Evaluation of dynamic properties in ABS and PLA thermoplastics across frequency ranges.

Additively manufactured thermoplastics are increasingly employed in vibration-sensitive applications across the automotive, biomedical, and aerospace industries, where mechanical performance under dynamic loading is critical. This study provides a novel integration of Dynamic Mechanical Thermal Analysis (DMTA) with frequency response function (FRF) evaluation to capture the sub-glass-transition viscoelastic behaviour of 3D-printed ABS and PLA within 5-100 Hz range, a comparative approach not previously reported in the literature. The narrow 35-60 °C range was selected to focus on sub-Tg behaviour relevant to service conditions at which applications include vibration control in automotive panels, biomedical housings, and electronic enclosures. Unlike prior DMTA-only studies, this work combines FRF and DMTA to provide novel frequency-domain insights. The results reveal distinct thermomechanical responses: ABS demonstrates superior damping near its glass transition temperature due to its amorphous structure, whereas PLA exhibits stable stiffness and frequency-independent damping at lower temperatures, attributed to its semi-crystalline morphology. Key findings reveal that ABS exhibits a peak damping factor (tanδ ≈ 0.25) around 55 °C, while PLA maintains a higher storage modulus at lower temperatures (while PLA retains a storage modulus of ~ 1.2E + 08 Pa at 35 °C) but shows a sharp decline beyond 50 °C, limiting its use in thermally elevated conditions. These insights elucidate structure-property relationships in 3D-printed polymers and inform material selection for vibration-damping applications requiring thermal and frequency stability within sub-Tg operating regimes.