Structural design of Cross Laminated Timber (CLT) by advanced plate theories

Cross Laminated Timber enjoys great popularity in structural engineering and is one of the upcoming building materials in the timber construction sector. To support the favorable development of this high-performance wood product and to strengthen its competitiveness towards other mass building materials, the mechanical behavior and its implications for the structural design are addressed here. From the mechanical point of view CLT is a multilayer, highly anisotropic and shear compliant laminated composite. Owing to the analytical solutions for laminated composites and sandwich plates, the actual deformation behavior of CLT will be presented, and the accuracy and computational efficiency of common and advanced plate theories will be demonstrated. Comprehending the effects of laminate lay-up, anisotropic material behavior and cross-sectional warping will lead to an enhanced understanding of its mechanical behavior and will contribute to trustworthy deformation and stress prognoses as well as to reliable structural design

Development of high-performance strand boards: multiscale modeling of anisotropic elasticity

The interrelationships between microstructural characteristics and anisotropic elastic properties of strand-based engineered wood products are highly relevant in order to produce custom-designed strand products with tailored properties. A model providing a link between these characteristics and the resulting elastic behavior of the strand products is a very valuable tool to study these relationships. Here, the development, the experimental validation, and several applications of a multiscale model for strand products are presented. In a first homogenization step, the elastic properties of homogeneous strand boards are estimated by means of continuum micromechanics from strand shape, strand orientation, elastic properties of the used raw material, and mean board density. In a second homogenization step, the effective stiffness of multi-layer strand boards is determined by means of lamination theory, where the vertical density profile and different layer assemblies are taken into account. On the whole, this model enables to predict the macroscopic mechanical performance of strand-based panels from microscopic mechanical and morphological characteristics and, thus, constitutes a valuable tool for product development and optimization

Development of high-performance strand boards: engineering design and experimental investigations

Strand-based engineered wood products such as oriented strand boards enjoy great popularity in structural engineering and are widely used for a variety of applications. To strengthen their competitiveness and to enlarge their range of utilization particularly in the load-bearing sector, the mechanical properties of these products need to be improved. This motivated the research efforts to use large-area, slender veneer strands for the production of strand boards with increased stiffness and strength. Target-oriented development of these products requires comprehending the effects of the relevant (micro-)characteristics, such as wood quality, strand geometry, and strand orientation and compaction during the production process, as well as layer assembly and density profile, on the mechanical properties of the finished strand boards. Comprehensive test series, in which these effects on tension, bending and shear properties of the boards have been studied individually, are presented in this paper. The obtained results provided insight into the microstructural load-carrying mechanisms and, thus, yielded valuable knowledge for product optimization and further improvement of custom-designed strand-based engineered wood products

Report on value determinants and transferability (Deliverable 4.3)

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Report on valuation results (Deliverable 4.2)

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