A multifunctional ultra-thin acoustic membrane with self-healing properties for adaptive low-frequency noise control

Abstract

This paper proposes a novel multifunctional ultra-thin membrane based on a Polyborosiloxane-based gel with stimuli-responsive sound absorption and sound transmission loss (STL) and characterised by excellent self-healing properties. This adaptive behaviour is the result of a dynamically activated phase transition in the membrane’s polymeric network which is given by the interaction with the travelling sound pressure wave. The presence and the extent of such phase transition in the material was investigated via oscillatory rheological measurements showing the possibility to control the dynamic response by modifying the Boron content within the polymer. Acoustic analyses conducted at different stimuli responses showed high and dynamic absorption (95%) at the absorption coefficient peaks and an adaptive shift to lower frequencies while sound amplitudes were increased. An average STL up to 27 dB in the frequency range between 500 to 1000 Hz was observed and an increased STL above 2 dB was measured as the excitation amplitude was increased. Results demonstrated that the new membrane can be used to develop deep subwavelength absorbers with unique properties (1/54 wavelength in absorption and 1/618 in STL) able to tune their performance in response to an external stimulus while autonomously regaining their properties in case of damage thanks to their self-healing ability.

Investigation of a dynamic active/passive noise cancellation of polyborosiloxane thin membrane gel

“…Additionally, the excitation levels of the secondary were selected as such (1.5, 3 and 9 kHz) in order to investigate the effect on the stiffening mechanism of the SSG outside the low frequency range between 300 and 650 Hz. At the lower excitation level of the primary sound source (Figure 7a and LSW = 0.1 V), the evaluated absorption coefficients demonstrated a clear trend observed in similar studies, with a clear shift of these peaks towards lower frequencies [15]. In detail, at the lower frequency range region (352 Hz), α remained virtually unchanged with a shift of frequencies of 10 Hz, whereas the same trend was observed at the higher range (624 Hz), with an approximate α reduction of 10% in this case.…”

“…The acoustic properties of the material underwent a dynamic change, since these are highly affected by the dynamic transport parameters such as permeability and tortuosity, in addition to morphology of the polymeric network and thermal-dependent parameters [31][32][33]. The uniqueness of each formulation of the SSGs, ought to the PDMS precursor employed and the environmental conditions during the synthesis, appeared to have a direct effect on the position, amplitude and shift of the sound absorption coefficient peaks, when these are compared to previous studies [15].…”

“…In the work presented by our group previously [15], an ultrathin (1/618 wavelength) polyborosiloxane-based membrane, successfully achieved high absorption coefficients (>0.9), in the low frequency range. .…”

Tunable and broadband low-frequency noise control via multifunctional polyborosiloxane thin membrane gels

“…In previous work 19 , we introduced these SSG based thin-membranes and managed to achieve high absorption coefficients (α > 0.9),in the low frequency range, which dynamically shifted to lower frequencies as the sound wave pressure wave was increased. In our following work we also demonstrated that this behaviour can be actively controlled, by the introduction of a secondary sound source, for applications where active noise control is required 20 .…”

Impact-responsive layer based on encapsulated solid/liquid non-Newtonian polymers

“…At low strain rates, SSG exhibits viscous characteristics with increased flowability, as there is sufficient time for the B-O bonds to break [16]. At higher strain rates, the B-O bonds will dynamically break and reconstruct resulting in increased molecular resistance and a high stiffness at the macroscale [19], with this behaviour also resulting in the self-healing performance of SSG [20]. This phase transition, from viscous to rubbery state, is responsible for the excellent energy absorption characteristics of the SSG, with energy consumed in this process.…”