Search Results (29)

To meet the European Green Deal targets, the construction sector must improve building thermal performance via advanced insulation systems. Eco-friendly sandwich panels offer a promising solution. Therefore, this work aims to develop and validate a new eco-friendly composite sandwich panel (basalt fibres and recycled extruded polystyrene) with enhanced multifunctionality for lightweight and energy-efficient building façades. Two panels were produced via vacuum infusion—a reference panel and a multifunctional panel incorporating phase change materials (PCMs) and silica aerogels (AGs). Their performance was evaluated through lab-based thermal and acoustic tests, numerical simulations, and on-site monitoring in a living laboratory. The test results from all methods were consistent. The PCM-AG panel showed 16% lower periodic thermal transmittance (0.16 W/(m²K) vs. 0.19 W/(m²K)) and a 92% longer time shift (4.26 h vs. 2.22 h), indicating improved thermal inertia. It also achieved a single-number sound insulation rating of 38 dB. These findings confirm the panel’s potential to reduce operational energy demand and support long-term climate goals. Full article

The aim of this study is to investigate the potential of wood composites as sustainable acoustic materials and to explore their integration with advanced manufacturing techniques for improved performance. Using a comprehensive review methodology, the paper analyzes recent innovations in wood composites, focusing on the combination with other sustainable materials such as expanded polystyrene (EPS) and natural fibers. The results show that wood composites can achieve sound absorption coefficients (α) of up to 0.9, with oak panels showing transmission losses of up to 11 dB. In addition, advanced designs, including biodegradable panels and lightweight honeycomb structures, significantly improve sound transmission loss, with an average sound transmission loss (TLeq) of up to 28.3 dB reported for composite panels made from waste tire rubber. In addition, the study highlights the environmental benefits achieved through the use of agricultural byproducts and industrial waste in the development of these materials, confirming the role of wood composites as a carbon-neutral alternative in the quest for green building solutions. This study provides valuable insights into the transformative potential of wood composites for sustainable acoustic applications. Full article

Urbanization and population growth have heightened the need for sustainable, efficient building materials that combine acoustic and thermal insulation with environmental and economic sustainability. Sandwich composite panels have gained attention as versatile solutions, offering lightweight structures, high strength, and adaptability in construction applications. This study evaluates manual, semi-automatic, and automatic production methods, selecting the automatic process for its efficiency, precision, and suitability for large-scale production. Extensive characterization techniques, including field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), Differential Thermogravimetry (DTG), Differential Scanning Calorimetry (DSC), and flammability tests, were employed to evaluate the morphological, thermal, acoustic, and fire-resistant properties of the panels. The P200 sample, produced automatically, demonstrated high acoustic absorption in the mid–high frequencies (2000–4000 Hz), strong interlayer adhesion, and low thermal conductivity (2.75 W/mK), making it effective for insulation applications. The flammability tests confirmed compliance with EPA 1030 standards, with a low flame propagation rate (1.55 mm/s). The TGA-DTG and DSC analyses revealed the thermal stability of the panel’s components, with distinct degradation stages being observed for the polyurethane core and non-woven textile layers. The FE-SEM analysis revealed a compact and homogeneous structure with strong adhesion between the core and textile layers. These results highlight the potential of sandwich composites as eco-friendly, high-performance materials for modern construction. Full article

Given the current need to improve the thermal and energy performance of buildings, special attention has been given to the building envelope and materials. Concrete sandwich panels (CSPs) are versatile composite construction elements whose popularity is increasing given their properties, e.g., good thermal and acoustic insulation, durability, and fire resistance. Nevertheless, besides their properties, it is important to evaluate the sustainability of composite panels under development. This work aims to assess the eco-efficiency of six CSPs with distinct insulation materials: lightweight concrete (LWC), cork, glass wool, and expanded polystyrene (EPS). Coupling both life cycle assessment (LCA) and life cycle costing (LCC) analysis, this study derives eco-efficiency indicators to inform decisions regarding CSP environmental and economic performances. The results of the LCA and LCC showed that the high-performance concrete (HPC) layer was the main hotspot of the CSPs in all scenarios. Moreover, the best scenario changed when different environmental impact categories were considered. Thus, using multiple environmental indicators is recommended to avoid problem-shifting. Considering the final cost, the CSP with cork is the most expensive panel to produce, with the other five options having very similar manufacturing prices. On average, raw material inputs, labour, and material delivery account for 62.9%, 18.1%, and 17.1% of the total costs, respectively. Regarding the eco-efficiency results, the most eco-efficient scenario changed with the environmental indicator used. Cork seems to be the best option when considering the carbon footprint of the panels, whereas when considering other environmental indicators, the recycled EPS scenario has the best eco-efficiency and the CSP with cork the worst. Full article

Effective sound absorption materials are essential for mitigating noise pollution in urban and industrial environments, which pose serious health risks to humans. This work develops a hierarchical natural fibre binderless composite based on porous luffa, modified with localised cellulose nanocrystals (CNCs), for application in acoustic panels. The impedance tube approach was employed to systematically evaluate sound absorption performance across a range of frequencies. Adding 3 wt.% and 7 wt.% CNCs to the porous luffa structure improved its sound absorption, especially in mid-to-high frequency areas. The binderless luffa panels with 3% CNC panels exhibited the most balanced performance across various thicknesses, while 7% CNC–luffa panels demonstrated excellent sound absorption averages across all frequency ranges, although increased rigidity and reflective tendencies were observed. The nano-modification successfully maintained the sound absorption coefficient with reduced panel thickness. This study establishes CNC-modified luffa composites as a sustainable and efficient alternative to conventional acoustic materials, leveraging renewable resources and lightweight characteristics. These findings highlight the potential of CNC-luffa composites for noise mitigation, paving the way for environmentally conscious acoustic solutions. Full article

To reduce the low-frequency noise inside automobiles, a lightweight plate-type locally resonant acoustic metamaterial (LRAM) is proposed. The design method for the low-frequency bending wave bandgap of the LRAM panel was derived. Prototype LRAM panels were fabricated and tested, and the effectiveness of the bandgap design was verified by measuring the vibration transmission characteristics of the steel panels with the installed LRAM. Based on the bandgap design method, the influence of geometric and material parameters on the bandgap of the LRAM panel was investigated. The LRAM panel was installed on the inner side of the tailgate of a traditional SUV, which effectively reduced the low-frequency noise (around 34 Hz) during acceleration and constant-speed driving, improving the subjective perception of the low-frequency noise from “very unsatisfactory” to “basically satisfactory”. Furthermore, the noise reduction performance of the LRAM panel was compared with that of traditional damping panels. It was found that, with a similar installation area and lighter weight than the traditional damping panels, the LRAM panel still achieved significantly better low-frequency noise reduction, exhibiting the advantages of lightweight, superior low-frequency performance, designable bandgap and shape, and high environmental reliability, which suggests its great potential for low-frequency noise reduction in vehicles. Full article

This paper presents the initial prototypes of solutions designed using plastic caps, seeking acoustic applications for both airborne sound insulation and the acoustic conditioning of rooms. Plastic caps are a waste product from the packaging sector and they constitute a major waste problem, given that, if they are not attached to the packaging, they get lost during the recycling cycle and end up in landfill. Finding an application for this waste that can provide acoustic improvements is a sustainable alternative. This paper shows the results of airborne sound insulation measurements obtained in a scaled transmission chamber and sound absorption measurements obtained in a scaled reverberation chamber for different combinations of single and double plastic caps and combinations with thin sheets of sustainable materials, such as jute weaving, textile waste, hemp felt and cork board. Tests have shown that obtaining sound reduction index values of up to 20 dB is possible with plastic cap configurations, or even up to 30 dB is possible at some frequencies with combinations of caps and certain eco-materials. With regard to the sound absorption coefficient tests, close to unity absorption values have been achieved with the appropriate configuration at frequencies that can also be selected. The results indicate that these panels can be eco-solutions for airborne sound insulation as lightweight elements, or they can be used for the conditioning of rooms, tailoring the sound absorption maximums to the desired frequencies. Full article

Acoustic metamaterials (AMs) composed of periodic artificial structures have extraordinary sound wave manipulation capabilities compared with traditional acoustic materials, and they have attracted widespread research attention. The sound insulation performance of thin-walled structures commonly used in engineering applications with restricted space, for example, vehicles’ body structures, and the latest studies on the sound insulation of thin-walled metamaterial structures, are comprehensively discussed in this paper. First, the definition and math law of sound insulation are introduced, alongside the primary methods of sound insulation testing of specimens. Secondly, the main sound insulation acoustic metamaterial structures are summarized and classified, including membrane-type, plate-type, and smart-material-type sound insulation metamaterials, boundaries, and temperature effects, as well as the sound insulation research on composite structures combined with metamaterial structures. Finally, the research status, challenges, and trends of sound insulation metamaterial structures are summarized. It was found that combining the advantages of metamaterial and various composite panel structures with optimization methods considering lightweight and proper wide frequency band single evaluator has the potential to improve the sound insulation performance of composite metamaterials in the full frequency range. Relative review results provide a comprehensive reference for the sound insulation metamaterial design and application. Full article

Broadband noise reduction over the low–mid frequency range in the building and transportation sectors requires compact lightweight sound absorbers of a typical subwavelength size. The use of multi-layered, closely spaced (micro-)perforated membranes or panels, if suitably optimized, contributes to these objectives. However, their elasticity or modal behaviors often impede the final acoustical performance of the partition. The objective of this study is to obtain insights into the vibrational effects induced by elastic limp membranes or panel volumetric modes on the optimized sound absorption properties of acoustic fishnets and functionally graded partitions (FGP). The cost-efficient global optimization of the partitions’ frequency-averaged dissipation is achieved using the simulated annealing optimization method, while vibrational effects are included through an impedance translation method. A critical coupling analysis reveals how the membranes or panel vibrations redistribute the locations of the Hole-Cavity resonances, as well as their cross-coupling with the panels’ first volumetric mode. It is found that elastic limp micro-perforated membranes broaden the pass-band of acoustic fishnets, while smoothing out the dissipation ripples over the FGP optimization bandwidth. Moreover, the resonance frequency of the first panels mode sets an upper limit to the broadband optimization of FGPs, up to which a high dissipation, high absorption, and low transmission can be achieved. Full article

Recently, there has been an attempt to implement increasingly significant prefabrication in building construction, since this method is considered to represent an opportunity to reduce impacts in the construction sector. For pitched roofs, there have been relevant developments, such as sandwich panels, asphalt shingles, lightweight roof panels, among others. However, in relation to flat roofs, the advances have been of little relevance and are mainly limited to the improvement of technical characteristics and prefabrication of the construction materials used. The main goal of this article is to demonstrate the possibility of developing new solutions for more sustainable flat roofs in the carbon footprint, and for this purpose a system was developed called ADAPTIVE—Advanced Production System for Sustainable and Productive Roofing Retrofit, which consists of developing a composite solution for the rehabilitation of flat roofs, completely prefabricated and with zero waste, with the aim of increasing energy behaviour, collecting and storing rainwater, and using the roof as a garden leisure space. To obtain the validation results, computerised theoretical modelling was conducted with theoretical assessment of the components and the set of components developed, which allowed us to conclude that the system meets the high hygrothermal, acoustic, and structural requirements. Full article

In an effort to reduce greenhouse gas emission, reduce the consumption of natural resources, and increase the sustainability of biocomposite foams, the present study focuses on the recycling of cork processing waste for the production of lightweight, non-structural, fireproof thermal and acoustic insulating panels. Egg white proteins (EWP) were used as a matrix model to introduce an open cell structure via a simple and energy-efficient microwave foaming process. Samples with different compositions (ratio of EWP and cork) and additives (eggshells and inorganic intumescent fillers) were prepared with the aim of correlating composition, cellular structures, flame resistance, and mechanical properties. Full article

Airborne and impact sound insulation of composite panels arranged in different configurations were investigated in this study. The use of Fiber Reinforced Polymers (FRPs) in the building industry is growing; however, poor acoustic performance is a critical issue for their general employment in residential buildings. The study aimed to investigate possible methods of improvement. The principal research question involved the development of a composite floor satisfying acoustic expectations in dwellings. The study was based on the results of laboratory measurements. The airborne sound insulation of single panels was too low to meet any requirements. The double structure improved the sound insulation radically at middle and high frequencies but the single number values were still not satisfactory. Finally, the panel equipped with the suspended ceiling and floating screed achieved adequate level of performance. Regarding impact sound insulation, the lightweight floor coverings were ineffective and they even enhanced sound transmission in the middle frequency range. Heavy floating screeds behaved much better but the improvement was too small to satisfy acoustic requirements in residential buildings. The composite floor with a dry floating screed and a suspended ceiling appeared satisfactory with respect to airborne and impact sound insulation; the single number values were R_w (C; C_tr) = 61 (−2; −7) dB, and L_n,w = 49 dB, respectively. The results and conclusions outline directions for further development of an effective floor structure. Full article

The applications of sensors in the aerospace industry are mostly concentrated in the middle and high frequencies, and low-frequency sensors often face the problems of low power and short working bandwidth. A lightweight, thin, high-power, low-frequency broadband transducer based on giant magnetostrictive material is designed. The design and optimization processes of the core components are introduced and analyzed emphatically. The finite element simulation results are validated by the PSV-100 laser vibration meter. Three basic configurations of the work panel are proposed, and the optimal configuration is determined by modal, acoustic, and vibration coupling analyses. Compared with the original configuration, it is found that the lowest resonant frequency of the optimal configuration is reduced by 24.6% and the highest resonant frequency within 2000 Hz is 1744.9 Hz, which is 54.2% higher than that of the original configuration. This greatly improves the vibration power and operating frequency range of the transducer. Then, the honeycomb structure is innovatively applied to the work panel, and it is verified that the honeycomb structure has a great effect on the vibration performance of the work panel. By optimizing the size of the honeycomb structure, it is determined that the honeycomb structure can improve the vibration power of the work panel to its maximum value when the distance between the half-opposite sides of the hexagon is H = 3.5 mm. It can reduce the resonant frequency of the work panel; the lowest resonant frequency is reduced by 12.8%. At the same time, the application of a honeycomb panel structure can reduce the weight of the transducer. Full article

Viscoelastic material can significantly reduce the vibration energy and radiated noise of a structure, so it is widely used in lightweight sandwich structures. The accurate and efficient determination of the frequency-dependent complex modulus of viscoelastic material is the basis for the correct analysis of the vibro-acoustic behavior of sandwich structures. Based on the behavior of a sandwich beam whose core is a viscoelastic layer, a combined theoretical and experimental study is proposed to characterize the properties of the viscoelastic layer constituting the core. In this method, the viscoelastic layer is bonded between two constraining layers. Then, a genetic algorithm is used to fit the analytical solution of the frequency¬ response function of the free–free constrained beam to the measured result, and then the frequency-dependent complex modulus is estimated for the viscoelastic layer. Moreover, by varying the length of the beams, it is possible to characterize the frequency-dependent complex modulus of the viscoelastic material over a wide frequency range. Finally, the characterized frequency-dependent complex modulus is imported into a finite element model to compute the complex natural frequencies of a sandwich beam, and a comparison of the simulated and measured results displays that the errors in the real parts are within 2.33% and the errors in the imaginary parts are within 3.31%. It is confirmed that the proposed method is feasible, accurate, and reliable. This provides essential technical support for improving the acoustic vibration characteristics of sandwich panels by introducing viscoelastic materials. Full article

To explore the lightweight structures with excellent vibration and acoustic properties, corrugated composite panels with different fiber reinforcements, i.e., carbon and glass fibers, were designed and fabricated using a modified vacuum-assisted resin infusion (VARI) process. The vibration and sound transmission loss (STL) of the corrugated composite panels were investigated via mode and sound insulation tests, respectively. Meanwhile, finite element models were proposed for the verification and in-depth parametric studies. For the vibration properties of the corrugated composite panels, the results indicated that the resin layer on the panel surface, despite the extremely low thickness, showed a significant effect on the low-order bend modes of the entire structure. In addition, the difference in the mode frequency between the panels consisting of different fiber types became more and more apparent with the increase of the frequency levels. For the sound insulation property of the panel, the initial frequency of the panel’s resonant sound transmission can be conveniently increased by increasing the layer thickness of surface resin, and the fraction of fiber reinforcements is the most predominant factor for the sound insulation property, which was significantly improved by increasing the thickness of the fiber cloth. This work can provide fundamental support for the comprehensive design of vibration and acoustics of the composite sandwiched panel. Full article