Manufacturing and qualitative properties of glass fiber/epoxy composite boards with added air bubbles for airborne and solid-borne sound insulation

Abstract Recently, composite materials contain not only good mechanical property but also they possess additional properties such as damage sensing, piezoelectricity. In this study, glass fiber reinforced composites (GFRC) containing air bubbles were manufactured by vacuum assisted resin transfer molding (VARTM) with potential uses as sound insulation. To verify the effectiveness of these bubbles for sound insulation, fragmentation testing with acoustic emission (AE) was introduced using single fiber composites (SFC). The SFC consisted of a single glass fiber which was covered with epoxy resin containing air bubbles. During the fragmentation tests, an AE sensor was installed on the SFC which detected fracture of glass fiber and measured the resulting AE amplitude and energy. In manufacture of GFRC, randomly-chopped glass fiber mats were used for collecting air bubbles in the epoxy resin. These air bubbles were relatively easily introduced into the mats. Four AE sensors were installed on the GFRC specimen to measure the wavespeed and change in amplitude. Finally, the qualitative sound pressure level (SPL) was measured to ascertain the retardation of sound by the GFRC using lab-made impedance tube which was comparative evaluation due to the allowable measurement deviation. The AE amplitude and energy resulting from fiber fracture during fragmentation were smaller in the specimen containing air bubbles than for those in neat condition specimens. In bulk tests, the SPL shielded by GFRC containing air bubbles was comparatively lower than that in the neat condition as well.