Creep behavior of 3D core wood-strand sandwich panels

Abstract

A preliminary experimental evaluation of duration of load and creep effects of lightweight wood-strand sandwich panels (lwW-SSP) was conducted following ASTM D6815-09 to determine the equivalence to the duration of load and creep effects of visually graded lumber as specified in Practice D245. The modulus of rupture (MOR) of lwW-SSP was obtained using four-point bending tests to evaluate their creep and load behavior at three stress levels (15, 40 and 65% of MOR). Two different widths were considered to observe the effect of this parameter. lwW-SSP preformed well under long-term loads, as tertiary creep was not observed at all stress levels and the strain rate decreased over time. The panels met the criteria specified in the standard. None of the specimens failed, the creep rate decreased and the fractional deflection was <2. Accordingly, the duration of load factors of visually graded lumber is applicable to these panels. For the theoretical evaluation of solid wood behavior, viscoelastic models can also be applied to describe the creep behavior of lwW-SSP with wood-strand corrugated cores. An exponential viscoelastic model consisting of five elements accurately approximates the experimental creep behavior of three-dimensional (3D) core sandwich panel.