Papers by Keyword: Continuous Fiber

Abstract: The application of Fiber Reinforced Thermoplastics (FRTP) is expected to reduce the weight of automobiles. The press and injection hybrid molding method was developed to mold FRTP with high strength and high stiffness by giving complicated shapes such as ribs and bosses to the outer shell structure of FRTP with continuous fiber. However, as this method uses high-cost FRTP laminated sheets, it is necessary to develop a low-cost FRTP manufacturing process. In this study, we aim at the development of Melted Thermoplastic-Resin Transfer Molding (MT-RTM) to mold FRTP with complicated shape at low cost by injecting melted short fiber reinforced thermoplastics into dry fabric. The effects of press condition on the mechanical properties of GFRTP molded by MT-RTM were clarified by bending tests. GFRTP molded at high mold temperature and high closing speed showed high mechanical properties because of good impregnation of injection resin into continuous fabric in the outer shell structure.

Abstract: The internal stress calculation of continuous fiber reinforced composites under transverse loads is a complex problem. This paper established a stress calculation model based on "equal strain method", which greatly simplify the formula derivation. Three internal stress formulas under the transverse loads were derived based on the model. The first is the fiber stress formula, which shows that the ratio of fiber stress to load gradually decreases with increasing of fiber volume fraction. The second is the matrix stress formula, which shows the ratio of matrix stress to load gradually increases with increasing of fiber volume fraction. The third is the formula of average shear stress at the interface of fiber and matrix, which curve shows there is a maximum value of interfacial shear stress. The three formulas have important role for checking intensity.

Abstract: Solving the internal stresses of continuous fiber reinforced composite materials is a complex problem, which was studied usally by experimental or numerical calculation method. This paper proposed the equal strain method with virtual external force compensation instead of considering the shear stress in the calculation of the stress in the fiber and matrix of composite materials. By the equal strain method, the formula of longitudinal elastic modulus of continuous fiber reinforced composite materials is derived. The same result was given by other literatures with other methods, which indirectly proved correctness of the equal strain method. Further the internal stress calculation formulaes of the fiber and matrix are derived. The formulaes show that the internal stress of fiber (or matrix) is proportional to the external load and the elastic modulus of the fiber (or matrix), and is inversely proportional to the elastic modulus of the composite material.

Abstract: A free form surface reconstruction method based on least square support vector regression is presented. Firstly in order to eliminate noise points, some sample points are chosen from the measured data to construct LS-SVM model. Thus a LS-SVM model to approximate the measured points is obtained. And the distribution probability of the approximation error is figured out. In result, the noise points are eliminated when their error probability is less than the specified threshold value. Then the boundary points are extracted. Lastly the surface model is reconstructed by use of the measured points from which noise points have been eliminated. The results indicate that the reconstruction precision can satisfy the demands of engineering application.

Abstract: More and more researchers took interests in FRP materials in civil engineering for their light weight, high strength and excellent durability performance. But common FRP rebars or plates used for reinforcing or strengthening in civil engineering are mostly made by fiber reinforced thermosetting polymer (FRSP) materials. While FRSP can not be reshaped so that many of the special shapes as bending rebar or hoop rebar cannot be easily obtained and handled at site. So, here we developed and fabricated Glass Fiber Reinforced Polypropylene (GFRPP) according to Fiber Reinforced Thermoplastic Polymer (FRTP) systems. This paper is focused on the experimental and theorial studies on the corrosion resistance of GFRPP rebar in alkali, acid and salt solution at different temperature. According to the corrosion experimental data, some durability life prediction would be concluded through FHWA method, and which may be valuable to a deeper understanding on the durability of GFRPP rebars. The results show that these kinds of GFRTP rebars have good resistance in acid and salt solution, and their mechanical properties can remain well, while bad resistance in alkali solution. As can be regarded that these FRTP rebars can be a vital support of common FRSP materials and which would play an important part in civil engineering in the future.

Abstract: The demand for lightweight structures in the automotive and aerospace industry increases permanently, and the importance of lightweight design principles is also increasing in other industrial branches, aiming towards improved energy efficiency and sustainability. Light metals are promising candidates to realize security relevant lightweight components because of their high specific strength; and amongst them, aluminum alloys are the most interesting materials due to their high plasticity and strain to failure, good processability, passivation in oxygen containing atmosphere, and low cost. However, for many applications, their stiffness as well as strength and fatigue behavior at elevated temperature are insufficient. Metal matrix composite (MMC) formation by integration of reinforcements in the form of continuous or discontinuous (short) fibers can yield a high increase in the alloys’ specific mechanical properties at room temperature and at elevated temperature. The integration of fibers with conventional manufacturing techniques like squeeze casting, hot pressing or diffusion bonding leads to restrictions in the component’s geometry. Moreover, these techniques result in elevated process costs mainly caused by long cycle times and the need of additional protective fiber coatings. In the present paper, an alternative method for the manufacturing of aluminum matrix composites is described, combining thermal spraying and semisolid forming (thixoforging) technologies for the formation of fiber prepregs and subsequent forming with simultaneous densification. Therefore, prepregs with the matrix alloy as a thick surface coating on the reinforcement fibers are manufactured in a fast, automated coating process, while reheating, densification and shaping are performed in a separate process, allowing an optimization of both processes towards cycle times and resulting material properties. Continuous fiber and short fiber reinforced aluminum matrix composites are manufactured using woven or parallel arranged continuous fibers, or short fibers as a fleece or fiber paper material. For the coating process, twin-wire electric arc spraying is applied as a well established, cost efficient thermal spray technology. The coating process is optimized towards microstructure of the matrix alloy prior to semisolid forming, which requires a globular alloy microstructure, and reduced fiber damage during the high-temperature liquid melt deposition. The thermally sprayed fine-grained matrix material enables semisolid forming at liquid contents of 40-60 vol% of the alloy, with short flow paths, reduced mechanical loads and short cycle times. Thus, limited fiber damage and residual stresses will occur, leading to good mechanical material properties. A production line for industrial-scale coating of fiber fabric coils in a continuous process is introduced in order to provide prepregs of various fiber-reinforcement materials and fiber architectures; moreover, a winding equipment for simultaneous fiber winding and coating is presented that enables local reinforcement for components with adapted, tailored composite material design.