A study on the new PETcomposite sound-absorbing material applicable to automotive interior materials Suk-Jun Yong 1 DAEHAN SOLUTION Co., LTD 30, Namdongdae-ro 369 Beon-Gil, Namdong-Gu, Incheon, Korea Jang-Seok Park 1 DAEHAN SOLUTION Co., LTD 30, Namdongdae-ro 369 Beon-Gil, Namdong-Gu, Incheon, Korea

ABSTRACT Various types of sound-absorbing materials are used in vehicles according to external noise and conditions.As sound-absorbing materials for automobiles, there are fiber-type materials such as PET fiber or glass fiber, and foam-type materials such as polyurethane.Among them, PET fiber materials have excellent advantages in terms of weight reduction and recycling, but urethane foam is applied due to their low NVH performance and compressive stress.Recently, as interest in eco- friendly vehicles increases, development of sound absorbing materials using PET fiber is required.To improve this problem, in this study, research was conducted on improving sound absorption performance and compression performance by changing the composition ratio of PET fibers constituting the sound absorption material. The acoustic properties were measured by ALPHACABIN and BUCK tests.

1. INTRODUCTION

Based on global automobile sales, expected sales of electric vehicles (HEV, PHEV, BEV) will grow from 3.3 million units in 2020 to 54.5 million units in 2040, with electric vehicle market share expected to overtake internal combustion engine vehicle market share in 2036. In an electric vehicle (HEV, PHEV, BEV) due to a driving motor having a relatively low transmission power compared to an internal combustion engine vehicle (ICV), an absolute level of indoor noise is reduced, but a masking effect is reduced due to an internal combustion engine member, thereby maximizing noise. Noise generated by the motor and the current conversion device provides a relatively quiet sound environment compared to an internal combustion engine, but high-frequency sound generated by the motor and the current conversion device provides an unpleasant sound environment for the driver and passenger. It is impossible to satisfy the high-frequency band noise reduction with polyurethane foam, and research was conducted to reduce the high-frequency band noise using PET composite materials. For PET materials, there is an advantage in environmental problems (CO2 emission during reaction, recycling problems) compared to polyurethane, so research was conducted to reduce high frequency as an eco-friendly sound absorbing material for electric vehicles.

1 sjyong@dhsc.co.kr

2. EXPERIMENT.

2.1. Manufacture In the case of PET composite materials, all fibers used Huvis products, and the yarn component is 100% Polyester. For the composition ratio and fineness, refer to Figure 1 below. The reason why the composition ratio is complicated is not only to improve sound absorption performance, but also to satisfy the compression performance and resilience required by automotive OEMs. Spunbond PP nonwoven 20gsm is included on both sides of PET Felt, which is for the purpose of enhancing the binding of the fiber and improving the structural rigidity through surface nonwoven fabric treatment. The weight of the Pet Felt is 600gsm, the thickness is 35mm, and the temperature condition of the heating bonding process is 150°C

Table1. PET Conmposite Felt composition ratio

Microfiber Hollow fiber Conjugate fiber LM(Low Melt)fiber

Denier Ratio Denier Ratio Denier Ratio Denier Ratio

0.7 25 4 25 3 25 4 25

2.2. Measurment Except for the compression restoration rate and restoration rate, sound absorption test (Alpha Cabin) and sound insulation test (BUCK Test) were conducted, and in the case of the actual difference evaluation, sound absorption materials were installed on the floor panel insulation and the RR motor. The condition is a constant speed condition of 60 kph on the Rough road, and the evaluation position is the driver's seat and second row right seat (VIP). Major band analysis and conversation clarity of electric motor radiation sound were also evaluated through RR motor covering in the rapid acceleration 20 to 120 km/h section. 3. RESULTS

3.1. Alpha-Cabin (Sound absorption performance)

The sound absorption performance of the existing urethane foam, Shoddy Belt, and PET composite materials were compared in Fig. A, and the sound absorption performance of the regular fiber, hollow fiber, and PET composite materials were compared in Fig. B. Through this, PET composite materials showed superior sound absorption performance compared to other materials.

Table2. Comparison sample

Sample PU Shoddy PET Composite fiber

Sound asorption PU 20T (D80, 1600gsm) Shoddy 20T (D50, 1000) PET 20T (D16.5, 600gsm)

Sound insulation (TPE 1.5T) + PU 20T (TPE 1.5T) + Shoddy 20T (TPE 1.5T) + PET 20T

(A) (B) Figure.1 (A) : Sound absorption performance results by material, (B) : Sound absorption results performance by PET fiber

3.2. BUCK Test PU Foam sound insulation performance is excellent when comparing sound insulation materials, but the difference in sound insulation performance is insufficient when combined with sound insulation materials (TPE 1.5T)

Figure.2 Sound insulation test results of BUCK TEST

3.3. Vehicle TEST Two parts were selected for actual vehicle evaluation and carried out, and in the case of floor panel insulation, the floor panel insulation was applied as a PET composite sound absorbing material for the purpose of improving road noise and ICCU high-frequency noise. In the case of RR motor covering, PET composite sound absorbing material + H/LAYER (TPE1.0T) was applied for the purpose of blocking the RR motor high frequency.

Table3. Automotive application parts

ITEM Before After Features and specifications

1) Improve Road Noise 2) Improvement of high frequency

Floor panel

noise such as ICCU

insulation

- PET composite fiber ( 30T) - FRONT COVERING

1) RR Motor High Frequency Cut-

RR Motor

off

Covering

- H/LAYER(TPE) + PET (30T)

Figure.3 Floor panel insulation (ROUGH ROAD: 60kph)

A

B

Figure.4 (A): Before RR motor covering, (B): After RR motor covering

(Sudden acceleration:20~120km/h) 4. CONCLUSIONS

A sound absorbing material for an electric vehicle was developed by mixing 4 types of PET fibers, and the compression modulus (restoration rate) and high-frequency noise were evaluated through various tests. As a result of the evaluation with sound absorption evaluation (alpha cabin), the sound absorption performance was excellent in medium and high frequency bands compared to other materials, and in the case of BUCK TEST, the urethane foam specifications were excellent, but the performance difference was insufficient. It was confirmed that road noise, which is highlighted as a masking effect during the actual driving test, was improved by up to 2.3 dB(A) by applying microfiber sound absorbing material, and the main order components, 24th and 48th high frequency noise, were improved by OPENA.I 4.3% based on the clarity.. 5. REFERENCES

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