Sandwich Composite Panels with Thermal and Acoustic Insulation Properties for Sustainable Buildings

Abstract

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.

1. Introduction

By 2028, the acoustic insulation market is projected to be valued at around USD 14,256.3 million. This growth is driven by several factors, such as awareness about increasing noise pollution [1,2], improvements in quality and living conditions [3], and regulations being implemented in each country [4]. The increase in population and the density of cities increasingly demand adequate indoor work, living, or customer service spaces with good distribution that also allow for an esthetic appearance and privacy [5]. In this context, urbanization and population growth have created a need for efficient and esthetically pleasing living and working solutions [6,7].

There is a growing demand for commercial construction, where the application of acoustic panels is required in walls, floors, ceilings, windows, wastewater pipes, machine rooms, and manufacturing. Among the materials that are used for the manufacture of acoustic panels are mineral wool, polymeric foams, and rock wool. In this context, the construction industry and building design require high-performance acoustic and thermal insulation materials that provide a healthy and comfortable environment at home and in workplaces, while allowing for reduced energy consumption and prioritizing sustainability [8,9,10]. Acoustic comfort includes reducing intrusive noise, such as impact sounds caused by footsteps, falling objects, and moving furniture, which are considered major sources of annoyance for residents in buildings [11]. However, effective insulation goes beyond noise reduction; it must also contribute to thermal efficiency by reducing heat loss. Additionally, to align with modern sustainability goals, potential insulation materials should have low environmental impacts (be eco-friendly) and be cost-effective to manufacture, ensuring a balance between performance, affordability, and ecological responsibility [12,13,14].

Recently, sandwich composite panel technology has been gaining more interest from the scientific community for construction applications. The interest in composite sandwich panels for construction and soundproofing applications is reflected in the number of publications that involve the words “(panel OR sandwich) AND composites AND (construction)” and “(panel OR sandwich) AND composites AND (acoustic OR soundproofing)” in the last 20 years (Figure 1).

The trend toward sustainable and energy-efficient buildings has driven significant research into the development of composite sandwich panels, focusing on material types, structural aspects, geometric configurations, and layer arrangements, tailored to the specific demands of each application [15].

Composite sandwich panels have been increasingly considered in structural applications due to their light weight, high strength, and ease of assembly. However, since transmission loss phenomena are usually governed by mass, their low weight renders composite sandwich panels inefficient in terms of acoustic performance, a subject that has received little attention in the past [16,17]. In this context, despite the growing interest in sandwich composite panels for building design and construction, there remains a lack of studies focusing on their acoustic performance. A review of the literature reveals no prior research on comparative analyses of production methods for a sandwich-type composite material. The aim of this study was the development of an acoustic panel designed to improve the sound conditioning of interior spaces. This technology is based on the use of commonly used textile materials that allowed for the creation of a sandwich-type composite material with acoustic absorption properties. Furthermore, a comparative analysis of three production methods for a sandwich-type composite material was carried out: manual, semi-automatic, and automatic. The objective was to determine the optimal method based on economic feasibility and industrial efficiency. Then, the acoustic performance, thermal properties, and morphological characteristics of the panel produced using the most efficient method were evaluated.

2. Methodology

Figure 2 presents a flowchart outlining the research methodology, which is structured into three main sequential stages: (i) preparation of the sandwich composite panel, including material selection, cutting, adhesive application, and layer assembly; (ii) the type of process, i.e., manual, semi-automatic, or automatic processes; and (iii) characterization tests to assess the morphological, acoustic, thermal, and flammability properties.

2.1. Materials

Sandwich composite panels are composed of non-woven textile layers (NWTs) and porous materials (PMs), adhered to an industrial adhesive. The NWT is protected by a microperforated polymeric cover (MPC) that gives the panel smooth and washable surface finishes.

Table 1. Technical specifications of the panel components.

Material	Technical Specifications
NWT	Weight	600 g/m2
	Composition
	Polyester fiber	55%
	Acrylic polymer	31.7%
	Polypropylene mesh	13.3%
PM	Density	27.1–32 kg/m3
	Tensile strength	83 kPa
	Tear resistance	0.220 N/cm
	Elongation at break	90%
	Material	Polyurethane (PU)
MPC	Weight	340 g/m2
	Temperature resistance	−30 °C a 70 °C
	Material base	Polyester (PES)
	Coating	Polyvinyl chloride (PVC)

presents the physical characteristics of these components. In the production of the panels, the thickness of the PM was 22 mm, and two thicknesses of NWTs were used: P150, with a thickness of 1.5 mm, and P200, with a thickness of 2.0 mm (Figure 3).

2.2. Preparation of the Sandwich-Type Composite Panel

The sandwich composite panel production process is carried out in several key stages, including material cutting, adhesive application, and pressing. These stages are essential to ensure the integrity and quality of the sandwich composite panel. Production is organized in three modes, manual, semi-automatic, and automatic, each with specific characteristics and procedures.

2.2.1. Manual Process

In this approach, operators perform all stages of production manually. The cutting of materials is carried out using tools such as scissors, knives, or guillotines prior to the application of the adhesive. The spraying of the adhesive is performed by hand, ensuring that all necessary surfaces are adequately covered. This method allows for direct control over the product quality, although it can be slower and more laborious.

2.2.2. Semi-Automatic Process

This method combines human intervention with machinery to improve efficiency. The cutting of the materials is carried out in a similar way to the manual process, but more advanced tools are used to make the work easier. The adhesive is applied using spray guns, allowing for more uniform and faster coverage. This process seeks to optimize the production time and reduce the manual workload, while maintaining a level of control over the product quality.

2.2.3. Automatic Process

In this process, mechanized systems are implemented to perform most of the operations. The cutting of the materials is carried out at the end of the process, once all the components are bonded, using cutting disks that are mounted on motors to manage the thickness of the materials. The application of the adhesive is carried out in an automated manner, which maximizes efficiency and reduces production time. This approach is ideal for high production volumes, although it requires a higher initial investment in machinery.

2.3. Characterization

The acoustic performance was evaluated experimentally in accordance with the ISO 10534-2 standard [18], testing nine samples, three from each material type, by placing each specimen in the impedance tube holder to ensure a complete fit without air leakage; measurements were taken over a frequency range of 400 to 5000 Hz under controlled ambient conditions of 22.7 °C and 59.9% relative humidity. The surfaces of the samples were analyzed using a JEOL JCM-6000 Plus field emission scanning electron microscope (FE-SEM, JEOL Ltd., Tokyo, Japan), operated at an acceleration voltage of 15 kV. The instrument was configured in high-vacuum (HV) mode and with standard pressure (PC-std.), using secondary electron detection (SED) to obtain detailed images of the material’s surface morphology. For the thermogravimetric analysis (TGA), thermal decomposition curves were recorded for approximately 5 mg samples in ceramic capsules using a heating rate of 10 °C min⁻¹, with an oxygen flow of 20 mL min⁻¹ across a temperature range of 35 to 996 °C. Finally, flammability was evaluated according to the EPA 1030 standards [19], ensuring a thorough and reliable characterization of the material properties.

3. Results and Discussion

3.1. Designs of Manufacturing Process

For the manual process, material rolls (1) are arranged vertically against the wall to optimize space and facilitate ergonomic adhesive application using a manual gun (3). After a brief solvent evaporation, the material is cut from the bottom to the top with fabric scissors (2) to the required size. The first adhesive-impregnated piece is placed adhesive-side-up on the first worktable level (4), and a second treated piece is placed adhesive-side-down on the second level (5). The operator then aligns both pieces for uniform adhesion before they pass through pressure rollers (6) that are operated by a crank, bonding them as they advance to the receiving table (7). This sequence is repeated until the final panel is complete, after which the production is stacked on a pallet (8). The process is illustrated in Figure 4.

For the semi-automatic process, material rolls (1) are arranged horizontally along the wall or on attached structures to optimize space and facilitate loading. A guide roller (2) directs each section to the next stage. Each section is extended on the second worktable level (5), cut to size with a guillotine (3), and then automatically impregnated with adhesive using a gun (6) on a CNC system (7). The first piece is placed on the worktable (4) with the adhesive side up, while the second piece is similarly processed and then flipped adhesive-side-down to align with the first piece using rollers or side guides. Both pieces are passed through motor-driven pressure rollers (8) onto the receiving table (9). This sequence is repeated until the final panel is assembled, after which the production is stacked on a pallet (10). The process is illustrated in Figure 5.

For the automatic process, material rolls (one per layer) are arranged horizontally in bases or attached structures to optimize space and ease roll loading. Each material line features a weight tension system (1), a cylinder with additional weights, and vertical guides to prevent undulations. A passage sensor (2) monitors the material supply and stops the system if a roll runs out, prompting operator replacement. The adhesive is applied simultaneously to all internal surfaces using 10 guns that are arranged in pairs on a rail system (3), which may be rodless pneumatic or CNC-driven. A designated ventilation area (4) facilitates solvent release for optimal bonding, while guide rollers (5) direct the materials to the pressure rollers (6) for bonding. A cutting system (7) moving along both the X and Y axes sizes the panel longitudinally without diagonal cuts, with the final length being confirmed by a step sensor (9) before the panel is stacked on a pallet (10). The process is detailed in Figure 6.

A comparison of the three production methods in terms of time, cost, and investment (robust and auxiliary machinery) is presented in Table S1 of the Supplementary Material.

3.2. Economic Viability

The acoustic insulation sector in the Colombian market was analyzed through the identification of key players, the segmentation of final consumers, and the evaluation of the competitiveness of the developed product. Using a quote for acoustic panels from a leading company in the sector in Colombia, the price of the sandwich composite panel developed in this work was compared with commercial products (

Table 2. Price comparison of acoustic panels in the sector.

Material	Price (USD/m2)
Sandwich composite panel (This work)	31.28
Black Teater (Fiberglass)	117.92
Aerocor (Fiberglass)	99.47
Phono Floor (Fiberglass)	110.73
Polyurethane Spray	64.20

). It was found that the composite offers an average saving of 72 USD/m² for the final consumer, being almost four times cheaper than the average market price.

Finally, of the three processes evaluated, the automatic process was selected as the optimal method for producing these panels. This choice is based on economic criteria and on the reduction in production time, since it allows for greater operational efficiency, uniformity in the quality of the final product, and scalability in manufacturing. Although it requires a higher initial investment in machinery, the automatic process is ideal for meeting large-scale market demands, optimizing resources, and minimizing manual intervention. In this context, the P200 sample, obtained by the automatic production method, was selected to evaluate its acoustic, thermal, and flammability performance. It should be noted that the evaluation of the physicochemical properties was carried out on this sample, since it was verified that the production method does not significantly influence them, thus ensuring that the results obtained are representative of the material itself.

3.3. Acoustic Performance

Figure 7 presents the sound absorption coefficient of the sandwich composite material, evaluated in different configurations (P200, P200 with a 14 cm air gap, P200 with retardant, and P200 with retardant and air gap). At low frequencies (<500 Hz), all materials exhibit low absorption coefficients, with values below 0.4, indicating higher sound reflection in this range. However, the addition of an air gap slightly improves absorption, demonstrating increased material efficiency in mitigating low-frequency sounds. From 1000 Hz onwards, the absorption behavior of all materials improves significantly, reaching coefficients close to 1.0 in the mid–high frequency range (2000–4000 Hz). This suggests that the material is highly efficient at absorbing high-frequency sounds, which is beneficial in environments where sound clarity and echo reduction are critical. The combination of retardant and an air gap offers marginal additional improvements, highlighting its utility in acoustically controlled spaces.

3.4. Microscopic Analyses (FE-SEM)

As illustrated in Figure 8, field emission scanning electron microscopy (FE-SEM) was used to analyze the surface microstructure of the sandwich composite material. Figure 8a–c show the components of the panel: MPC, NWT, and PM, respectively. In Figure 8b, a structure composed of fibers with an average diameter of 29.75 µm is observed, arranged in an interconnected manner and forming a significant porous network. This structural configuration plays a key role as a support in the composite material, contributing to its integrity and functionality. Additionally, the porosity quantification of the PM material was performed using ImageJ software (Version 1.54p), revealing that approximately 51.52% of the total area corresponds to porosity, with a standard deviation of σ = 3.92%. This indicates that over half of the evaluated surface consists of void or interconnected spaces (Figure 8c), which is ideal for acoustic applications, as these pores enable efficient absorption and dissipation of sound waves. Figure 8d shows the frontal view of the P200 sample, highlighting the MPC layer on the top as a denser and more compact structure, while the NWT layer on the bottom is characterized by an arrangement of interwoven fibers. The interaction between these components creates a structure that combines rigidity and porosity, making it ideal for acoustic applications by enabling both the absorption and dissipation of sound waves. Figure 8e presents the cross-sectional view of the P200 sample, where a well-defined integration of the different panel layers (MPC, NWT, and PM) is observed, indicating strong adhesion. The interfaces between the MPC, NWT, and PM components appear continuous, homogeneous, and compact, without major defects such as delamination or cracks, suggesting good compatibility among the materials. Finally, Figure 8f shows a magnified view of the interface between MPC and NWT within the sandwich composite material.

3.5. Inflammability

The results obtained from the flammability test, conducted according to the EPA 1030 standard, which assesses materials for ignition resistance and flame spread, demonstrate that the P200 sample achieved a negative result, indicating compliance with the flammability standard. The flame propagation rate was measured at 1.55 mm/s, remaining below the threshold defined by the methodology and confirming the panel’s flame-retardant properties.

3.6. Thermal Analysis

A TGA-DTG analysis was also carried out to investigate the thermal stability of the PMs and NWT materials of the P200 sample. The TGA-DTG curves of the PM shown in Figure 9 exhibit two-step weight loss on heating in the temperature range of 35 to 1000 °C under the air atmosphere. The first weight loss up in the temperature range between 200 °C and 308 °C is assigned to the degradation of the polyurethane polymer backbone [20,21]. In the subsequent phase, between 308 °C and 405 °C, the breakdown of any remaining stable polymeric structures occurred [22,23]. The DTG curve (blue) shows two prominent peaks at approximately 284.74 °C and 370.07 °C, corresponding to the maximum weight loss rates in the two primary stages of degradation. These peaks highlight the distinct phases of thermal decomposition within the material [24].

In contrast, the TGA-DTG curves of the NWT material shown in Figure 10 indicate that the first mass loss occurs around 208 °C, likely due to the removal of moisture and volatile compounds. The second major decomposition stage appears between 350 °C and 460 °C, with a mass loss of about 40%, suggesting the degradation of polyester fibers and organic polymers in the textile [25]. In the next phase, between 460 °C and 700 °C, there is an additional 20% loss, associated with the breakdown of the material’s more stable components.

3.7. Differential Scanning Calorimetry (DSC) Analysis

The DSC analysis of the PMs (blue) and NWTs (red) of the P200 sample is presented in Figure 11. Both materials exhibit similar behaviors in the 100–150 °C region, likely due to dehydration or a loss of surface moisture. In the 450–500 °C range, the NWT material shows a more pronounced peak compared to the PM, indicating a higher proportion of organic components being susceptible to exothermic degradation. Finally, between 550 and 600 °C, the NWT displays higher intensity, which could be associated with the composition of the non-woven textile, making it more prone to complete oxidation. Overall, both materials demonstrate comparable thermal stabilities, with major decomposition occurring above 550 °C. The combination of these materials could leverage the porosity of the MP and the thermal resistance of the NWT.

4. Conclusions

Sandwich composite panel presents an innovative, cost-effective solution for space division and soundproofing, addressing the growing demand for sustainable construction materials. To the best of our knowledge, this is the first comparative study of panel manufacturing processes in the acoustic insulation sector in Colombia. To date, most acoustic panels that are available in the domestic market are imported, which shows a significant opportunity for the development of materials with local technology. In this context, the creation of a panel with outstanding soundproofing properties and economic viability represents an innovative and attractive advance for the local industry. This study not only validates the technical and economic feasibility of the evaluated manufacturing processes but also lays the foundations for promoting competitiveness and technological self-sufficiency in the acoustic insulation sector in Colombia. This study demonstrated that the automatic production process is optimal for manufacturing sandwich composite panels due to its precision, efficiency, and ability to meet large-scale market demands. The P200 panel produced through this method exhibited excellent performance in key areas. The morphological analysis revealed a compact and homogeneous structure with strong interfacial adhesion, which is essential for durability and mechanical integrity. The acoustic evaluations highlighted the panel’s high absorption efficiency in the mid-to-high frequencies (2000–4000 Hz), making it suitable for environments requiring sound clarity and reduced echo. The TGA-DTG and DSC analyses further validated the thermal stability and decomposition behavior of the panel’s core and outer layers, providing insights into the material’s reliability under varied conditions. These results highlight the potential of composite panels being produced via automatic processes to meet the dual demands of sustainability and performance in modern building applications. Future work could explore further optimization of material formulations and production parameters to enhance the low-frequency acoustic absorption and improve the environmental footprint of the panels.