Thermal and viscoelastic characterization of Glass Fiber/Elium®150 laminates: adhesively bonded and infrared-welded joints

The growing demand for lightweight, recyclable, and high‑performance materials is driving the adoption of thermoplastic composites for structural applications. Among these, Elium®150, an acrylic‑based thermoplastic resin, offers low viscosity, room‑temperature curing, and thermoformability, making it a promising alternative to conventional thermosets. This study characterizes the viscoelastic behavior of Elium®150 and its glass fiber composites via Dynamic Mechanical Analysis (DMA) and relates these properties to welding and bonding performance. VARTM‑manufactured laminates were evaluated under oscillatory loading from 25 °C to 200 °C. Results show a glass transition temperature (Tg) of 104 °C by DSC. Above Tg, the storage modulus (E′) decreases sharply, showing loss of rigidity and the onset of viscoelastic behavior. These thermal mechanical trends explain the superior lap‑shear strength of adhesively bonded joints processed below Tg, where matrix stiffness is preserved, compared to infrared‑welded joints processed at 150-200 °C, where matrix softening and resin flow reduce interfacial adhesion. Overall, the study highlights DMA as a critical tool for defining processing windows and optimizing joining parameters in thermoplastic composites, supporting enhanced structural performance and recyclability.