Short- and long-term creep performance of timber-cardboard sandwich beams

Timber-Cardboard Sandwich (TCS) composites have emerged as sustainable, lightweight structural systems for rapid deployment in temporary housing, particularly in post-disaster contexts. While prior studies have addressed structural configuration and assembly methods, little is known about their long-term serviceability, particularly time-dependent deformation due to creep under natural environmental exposure. This study presents the first investigation into the short- and long-term creep performance of TCS beams under uncontrolled ambient weather conditions. Twelve full-scale TCS beams incorporating either recycled or scrap cardboard cores were subjected to sustained flexural loading over periods up to 9 months. Key variables included core material type, loading duration and exposure to hygrothermal conditions. Post-creep flexural testing was conducted to evaluate residual strength, stiffness and failure modes. Results show that beams with recycled cores exhibited more stable and consistent creep performance than those with scrap cores. Both variants met acceptable deflection criteria under short-term loading, supporting their viability for service conditions. While environmental exposure significantly influenced creep deformation, post-creep bending strength and failure modes remained consistent with control specimens, indicating no substantial degradation of structural performance. The findings establish a foundational dataset for evaluating the long-term behaviour of TCS composites and provide critical insights for their application in sustainable temporary construction.