The aim of this study was to create a reinforced composite wood-based panel that would be leaned towards the environment Plywood was used as a core material and fiber-reinforced polymer was used as a reinforcement. Conventional resin for the fiber-reinforced polymer was substituted with polyvinyl acetate (PVAC), which has several advantages, such as a lower price, easier handling, and better degradability. The second chosen component, basalt fiber, is cost attractive and environmentally friendly. The combination of one and two layers of fabric with three fiber fractions and 4 mm thick plywood was investigated. The best results were achieved with two layers of fabric and the highest fiber fraction. The improvements of the ultimate bending load and bending stiffness of the plywood in the perpendicular direction were 305% and 325%, respectively. The ultimate load and stiffness of the parallel direction were improved by 31% and 35%, respectively. However, specimens always failed in the compressional zone. The highest reinforcing effect was found with the impact test: The energy required to fracture specimens increased by 4213% and 6150% for one and two layers of fabric, respectively. In conclusion, specimens exhibited high ductility due to the PVAC and basalt fiber. The amount of work and energy required to cause fractures was extensive.

© iForest -Biogeosciences and Forestry Introduction 1Proper management of forest ecosystems from a biological perspective is dependent on classification of the natural environment for the purposes of phytotechnology (e.g., thinning operations) and forestry management. Functional management goals may include timber production as well as other important functions of forests in the landscape, such as water sources for people, but also for control of climate, maintenance of biological diversity, recreation, etc. for which importance often increases with time. Such functions have been working automatically in the past, but serious environmental impacts on forests associated with anthropogenic activities (e.g., air pollution, soil acidification) and global climatic change became apparent at the end of the 20 th century.Therefore long-term experience of foresters should be supplemented with additional objective information, which may be used to help solve new problems. This includes application of modern electronics, computers and other technologies, as well as collection of necessary data in the field especially pertaining to ecophysiology. This review provides only a brief description of methods suitable for studies at the whole tree and stand levels (and even higher levels). The methods are applicable under open forest conditions using mobile instrumentation approaches that can be used almost everywhere. They were tested in more than 60 sites and in over 50 woody species in Europe, USA and Australia. We focused on measurement and evaluation of macrostructure and water flow, because the maximum energy flow in ecosystems goes through water and water is the most frequent natural limiting factor of tree growth and functional states of whole trees and stands (if not considering polar regions and tops of high mountains). Ecologically oriented scientific fields and practically oriented field activities in forestry, arboristics, horticulture, hydrology, remote sensing and forensic engineering use many traditional and modern methods.Annual and seasonal stem growth are probably the most frequently studied processes in forestry. Usually institutions for forest management (IFM) base their practices on this valuable data on a large scale (e.g., national), which provide crucial information about timber production and yield. A great body of literature is available on this topic. However, strategy for the management of forest ecosystems in Europe elaborated over several centuries is focused on classification of the natural environment and determining potential natural vegetation and oriented not only toward production but also on preserving other important functions of forests in the landscape. A detailed version of this approach was successfully applied for over 80 years. The eventual impact of anthropogenic activities and global climatic changes led to development of ecophysiological methods applied to evaluate the functional state and development of forest ecosystems.These methods were usually overlooked in the past because prev...

The standard formula for geometric stiffness matrix calculation, which is convenient for most engineering applications, is seen to be unsatisfactory for large strains because of poor accuracy, low convergence rate, and stability. For very large compressions, the tangent stiffness in the direction of the compression can even become negative, which can be regarded as physical nonsense. So in many cases rubber materials exposed to great compression cannot be analyzed, or the analysis could lead to very poor convergence. Problems with the standard geometric stiffness matrix can even occur with a small strain in the case of plastic yielding, which eventuates even greater practical problems. The authors demonstrate that amore precisional approach would not lead to such strange and theoretically unjustified results. An improved formula that would eliminate the disadvantages mentioned above and leads to higher convergence rate and more robust computations is suggested in this paper. The new formula can be derived from the principle of virtual work using a modified Green-Lagrange strain tensor, or from equilibrium conditions where in the choice of a specific strain measure is not needed for the geometric stiffness derivation (which can also be used for derivation of geometric stiffness of a rigid truss member). The new formula has been verified in practice with many calculations and implemented in the RFEM and SCIA Engineer programs. The advantages of the new formula in comparison with the standard formula are shown using several examples.

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