MINISTRY OF EDUCATION AND TRAINING NHA TRANG UNIVERSITY DINH DUC TIEN STUDY ON SOUND TRANSMISSION LOSS THROUGH COMPOSITE SANDWICH PLATES AND APPLICATION TO NOISE REDUCTION IN SHIPS Major: Mechanichal Dynamics Engineering Major code: 9520116 DOCTORAL DISSERTATION SUMMARY KHANH HOA – 2019 Research was accomplished at Nha Trang University Supervisor: Prof Ph.D Tran Ich Thinh PhD Nguyen Van Dat Reviewer 1: Prof Ph.D Nguyen Thai Chung Reviewer 2: Prof Ph.D Tran Xuan Lam Reviewer 3: Prof Ph.D Ngo Nhu Khoa INTRODUCTION THE RATIONALE In the field of ships, composite materials (fiberglass reinforced with organic resins) are used increasingly, especially in the manufacture of tourism canos, high speed boats, fishing vessels, For military use, shell wrapping, superstructure, masts, chimneys, Due to the low elastic modulus, composites often suffer large deformations when loaded, especially when loaded The resonance phenomenon (inertial force from the rotating parts of the main machine, the auxiliary machine, the force from the propeller ) is more likely to occur in the resonance phenomenon, which causes both noise and vibration, affecting the durability and effective use of equipment, to the health of the ship’s passengers When the noise exceeds the allowable limit (greater than 80dB [1]), the composite material will cause excessive vibration Impact of noise phenomenon will cause vibration, affecting the health of passengers, ship’s staff For the above reasons, the thesis focuses on “Study on sound transmission loss through composite sandwich plates and application to noise reduction in ships” as a basis for the selection and fabrication of composite ship structures, they are beneficial in terms of noise reduction RESEARCH OBJECTIVES Understand the basis of sound transmission and determine the sound transmission loss of through composite sandwich plates with fiberglass polyester matrix and foam core resistant to various dynamic links; Understand and implement the experimental process to determine the sound transmission loss of through composite sandwich plates used in ships in Vietnam; Application of research results on the reduction of engine room composite shell ship was built at the Institute of Ship Research and Development, Nha Trang University RESEARCH OBJECTS AND SCOPE Research objects - Composite sandwich plates symmetrical; - Beams of composite sandwich cut out from plates; - Small composite ships shell; - Small composite ships shell with engine room Research scope Theoretical: Theoretical study of sound transmission loss through composite sandwich plates Experiment: - Experimental study to determine the sound transmission loss of some composite sandwich plates - Research on application of reduction noise of engine room of small composite ship shell RESEARCH CONTENTS Experimental study of sound transmission loss through composite sandwich plates; Study on calculation of sound transmission loss through composite sandwich plates Study on the application of noise reduction in ship's engine room composite shell RESEARCH METHODS The thesis uses theoretical research methods, simulation and experimental verification THE MEANING OF SCIENCE AND PRACTICAL OF THESIS The meaning of science So far, the problem of sound insulation, noise reduction in the field of aviation, space, cars, trains, ships, etc has been researched by many domestic and foreign scientists, but there are some problems with loss of transmission through composite sandwich plates have not been resolved thoroughly and thoroughly Therefore, the content of the thesis is laid out and implemented is of scientific significance The practical meaning The theoretical as well as experimental results of the dissertation will be the scientific basis for selection and application in the manufacture of structural composite shell ships at the Institute of Ship Research and Development Nha Trang University has the best noise reduction capability THESIS STRUCTURE The thesis includes chapters and conclusions, recommendation: Chapter 1: Overview Chapter 2: Experimental study identifies the sound transmission loss of composite sandwich plates Chapter 3: Study on calculation of sound transmission loss through composite sandwich plates used in ship building Chapter 4: Study on the application of noise reduction in ship's engine room composite shell Conclusions and recommendation LIMITATIONS OF THESIS The dissertation has not studied the loss of sound transmission through composite sandwich plates with core materials such as honeycomb, Divinycell - H, Sphere - core are also commonly used in structural composite shell ships when impacted The source of sound is variable frequency CHAPTER OVERVIEW 1.1 Methods for determining sound transmission loss 1.1.1 Wave impedance analysis method Piana [48], Nilsson [88], investigated transmission losses through aluminum composite sandwich plates, core materials were honeycomb, nomex, foam by wave analysis The results have established the bending oscillation equations of the beams, in the experimental section to determine the first eight individual vibration frequencies of the beams, the author has used the measurement method, from the individual vibration frequencies conducted Determine the apparent bending strength of the beams and determine the sound loss of the sheet Pellicier and Trompette [91], when evaluating the transmission losses of aluminum sandwich plates, are also based on wave analysis The result is suitable for modeling single or dual partitions However, this method only applies to simple partitions, with complex partitions this method fails Kurtze and Watters [69], investigating the transmission losses of sandwich plates by wave impedance The results show that in the tangential region, the sound loss of the sandwich can be equal to the transmission loss of the core layer in the middle frequency region 1.1.2 Boundary element analysis method The boundary element method was studied by Mariem and Hamdi [78], using finite element analysis to calculate the sound loss of a partitioned sheet The numerical results show that the source of radiation energy may be greater than the energy from the first few resonant frequencies Except for the near frequencies, the calculation results are consistent with the experimental values However, there are some errors in the expression for the total load on the plate Barisciano [24], studying the transmission losses of honeycomb sandwich plates using the marginal element model The result is not suitable for sandwich plates with foam core Thamburaj and Sun [116], studied the effect of material properties on the sound absorption of sandwiches The equations apply to Lagrange sandwiches Assuming that the external loads of beams are due only to the pressure components caused, the resultant fonts match the sandwich 1.1.3 Statistical energy analysis method (SEA) Statistical energy analysis (SEA), is a method of using energy relations to calculate the theoretical levels of vibration response and radiated noise from structures in resonant motion Lyon and Maidanik [74], the wage function between the two stimulus flows, random linear oscillations with small junctions between them The result has given an expression of sound reflection Smith [111], calculates the response and radiation of a sound to a linear resonant mode of an excited structure by a pure tone The results show that when vibrations in this mode are mainly impeded by sound radiation, that is, the perpendicular velocity is inversely proportional to the average hardness Maidanik [76], extends the results presented in the two papers discussed above, from monosyllabic to polyphasic by two main assumptions The study predicts the mean radiation impedance of single-layer plates simultaneously comparing the predicted values with the experimental results 1.2 Conclusion of chapter 1: Chapter of the thesis has introduced methods for determining transmission losses through composite sandwich structures, including: - Wave impedance analysis method; - Boundary element analysis method; - Statistical energy analysis method (SEA); - Experimental method - Within the research scope of the thesis, the thesis developed the wave analysis method, the energy statistical analysis method and the experimental method to determine the transmission loss through composite sandwich plates with two layers of skin composite fiberglass / polyester unsaturated and foam core (foam PU) CHAPTER EXPERIMENTAL RESEARCH DETERMINATION OF SOUND TRANSMISSION LOSS BY COMPOSITE SANDWICH 2.1 Development of experimental formula according to energy statistical analysis 2.1.1 Introduce Statistic Energy Analysis (SEA), was born in the 60s of the last century, from the study of the energy flow between two sources of vibration caused by linear stimuli Fig 2.1 The energy flow between the structure and the reverberate field [74] Emerving a communicator model model include system that are Fig 2.2 Fig 2.2 Block diagram for energy flows between the structure and two reverberate rooms [74] 2.1.2 The empirical formula determines the sound transmission loss It is possible to determine the experimental loss of sound transmission through the partition by two-room method Negative energy Π12 from the broadcast room to the studio must be Π21 from the studio to the room plus negative Πα energy, absorbed in the studio, as illustrated in Fig 2.3 CHAPTER CALCULATED AND RESEACH OF SOUND TRANSMISSION LOSS THROUGH COMPOSITE SANDWICH PLATES USED IN MANUFACTURING SHIP CONTRUCTIONS 3.1 The theory of composite sandwich plate Kirchhoff's theory for class composite sheets accepts the following hypotheses [13]: • The fence with the average surface of the sheet is always straight and perpendicular to the average surface • Ignore the cross sectional stress components (σxz = σyz = 0) • Ignore the normal distortion (εzz = 0) Fig 3.1 Model composite sandwich plate 3.2 Modeling of sound transmission loss through composite sandwich plates 3.2.1 Theoretical formulation 3.2.1.1 Plate geometry and assumptions Consider a finite, rectangular composite sandwich plate clamped in an infinite acoustic rigid baffle, as shown in Fig 3(a) and 3(b) The sandwich plate for this study refers to a structure consisting of two thin laminated composite sheets bonded to a polyurethane foam core The sandwich plate has length a along x-direction, width b along y-direction and thickness along z-direction Fig 3.1 Schematic of sound transmission through a clamped rectangular composite sandwich plate: (a) Composite Sandwich (b) overall view; (c) side view from the direction of arrow in (a) 12 3.2.1.2 Composite sandwich plate dynamics In most applications, and for simplicity, the composite sandwich plate can be regarded as an orthotropic single plate [59] The dynamical displacement of an orthotropic symmetric composite plate in the air on both sides and subjected to uniform, plane sound wave varying harmonically can be described by [59]: Dx  4w x, y; t  4 w x, y; t  4 w x, y; t  2 w( x, y; t )  Dx Dy  Dy  m*  j0 1 ( x, y, z; t )  2 ( x, y, z; t )  2 x x y y 2t (3.1) where: w is the normal displacement of the plate, Dx and Dy are the apparent bending stiffness in x and y directions, respectively, m* is the surface density of the plate, ρ0 is the air density, ω is the angular frequency of the incident sound and  i (i  1, 2) denote the velocity potentials for the acoustic fields in the proximity of the plate, corresponding to the sound incidence and the structure radiating field, respectively 3.2.2 Definition of sound transmission loss The diffuse field sound transmission coefficient over all angles of incidence φ and θ is calculated by: 2  L   , , f sin cosdd d  0 2  L   sin cosdd 0 (3.1) The integral (3.1) has been evaluated numerically by using Simpson’s 1/3 rule with 150-angular increments in φ and θ θL is the limiting angle of incidence and is taken as 780 for field-incidence calculations Then the sound transmission loss across the composite sandwich plate is defined by: 1 STL  10log10   d    (3.2) 3.2.3 Determination of apparent bending stiffness According to Nilsson [88], the bending strength of a composite sandwich sheet is determined by the bending strength of a beam with the same dynamic properties as the sheet structure at certain frequencies 13 Beams Ax(A0) and Ay (A90) are cut from the A plates in the x and y directions respectively Perform the same for the beams of the remaining plates A0 beams are l x b = 1200mm x 50mm; The A90 has a size of x b = 1100mm x 45mm [88] Fig 3.2 Composite sandwich plate and beams Ax, Ay 3.2.3.1 Results of individual oscillation frequency calculation The first ten individual frequencies of composite sandwich beams (from A0, A90, and B0, B90) are shown in Table 3.1 Table 3.1 The first ten fre- quency frequencies of beams A, B Mode A0 - f(Hz) A90 - f(Hz) B0 - f(Hz) B90 - f(Hz) 82,3340 95,6430 100,1300 115,0300 173,5900 196,2600 192,8500 215,6000 267,0700 298,1000 285,7400 316,7100 356,8700 395,3000 373,2600 411,4000 445,4100 491,5900 461,4400 507,8200 532,3200 586,0400 547,5900 601,6600 619,1800 680,9300 635,5800 698,4800 705,5400 775,2400 722,6400 793,8500 792,5200 870,7200 812,3300 893,2200 10 879,5600 966,2000 901,3900 991,1300 Some of the free-floating modes of beam A0 correspond to the frequencies shown in Fig 3.3 Mode 14 Mode Mode Fig 3.3 Some of the free-vibration modes of the Ax (A0) The vibration modes of other beams are shown in Appendix of the thesis 3.2.3.2 Determination of apparent bending stiffness The apparent bending stiffness of the beam is obtained according to the following equation [88] Dxn  4 f n2 m * L4 /  m4 (3.3) Where: fn is the eigenfrequency for mode n, L is the length, and m* is the mass per unit area Here, for the beam tested with free-free boundary conditions, the values of αn can be found in Ref [88] Mode No n n>5 Free and clamp αn 4,73 7,85 11,00 14,14 17,28 nπ + π/2 Rather than the known parameters in Equation (3.3), we obtain the values of apparent bending stiffness for beams A and B (Table 3.2) Table 3.2 The apparent bending stiffness of beams A, B Mode 10 Dx (A0 - Nm) 10523,8140 6166,3771 3799,4326 2482,6228 1733,0451 1268,9159 968,5666 762,2690 616,4058 508,7617 Dy (A90 - Nm) 10026,9043 5565,3184 3342,2446 2150,7505 1490,5336 1085,8943 827,0778 649,8051 525,3504 433,4743 15 Dx (B0 - Nm) 20736,1221 10139,2150 5794,2200 3618,2446 2478,0200 1788,8860 1359,6292 1065,3526 862,7712 711,8580 Dy (B90 - Nm) 19322,6686 8947,6361 5025,9968 3103,4829 2119,0426 1524,8239 1159,4012 907,7621 736,5348 607,6799 3.3 Determination of sound transmission loss of A-K plates Determine the Dx and Dy of the beams A through K, instead of Equation (3.1) Using the calculation program in the Matlab R14 environment [138], we have the results of transmitting loss through the sheets from A to K The results shown in Table 3.3 Table 3.3 Calculated value of STL through from A to K plates f( Hz) 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 A 27,76 24,86 11,58 17,79 15,53 16,87 16,44 18,55 22,79 25,06 25,32 27,73 26,52 31,99 32,46 32,66 34,30 37,91 40,22 39,91 44,71 47,45 51,23 52,55 B 26,23 23,68 11,07 18,87 19,15 17,29 21,93 21,75 23,98 28,69 28,02 28,51 32,41 33,39 33,24 36,42 39,77 41,51 43,68 44,69 47,34 51,58 52,62 54,42 C 26,75 22,43 11,96 18,68 16,95 17,91 20,10 21,52 23,13 28,39 27,73 28,21 32,08 33,05 32,90 36,04 36,46 40,18 43,23 44,23 46,85 48,05 52,08 53,86 Sound transmission loss STL (dB) D F G E 25,82 25,75 26,76 27,64 23,57 22,43 23,23 24,05 10,58 10,86 11,26 11,25 18,98 16,48 16,59 17,17 18,29 14,95 14,76 16,45 16,51 17,91 17,52 17,56 20,95 18,10 18,11 17,27 20,77 21,02 20,43 19,09 23,86 23,33 21,34 22,35 27,40 27,29 25,30 23,14 26,76 26,93 24,93 22,85 27,23 28,41 29,72 25,95 30,96 31,38 31,18 26,91 31,90 33,55 33,56 29,91 34,71 32,80 33,40 31,76 37,65 35,84 36,75 37,58 37,99 36,46 37,17 37,09 39,65 41,08 41,89 40,15 41,72 42,23 42,74 42,36 42,68 45,23 45,64 44,08 45,22 47,25 47,56 46,07 49,26 48,05 48,45 49,38 51,22 50,58 51,28 50,44 51,98 51,86 52,76 52,06 H 26,33 22,78 11,52 16,98 16,27 17,56 17,08 18,87 20,10 23,18 22,60 26,16 26,61 29,88 31,40 37,16 36,67 40,70 41,38 43,59 45,55 48,82 50,87 51,88 I 26,29 22,25 11,51 16,96 15,24 16,54 17,06 20,85 22,78 23,15 22,57 26,13 26,58 31,34 31,66 35,11 36,63 40,65 41,13 43,53 45,50 49,76 50,81 53,81 K 27,60 23,20 11,51 18,44 16,58 18,99 19,05 22,68 24,77 25,17 25,84 28,41 28,91 33,78 34,43 38,19 39,83 41,21 44,73 45,34 47,48 50,12 52,25 55,53 From the calculated values in table 3.3, we construct the (f-STL) from plate A and B Fig 3.7 Sound Transmission loss through plate A 16 Fig 3.8 Sound Transmission loss through plate B 3.4 Conclusion Chapter In Chapter 3, the thesis established a major negative oscillation equation for the composite sandwich plate symmetrically with the skin layers of glass composite / unsaturated polyester and the core of polyurethane (PU) Determine the first ten (10) oscillation frequencies for the composite sandwich beams cut from the studied sheet structures From there, construct regression curves as a basis for calculating the apparent bending strength of plates in the 1/3 octave frequency band Based on the established transmission loss calculation (STL) formula, a computer program written in a Matlab environment has been developed The numerical results of negative transmittance losses through composite sandwich plates (denoted by A to K) are consistent with the experimental results 17 CHAPTER APPLICATION TO REDUCTION NOISE FOR ENGINE ROOM OF SHIP 4.1 Noise from the engine According to Man B & W [77], on ships, when diesel engines work, the friction and impact of moving parts due to force and moment of inertia cause mechanical noise; The motor's vibration comes from the maximum fire pressure and the very high fire rate, spreading on its surface, causing the emission of noise in the air of a mechanical origin At the intake and outlet of the diesel engine, there is a turbulence that causes pressure difference, which causes the air to vibrate Figure 4.1 Some areas generate the source noise of the engine [77] According to Man B & W [77], when the engine is working, the sound sources are emitted at the main locations: Exhaust gas noise; Airborne noise; Structure – born noise Fig 4.2 Areas of concentrated noise of marine diesel engines [77] 18 4.2 Application to reduction noise for engine room of ship 4.2.1 General introduction of research vessels [14], [15] - Length Ltk = 11.68 m - Width Btk= 2.68 m - Engine name : YANMAR 4LM-HT - Power: 72 HP - Rpm: 3000 v / p - Fuel: Diesel 4.2.2 Overall ship layout Fig 4.3 GW01 ship [14] Fig 4.4 VQGNC ship [15] 4.2.3 Cover the machine chamber Fig 4.5 Lay out of the engine room 02 ship [14], [15] Configuration of the engine bay plate of GW01 ship, [14]: [WR800/WR800/WR800/PU1/WR800/WR800/WR800] With PU1: is Foam with density of 46,88 kg/m3 19 4.3 Measurement results noise of GW01 ship 4.3.1 Method, equipment, measuring position and measurement procedure 4.3.1.1 Measurement tools Using Measurement tools 2310 SL of the laboratory of Institute Research and manufacture of ship Fig 4.6 Measurement tools 4.3.1.2 Measurement location Fig 4.7 Measurement location 4.3.1.3 Process of measuring and processing data a / The steps of the process Step 1: Prepare ships and Measurement tools Step 2: Mark the location to be measured Step 3: Measure the noise level b / Applicable standards [62], [63]: ISO 140 – 4(1998); ISO 3740 (2000) 20 4.3.2 Measurement result of GW 01 ship’ In side the engine room Outside the engine room Fig 4.8 Noise level measurement of the GW 01 ship when rpm = 1500v/ph Comment: Experimental results show that in the frequency region ƒ = 32 - 4000 (Hz), the average outside noise level of the engine compartment is rather high (L2> 80dB), [8] 4.4 Noise processing New configuration of the engine bay plate of VQGNC ship, [15]: [WR800/WR800/WR800/PU2/WR800/WR800/WR800] With PU2: is Foam with density of 57,87 kg/m3 4.4.1 Results of noise measurement when VQGNC ship’ operates The measurement procedure is similar to the GW01 ship In side the engine room Outside the engine room Fig 4.9 Noise level measurement of the VQGNC ship when rpm = 1500v/ph 21 4.4.2 Comparing the noise measurements of the two ships Table 4.1 Comparison of noise outside the engine room of two ships Freq rpm = 1000 (v/ph) rpm=1500 (v/ph) rpm = 1800 (v/ph) rpm = 2000 (v/ph) rpm = 2350 (v/ph) GW01 VQGNC GW01 VQGNC GW01 VQGNC GW01 VQGNC GW01 VQGNC (dB) (dB) (dB) (dB) (dB) (dB) (dB) (dB) (dB) (dB) 32 96,90 92,20 78,50 76,10 78,30 76,30 92,10 83,20 77,80 76,80 63 99,80 82,50 80,90 76,10 82,90 79,10 99,30 93,90 89,30 77,80 125 82,00 80,10 86,80 79,60 85,60 84,40 87,20 86,60 93,70 85,60 250 79,70 76,80 81,10 74,00 82,60 78,80 83,90 79,60 89,40 86,10 500 72,60 70,70 75,90 74,10 76,60 73,10 78,30 75,50 82,60 74,00 1000 77,00 73,40 81,80 77,70 79,10 78,50 83,50 81,00 84,90 80,70 2000 75,30 74,70 76,10 75,50 78,70 78,50 78,40 78,20 82,40 79,50 4000 71,30 67,60 70,00 69,50 74,80 71,30 76,30 74,30 80,50 77,10 8000 60,80 55,00 70,10 66,80 64,40 64,20 68,50 65,50 68,60 66,30 16000 50,90 45,30 52,90 49,50 54,00 51,80 54,20 51,90 56,80 55,40 ƒ(Hz) Fig 4.10 Comparing the noise level of two ships at rpm = 1000 (v/ph) Fig 4.11 Comparing the noise level of two ships at rpm = 1500 (v/ph) Fig 4.12 Comparing the noise level of two ships at rpm = 1800 (v/ph) 22 Fig 4.13 Comparing the noise level of two ships at rpm = 2000 (v/ph) Fig 4.14 Comparing the noise level of two ships at rpm = 2350 (v/ph) 4.4.3 Comment - When rpm = 1000 v/ph, the noise level of the VGQNC ship’ decreased by an average of 6,2% - When rpm = 1500 v/ph, the noise level decreases by an average of 4,6% - When rpm = 1800 v/ph, the noise level decreases by an average of 2,8% - When rpm = 2000 v/ph, the noise level of the decreases by an average of 3,9% - When rpm = 2350 v/ph, the noise level of decreases by an average of 5,5% The noise level of the VGQNC has decreased by an average of 4.6% corresponding to all modes of operation and the sound frequency of the diesel engine 4.5 Conclusion Chapter Chapter deals with some problems in terms of the objectives of the thesis Include: • Apply theoretical research results to calculate noise reduction for the small shipbuilding chamber • Composite sandwich plate structure has been selected In the case of composite sandwich plates, the structure of the upper and lower skin is identical (symmetric) When changing the density of the core layer, the noise level When the density of the core is increased, the noise level decreases • From the results of applied research, the thesis can develop and apply noise reduction for the structure of fishing vessel, patrol boat and big passenger ship 23 CONCLUSIONS AND RECOMMENDATION CONCLUSIONS From the research results presented in the chapters of the thesis, some conclusions are drawn as follows: Provided both theoretical and experimental approaches in a reliable and scientific manner to determine sound transmission losses across composite sandwich plates in order to reduce noise in ships Fabricated samples and carried out the experiment to measure sound transmission losses across composite sandwich plates using the sound pressure levels Established the computational model and governing vibro-acoustic equation for composite sandwich plates with fiberglass/polyester orthotropic face sheets and polyurethane - PU foam isotopic core On that basis, developed an explicit formula, procedure and computer program in Matlab R14 to calculate sound transmission losses across clamped composite sandwich plates A noticeable achievement is the determination of the apparent bending stiffness of the composite sandwich plates by applying the finite element method on the sandwich beams cut out from the plates instead of costly experiments Experimental data and numerical results presented in the thesis ensure reliability and practical implications The research results have been applied to manufacture the noise reduction structure of a typical ship’s engine room at Institute of Ship Research and Development, Nha Trang University RECOMMENDATION In order to fully solve the problem of sound transmission loss through composite sandwich plates, it is necessary to continue studying the following issues: Study the effect of sub machine and shipboard equipment on sound transmission through composite sandwich plates Study on sound loss through composite sandwich plate structure with honeycomb core material, Divinycell - H, Sphere - core, are the types of cores that are often used in composite shell ship structure when affected by the source The sound has a variable frequency Study identified negative transmission losses through composite sandwich panel structures of any configuration using numerical methods and analytical methods 24 Thesis title: “Study on sound transmission loss through composite sandwich plates and application to noise reduction in ships” Major : Mechanical Dynamics Engineering Major code : 9520116 PhD Student : Dinh Duc Tien Course : 2013 Supervisor : Prof PhD Tran Ich Thinh; PhD Nguyen Van Dat Education Institution: Nha Trang University Key Findings: Provided both theoretical and experimental approaches in a reliable and scientific manner to determine sound transmission losses across composite sandwich plates in order to reduce noise in ships Fabricated samples and carried out the experiment to measure sound transmission losses across composite sandwich plates using the sound pressure levels Established the computational model and governing vibro-acoustic equation for composite sandwich plates with fiberglass/polyester orthotropic face sheets and polyurethane - PU foam isotopic core On that basis, developed an explicit formula, procedure and computer program in Matlab R14 to calculate sound transmission losses across clamped composite sandwich plates A noticeable achievement is the determination of the apparent bending stiffness of the composite sandwich plates by applying the finite element method on the sandwich beams cut out from the plates instead of costly experiments Experimental data and numerical results presented in the thesis ensure reliability and practical implications The research results have been applied to manufacture the noise reduction structure of a typical ship’s engine room at Institute of Ship Research and Development, Nha Trang University PhD Student Dinh Duc Tien 25 LIST OF PAPERS Dinh Duc Tien, Nguyen Van Dat, Tran Ich Thinh, Determination of sound transmission loss through composite sandwich plate structure of ship engine room, Proceedings of the National Conference on Mechanics of Solids deformation XIIth, Duy Tan University, Da Nang 6-7/8/2015 Dinh Duc Tien, Nguyen Van Dat, Tran Ich Thinh and Pham Ngoc Thanh, Experimental research of sound transmission loss through composite sandwich plates used in ships, Proceedings of the National Science Conference "Materials Composite Mechanics, Technology and Applications ", Nha Trang University 28-29/7/2016 Dinh Duc Tien, Nguyen Van Dat, Tran Ich Thinh, Experimental research of sound transmission loss through ship engine room composite shell’, Proceedings of the National Science Conference "Materials Composite Mechanics, Technology and Applications ", Nha Trang University 28-29 / 7/2016 Dinh Duc Tien, Nguyen Van Dat, Tran Ich Thinh, Effect of core density of sound transmission loss of composite sandwich plates used in ship engine room, Proceedings of the National Conference on Mechanics and Mechanics - Dynamics 2016, Hanoi University of Science and Technology 13/10/2016 Dinh Duc Tien, Nguyen Van Dat, Tran Ich Thinh, Determining of sound transmission loss through composite sandwich plates used in ship structure by statistical energy analysis, Proceedings of the XIVth National Coference on Mechanics of Solids, Tran Dai Nghia University, Ho Chi Minh City, 19-20/7/2018 Tran Ich Thinh, Pham Ngoc Thanh and Dinh Duc Tien, Prediction and Measurement of Sound Transmission Loss for Finite Composite Sandwich Plates, ACCMS-Theme Meeting on Multiscale Modelling of Materials for Sustainable Development, September 7-9, 2018, Sunwah Cultural Center, Vietnam National University, Hanoi, Vietnam 26 ... through composite sandwich plates 2.3.1 Composite sandwich M2 plate Fig 2.8 Measure STL through composite sandwich M2 plate Fig 2.9 The experimental STL through composite sandwich M2 plate 2.3.2 Composite. .. OBJECTS AND SCOPE Research objects - Composite sandwich plates symmetrical; - Beams of composite sandwich cut out from plates; - Small composite ships shell; - Small composite ships shell with engine... through composite sandwich plates 11 CHAPTER CALCULATED AND RESEACH OF SOUND TRANSMISSION LOSS THROUGH COMPOSITE SANDWICH PLATES USED IN MANUFACTURING SHIP CONTRUCTIONS 3.1 The theory of composite sandwich