A comprehensive experimental study on the development of high-performance sandwich panels using polyether sulfone (PESU) thermoplastic core and skin for aircraft interior applications

Thermoplastics are increasingly used in aircraft sandwich composites due to their recyclability; however, their effective application relies on achieving strong core-to-skin bonding. This work focuses on developing advanced sandwich panels using Polyethersulfone (PESU) thermoplastic to accomplish these goals. The approach involves combining a PESU core with skin layers composed of glass fiber reinforced PESU film (rGF/PESU skin). The materials are processed using lower side hot pressing at different temperatures (265 °C and 270 °C) and durations (45 and 60 s) to optimize their properties. A comprehensive set of chemical and morphological analyses is performed to assess the characteristics of the PESU core, rGF/PESU skin, and the resulting hot-pressed sandwich panels. XRD analyses show that the PESU core exhibits semi-crystalline behavior, which decreases with the addition of amorphous glass fibers and is further reduced under hot press processing due to foam structure disruption. Results demonstrate a significant improvement in thermal performance, with the thermal conductivity of the hot-pressed sandwich panel at 270 °C for 60 s increasing by approximately 145 % compared to the unmodified PESU core, indicating enhanced heat transfer capabilities. The highest flexural strength of 20.1 MPa is attained for three-point bending tests. Advanced imaging techniques, such as computed tomography (CT) scans and Scanning Electron Microscopy (SEM), and Optical Microscopy (OP), reveal three distinct phases within the structure: the PESU core, the rGF/PESU skin, and an interlayer phase that forms between them during hot pressing. Based on the OP analysis, the sandwich panel processed at 270 °C for 60 s exhibits the maximum interlayer transition phase thickness, reaching approximately 500 μm.