Foreword
The material in this course owes its origin to the series of 5 articles published for general readership in the ResearchGate site without critical feedback from the designated reviewers. Nevertheless, they had enjoyed a considerable number of reads worldwide and, most importantly present verifiable and experimentally supported new results for the OSB practitioners and engineering students. This author did not want to dwell on the information easily available from textbooks and specialized free-access web courses on the topic of solid body mechanics. Therefore, in order to follow present course one should be familiar with the basics of Mechanics of Materials, the discipline which is taught as a part of Mechanical Engineering studies, in particular a simple beam bending theory, and the understanding of Calculus I techniques.
Introduction
This brief course for students of wood construction engineering presents a phenomenological analysis of the mechanical properties of the most promising (in this author’s opinion) construction material of the present and foreseeable future. The Oriented Strand Board (OSB), introduced to the North American market about half a century ago, became by now nearly universally accepted as a major component of the individual home construction set, steadily increasing its share in the industrial, recreational and other construction segments, including multistory apartment and office buildings with virtually unlimited potential to replace concrete and bricks, the latter two being made via intense thermal energy consuming processes. The attractiveness of the OSB has been apparent as soon as it was realized that it could be made out of plantation grown wood species, which at presently used harvesting practices are virtually unsuitable in any other form and shape except the thin flakes or bulk particulate material as the ingredients for the production of the composite board. That product is approaching the mechanical strength properties of the solid wood components, and definitely beating the latter ones on the basis of cost and uniformity, thereby being a true engineering material with well-defined performance which can be used in architectural design practices. In other words, thanks to OSB the truly sustainable resource material, such as wood becomes a dominant material for environmentally friendly  dwelling construction in America, Europe, and no doubts, given enough time, everywhere else on Earth.
The OSB belongs to the family of composite materials which can be loosely defined as the homogeneous on a scale of the product and heterogeneous at the microscale being made from strong and often acicular particles, and more resilient at the manufacturing stage and normally homogeneous down to the molecular level, matrix. In the case of OSB, the thermoset glue matrix is quantitatively a very small component (being up to 5 % by weight of the composite), but its role remains the same – being responsible for forming links between the strength providing filler (wood flakes) and consolidation of the entire composite into macroscopic products, usually in the form of flat panels, intended for house construction. The usual objectives include maximizing the panel strength in the direction of longer side, while ensuring some minimum value of strength in perpendicular direction, i.e. parallel to  the short end of the panel. Like many other composite materials, the OSB is made by blending of the two main ingredients (wood and adhesive) and some functional additives, forming a preliminary shape (in this case - a mat of flakes and glue) and consolidating of the flat panel by applying heat and pressure. The overlapping wood flakes are bonded to each other in z direction, normal to panel plane, and the strength of this bond is determined by conducting pull-to-failure test, the  maximum stress  value measured being called internal bond (IB). The strength of the entire panel in the two flat dimensions mostly relies on the strength of the wood strands themselves. The latter could be stronger than the original wood due to the compression applied in the manufacturing step. Nevertheless, the panel strength in practice, rarely approaches the strength of the original solid wood due discontinuous structure on a smaller scale and cost-benefit considerations by the producers (this topic will be touched upon in subsequent chapters). We shall define OSB as an essentially flat construction panel made of a set or two sets (face and core types) of thin rectangular wood pieces with the larger dimension preferably oriented along the tree axis (by far the strongest) These pieces called “strands”, “wafers” , or even “flakes”, are bonded together by point-like glue particles/droplets, the bonding being subsequently effected by pressing together of the mat of strands while simultaneously providing heat necessary to activate the glue action between the individual strands. The bonding might be the result of mechanical hook-up and/or forming covalent bonds between the glue and the wood surface. The mat of strands prior to pressing is being formed over a moving belt usually in minimum 3 distinct layers, one on top of the other, the one in the middle being the “core”, the two outer ones called “faces”. Commonly the strands constituting the core, are smaller in size than those used for making the faces for the reasons, which are obvious because of the key target property to be achieved, namely bending strength along the longest principal axis.