Comparative analysis of manufacturing processes for tests specimens orientation [0/±45] s of carbon fiber 3k and polyester resin

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1 Mex. J. Mat. Sci. Eng. xxxx (2017) x-y Comparative analysis of manufacturing processes for tests specimens orientation [0/±45] s of carbon fiber 3k and polyester resin M.Siqueiros 1*.; A. Nava 1.; Y. Vega 1.; B. González 1. 1 Escuela de Ciencias de la Ingeniería y Tecnología, Universidad Autónoma de Baja California, Blvd. Universitario #1000, Unidad Valle de las Palmas. Tijuana Baja California, C.P , México. *miriam.siqueiros@uabc.edu.mx Abstract. In this document a comparison is shown between two manufacturing processes for the fabrication of test specimens of carbon fiber 3k and polyester resin with an orientation [0 / ± 45], which are made according to the ASTM D303 standard. The first test specimens were molded manually (Wet Lay-Up) and the others were made by the method of Vaccum Bag Wet Lay-Up, which underwent stress tests. The objective is to know which of the two manufacturing processes is the most viable for the study of the manufacture of a tibial prosthesis. It is important to consider that both methods are efficient for conducting composite, being careful of controlling the manufacturing process. Based on the results, the most feasible manufacturing process was the Vaccum Bag Wet Lay-Up, which produced a modulus of elasticity of 5.83E+0 GPa, thus allowing to make a better study. Keywords: Specimens, carbon fiber 3k, wet lay-up, vaccum bag wet lay-up. Introduction The comparison between two manufacturing processes for the carbon fiber is fundamental for the investigation and experimentation of a tibial prosthesis. The first one which is the manual, known as Wet Lay-Up and the second one is the Vacuum Bag Wet Lay-Up [1]. With this comparison we can see which of the two methods are closer to the theoretical results. The results of the tests will give validity for the application of a transtibial prosthesis. It is important to consider that in the measurements made in both tests may exist variables that can t be controlled such as: tempeture, humidity, curing time of the resins. For that reason, a comparative analysis between the results of the two methods will provide us the method that approaches the theoretical results. Methodology or experimental section The specimens were manufactured according to the ASTM D303 standard [2], with the following specifications. Table 1: Tensile specimen geometry recommendations from ASTM D303. Fiber orientation Balanaced and simmetric Width Overall Length Thickness Tab Length mm [in] mm [in] mm [in] mm [in] 25 [1.0] 250 [10.0] 2.5[0.100] emery cloth Article history: Received ; Accepted ; Available online. ISSN:

2 Figure 1. Tension Test Specimens from ASTM D303 [2] Figure 2.Carbon fiber impregnated with resin by the manual method Drawing notes (see figure 1): 4. Ply orientation direction tolerance relative to [-A-] within ±5. 5. Finish on machined edges no to exceed 1.6. With roughness height in micrometers. In this study, five specimens are manufactured by the manual method (Wet lay-up) and five others by the Vaccum, bag wet lay-up method, which have a laminate orientation [0/±45]s, which is known as a symmetric and balanced quasi-isotropic laminate [3]. The main objective of the specimens was to undergo stress tests. Subsequently, the values obtained by the universal tests machine Shimadzu AG-IC [4] were analyzed. After that, the elasticity module of the specimens was calculated, which was compared with the theoretical elasticity module which gave us a value of Gpa. Manual method (Wet Lay-up): Is the simplest and most widely used manufacturing process. It involves manual placement of the dry reinforcements in the mold and subsequent application of the resin, at is shows in the figure 2. This process may be divided into four steps [1] : 1. Mold preparation. 2. Gel coating. 3. Lay-up. 4. Curing. With this method five specimens were fabricated standardized by ASTM D303. Figure 3. Test Specimens ASTM manually. After 72 hours the composite was cut in the number of specimens that is requesting by ASTM D303, as it s shown in figure 3 and figure 6. The five specimens were calibrated with measurements for apply stress test. (See figure 4 and 7). Figure 4.Stress test in specimen ISSN:

3 Vacuum method (Vacuum bag wet lay-up): Manufactured by the method of vacuum with a pump to help absorb pressure and create a vacuum which helped further impregnating the polyester resin to the fiber. The vacuum is applied to the outlet of the load and the resin drawn in to the mold by vacuum only, as it s shown in figure 5. Resin flow can be assisted by microgroove built into the mold or into a distribution medium placed beneath the vacuum bag. [5] Figure 7. Vacuum test specimens stress test. A tile cutter with metal cutter disc at a speed of 3,500 RPM and a power of 550 W was used for cutting of the composite specimens from both manufacturing methods. The surface of the composite showed no damage and thus obtaining a good cut surface. [6] Figure 5. Vacuum resin impregnation. Figure 8. Composite cut with the tile cuter. Figure 6. Vacuum test specimens. For the vaccum process, the curing time for the composite was the same from lay-up process, since the same resin was used for both processes. For performing stress tests a universal testing machine SHIMAD ZU AUTOGRAPH AG-IC was used, which allows full use with a system suitable for mechanical testing, as it has devices and software based on the needs that are required. ISSN:

4 Figure 10. Clamps for subjection. Figure. Shimadzu machine for tensile test The specifications from Shimadzu machine, for stress tests are described in table 2, the head speed for the specimens is recommended by ASTM D303. Table 2: Specifications universal testing machine. [4] AG-100kNIC Head speed test 2 mm/min [0.05 in/min] [3] Load cell Test Force Precision Software 100 Kn Within ±1% of indicated tes force (at 1/500 to 1/1 load cell rating) Within ±1% of indicated tes force (at 1/250 to 1/1 load cell rating) Trapezium For holding the specimens in the universal testing machine, steel jaws were used with a good knurling for proper subjection, as shown in figure 10, without using emery cloth in the area of clamping, as is recommended in ASTM. Results and discussion Results The specimens manufactured by the two methods underwent to stress tests, then a comparative analysis was made between the obtained results in the universal test machine Shimadzu Ag-Ic in both manufacturing processes. The mechanical properties of each of the samples were obtained and averaged in order to have a more accurate result. We can see the results of the manual method in Table 3, and the results of the vacuum method are shown in Table 4. Table 3. Results of stress tests, manufactured manually. Name Load (N) Displacement (mm) σ ε (%) E Test E E+08 Test E E+08 Test E E+08 Test E E+08 Test E E+08 Average E+08 ISSN:

5 Name Table 4. Results of stress tests, manufactured under vacuum. Load (N) Displacement (mm) σ ε (%) E Laminating stiffness matrix of 45º Test E Test E Test E Test E E+0 6.5E+0 8.3E E+0 Laminating stiffness matrix of -45º Test E E+0 Average E E E+0 Stiffness matrix strain, flat to the laminate The experimental results were used to obtain the elasticity module in each specimen, using the eq. 1, where the values of stress and area were used: In this case the matrix is: (3) For the theoretical results of the composite material, the laminating stiffness matrix was used for [0, ± 45] s, the expression for calculating any laminate with fiber orientation is defined in eq. 2 [7] : (2) Matrix for a laminate 3K carbon fiber in polyester matrix having the following sequence of laminate [0, ± 45] s, the stiffness matrix of a laminate materials axes [7] : By obtaining both experimental and theorical results, a comparative analysis is shown in Table 5, which compares the two practical methods with the theoretical results. ISSN:

6 Table 5. Comparison of results. Method Theoretical Experimental Method Manual (WET LAY- UP) Vacuum Method (VACCUM BAG WET LAY-UP) Estadísticos Table 6. Variation of results. Módulo de Elasticidad (GPA) Proceso Manual GPa Módulo de Elasticidad (GPA) Proceso al Vacío 2.58E+08 GPa 5.83E+0 GPa Diferencia Media 2.55E E E+0 Error típico 4.38E E E+08 Desviación estándar.80e+07.53e e+08 Rango 2.37E E E+0 According to statistical analysis of data obtained the variation between the two methods are similar to the behavior of test results, nevertheless we can appreciate that the modulus of elasticity is greater in the vacuum bag method with a value of 5.83E+0 Gpa, whence in this investigation it s the most viable method for our application, although it should be noted that there is an area of opportunity for the standardization process by data obtained in the range in the table 6. Figure.6 Graph results of samples under vacuum. Discussion According to the results, it s concluded that the most suitable manufacturing process is the vacuum, because the results are closer to the theoretical value obtained by the laminating stiffness matrix. Also, the material finish is more aesthetic and meets the expected mechanical properties. According to author A. Besednjak [5] the vacuum molding techniques allows to obtain composite materials with better physical properties and higher quality than their predecessors stratified methods. Thus, the percentages of reinforcement - matrix obtained are higher than those obtained using the manual method. In addition to providing excellent relationship between percentage of fiber and resin percentage, perfectly permeating every fiber and producing a laminate without failure and without trapped air. However it is required to continue experimenting with the same method, just by modifying the laminate angles of the material in order to find even better or superior results to the already obtained, therefore it can be applied to the research of the manufacture of a tibial prosthesis. Bibliography [1] Barbero, E. J. (2011). Introduction to composite materials design. (s. edition, Ed.) CRC Press Taylor & Franciss Group [2] ASTM. (s.f.). D303/D 303M-00 Standart Test Methood for Tensile ISSN:

7 Propetiesof Polymer Matrix Composite Material [3] Escudero, J. S. (2004). Micromecanica computacional de materiales compuestos reforzados con particulas. Madrid. [4] Shimadzu Prescision Universal Taster. (s.f.). Autograpfh AG-IC Series. 04, 05. [5] Besdnjak, A. (s.f.). Moldeo por Vacio. [6] Hernandez, M. S., Moreno, V., & Angeles, A. G. (2015). Compative Analysisin a Straight section of an orthogonal symmetric balaced composite with aluminum 6061T6. ANSINET, [7] Escudero, J. S. (2004). Micromecanica computacional de materiales compuestos reforzados con particulas. Madrid. [8] Pérez Sánchez, F. L., Santos Castillo, J. R., & Chigo Anota, E. (2014). Mexican Journal of Materials Science and Engineering, 1(3), ISSN: