Acoustic Shielding of Nano-Particle Reinforced Composites

Acoustic Shielding of Nano-Particle Reinforced Composites

Asim Sneh*, Manshu Gupta*, Akansh Vishwakarma*, Anuj Gupta*

*B. Tech Mechanical Engineer, SMEC, Vellore Institute of Technology Chennai, Tamil Nadu 600127

Lakshmi Ramya Marineni**

**B. Tech Electronics And Communication Engineer, SENSE,Vellore Institute of Technology Chennai, Tamil Nadu 600127

Abstract Sustainable flexible foam reinforced with different mixtures of Multiwall Carbon Nanotubes (MWCNT), Copper Oxide (CuO) and Bamboo Charcoal nanoparticles has been prepared using a general mixing process. The sound damping capacity of in total five reinforced samples and an unreinforced sample has been found using sound absorption measurement Setup also called impedance tube setup. The sample A5 performed well in the frequency range of 200-440Hz. Sample A3 has the best sound damping capacity in the range of 440-680 Hz and sample A2 did well in the frequency range of 680-1600 Hz. Sample A5 saw a dropdown in the sound absorption in the higher frequency range in comparison to the non-reinforced foam.

Keywords Sustainable flexible foam, Sound damping capacity, Nanoparticles, Impedance tube, frequency

1. INTRODUCTION

   Sound is the propagation of disturbance in fluid or in solid, principally; a wave motion is set off when an element sets the nearest particle of air into motion, which then creates a difference in pressure in the medium where the wave travels [1]. Though the sound is a very important physical phenomenon in the modern world the unwanted sound also known as noise is a big problem and creates sleep disorders and other health-related issues [3-5]. So, sound absorption becomes a required feature of many material applications [2]. From building material, to protect the living and working spaces from unwanted noise to aerospace material to protect the passenger chamber from loud ear bursting sound of the engine in the case of an airplane and propellant reaction in the case of a rocket, all require very good sound damping capacity. A material can become sound damper by four means. The first is the thickness, with the increase of it the material is more soundproof. The second is wave scattering capability which reduces the energy of the sound wave by scattering it into different directions. The third is the wave trapping capability and the fourth is the capability to stop a vibration to build up and radiate as a sound. Based on the required application, with any of the four or a number of combinations of the above capabilities, good sound-absorbing material can be made. Foams especially flexible foams are considered as very good sound damping materials. The only limitation to them is that they require large thickness to provide good sound absorption capability. So, it becomes important to find out some materials that can overcome this limitation. As always composites can be the solution. The only requirement is to test different composites and

   investigate that can they be the required material for better sound absorption. We have taken an endeavor to achieve the required goal and are trying the flexible foam with different mixtures of nanoparticles such as MWCNT, CuO and Bamboo Charcoal as a reinforcement. We are investigating the sound-absorbing capacity of these reinforced samples and making and comparative study of them with that of the normal foam sound damping ability.

2. METHODOLOGY
   1. 1. Fabrication

         A flexible foam without any reinforcement can be prepared by carrying out an exothermic reaction of synthetic Polyol and isocyanides in the ratio of 2:3 by volume [6]. The effervescence of carbon-dioxide is released and the whole process can be carried out in a container with waxed walls for easy removal of the product as shown in figure 1. For the preparation of Nano-particle reinforced foam, the nanoparticles are added directly in the reaction container with the other chemicals of the process stated above. Five nanoparticles reinforced foams have been prepared with mixtures of MWCNT, CuO and Bamboo Charcoal in different ratios by weight as mentioned in Table 1.

         Table1. Different weight proportions of nanoparticles

         Specimen	MWCNT (wt.%)	CuO (wt.%)	Bamboo Charcoal (wt.%)
         A1	1.00	2.0	2.0
         A2	0.75	0.5	1.5
         A3	0.75	1.5	1.5
         A4	0.75	1.5	0.5
         A5	0.75	1.5	2.5

         Figure 1. Waxed wall reaction container

      2. Sound Absorption Measurement Setup

   A test setup containing an impedance tube of length 900mm and internal diameter 56mm, a speaker with a frequency range of 200Hz- 1600Hz a pair of microphones, a PC

   automated measurement controller using MATLAB software has been installed. The sample is positioned at one end of the setup with the speaker at the other end and the microphones in the middle. The microphones and the speaker are connected to the controller and MATLAB software is used to calculate the Sound Absorption Coefficient of the sample from the collected data. A simple diagram of the whole setup has been represented in Figure 2.

   Figure 2. Sound Absorption Measurement Setup

   2.2.1 MATLAB code used

   clc clear all

   lower_frequency_limit = 200;

   higher_frequency_limit = 1600;

   dataset = xlsread(xyz.csv, A3:C8194); t = dataset(:,1); %Time data

   m1 = dataset(:,2);%Microphone1 data m2 = dataset(:,3); %Microphone2 data

   %Transfer Function

   period = 60; %period of recording temperature = 28; %room temperature

   pressure = 101.325; %atmospheric pressure, kPa f = 6400; %sampling rate

   = 1.21; %density of air, kg/m^3 c = 343; %speed of sound, m/s

   I = *c; %characteristic impedance of air, kg/m^2/s s = 0.077; %microphone spacing, m

   x1 = 0.290;

   [H12,frequency]= tfestimate((m1),(m2),[],[],[],f,onesided); k = (2*pi*frequency)/c;

   R = ((H12-exp(-1i.*k.*s)))

   = 1-absI.^2; %sound absorption coefficient Is = I.*((1+R)./(1-R)); %surface impedance

   Is_n = ((1+R)./(1-R)); % Normalized surface impedance Plot(frequency, ,-);

3. RESULTS AND FINDINGS
   1. 1. FTIR Test

         According to the plots obtained from the Fourier Transformation Infrared (FTIR) Spectrum, we have identified the functional groups present in the different foams. The plots obtained are shown below.

         • Normal Foam: In the below graph, we can observe the broadening of the peaks in the range near 3500cm-1 which confirms the presence of -OH functional group. The stretching of the peaks near the range of 3000cm-1 confirms the presence of -C-H groups. The absorption in the range of 2165-2110 cm-1 shows the presence of cyanide group.

           Figure 3. FTIR of Non Reinforced foam

           • Reinforced Foam: We can see that figure 4 is different when compared with figure 3. This indicates that some reinforcement has been added to the normal foam. A peak in the range of 1600-1700 cm-1 indicates the presence of SP2 hybridized carbon which is a characteristic of MWCNT due to the presence of carbon-carbon double bond (C=C). A descent amount of transmittance percentage and deviation from the normal foam FTIR graph indicates that the sample does not has the only MWCNT but also some other reinforcements. The data so ollected are not very clean and a lot of noise can be found because of the presence of MWCNT and bamboo charcoal which a mixture of a lot of compounds.

         Figure 4. FTIR of Reinforced foam

      2. Sound Absorption Capability

   Sound absorption capability is characterized by the sound absorption coefficient of the sample, which is calculated using the MATLAB code as mentioned in 2.2.1. The results have been summarized in Table 2 and for a comparative outlook, has also been represented in the form of a graph in figure 3. If we see in the lower frequency range (i.e. 200-440 Hz), sample A5 is performing better than any other samples, In the lower-middle frequency range (i.e. 440-680 Hz), sample A3 shows the highest sound absorption and in the higher-middle frequency range (i.e. 680-1100 Hz) and in the higher frequency range (i.e. 1100-1600 Hz) A2 is the best result showing sample.

   Sample	Sound Absorption Coefficient
   Frequency
   	Normal	A1	A2	A3	A4	A5
   200	0.138978	0.06607	0.115342	0.169534	0.050718	0.21081
   256	0.05616	0.043726	0.186852	0.118155	0.069248	0.15802
   320	0.20808	0.098869	0.253094	0.345706	0.279346	0.420389
   352	0.198501	0.133144	0.305122	0.407951	0.288025	0.416755
   400	0.209242	0.114226	0.364487	0.435243	0.398171	0.414222
   440	0.18572	0.130884	0.382006	0.470211	0.383355	0.396926
   560	0.205715	0.183492	0.474183	0.559018	0.449007	0.542663
   600	0.240355	0.209532	0.525623	0.594352	0.408137	0.527393
   680	0.218655	0.144373	0.636581	0.666356	0.389486	0.453416
   730	0.150515	0.21995	0.710428	0.655664	0.486757	0.394403
   800	0.187007	0.161395	0.766682	0.654528	0.56892	0.373135
   900	0.256732	0.18044	0.801372	0.642848	0.659892	0.387319
   1000	0.295485	0.291116	0.766885	0.581007	0.579474	0.321096
   1100	0.318448	0.355314	0.688088	0.520552	0.491932	0.294692
   1200	0.272581	0.298937	0.639919	0.414142	0.510692	0.262151

   Sample	Sound Absorption Coefficient
   Frequency
   	Normal	A1	A2	A3	A4	A5
   200	0.138978	0.06607	0.115342	0.169534	0.050718	0.21081
   256	0.05616	0.043726	0.186852	0.118155	0.069248	0.15802
   320	0.20808	0.098869	0.253094	0.345706	0.279346	0.420389
   352	0.198501	0.133144	0.305122	0.407951	0.288025	0.416755
   400	0.209242	0.114226	0.364487	0.435243	0.398171	0.414222
   440	0.18572	0.130884	0.382006	0.470211	0.383355	0.396926
   560	0.205715	0.183492	0.474183	0.559018	0.449007	0.542663
   600	0.240355	0.209532	0.525623	0.594352	0.408137	0.527393
   680	0.218655	0.144373	0.636581	0.666356	0.389486	0.453416
   730	0.150515	0.21995	0.710428	0.655664	0.486757	0.394403
   800	0.187007	0.161395	0.766682	0.654528	0.56892	0.373135
   900	0.256732	0.18044	0.801372	0.642848	0.659892	0.387319
   1000	0.295485	0.291116	0.766885	0.581007	0.579474	0.321096
   1100	0.318448	0.355314	0.688088	0.520552	0.491932	0.294692
   1200	0.272581	0.298937	0.639919	0.414142	0.510692	0.262151

    

   Figure 5. Sound Absorption Coefficient Vs Frequency for different samples prepared Table 2. Sound Absorption Coefficient of different samples at a frequency range of 200-1600 Hz.

4. CONCLUSION

1. The chemical composition of the samples has been characterized by FTIR test.
2. Many times, the acoustic shielding of nanoparticles reinforced foam has been investigated but a mixture of different nanoparticles reinforced foam has been tried for the first time highlights the novelty of the new work studied.
3. It was found that sample A5 with an average Sound absorption coefficient of 0.32 has better sound absorption ability than other samples in the lower frequency range of 200-440 Hz.
4. A3 with an average sound coefficient of 0.57 showed better sound absorption in the lower-middle frequency of 440-680 Hz.
5. A2 with an average sound absorption coefficient of

   0.67 showed the best result in the frequency range of 680-1600Hz.

6. Except for sample A5, in higher frequency range all the reinforced samples showed better sound absorption than the non-reinforced foam.

REFERENCES

1. C. H. Hansen, “Fundamental of Acoustics,” University of Adelaide, Adelaide, 2001.
2. M. N. A. A. Nordin, L. M. Wan , M. H. Zainulabidin , A. S. M Kassim and A. M.Aripin, Research finding in natural fibers sound absorbing material, APN Journal of Engineering and Applied Sciences, ISSN 1819-6608, VOL. 11, NO. 14, JULY 2016.
3. Hiral J. Jariwala , Huma S. Syed , Minarva J. Pandya , Yogesh M. Gajera, Noise Pollution & Human Health: A Review,

   Conference: Noise and Air Pollution: Challenges and Opportunities

4. Babisch, W. (1998) Epidemiological studies of the cardiovascular effects of occupational noise – a critical appraisal. Noise & Health 1:24-39
5. Carter, N.L., Hunyor, S.N., Crawford, G., Kelly, D., Smith,

   A.J.M. (1994) Environmental noise and sleep – a study of arousals, cardiac arrhythmia and urinary catecholamines. Sleep 17: 298-307

6. Manshu Gupta, Asim Sneh, Yuvaraj L., Jeyanthi Subramanian, An Experimental Investigation on the Acoustic and Thermal Properties of Copper Reinforced Sustainable Foam, International Journal of Engineering Research & Technology (IJERT), Vol. 8 Issue 08, August-2019.

AUTHORS PROFILE

Asim Sneh: B.Tech Mechanical Engineer, School of Mechanical Engineering Chennai (SMEC), Vellore Institute of Technology Chennai. Research areas are Heat Transfer,nanopaticles and nanofluids, EMI and acoustics materials development. Published 3 articles in reputed international journals.

Manshu Gupta: B.Tech Mechanical Engineer, School of Mechanical Engineering Chennai (SMEC), Vellore Institute of Technology Chennai. Research areas are internal combustion engines, nanopaticles, EMI shielding and acoustics materials development. Published 5 articles in reputed international journals.

Akansh Vishwakarma: B. Tech Mechanical Engineer, School of Mechanical Engineering Chennai (SMEC), Vellore Institute of Technology Chennai. Research areas are Materials, Thermodynamics, EMI and Automotive Technologies. Published 1 article in reputed international journals.

Anuj Gupta: B. Tech Mechanical Engineer, School of Mechanical Engineering Chennai (SMEC), Vellore Institute of Technology Chennai. Research areas are Fabrication and design modelling of student F1 cars, acoustic materials property study. Published 1 article in reputed international journals.

Lakshmi Ramya Marieneni : B. Tech Electronics And Communication Engineer, School of (SENSE), Vellore Institute of Technology Chennai. Research area are VLSI systems, Remote controlled systems, communication devices, wave generation and absorption.