KR101304879B1 - Method for manufacturing floor under cover composite - Google Patents

Abstract

The present invention relates to a floor undercover composite material for a vehicle, and more specifically, an upper skin layer made of 2 to 3 wt% polyester; Main core layer made of 50 to 55% by weight of glass fibers to maintain the strength and 20 to 25% by weight of polypropylene bonding the glass fibers; A film layer consisting of 10 to 15% by weight of polypropylene; And a bottom skin layer composed of 5 to 10 wt% of a polyethylenic water repellent nonwoven fabric, and is characterized by absorbing noise by pores formed in the main core layer.

Description

Method for manufacturing floor undercover composite material for vehicle {Method for manufacturing floor under cover composite}

The present invention relates to a vehicle floor undercover composite material and a method for manufacturing the same, and more particularly to a vehicle floor undercover composite material and a method for manufacturing the same that can improve sound absorption performance.

In general, the floor undercover mounted on the vehicle floor is installed at the bottom of the engine or the transmission and the cooling fan to protect the engine and the transmission from external shocks, as well as the noise generated from the engine or the transmission during driving. It is prevented from being discharged to the outside, and serves to prevent foreign matters from entering the inside of the vehicle from the outside.

Conventionally, GMT (Glass fiber Mat Thermoplastic) was used as the material of the floor undercover, and GMT sheet refers to a composite material in the form of a plate made of polypropylene resin and a glass fiber mat reinforcing material, and a thermoplastic resin matrix (Matrix) refers to the intermediate finished product in the form of a sheet reinforced with a fiberglass mat therebetween.

Such a GMT is a composite material for molding parts having both the light weight of plastic and the mechanical properties of the reinforcing material, and has an advantage that the desired physical properties can be obtained relatively inexpensively by an appropriate combination of the matrix resin and the reinforcing material.

However, since the GMT material does not have pores and cannot be manufactured in different thicknesses according to parts, there is almost no sound absorption performance, and it is impossible to implement an integrated full undercover as manufactured by a compression and injection molding method. In addition, since the density of the material itself is high, the total weight of the vehicle is increased.

As a result, this is caused by road noise generated at the underside of the vehicle. All noises are collectively referred to as problems such as, for example, the sound of sand, gravel, etc. splashing out of the lower part during driving and hitting the vehicle body, the noise from the exhaust system during driving, the noise from the air flowing under the vehicle, and the like. It causes a problem of sand noise coming from the bottom of the vehicle (high frequency noise generated when sand or gravel breaks out).

The present invention has been invented to solve the above problems, by forming pores in the main core layer in a manner to inflate the main core layer through the heating oven, thereby absorbing noise by the pores to improve sound absorption performance. The purpose of the present invention is to provide a floor undercover composite material for a vehicle and a method of manufacturing the same, which can vary the degree of compression and the sound absorption performance of each part by varying the degree of compression in the low pressure press for each part.

In order to achieve the above object, the vehicle floor undercover composite material according to the present invention comprises an upper skin layer composed of 2 to 3 wt% polyester; Main core layer made of 50 to 55% by weight of glass fibers to maintain the strength and 20 to 25% by weight of polypropylene bonding the glass fibers; A film layer consisting of 10 to 15% by weight of polypropylene; And a bottom skin layer composed of 5 to 10 wt% of a polyethylenic water repellent nonwoven fabric, and is characterized by absorbing noise by pores formed in the main core layer.

In addition, the method for manufacturing a floor undercover composite material for a vehicle according to the present invention comprises the steps of preparing a slurry form by mixing polypropylene and glass fibers in a wet method; Transferring the mixed slurry prepared in the step through a conveyor, and draining water contained in the mixed slurry down; Forming a main core layer while passing the mixed slurry precipitated in the conveyor through a heating oven; Supplying the upper skin layer and the film layer together with the main core layer to the upper and lower surfaces of the main core layer and passing them through a pressure roller to laminate the layers in a heat fusion method; wherein the mixed slurry passes through the heating oven. Polypropylene combines the glass fibers, characterized in that the noise is reduced by the pores generated by the swelling phenomenon of the mixed slurry.

Particularly, after laminating and combining the upper skin layer, the main core layer and the film layer, the lower skin layer made of a polyethylene water-repellent nonwoven fabric is pressed to the bottom of the film layer with a low pressure press to produce a final part, and the low pressure for each part of the material By varying the degree of compression of the press is characterized in that each has a different characteristic value for each part.

Referring to the advantages of the floor undercover composite material for a vehicle and a method of manufacturing the same according to the present invention.

First, by passing a main core layer made of polypropylene and glass fibers through a heating oven to form pores therein in a manner that the material is inflated by high temperature, sound absorption performance can be improved.

Second, by varying the thickness and shape for each part of the material to change the characteristic value and sound absorption performance for each part, it is possible to reduce the road noise and sand noise, the weight of the vehicle.

1 is a cross-sectional view showing a laminated structure of the vehicle floor undercover composite material according to an embodiment of the present invention
2 is a partially enlarged view showing a state before and after heating of the main core layer in FIG.
Figure 3 is a schematic diagram showing a method for manufacturing a floor undercover composite material for a vehicle according to another embodiment of the present invention
Figure 4 is a graph showing the sound absorption performance of the present invention (after modification) compared to the existing GMT (before modification)
5 is a graph showing the sand noise reduction effect of the present invention (after modification) compared to the existing GMT (before modification)
6 is a graph showing the effect of reducing the road noise of the present invention (after change) compared to the existing GMT (before change)

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

1 is a cross-sectional view showing a laminated structure of a vehicle floor undercover composite material according to an embodiment of the present invention, Figure 2 is a partially enlarged view showing the state before and after heating of the main core layer in Figure 1, Figure 3 Is a schematic view showing a method for manufacturing a floor undercover composite material for a vehicle according to another embodiment of the present invention.

The present invention relates to a floor undercover composite material (15) and a composition thereof, which can improve sound absorption performance due to pores generated by heating the main core layer (11), and can vary in thickness according to each part. .

The composition of the floor undercover composite material 15 is composed of 2-3 wt% polyester, 50-55 wt% glass fiber 14, 10-15 wt% polypropylene film, 5-10 wt% polyethylene.

The floor undercover composite material 15 is composed of an upper skin layer 10, a main core layer 11, a film layer 12, and a lower skin layer 13 from above.

The top skin layer 10 is located in the first layer from above, and consists of polyester, for example spunbonded polyester nonwoven, and covers the top of the main core layer 11 to prevent contamination of the main core layer 11. It plays a role.

The main core layer 11 is located in the second layer from above, and serves to maintain the strength of the material in the component ratio, and is composed of glass fiber 14, polypropylene resin, polypropylene matrix reinforced glass fiber 14, At this time, the polypropylene resin serves to connect the glass fibers (14).

When the main core layer 11 passes through the heating oven at 190 to 205 ° C. at a predetermined temperature, a swelling phenomenon occurs.

In other words, a phenomenon in which the resin is stretched occurs at 190 to 205 ° C., which is a heat deformation temperature of the polypropylene, generates pores while the glass fiber 14 is widened, and the pores exhibit sound absorption performance.

In fact, as the noise energy coming from the outside (outside the vehicle) hits the wall surface of the pores, that is, the glass fiber 14, and causes diffuse reflection, the glass fiber 14 vibrates and generates heat. The noise energy is converted into thermal energy to reduce the noise.

The strength of glass fiber 14 increases as the ratio of glass fiber 14 increases. However, when the content of glass fiber 14 exceeds 55% by weight, the amount of polypropylene is too small to decrease the adhesion between glass fibers 14. As a result of the problem that the strength of the material is further lowered, the content of the glass fiber 14 is preferably 50 to 55% by weight.

The length of the glass fiber 14 has a restriction of 10 to 15 mm, because the longer the length of the glass fiber 14, the greater the strength, but if the length of the glass fiber 14 is 15 mm or more, each glass Since the fibers 14 are laminated, there is a problem that pores are not easily generated, and it is preferable to limit the length of the glass fibers 14 to the above range.

The film layer 12 is located at the third from the top of the material, and is composed of a polypropylene film, and serves as a barrier that prevents water coming from the underside of the vehicle from going directly to the main core layer 11.

The lower skin layer 13 is located at the bottom of the material and is composed of polyethylene water repellent nonwoven fabric (PET), which is visible from the underside of the vehicle.

Thus, the floor undercover composite material 15 having a laminated structure is light and reinforced with lightweight reinforced thermoplastics (LWRT; Low Weight Reinforced Thermo-plastics)

Referring to the manufacturing method of the floor undercover composite material 15 configured as described above are as follows.

In order to produce the main core layer 11, separate polypropylene (PP) and additives, and finely crushed glass are mixed with water by a wet method to prepare a slurry, and then the mixture is prepared in a headbox 24 (head). It is put in a box) and transferred to the heating oven 21 through a conveyor.

At this time, the mixture is transported in the conveyor 20 made of a network structure while the water is drained down and the remaining substrate is transported to the heating oven 21 while being caught in the mesh, the substrate is passed through the heating oven 21 Polypropylene connects the glass fibers 14 to form the main core layer 11.

Then, the main core layer 11 is the polyester scrim of the upper skin layer 10 and the polypropylene film of the film layer 12 on the upper and lower portions of the main core layer 11, respectively, before passing through the pressure roller 22. The upper skin layer 10, the main core layer 11, and the film layer 12 are press-bonded with each other in such a manner that they are pressed while being heat-sealed through the pressing roller 22.

The upper skin layer 10, the main core layer 11, and the film layer 12 laminated in this manner are made of a final material through a cutting operation.

Finally, the polyethylene water-repellent nonwoven fabric of the lower skin layer 13 is laminated at the bottom of the final material in a low pressure press (250 tons) to produce the final part to make the final part.

The floor under cover of the actual vehicle is manufactured using the material configured as described above, and the inflated material is processed in a low pressure press in a single state while passing through the heating oven 21. In this case, the compressive strength is different for each part. The thickness and shape can be made different.

As described above, the unit having a different thickness and shape for each part has different characteristic values for each thickness as shown in Table 1 below.

Property measurement

In order to measure the mechanical properties of the final parts manufactured by the above method, a low pressure press was molded into the specimens of ASTM D638, SAE J949 measuring method, and then the physical properties were measured by the method described in the above measuring method. Indicated.

As shown in Table 1, it can be seen that the characteristic values (tensile strength, tensile modulus, flexural strength, flexural modulus) differ depending on the thickness of each part. Through the difference in the characteristic value according to the thickness of each part, the shape of the undercover for each part, for example, strength, thermal degradation performance, sound absorption performance, watertight performance, aerodynamics, appearance performance can be reflected.

As described above, the present invention reduces the weight (3.3 kg after the change) compared to the load noise and sand noise of the vehicle and the existing technology (4 kg) by applying the composite material 15 having different characteristic values and sound absorption performance for each part. can do.

Experimental Example

4 is a graph showing sound absorption performance of the present invention (after modification) compared to the existing GMT (before modification), and FIG. 5 is a graph showing the sand noise reduction effect of the present invention (after modification) compared to the existing GMT (before modification). 6 is a graph showing the effect of reducing the load noise of the present invention (after change) compared to the existing GMT (before change).

In order to confirm the sound absorbing performance of the material, a sound absorption test was performed using an alpha cabin capable of random incidence similar to a real vehicle.

As a result, as shown in FIG. 4, the sound absorption rate increased more than four times compared to the existing GMT undercover. In particular, it was confirmed that the influence on the high frequency noise of more than 1000Hz.

In addition, the noise characteristics test was carried out to check the sand-noise gear diagram in the actual vehicle state, and the test method was to place the undercover separately and drop the beads at a position of 1.5m above the ground to measure the impact sound.

As a result, it was confirmed that the high frequency blow noise of 1000 Hz or more improved by 11 dB or more as shown in FIG.

Therefore, it was confirmed that the sand noise effect is excellent in the actual wet road condition or unpaved road.

In addition, the test was conducted by a method registered on the road noise TDP (60KPH constant speed driving, general purpose test furnace) to confirm the effect of road noise in the actual vehicle state. As a result, as shown in FIG. Compared with the existing technology, the effect of front seat 1.3 dB and rear seat 0.8 dB can be confirmed.

10: upper epidermal layer 11: main core layer
12: film layer 13: bottom skin layer
14 glass fiber 15 composite material
20: conveyor 21: heating oven
22: pressure roller 23: cutter
24: headbox

Claims (3)

delete delete In the method of manufacturing a floor undercover composite material for a vehicle,
Mixing the polypropylene and glass fibers 14 by a wet method to prepare a slurry;
Conveying the mixed slurry prepared in the step through the conveyor (20), and draining water contained in the mixed slurry down;
Forming a main core layer (11) while passing the mixed slurry precipitated in the conveyor (20) through a heating oven (21);
The upper skin layer 10 and the film layer 12 together with the main core layer 11 are supplied to the upper and lower surfaces of the main core layer 11 and passed through the pressure roller 22 to be laminated and bonded in a heat fusion method. step;
When the mixed slurry passes through the heating oven 21, polypropylene bonds the glass fibers 14, and reduces the noise by the pores generated by the swelling phenomenon of the mixed slurry,
After the upper skin layer 10, the main core layer 11, and the film layer 12 are laminated and bonded, the lower skin layer 13 made of a polyethylene water-repellent nonwoven fabric is pressed at the bottom of the film layer 12 with a low pressure press to form a final part. The manufacturing method of a floor undercover composite material for a vehicle, characterized in that it comprises a different characteristic value and sound absorption performance for each part by varying the degree of compression of the low pressure press for each part of the material.

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