Abstract
This research article examines the application of various methods to determine the effective elastic properties of beech veneer-wood composites. Using laminate theory, the theoretically calculated effective values of the in-plane and out-of-plane modulus of elasticity as well as shear modulus are compared with the values determined from the natural frequencies of flexural, torsional and longitudinal vibrations of samples having different orientations and numbers of composite layers. The samples are also modelled using the finite element method, and their natural frequencies are calculated by the modal analysis. Research has shown that the laminate theory, which is well established and applied in the world of synthetic composites, can also be applied to beech plywood composites, where the theoretically calculated effective values can be up to 15% higher. Similarly, due to the higher calculated effective elastic properties, higher natural frequencies of flexural, torsional and longitudinal vibrations are also calculated by the finite element method.
Highlights
Plywood is a widespread and long used building material
The research showed the application of the experimental determination of the modulus of elasticity and shear modulus from the natural frequencies of flexural, longitudinal and torsional vibrations of plywood samples with various combinations of the orientation of the individual layers
It has been shown that the method is useful for slender and wide elements where it is possible to excite and accurately determine both flexural and torsional frequencies from which the modulus of elasticity and shear moduli can be calculated
Summary
Plywood is a widespread and long used building material. It is usually made from peeled veneer, where poor quality veneers can be used on the inside and higher quality veneers of various species are used on the visible outside. One of the first who experimentally analysed the relationship between the number of layers, fibre angle, modulus of elasticity and strength, was undoubtedly Norris [1,2]. He was later followed by many other researchers. Kallakas et al [3] investigated the influence of different layer structures and the use of various wood species on the mechanical properties of plywood, while Biadala et al [4] carried out similar research trying to develop water-resistant plywood with combinations of different wood species
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