JPS6051320B2 - FRP material for acoustics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an acoustic FRP (fiber reinforced plastic) material, and more specifically, for use in speaker cabinets, speaker cones, back decks of stringed instruments such as guitars, tone plate instruments such as marimba and xylophone, etc. Concerning sounds useful for tone plates, etc.: WRPt1' material.

So-called acoustic materials, such as speaker cabinets, speaker cones, back decks of stringed instruments such as guitars, and tone plates of tone plate instruments such as marimbas and xylophones, are required to have high rigidity and vibration damping properties. Therefore, in the past, wood such as lauan plywood and loinwood and wood pulp were frequently used, but recently FRP has also come into use.

However, compared to wood, FRP acoustic materials can be obtained in large quantities with homogeneity, and are less likely to change over time due to moisture absorption, etc., - can be obtained with high rigidity, and have a large density. Although it has the following advantages, it has the disadvantage of low vibration damping properties.

An object of the present invention is to solve the above-mentioned drawbacks of conventional acoustic materials and to provide an acoustic FRP material that has high rigidity and high vibration damping properties.

The above-mentioned object of the present invention is to provide a composite of resin and carbon fiber, and in the resin, one kind of substance selected from polyethylene glycol, polypropylene glycol, and polysulfide has a molecular weight of 5 to 50% relative to the resin. weight%
) is achieved by an acoustic FRP material characterized by being mixed.

Next, the acoustic FRP material of the present invention will be explained in more detail. The acoustic FRP material of the present invention is made of a composite material of a resin serving as a base material and carbon fibers reinforcing this resin, that is, FRP (fiber reinforced plastic). Contains polyethylene glycol, polypropylene glycol or polysulfide to improve damping properties.

As the base resin, thermosetting resins such as epoxy resins, unsaturated polyester resins, and polyimide resins, or thermoplastic resins such as polyamide resins, vinyl chloride resins, and polyphenylene sulfide resins are used.

Among them, epoxy resins and unsaturated polyester resins are preferably used. It is preferable that the carbon fiber reinforcing the resin has as high elasticity as possible.

Here, the term carbon fiber has a broad meaning that also includes graphite fiber. Carbon fibers are usually contained in a resin serving as a base material in an amount of 30 to 70 (wt%) based on the resin.

Carbon fibers may be arranged in parallel in one direction, in the form of continuous fibers with their fiber axes intersecting each other, or in the form of short fibers dispersed in completely random directions. It may be hot. As mentioned above, polyethylene glycol, polypropylene glycol, or polysulfide is mixed into the base resin.

All of these particles enter between the molecules of the base resin,
Since it inhibits the bonding of the main chains, the glass transition point is lowered and the vibration damping properties of FRP are greatly improved. Polyethylene glycol, polypropylene glycol, and polysulfide contain 5 to 50% of the resin in the base resin.
weight%) must be mixed.

If it is less than 5 (wt%), the effect of improving the vibration damping properties of FRP will hardly be obtained.

If it exceeds 50 (wt%), the vibration damping properties will improve, but the rigidity will drop significantly, making it unusable as an acoustic FRP material. To manufacture the acoustic FRP material of the present invention, for example, first, carbon fibers are impregnated with a resin mixed with a desired amount of polyethylene glycol, polypropylene glycol, or polysulfide to make a prepreg.
Next, the required number of prepreg sheets are laminated and heated under pressure to be integrally formed.

Hereinafter, the effects of the present invention will be further explained.

FIG. 1 shows the frequency dependence of vibration damping at 20'C, with frequency F on the horizontal axis and damping factor DF on the vertical axis.

In Figure 1, the mark 0 indicates epoxy containing 25% (by weight) of polyethylene glycol having a molecular weight of approximately 400. These are the characteristics of the material of the present invention (hereinafter referred to as "invention material A") which is a composite of resin and unidirectionally aligned carbon fibers. Approximately 60 (volume %) carbon fibers are contained in the material.
Also,? The mark indicates that the amount of polyethylene glycol mixed in inventive material A is half the amount of 12.5 (wt%).
(hereinafter referred to as invention material B). On the other hand, what is marked with an x mark is the invention material A in which the amount of polyethylene glycol mixed is zero, that is, only the epoxy resin is contained (hereinafter referred to as comparative material A).
From this Figure 1, the damping factor of Inventive Materials A and B is approximately twice as high as that of Comparative Material A, which does not contain any polyethylene glycol, and approximately 1.7 times as high as that of Inventive Material B. It can be seen that the vibration damping properties are significantly improved. In addition, in Figure 2, both thicknesses are 5
(Tmn), the above-mentioned invention material B and comparative material A are used as a full plate on the front of a speaker cabinet with an internal volume of 450J, and the frequency F when excited with an input of 1 (W). This shows the relationship between acceleration AS and acceleration AS. In FIG. 2, the solid line shows the case where the invention material B was used, and the dotted line shows the case where the comparative material A was used. From FIG. 2, it can be seen that when inventive material B is used, vibrations are significantly suppressed compared to when comparative material A is used.

This means the following: That is, a speaker cabinet is originally a baffle that blocks interference between sounds before and after the speaker, and must not vibrate.

However, in reality, it is excited by the speaker and vibrates, producing a faint sound. This is generally called box ringing, and when this occurs, the sound becomes less crisp.
Although the sound is muddy, if the material of this invention is used, the scale can suppress the box noise, or it can be brought to an early end. Figure 3 shows F5 (698
．． The envelope shows the vibration waveform of the sound when a marimba tone plate (with resonance tube) adjusted to 46 Hz is struck with the same force. In FIG. 3, a represents the invention material B, and b represents the comparative materials A, . c is made of rosewood. From FIG. 3a, it can be seen that the half-life time of vibration of the invention material B is about 90 (milliseconds), making it ideal as a marimba tone plate.

In addition, one of the factors that determines how well a sound resonates is the time from when the tone plate is hit until the volume reaches its peak, that is, the rise time, and the rise time of the material made from Inventive Material B is approximately 30 mm (mm). seconds), which is also ideal. On the other hand, the vibration half-life time of the comparative material A is about 165 (milliseconds), which is too long, and there is a concern that the previous and subsequent sounds may overlap during performance. On the other hand, the one made of rosewood is too short at about 60 (milliseconds), and is inferior to the one made of invention material B in terms of resonance. In addition, the waveform made from comparative material A has unevenness, indicating that the sound quality is not good, but the waveform made from the invention material is relatively flat, and it is often said that it is made from rosewood, which is said to be the highest grade. resemble. Figure 4 shows polyethylene glycol
A material made of a composite of an epoxy resin containing 2.5% by weight and a carbon fiber fabric (hereinafter referred to as invention material C), and a material made of a composite of only an epoxy resin and the carbon fiber fabric (hereinafter referred to as invention material C) This figure shows the relationship between the frequency F and the output sound pressure level L of a speaker obtained using comparative material B).

The speaker input is 1 (W), and the sound pressure level is the value at front 1 (7T1.) of the speaker box.
From this Fig. 4, the material made of invention material C (solid line) is 1
000 (Hz) and above, there are few irregularities in the high frequency range, and the characteristics are relatively flat, whereas those made of comparative material B (dotted line) have large peaks and valleys. Thus, the material of the present invention is also very suitable as a material for speakers that are required to be lightweight and highly rigid. Although the case where polyethylene glycol is mixed has been described above, the same effect can be obtained even if polyethylene glycol or polysulfide is mixed.

As explained above, the acoustic FRP material of the present invention is a composite of carbon fiber and a resin containing 5 to 50 (wt%) polyethylene glycol, polypropylene glycol, or polysulfide. It has high rigidity and significantly improved vibration damping properties. Therefore, the acoustic FRP material of the present invention can be used, for example, in speaker cabinets, speaker cones, and the back shell of stringed instruments such as guitars. It is particularly useful as a tone plate for tone plate instruments such as boards, marimbas, and xylophones. That is, when used in a speaker cabinet, especially a baffle plate thereof, an excellent speaker cabinet with less box noise can be obtained.

When used in a speaker cone, split resonance is suppressed and a speaker with flat sound pressure and frequency characteristics can be obtained. Furthermore, when used on the back deck of a stringed instrument such as a guitar, the strong wolf tone that occurs when the natural frequency of the back deck and the frequency of the strings match is suppressed, improving the tone. Furthermore, when used on the tone plate of a tone plate instrument such as a marimba or xylophone, there is less weight with the previously struck sound, resulting in a tone plate instrument with clear pitch and well-balanced sound. . In addition, when the acoustic FRP material of the present invention is used for the tone plate of a tone plate instrument, polyethylene glycol,
If the amount of polypropylene glycol or polysulfide is increased in the lower range and decreased in the higher range, the difference in reverberation time between each tone plate will be reduced, and a more balanced tone plate instrument can be obtained. At this time, tone plates may be prepared in which the amount of the above-mentioned mixture gradually increases from the high range to the low range, or the tone plates may be divided into groups such as high range, middle range, and low range. However, the above-mentioned mixing amount may be prepared for each group in the order of treble, middle, and bass.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between frequency F and damping factor DF for the present invention and conventional materials. FIG. 2 is a graph showing the relationship between frequency F and acceleration AS for the present invention and conventional materials. Figure 3 is a graph showing the vibration waveforms of marimba sound plates using the present invention and conventional materials, and Figure 4 is a graph showing the frequency, F, and output sound pressure level L for speakers using the present invention and conventional materials. It is a graph showing the relationship between.

Claims (1)

[Claims] 1 Composite of resin and carbon fiber, and in the resin, 5 to 50 (wt%) of one substance selected from polyethylene glycol, polypropylene glycol, and polysulfide is mixed with respect to the resin. An acoustic FRP material characterized by: