Comparative study on measurement methods of compressive elastic modulus of wood along grain

Elastic modulus is an important mechanical parameter of wood. The most common low-cost elastic modulus measurement method is based on short column specimens, but this measurement method usually relies on strain gauges for measurement due to the small size and small deformation of the specimens, which is easily affected by factors such as strain gauge size, adhesive layer thickness, end face flatness, and defects, resulting in large measurement errors and high data dispersion. This paper proposes a method for measuring the compressive elastic modulus of wood along the grain based on long column specimens. The long column specimen method significantly increases the deformation by increasing the length of the specimen. The deformation can be directly measured by the displacement of the testing machine's indenter, avoiding errors introduced by strain gauges and significantly improving measurement accuracy and stability. To demonstrate the advantages and disadvantages of the two measurement methods, finite element (FE) models were established separately. The FE and experiment results show that the measurement dispersion error of the short column specimen method can reach 30%, while the measurement dispersion error of the long column specimen method is easily controlled within 10%. The experimental operation of long column specimen method is more convenient, and uncertain factors have less impact on the elastic modulus measurement results, which improves the reliability of the measurement results.