Full Paper Proc. of Int. Conf. on Advances in Industrial and Production Engineering 2011
Carbon Fiber Reinforced Composite Coil Springs First Dr. D. Abdul Budan 1, Second T.S. Manjunatha2 1
UBDT College of Engineering, Department of Studies in Mechanical Engineering, Davangere-577004, India abdul_budan@rediffmail.com 2 GM Institute of Technology, Department of Mechanical Engineering, Davangere-577006, India tsmdvg@rediffmail.com
Abstract—Three types of coil springs are fabricated using carbon fibers in unidirectional, 0/90 and + 45 degree orientations. Carbon fiber springs in + 45 degree orientations give better results. Stiffness obtained by these springs are 10% more than the unidirectional carbon fiber springs and 27 % more than the 0/90 degree orientation springs. Weights of the fabricated springs are 60% less than the steel springs. The fabrication methods can be used for mass production. Results compared with steel springs shows that steel springs can be replaced by high strength carbon fiber springs.
not popular due to manufacturing difficulties. This paper discusses about the use of carbon fibers in three different orientations for coil spring manufacturing. Three types of springs are fabricated using carbon fibers in unidirectional (CFR), 0/90 (CF0/90) and ± 45 (CF ± 45) degree orientations. The results of these springs are compared with the steel spring.
Index Terms—Composite springs, coil springs, fiber springs
A. Specific strain energy The main factor to be considered in the design of a spring is the strain energy of a material used. Specific strain energy in the material can generally be expressed as
II. THE PRINCIPLE OF CYLINDRICAL HELICAL SPRINGS
I. INTRODUCTION The fuel efficiency and emission gas regulation of automobiles are two important issues in these days. The best way to increase the fuel efficiency is to reduce the weight of the automobile by employing composite materials in the structure of the automobiles. The principal advantages of fiber reinforced polymer matrix composites for automotive parts are weight savings, part consolidation, and improvement in Noise, Vibration, and Harshness (NVH) [12]. The randomly oriented chopped E-glass fiber reinforced polymer matrix composites which are not load bearing structural materials are mainly used in automotive industry due to their low cost. However there have been several attempts and some successful applications of fiber reinforced composite structural members to various parts of automobiles including load bearing structural parts [5-6]. Especially glass fiber reinforced polymer composites have been used for static and dynamic load bearing structures such as bumpers and leaf springs [4]. Springs are crucial suspension elements on automobiles which are necessary to minimize the vertical vibrations, impacts and bumps due to road irregularities and create a comfortable ride [3]. Coil springs are commonly used for automobiles suspension and industrial applications. Metal coils springs can be replaced by composite springs because of weight reduction and corrosion resistance. Composite coil springs can be manufactured using carbon/graphite/glass fibers and resin impregnation. Composite coil springs, compared to standard metal coil springs reduces weight from 45% to 25%, gives high natural frequency, Excellent NVH property, and corrosion free behavior [11]. Some researchers have used the E-glass fibers and carbon fibers and low cost resin for fabricating the coil spring [7]. The composite leaf springs are successfully used in the suspension of the light vehicle [10-13]. Many researchers [7-14] have investigated on leaf springs, elliptic springs, circular springs and springs of arbitrary shape. However the composite coil springs are © 2011 AMAE DOI: 02.AIPE.2011.01.508
U
2 E
(2.1)
This indicates that a material with lower young’s modulus (E) or density (ρ) will have higher specific strain energy under the same stress (σ) condition [12]. Thus the composite materials offer high strength and light weight. B. The spring constant of a cylindrical helical spring As shown in Fig. 1, when a cylindrical helical spring with rectangular cross section is under the action of an applied compression force F, the primary reaction force on the coil is torsion and thus induces shear stresses on the cross section. For homogeneous and isotropic materials, both the spring constant, K, and the induced shear stress under torsion, τ, for rectangular wire spring can be approximately derived as [3]:
K
F Gt 2 b 2 nD 3
(2.2)
PD tb tb
(2.3)
Where and in Fig. 1, F is the applied load on spring (kgf); D, the mean coil diameter (mm); L, the free length (mm); α, the helical angle (degree); δ, the deflection (mm); G, the modulus of rigidity (N/mm2); n, the no of active coils in the spring; t, the side parallel to axis of spring, b the side perpendicular to axis of spring and c is spring index (D/b). β is a factor depend upon b/t and γ is a factor depend spring index.
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