This project will create advanced computational tools to predict the strength of Structural Composite Lumber (SCL) ? an engineered wood product that is used extensively in light-frame construction. This predictive capability is critical to encouraging the design of new SCL products and allowing engineers to predict the strength of structures built of SCL. Project goals are to be accomplished through experiments and analytical and numerical modeling of two SCL materials, Parallel Strand Lumber and Laminated Veneer Lumber. The research will be conducted in four phases: (1) an experimental phase that will establish the strength of SCL under different loadings and will measure the internal structure of SCL through x-ray computer tomography; (2) computational modeling that incorporates explicit representations of the material structure and properties (3) the development of models for the behavior of SCL that can be used in structural design, and (4) making these material models available to practicing engineers who use commercial analysis programs.
The project will deliver long-needed tools for strength analysis of SCL - free to manufacturers and inventors to develop and use. Quick and inexpensive numerical evaluation of SCL will foster innovation in new wood product design with significant environmental and economic benefits. By making the predictive capability widely available, this project marks a first step in advancing the practice of wood design to a state comparable to that of steel and concrete. The work will lay a scientific foundation for investigations into other wood products such as glue laminated timber or plywood. Graduate level course modules on wood composite modeling are part of an integrated plan for research and learning.
This project has advanced understanding of the structure and properties of structural composite lumber products, Laminated Veneer Lumber (LVL) and Parallel Strand Lumber (PSL), that are widely used in structural engineering applications. LVL is composed of thin wood veneers glued together to form structural members that are superior in strength and stiffness to dimensional lumber. Similarly, PSL is manufactured from long thin strands of wood and can be produced in cross section dimensions of up to 18 inches. Because of the manufacturing process, in which structural members are built up of small pieces of wood, the material has a complicated structure that may include a large numbers of voids, and high degrees of variability in the source material properties. This project has therefore focused on characterizing the structure and properties of the material and forging links between the structure and properties. Particular attention has been paid to the propagation of randomness from the material structure to uncertainty in the material properties of PSL. The project outcomes can be divided into two categories, those with core intellectual merit and those with broader impact. Intellectual merit: The variation of the material stiffness and strength along the length of a structural member has been characterized experimentally and correlated to length scales in the structure of the material A size effect, whereby the strength of a member is inversely proportional to its size has been identified experimentally and the presence of such an effect has been linked to the void structure of the material New fabrication techniques have been proposed for making composite lumber from bamboo, and observations of the process-structure link for such materials have been made The void structure of PSL has been characterized probabilistically by experimental imaging of the material and probabilistic models have been built that can replicate such void structures. The torsional shear strength of 1.9 E Eastern Species LVL has been determined using a novel Universal-Type Test Machine set-up. A depth effect has been found statistically insignificant for torsional shear strength of commercial size LVL. Nonlinear computational simulation tools have been used to evaluate the quality of probabilistic models for the material void structure and to investigate the link between void structure and properties such as the size effect Broader impacts: Five journal publications have appeared with one other in preparation Numerous conference presentations and papers have been given to disseminate findings of the project. Four graduate students and three undergraduate students have been involved in the research supported by this project. Three of the seven students were women and the undergraduate researchers, both women, continued to graduate study in engineering.
