Abstract

Thermoplastic composite sandwich structures represent an innovative solution in structural engineering, offering a lightweight yet durable alternative for various applications such as construction, aerospace, and automotive. These structures typically consist of two outer layers of thermoplastic composite sheets (facesheets) encapsulating a core material such as lightweight foams or honeycomb structures. Sandwich panels with recycled foam core offer a remarkable synergy between advanced engineering and sustainable practices. This study primarily focuses on the diffusion behavior of 100% recycled Polyethylene Terephthalate (rPET) foam cores with four different densities (70, 80, 100, and 150 Kg/m3), Glass/ Polypropylene facesheets, and sandwich panels made of PET foam core with a density of 80 Kg/m3. All the specimens were immersed in water at a temperature of 40 degrees Celsius for prolonged durations. It is observed that the diffusion behavior of the PET foams and facesheet is governed by the classical Fick’s law. The experimental results indicated that the presence of facesheets in the sandwich structure acts as a moisture barrier and decreases the ingress of water into the composite sandwich panels by approximately 32%. The sandwich panels utilized in this investigation are manufactured using the double-belt lamination technique. To evaluate the influence of prolonged exposure to moisture on the mechanical characteristics of the structure, flatwise compression tests were conducted on the foam cores, revealing a significant decrease in compressive strength when exposed to moisture. Additionally, multiple flatwise tensile tests were conducted under both dry and wet conditions. The results revealed that wet samples demonstrate failure at the interface between the foam core and facesheet, while dry samples predominantly experience failure within the foam core. The study found that moisture exposure significantly reduced flatwise tensile strength, with bonding strength decreasing by approximately 55% after 730 hours of immersion. These findings highlight the significance of optimizing double-belt lamination parameters to have stronger and more uniform adhesion between facesheet and core under conditions of water exposure.