JPS6358297B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fiber-reinforced resin leaf spring, and more particularly to a fiber-reinforced resin leaf spring in which a matrix resin is reinforced with short reinforcing fibers to improve interlayer peel strength.

Various types of leaf springs made of fiber-reinforced resin have been proposed in the past, but since these leaf springs are constructed as a laminate of reinforcing fibers such as carbon fibers and matrix resin, the peel strength between each layer depends solely on the strength of the matrix resin. The problem was that the delamination strength was significantly weaker than the extremely high strength of the reinforcing fibers themselves. As a result, the conventional example has the disadvantage that the leaf spring is damaged due to interlaminar shear stress, and it is currently difficult to put it into practical use.

The present invention has been made to eliminate the drawbacks of the prior art described above, and its purpose is to provide a fiber-reinforced resin board constructed as a laminate of reinforcing fibers such as carbon fibers and matrix resin. In springs, by mixing short fibers of reinforcing fibers into the matrix resin, the strength of the matrix resin is increased, the delamination strength of the fiber-reinforced resin leaf springs is improved, and the breakage of the leaf springs due to interlaminar shear stress is reduced. The purpose is to prevent it. Another purpose is to increase the strength in the thickness direction of a leaf spring, which has been difficult to strengthen in the past, by dispersing short fibers without directionality and mixing them into a matrix resin. Still another object is to increase or decrease the amount of short fibers mixed in depending on the magnitude of interlaminar shear stress, eliminate wasteful use of expensive short fibers, and most effectively improve the strength.

Furthermore, the present invention provides a leaf spring configured as a laminate of reinforcing fibers such as carbon fibers and a matrix resin, in which the short fibers of the reinforcing fibers are placed in the matrix resin in a non-directional state, and furthermore, the reinforcing fibers are disposed between the layers. It is characterized in that it is mixed in a state in which it is gradually reduced from the center layer where the shear stress is high to the surface layer to improve the delamination strength.

The present invention will be explained below based on embodiments shown in the drawings. In FIGS. 1 to 3, a leaf spring 1 made of fiber reinforced resin (hereinafter referred to as FRP) is constructed as a laminate of reinforcing fibers 2 such as carbon fibers and glass fibers and matrix resin 3. When a bending load is applied to the leaf spring 1, as shown in FIG. Interlaminar shear stress of magnitude τ
occurs, and this stress causes delamination,
The FRP leaf spring 1 will be partially broken inside. As shown in FIG. 4, the magnitude of this interlaminar shear stress τ is maximum at the neutral axis 4 of bending, gradually decreases as the plate thickness t increases, and reaches 0 at the upper surface 1a and the lower surface 1b.

Therefore, in the present invention, the short fibers S of the reinforcing fibers 2 are dispersed and mixed in the matrix resin 3 without directionality, as shown in FIGS. 5 and 6, in order to improve the interlayer peel strength. The short fibers S have a fiber length of 1 mm or less, for example. In addition, if the amount of the short fibers is mixed in such a way that it is the largest in the center layer 1c and gradually decreases toward the surface layer 1d, depending on the magnitude of the interlayer shear stress τ, expensive short fibers can be used without consuming more than necessary amount. S can be saved and interlayer peel strength can be efficiently improved.

Carbon fiber is suitable as the short fiber S. Carbon fiber is made by thermally decomposing organic fibers such as viscose rayon (suffu) and polyacrylonitrile fibers, and has a Young's modulus E of 17,500 Kg/mm ²
It reaches 35000Kg/ ^mm2 . As the matrix resin, thermosetting resins such as epoxy resins, unsaturated polyester resins, and phenolic resins, and thermoplastic resins such as polyester resins, polyamide resins, polyimide resins, and polyamide-imide resins are selected.

The present invention is configured as described above, and its operation will be explained below. By mixing short fibers S of reinforcing fibers such as carbon fibers, the highly anisotropic FRP leaf spring 1 also takes on isotropic properties, and the strength of the matrix resin 3, especially The toughness is strengthened, the force for fixing the reinforcing fiber layer 2 is increased, and the delamination strength is improved. In addition, since many short fibers S are mixed in the center layer 1c with the largest interlayer shear stress τ, sufficient strength can be obtained.
Partial breakage of the FRP leaf spring 1 due to delamination is prevented.

Since the present invention is constructed and operates as described above, in an FRP leaf spring constructed as a laminate of reinforcing fibers such as carbon fibers and matrix resin, the short fibers of the reinforcing fibers are added to the matrix resin. Since it is mixed in, it is possible to increase the strength of the matrix resin and improve the delamination strength of the FRP leaf spring, thereby preventing breakage of the FRP leaf spring due to interlaminar shear stress. can. In addition, since the short fibers are dispersed without directionality and mixed into the matrix resin, it is possible to make the FRP leaf springs isotropic, which is particularly difficult in the past due to the lack of strength in the thickness direction due to the anisotropy of FRP leaf springs. This produces an effect that can be resolved by
Furthermore, the amount of short fibers mixed in is varied according to the magnitude of the interlayer shear stress, such as gradually decreasing the amount of short fibers mixed from the center layer where the interlayer shear stress is high to the surface layer where the interlayer shear stress is low. This eliminates the wasteful use of expensive short fibers, making it possible to improve strength most efficiently.

[Brief explanation of drawings]

Fig. 1 is a side view of an FRP leaf spring, Fig. 2 is a plan view, Fig. 3 is a vertical cross-sectional view of a portion taken in the direction of - arrow in Fig. 2, and Fig. 4 is an interlaminar shear diagram with respect to the plate thickness of an FRP leaf spring. Diagram showing changes in stress magnitude, 5th
6 and 6 relate to an embodiment of the present invention, FIG. 5 is a partially cutaway perspective view of an FRP leaf spring reinforced with short fibers, and FIG. 6 is a longitudinal cross-sectional view of the same. 1 is an FRP leaf spring, 1c is a center layer, 1d is a surface layer, 2 is a reinforcing fiber, 3 is a matrix resin, S
is the short fiber and τ is the interlaminar shear stress.

Claims (1)

[Claims] 1. In a leaf spring configured as a laminate of reinforcing fibers such as carbon fibers and a matrix resin, the short fibers of the reinforcing fibers are contained in the matrix resin without directionality, and most in the center layer as they reach the surface layer. A leaf spring made of fiber-reinforced resin, characterized in that it is dispersed and mixed in a gradually reduced state.