Sound transmission loss and flexural strength assessment of hybrid composite reinforced with natural fibers and kevlar

Noise pollution has become a major environmental concern for our society. Natural fibers have better acoustic properties. When these fibers are used along with synthetic fibers, it improves mechanical strength in addition to the acoustic property. Such Fiber Reinforced Polymer (FRP) panels can be used as structural members in various applications such as furniture, prefabricated elements, HVAC ducts etc. Four varieties of hybrid FRP panels made of jute, flax, sisal and hemp in combination with Kevlar-29 are fabricated using vacuum bagging technique. These panels are represented as J-FRP, F-FRP, S-FRP and H-FRP respectively. Sound Transmission Loss (STL) and flexural strength are experimentally determined. Sound impedance tube technique was used to study STL. Experiments were conducted at lower frequency range from 63 Hz to 1600 Hz; and higher frequency range from 1000 Hz to 6300 Hz. Circular specimens of diameter 100 mm for lower frequency and 30 mm for higher frequency were used. Among all hybrid FRP's, S-FRP showed maximum STL value of 31.28 dB whereas J-FRP showed minimum STL value of 20.92 dB till 6300 Hz. There was substantial increase of STL values upto 1600 Hz, whereas slight increase (around 15%) was observed at higher frequency of 6300 Hz in all FRPs. H-FRP also showed higher STL values close to S-FRP with marginal difference of 2%. In addition, H-FRP has the highest flexural strength to weight ratio among all the FRP panels and hence H-FRP would be a better option for structural applications. (C) 2019 Elsevier Ltd. All rights reserved.