JPH0554825B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fiber-reinforced composite material used as a structural material for space structures such as artificial satellites, office automation equipment, automobiles, and leisure goods such as golf clubs.

[Conventional technology]

Conventionally, CFRP and the like have been known as fiber-reinforced composite materials used for the above purpose.

Fiber-reinforced composite materials such as CFRP are made by solidifying inorganic fibers such as carbon and glass fibers or organic fibers such as aramid fibers with resins such as epoxy resins, polyimide resins, and polyether ether ketone resins.

Fiber-reinforced composite materials are superior to conventional metal structural materials in that they are lightweight and strong, and desired mechanical properties can be achieved by controlling the fiber orientation angle. For this reason, it has come to be widely used as a structural material for space structures, aircraft, automobiles, leisure goods, etc., where weight reduction is strongly required.

[Problem to be solved by the invention]

By the way, as the uses of structures using this type of composite material expand, vibration of the structures has become a problem.

Fiber-reinforced composite materials are lightweight and have small vibration damping properties (loss coefficient η
= 0.001 to 0.02), it is easy to cause vibration.
In addition, structures are often manufactured by integral molding,
Unlike conventional metal structural materials, structural damping due to friction at joints cannot be expected.

For example, in space structures such as artificial satellites, vibrations of the structure cause damage to onboard equipment and a decrease in antenna position accuracy. Therefore, increasing the vibration damping properties of fiber-reinforced composite materials has become an important issue.

In order to solve these problems, a method is being considered that uses a sandwich structure in which a restrained damping material is applied to a part of a fiber-reinforced composite material, and increases the vibration damping characteristics by a restrained vibration damping mechanism. However, in the case of the above method, although a large vibration damping property can be achieved, the property changes rapidly depending on the temperature, so it is not effective as a structural material.

The present invention is intended to solve the above problems, and its purpose is to provide a fiber-reinforced composite material that has large vibration damping properties over a wide temperature range.

[Means to solve the problem]

In order to achieve the above object, the fiber-reinforced composite material of the present invention includes a composite material layer in which a resin is filled with inorganic fibers such as carbon fibers and glass fibers, or organic fibers such as aramid fibers, and a composite material layer that is interposed between the composite material layers. It has two or more types of constrained vibration damping material layers having different glass transition temperatures.

[Effect]

First fiber reinforced composite material layer/damping material layer/second
The loss coefficient η _c of a sanderch structure consisting of fiber-reinforced composite material layers is given by the following equation.

η _c =13E ₃ h ₃ /E ₁ h ₁ (h ₁ +2h ₂ +h ₃ /2h ₁ ) ²・g・η ₂
/(1+g) ² +(g・η ₂ ) ² …(1) Here, E: Young's modulus, h: thickness, G: shear modulus, f: frequency, ρ: density, η: loss coefficient.

Subscripts 1, 2, and 3 indicate the first fiber-reinforced composite material layer, the damping material layer, and the second fiber-reinforced composite material layer, respectively.

As is clear from equation (1), the loss coefficient η _c increases as the loss coefficient η ₂ of the damping material layer increases. The loss coefficient η ₂ of the damping material layer is maximum in the glass transition temperature region, but it changes rapidly with temperature, so the loss coefficient η _c
The temperature range in which the value of was large tended to be limited.

In the composite material of the present invention, two or more layers of constrained damping materials having different glass transition temperature ranges are provided. Assuming that each glass transition temperature T ₀ , T ₁ , T ₂ ...T _o is (T ₀ < T ₁ < T ₂ ... < T _o ), in the vicinity of the temperature T ₀ , the damping material layer with the glass transition temperature T ₀ is Become the subject,
Fiber-reinforced composite material layer and glass transition temperature T ₁ , T ₂ ...
A composite material layer in which vibration damping material layers having T _o are laminated and integrated corresponds to the above-mentioned first and second composite material layers. As is clear from the above equations (1) and (2), the loss coefficient η _c has a large value due to the action of the damping material layer having the glass transition temperature T ₀ .

Furthermore, at temperatures higher than T ₀ , the glass transition temperature T ₁
...The damping material layer with T _o becomes the main body,
Due to the action of the damping material layer, the loss coefficient η _c has a large value.

Therefore, the composite material of the present invention has a large loss coefficient η _c in the temperature range T ₀ to _{T o} , that is, in a wide temperature range.
have.

Restraint-type damping materials include thermosetting resins such as bisphenol-type epoxy resins, epoxy resins that are polyglycidyl ethers of polyols or their polymers, and polyurethane resins obtained by reacting polyisocyanate compounds and polyol resins. Based on or polyolefin resin,
Known materials such as those based on thermoplastic resins such as vinyl chloride resin and acrylic resin can be used. In addition, these materials have an elastic modulus of 50 Kgf/mm ² or less, preferably 10 Kgf/mm ² or less, and a mechanical loss tan δ of 0.1 in each glass transition region.
or more, preferably 0.5 or more can be used.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross-sectional view of the fiber-reinforced composite material of the present invention.

In the figure, the example shows a composite material layer 1 made of epoxy resin filled with carbon fiber (unidirectional) and -10
An example is shown in which restrained vibration damping material layers 2 to 4 having glass transition temperatures of 20°C, 20°C, and 50°C are alternately laminated and integrated.

The constrained vibration damping material layers 2 to 4 are bisphenol A
A material was used that was made based on a type epoxy resin and the glass transition temperature was adjusted by adding a monoepoxy resin.

In the example, a carbon fiber prepreg coated with the damping material layers 2 to 4 was laminated and integrated by heating and curing under pressure.

The average thickness of the composite material layer 1 is 200 μm, and the average thickness of the damping material layers 2 to 4 is 20 μm.

Figure 2 shows the fiber-reinforced composite material of the example shown in Figure 1 and a conventional fiber-reinforced composite material using only a damping material having a glass transition temperature of 20°C in place of the damping material layers 2 to 4 of the example. A comparison of loss factors of composite materials is shown. In the figure, the black circles are the characteristics of the conventional composite material, and the white circles are the characteristics of the composite material of the present invention. The loss coefficient η _c was determined from free damping vibration at the resonant frequency using a beam material with a length of 300 mm.

As shown in the figure, in the conventional composite material, the temperature range in which the loss coefficient is 0.1 or more is ~30°C, but in the composite material of the present invention, the temperature range is ~80°C, which is more than double.

The flexural modulus of the fiber-reinforced composite material of the example shown in Figure 1 is 9500 Kg/mm ² , which is slightly smaller than 14000 Kg/mm ² when no damping material layer is provided. There is no problem in using it as

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize a fiber-reinforced composite material with high vibration damping characteristics over a wide temperature range. This has the effect of solving noise problems caused by automobiles, etc.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an embodiment of the present invention, and Fig. 2 is a composite material in which the composite material of the embodiment of Fig. 1 is laminated and integrated with a conventional single vibration damping material layer and a fiber reinforced composite material layer. FIG. 3 is a diagram showing a comparison of loss coefficients of materials. 1...Composite material layer, 2-4...Restricted vibration damping material layer.

Claims (1)

[Claims] 1. A composite material layer in which a resin is filled with inorganic fibers such as carbon fibers and glass fibers, or organic fibers such as aramid fibers, and two or more types of constrained vibration damping devices each having a different glass transition temperature and interposed between the composite material layers. A fiber-reinforced composite material comprising a material layer.