Abstract
Problem definition and objectives: One of the most critical components of sandwich panels significantly influencing overall structural performance is the adhesion line between the outer layers and inner core. This adhesion line functions as a critical junction in mechanical load transfer, particularly tensile, compressive, and shear forces. Effective adhesion between different layers is a key factor ensuring sandwich structure stability and strength. Any deficiency in this adhesion interface can lead to serious issues such as layer delamination, mechanical cracking, and ultimately structural failure. To improve mechanical adhesion and enhance sandwich panel strength, surface processing techniques represent an effective methodology. Surface processing involves creating modifications on the outer layer surface, including generating grooves, patterns, and various designs that increase contact surface area and improve mechanical bonding between layers and the inner core. Consequently, this research investigated the impact of groove design and depth on the flexural performance of sandwich panels with medium-density fiberboard (MDF) skin layers.
Materials and Methods: In this study, medium-density fiberboard with a density of 690 kg/m³ and 3mm thickness (manufactured by Pak Chub Company) was utilized for panel skin, while expanded polystyrene foam with a density of 25 kg/m³ and 30mm thickness (produced by Arya Building Industry) served as the core material. Grooves with various designs (parallel and combined parallel-perpendicular) and different depths (0.5 and 4mm) were created on the lower surfaces of MDF layers using a CNC machine with controlled feed rate. Two adhesive types were employed: polyvinyl acetate (PVA) and two-component polyurethane (PU). Mechanical tests were conducted according to international standards, and results were analyzed using SPSS statistical software.
Results: Findings demonstrated that polyvinyl acetate adhesive exhibited superior performance in improving sandwich panel flexural properties. Changing the adhesive from polyurethane to polyvinyl acetate increased flexural resistance and elastic modulus by approximately 67% and 59%, respectively. Creating parallel and combined grooves enhanced flexural resistance by 29% and 15%, and elastic modulus by 39% and 21% compared to control samples. Additionally, increasing groove depth to 0.5 and 1mm resulted in flexural resistance increases of 36% and 17%, and elastic modulus improvements of 40% and 17%, respectively.
Conclusion: The research results effectively illustrated that groove pattern and depth combinations can uniformly distribute bending forces across the panel surface and prevent stress concentration at critical points. These findings highlight the significance of optimal groove design and appropriate adhesive selection in improving sandwich panel mechanical properties. The combination of PVA with combined grooves at 1mm depth can be considered an ideal solution for achieving high flexural strength panels in industrial and engineering applications. Furthermore, the results suggest that polyurethane adhesive utilization requires optimizing production process conditions and groove design to compensate for its inherent limitations.