BasmaBenhadou, Mariam Benhadou, AbdellahHaddout, Study and Molding Cycle Optimization of Injected Automotive Part with Polypropylene Composites/Short Hemp Fibers, International Journal of Mechanical Engineering and Technology 8(8), 2017, pp T/issues.asp?JType=IJMET&VType=8&IType=8 1. INTRODUCTION The use of bio composites based on plant fibers is expanding with many industrial applications. Vegetable fibers are sought after for the many environmental, economic and health advantages that industries could benefit from: renewable raw material, biodegradability

2 Hamid Bakhtari, BasmaBenhadou, Mariam Benhadou, AbdellahHaddout and carbon neutral balance, low density, energy saving, flexibility, low cost, less or no Health problem with operators on manufacturing lines [1-4]. Bio-composites made from hemp fibers can be applied in the automotive field for applications such as interior door cladding, roof boxes, bumpers [3,4 7,11].Today, the main axes of technical development of the fibers and the associated bio-materials reside in the improvement of the properties of the fibers by the selection, in the optimization of the industrial processes. [2-6]. The injection molding process is the most commonly used for the transformation of these composites.this process makes it possible to obtain parts of various geometric sizes and complexities and remains an economical process, well adapted to large series. Therefore, control of the injection molding process seems indispensable [6-8]. This approach may be possible only by increasing the production of quality parts and / or by reducing the overall time of the injection cycle. The aim is to find the optimum parameters to guarantee, on the one hand, parts having the required properties and on the other hand, to optimize the production cycles [9-14]. The use of natural fibers for composite applications is studied throughout the world. Many automotive parts (interior and exterior) arenow made from these materials. The Composites are based on reinforced polypropylene with jute, flax, hemp, kenaf and wood fibers. [15-22]. The major challenge for the automotive industry is the reduction of the weight of the parts: reduction of 30% possible with the use of natural fibers instead of glass.savings on raw materials are another important factor. Therefore, using natural fibers to replace glass fibers has a huge advantage for the automotive industry. This economic and ecological gain is a charming asset for large companies. In this work, we try to highlight the influence of injection parameters and mold cavity geometry on the technical and morphological characteristics of an automotive part with a complex geometry made of polypropylene reinforced at 30% short hemp fibers 2. EXPERIMENTAL PROCEDURE 2.1 Materials For industrial applications, homopolymer polypropylene is the most used since it offers the best mechanical and thermal characteristics. The polypropylene characteristics are: Density ρ = 900kg/m 3 and melt flow index I = 25g/10min and melting temperature T=166 C and Thermal conductivity at 25 C λ = 0,3w/mK. In order to improve their properties to use them as reinforcements for composite materials, the hemp fibers are alkali treated. The used hemp fibers have a diameter of 250 µm and a length ranging from 1.5 to 2 mm. For better fiber / matrix interfacial adhesion, we added to the mixture 5% of maleic anhydride grafted polypropylene. The polypropylene granules reinforced at different hemp fibers rates were produced by the extrusion process. 2.2 Injection molding of samples To study the composites behavior subjected to different injection parameters, we used an industrial injection-molding machine. This machine has a closing force of 130 tons, equipped with a standard screw of 55 mm diameter and an instrumented mold. It is controlled by a microprocessor. In particular, this system allows the press automatic adjustment (The mold closing force, heating collars temperature of the barrel and the nozzle, etc.) and the parameters adjustment of the injection cycle (injection speed, holding pressure, holding time, cooling time, injection pressure, injection temperature, etc.) editor@iaeme.com

3 Study and Molding Cycle Optimization of Injected Automotive Part with Polypropylene Composites/Short Hemp Fibers First, we used the single-cavity specimen mold, with a sheet feed, the specimen dimensions are standardized according to the ISO 527 standard. Next, we used a mold for automotive parts with a complex geometry. The main molding parameters used in our experimental design are summarized in Table 1 below: Table 1 Main polypropylene composite / short hemp fibers (70/30) injection parameters Parameters Normal settings Temperatures in C Molding temperature 170 à 190 Mold Temperature 30 Demolding temperature 60 Time in s Cooling time 40 Holding time 5 Dosing time 1.38 Speed Screw rotation speed rpm 30 Injection speed mm / s 40 Volume in mm Dosing volume 42 Switching point 8 Mattress in cm 3 7,5 Pressure in bars Injection pressure 65 Holding pressure RESULTS AND DISCUSSION 3.1 Morphological characterization Firstly, we conducted a series of morphological analysis on our specimens in order to validate chosen injection parameters. These tests were carried out using a reflection optical microscope in order to study orientation and distribution and breakage of fibers in several zones in the specimen: injection threshold, medium, extremities, and filling end editor@iaeme.com

4 Hamid Bakhtari, BasmaBenhadou, Mariam Benhadou, AbdellahHaddout Figure 1 gives the standardized specimen view at different zones.the fibers are well distributed; fibers orientation is random, except in the middle zone where they are oriented in the flow direction. The injection speed effect Figure 1: Visualization by reflection microscopy of the PP with 20% hemp implemented at injection speed 30 mm / s A better fibers distribution is obtained at the speed 30 mm / s, for higher speeds a high concentration is noted at the filling end, the specimen surface state at high speed is better. The screw rotation speed effect Figure 2 Visualization by reflection microscopy of the PP 30% hemp implemented in screw rotation speed 240 rpm A better filling stability of the part is obtained at a screw rotation speed of 240 rpm.for the higher screw rotation speeds, the dosing is unstable, with an odor released during the dosing; the most important remark is that the fiber length falls this is explained by fibers breakage during plasticizing. 3.2Automotive technical parts molding According to our results demonstrated on the specimens with the parameters determined experimentally, we can say that the injection process of polypropylene short hemp fibers composites is controlled, but the specimen geometry is simple.for this, we have chosen a complex geometry part to study the injection process in real industrial parts Figure 3. Implementation by injection We used the same parameters called "validated" in the specimen first experiment, with adjustment in the parameter, which depends on parts size and the press used such as: dosing volume, mattress, switching point, etc. Table 2 summarizes the parameters set adopted for this part.

5 Study and Molding Cycle Optimization of Injected Automotive Part with Polypropylene Composites/Short Hemp Fibers Table 2 Molding sheet for the automotive part made of PP30% hemp Parameters Normal settings Temperatures in C Molding temperature 170 à 190 Mold Temperature 30 Demolding temperature 60 Time in s Cooling time 12 Holding time 5 Dosing time 10 Speed Screw rotation speed rpm 35 Injection speed mm / s 55 Volume in mm Dosing volume 152 Switching point 15 Mattress in cm 3 12 Pressure in bars Injection pressure 1300 Holding pressure 1000 Visual and dimensional control: After the press was stabilized, we carried out comparative visual checks with the PP / glass part, table 3 summarizes the checks carried out. Figure 3 Left part injected with PP 30% hemp and right PP 30% glass fibers Table 3 Controlled appearance characteristics in the injected part of PP 30% hemp. Characteristic of aspect to be checked No incomplete in general and mainly at the filling end No burr making it impossible to assemble No burrs on the clips making it impossible or difficult their functionality No burr in the cable passage areas Presence of the 4 evacuation holes Presence of passage holes of collars emerging Result Conform Conform Conform conform conform conform

6 Hamid Bakhtari, BasmaBenhadou, Mariam Benhadou, AbdellahHaddout According to aspects control that are carried out on this automotive part are in conformity with the plan and ditto to the part injected in PP fiber glass except the color is not brilliant, it is a point to improve. Despite parameters tests, that we did on, having a direct impact on appearance such as mold temperature, injection speed but no improvement is noticed. We also carried out a very important check to verify the porosities presence; we used the 2 D machine with a magnification of 120 times. Controls are made after cutting and polishing the part in three areas, injection beginning and middle and filling end. No porosity is observed. Dimensional control and injection process stability: The dimensional control is carried out with respect the workpiece plane, all controlled dimensions are within the tolerance. The most critical dimension = ± 0.75, to ensure that our process is capable we have performed an SPC calculation to calculate the capability of our machine by transforming these composite materials with vegetable fibers. Figure 4 The gauss curve obtained during the injection of the automobile part According to results obtained, the process is capable since the Cm/Cp are well above 1.33 Table 4 Injection process SPC data used Average 138,060 Maxi 138,250 Mini 137,900 Extended 0,350 Standard deviation 0,0916 Cm / Pp 2,73 Cmk / Ppk 2,22 ± 4s 137, , CONCLUSION The objective of this study is to control the injection molding of polypropylene composite reinforced by short hemp fibers for their vast current use in various industrial fields. Initially, we conducted an injection molding study on polypropylene composites reinforced with 30% short hemp fibers, using a standard tensile test specimen. In order to define the optimum parameters of the production cycle and their influence on the

7 Study and Molding Cycle Optimization of Injected Automotive Part with Polypropylene Composites/Short Hemp Fibers morphological, mechanical, dimensional, appearance and odor properties of manufactured parts. The parameters chosen and which require good control are the transformation temperature, the screw rotation speed, it must be average and must not exceed a limiting speed, counter pressure and holding pressure to avoid porosity defects. We defined the optimum parameters and determined a molding sheet for each material. In the industrial aspect, we used the established molding parameters, in order to inject an automotive part with complex geometry. We have shown that molding complex parts is possible with a stable and capable process. REFERENCES [1] Faris M. AL-Oqla, S.M. Sapuan, M.R. Ishak, Nuraini A.A. Predicting the potential of agro waste fibers for sustainable automotive industry using a decision making model Computers and Electronics in Agriculture 113, [2] Hoi-yan Cheung, Mei-po Ho, Kin-tak Lau, Francisco Cardona, David Huic Natural fibre-reinforced composites for bioengineering and environmental engineering applications. Composites Part B: Engineering Volume 40, Issue 7, Pages [3] H.M. Akil, M.F. Omar, A.A.M. Mazuki, S. Safiee, Z.A.M. Ishak, A. Abu Bakar. Kenaf fiber reinforced composites: A review. Materials & Design, Volume 32, Issues 8 9, Pages [4] M.M. Davoodi, S.M. Sapuan, D. Ahmad, Aidy Ali, A. Khalina, vmehdijonoobi.. Mechanical properties of hybrid kenaf/glass reinforced epoxy composite for passenger car bumper beam. Materials & Design, Volume 31, Issue 10, Pages [5] Fauzani Md. Salleh, Aziz Hassan, RosiyahYahya, Ahmad DanialAzzahari. Effects of extrusion temperature on the rheological, dynamic mechanical and tensile properties of kenaf fiber/hdpe composites. Composites Part B: Engineering, Volume 58, Pages [6] N. Saba, M.T. Paridah, M. Jawaid. Mechanical properties of kenaffibre reinforced polymer composite: A review. Construction and Building MaterialsVolume 76, Pages [7] K.L. Pickering, M.G. AruanEfendy, T.M. Le. A review of recent developments in natural fibre composites and their mechanical performance. Composites: Part A [8] M. Ramesh Kenaf (Hibiscus cannabinus L.) fibre based bio-materials: A review on processing and properties, Progress in Materials Science 78-79, [9] Elwathig Hassan. Plant fibers reinforced poly (lactic acid) (PLA) as a green composites: Review International Journal of Engineering Science and Technology (IJEST) Vol. 4 No [10] Shalwan A, Yousif BF. Influence of date palm fibre and graphite filler on mechanical and wear characteristics of epoxy composites. Materials &Design Vol 59, Pages [11] Kim Hill, Bernard Swiecki, Joshua Cregger, The Bio-Based Materials Automotive Value Chain Center for Automotive Research [12] Mohanty, A.K., Misra, M., and Drzal, L.T., Sustainable bio-composites from renewable resources: Opportunities and challenges in the green materials world. Journal of Polymers and the Environment, 10: pp [13] Elkhaoulani A, Arrakhiz FZ, Benmoussa K, Bouhfid R, Qaiss A. Mechanical and thermal properties of polymer composite based on natural fibers: Moroccan hemp fibers/polypropylene. Materials & Design; 49: editor@iaeme.com

8 Hamid Bakhtari, BasmaBenhadou, Mariam Benhadou, AbdellahHaddout [14] NadjlaMostefai, RabahHamzaoui, SofianeGuessasma, Amadou Aw, HediNouri Microstructure and mechanical performance of modified hemp fibre and shiv mortars: Discovering the optimal formulation Materials and Design [15] Ahmed N. Oumer and Othman Mamat. A Review of Effects of Molding Methods, Mold Thickness and Other Processing Parameters on Fiber Orientation in Polymer Composites. Asian Journal of Scientific Research. Volume: 6, Issue: 3 Page [16] KaminiSewda. S. N. Maiti. Dynamic mechanical properties of high density polyethylene and teak wood flour composites. Polym. Bull. (2013) 70: [17] PriyaSinghal and S.K. Tiwari..Effect of Various Chemical Treatments on the Damping Property of Jute Fibre Reinforced Composite International Journal of Advanced Mechanical Engineering. ISSN Volume 4, Number 4 (2014), pp [18] Joshi SV, Drzal LT, Mohanty AK, Arora S. Are natural fiber composites environmentally superior to glass fiber reinforced composites; Compos Part A ApplSciManuf 2004;35:3716. [19] IndraReddy, V. Srinivasa Reddy. Dynamic Mechanical Analysis of Hemp Fiber Reinforced Polymer Matrix Composites International Journal of Engineering Research & Technology (IJERT) ISSN: Vol. 3 Issue 9, September [20] M. Indra Reddy Dynamic Mechanical Analysis of Hemp Fiber Reinforced Polymer Matrix Composites. International Journal of Engineering Research & Technology (IJERT) Vol. 3 Issue 9, September [21] A. Haddout; M. Benhadou; F. Rhrich; L. Safraoui; G. Villoutreix; Study of The Morphological and Mechanical Behavior of Injected Polypropylene Composites Reinforced with Short Glass Fibers; International Journal of Recent Development in Engineering and Technology; Volume 2, Issue 5 May 2014 [22] BasmaBenhadou, AbdellahHaddout, Mariam Benhadou, Hamid Bakhtari study and optimization of the injection molding of composites based on short hemp fibers; International Journal of Mechanical Engineering and Technology (IJMET)Volume 7, Issue 4, July Aug 2016, pp , [23] e Mariam Benhadou, Abdellah Haddout, Basma Benhadou, Hamid Bakhtari and Hassan Rhimini, Experimental Study of Thermo mechanical Behavior of Polypropylene/Short Hemp Fibers Injected Composites. International Journal of Advanced Research in Engineering and Technology, 7(4), 2016, pp [24] BasmaBenhadou, Mariam Benhadou and AbdellahHaddout Prediction of Shrinkage and War page in Injected Thermoplastic Composites reinforced With Hemp Fibers. International Journal of Mechanical Engineering and Technology 8(5), 2017, pp editor@iaeme.com