Papers by Keyword: Fiber Volume Fraction

Abstract: This paper presents an experimental study of the influence of the orientation of the outer layer of polypropeylene (PP) reinforced with E-glass fiber laminate (GF/PP) and the influence of the fiber volume fraction on the quality of the welded joint using an ultrasonic welding process. An orthogonal L 16 array (OA) design of experiment was conducted in this paper based on the Taguchi method to evaluate the effect of the orientation of the outer layer and the fiber volume fraction, on the welding process parameters; the welding energy, the amplitude of vibration, the welding pressure, the holding pressure and the holding time were considered in order to achieve a high weld quality. The experiments were carried out using a 15 kHz ultrasonic welding unit with a maximum supplied power of 4000-Watt. GF/PP laminates with fiber volume fraction of 36% and 46% were used in this paper, and the GF/PP laminates were either unidierctional or had a 90 degree outer layer orienation. A 0.127 mm thick polypropeylene film was used as a flat energy director (ED). The evaluation of the weld quality was measured by the apparent shear strength of the single lap welded joints, and by using laser shearography as a non-destructive inspection technique . The failure mechanism of the single lap joint was monitored, using a high speed digital imaging system. A combination of the highest selected level of welding energy, lowest level of amplitude, lowest level of welding pressure, and the lowest level of both hold time and hold pressure of a unidirectional GF/PP with the lowest fiber volume fraction, were found to achieve a higher apparent shear strength of the welded adherends, as compared with the apparent shear strength obtained with the presence of the flat energy director for the same level of factors. A confirmation experiment was conducted to measure the predicted apparent shear strength and compare it with the measured apparent shear strength from the test.

Abstract: This study aimed to determine the influence of fiber volume fraction towards composite toughness and the composite hybrid fracture pattern models reinforced by hemp fiber and fiberglass to find out the ratio of composite toughness from variation of hemp fiber volume fraction and fiberglass A1 (15 : 25), A2 (20 : 20), A3 (25 : 15)%. This research is an experimental method research with the dependent variable is composite toughness and the independent variable is the fiber volume fraction. Based on the test and data analysis, the results for fraction A1 (15 : 25)% have the greatest impact absorption of 10834.6 J/m² compared to A2 (20 :20)% that have absorption of 8470.828 J/m² and A3 (25 : 15)% is 7168.813 J/m². The most prominent one of the three variations of volume fractions on this fracture pattern analysis is the existence of (delamination) or there are fibers which are not perfectly exposed to the matrix. The Delamination usually occurs due to overly tightening of the fibers.

Abstract: This paper represented a new unit cell of 3D four directional braided composite for mechanical properties calculation. There are three disadvantages of unit cells in most previous works such as the fiber volume fraction hard to touch the reality despite the packing factor is maximum 1, the yarns are curved subjectively which is far away from realistic geometry structure, a quantity of connected surfaces are neglected as the yarns are not match the real appearance. A new unit cell established based on the real manufacturing process and structure could improve these aspects in this work. The yarn in the unit cell was similar to the real one which was constructed by photos. The details at the conjoined position were also expressed thoroughly. The result of finite element simulation was in good agreement with the available experimental data.

Abstract: Raw bamboo is a composite graded naturally material with variable distribution of fibers in the culm wall thickness and also in height. The strength and fiber volume fraction obtained in tests of round bamboo are very variable, while laminated bamboo has more uniform properties. The fiber volume fraction was determined in two groups of specimens of laminated bamboo Guadua angustifolia and also in two groups of bamboo clapboards. Although the average values of fiber volume fraction was around 45% for all cases, it was found that the coefficient of variation in the groups of specimens of laminated bamboo guadua was 6%, while in the groups of slats was 29%.

Abstract: The hygrothermal effect is introduced by using empirical relations for degrading the material stiffness properties of the matrix. A parametric study is conducted by varying the fiber volume fraction and the fiber orientation of the angle plies in the laminate. It is possible to minimize the environmental effect by judiciously selecting the laminate configuration.

Abstract: The purpose of this study is to investigate the compressive and flexural properties of high-strength steel fiber reinforced concrete (SFRC). For this purpose, a total of 5 mixture whose variable is fiber volume fraction, were made and tested in a range of high strength with 70MPa. In case of normal and ultra-high strength, experimental results were collected from existing literatures on the tests conducted in South Korea. Flexural behavior of SFRC is enhanced according to the fiber volume fraction and compressive strength. Experimental and collected data were applied to existing equations, so it was found that the distinctions occurred between experimental or collected data and calculated values. Thus, more efforts are required to predict the flexural behavior of SFRC manufactured in South Korea with respect to the fiber volume fraction.

Abstract: Orthogonal experiment is used to study the influence of splitting load and mixing of polypropylene fiber of different volume fraction, different length and different mass ratio of long and short fiber on permeability of chloride ion in concrete. The results show that the chloride ion diffusion coefficient increases as the stress ratio increasing, and the relationship between them approximately agrees with exponential function. The influences of fiber volume fraction and fiber length on permeability of chloride ion in concrete are significant, and using shorter polypropylene fiber in the range of low volume fraction can lower permeability of chloride ion in concrete, whereas long fiber and large volume fraction will increase the permeability. The effect of lowering permeability of chloride ion in concrete is most obvious, when the fiber volume fraction is 0.1%, the fiber length is the combination of 6mm and 9mm, and the mass ratio of long and short fiber is 1:2.

Abstract: Bamboo is a fiber-reinforced bio-composite with superior structural behavior. For the purpose of analyzing the correlations between the mechanical properties of bamboo and fiber volume fraction, tensile tests were performed on bamboo test specimen, and the corresponding volume fractions of fiber and parenchymatous ground tissue were measured. Linear and curvilinear regressions were done from tested data of elastic modulus, tensile strength and volume fractions of fiber. The results display that there is an obvious correlation between bamboo tensile properties and fiber volume fraction. In order to analyze the effects of fiber gradient distribution on bamboo structural behavior, models composed of fiber and parenchymatous tissue were built based on different fiber distribution for comparative analysis. The analysis results show that the maximum deformation of 4 layers model is 3.86% less than 1 layer model, and the maximum deformation of 8 layers model is 8.87% less than 4 layers model. In the part of maximum axial stress, the maximum axial stress of 4 layers model is 3.27% less than 1 layer model, and the maximum axial stress of 8 layers model is 8.90% less than 4 layers model. Conclusion can be drawn from the comparison that the strength and stiffness of the model appear to be growing with the degree of fiber gradient distribution deepening from 1 layer model to 4 layers model, and 4 layers model to 8 layers model.It can be concluded that the mechanical properties of bamboo structure are significantly improved because of fiber gradient distribution.

Abstract: In fiber reinforced thermosetting plastic (FRP) the fiber volume fraction is always up to 60 percent, but in fiber reinforced thermoplastic (FRTP) it is low to about 30 percent which greatly limit their performance. In this paper, for increasing the fiber volume fraction of thermoplastic composite, a new impregnation method for molding continuous fiber reinforced thermoplastic was explored; the fiber volume fraction was significantly raised to 60 percent which is equal to that of FRPs. Then the tensile property was investigated and made a contrast with FRP with the same reinforcement fiber. The results showed that both the FRP and FRTP composites have the similar tensile properties and indicated that the molding method is effective for FRTP manufacture.

Abstract: In this paper, a micromechanical model based on Generalized Method of Cells(GMC) for predicting stress-strain behaviors of polymer-matrix composites is presented. Improved Bodner-Partom viscoplastic model is incorporated into GMC to describe nonlinear mechanical behavior of composites. On this basis, strain rate and fiber volume fraction(FVF) influence on nonlinear behaviors of composites are discussed. The results show that strain rate influences on stress-strain behaviors of composites in inelastic region can be clearly discerned. Moreover, FVF tends to clearly increase stiffness behaviors of polymer-composites.