Degradation of Mechanical Properties of Pine Wood Under Symmetric Axial Cyclic Loading Parallel to Grain

Abstract

The mechanical properties of wood, respectively the elastic, plastic, and strength properties, depend on a large number of factors, due both to its structural and physical characteristics, as well as to the size, direction, nature, and speed of application of forces. Wood, generally considered to be a viscous-elastic material, has creep deformations over time under the effect of a constant load. In this study the behavior of pine wood samples was investigated due to its large utilization in different finished products, such as roof construction, furniture, outdoor applications, garden furniture, and toys. The paper aims to analyze the viscoelastic behavior of pine wood subjected to cyclically loading to traction-compression with different loads (1 kN; 1.5 kN; 2 kN), applied at different speeds (1 mm/min; 10 mm/min). It was observed that, at low speeds (1 mm/min) and low intensities of the applied force, it was possible to distinguish the three creep regions specific to wood: the primary area (primary flow), the secondary area, and finally the tertiary creep. As the force increases, the law of variation of the wood flow changes. The degradation of longitudinal elasticity modulus occurs with the increase of the number of cycles, so after 20 alternating symmetrical cycles of traction-compression of the pine wood samples, there is a decrease of its values by 35%.

Novel transparent lignin/epoxy resin nanocomposite film development with enhanced UV resistance performance

“…The storage modulus ( E ′) demonstrates the withstanding capability of the composites against applied loads in terms of elastic constant. In contrast, the E ′ denotes the energy dissipation for internal frictions of the composite materials, which also represents the viscous modulus 49 . On the other hand, the proportion between the storage and energy modulus is expressed by the tan δ .…”

“…In contrast, the E 0 denotes the energy dissipation for internal frictions of the composite materials, which also represents the viscous modulus. 49 On the other hand, the proportion between the storage and energy modulus is expressed by the tanδ. The DMA investigation was further used for determining the T g and crosslink density (ρ) of cured sample.…”

Monotonic and cyclic load of pine wood under uniaxial compression: experiments and modeling

“…Useful tools for further analysis of wood loading behavior are numerical and analytical models, the visualized results of which are load-displacement curves under monotonic and cyclic deformation [6,7,10,11,15]. In this paper, we used an analytical model belonging to a certain class of models [16].…”

“…The area of the largest theoretically possible load values is bounded by a curve called the envelope [10]. The construction of the shell and the analysis of the cycle performance with respect to the degradation of the mechanical properties of wood related to key issues in the analysis of the cyclic deformation behavior of this composite [6,10,11].…”

Monitoring the physical state of wood during multiple tensile load-unload cycles by the eigenvalue distribution of near infrared spectra

“…[1][2][3] In addition, cyclic loadings, assuming long-term use of wood, have been investigated to elucidate the lifetime of wood products, such as furniture and construction components. [4][5][6] On a larger timescale, these discussions have evolved to studies of archaeological timber. [7][8][9] Moreover, detailed examinations of cell wall components have been extended to the microscopic level.…”