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Mass Plywood Panels
Mass Plywood Panels (MPP) are an engineered wood material consisting of layers of laminated vener lumber (LVL) that are glued together[Puettmann]. The majority of the LVL layers are oriented in one direction, called the long-ply direction, while the remaining layers are oriented in the cross-ply direction, perpendicular to adjacent long-ply layers. Recent research on MPPs provides initial estimates of mechanical properties and environmental impact of the material.

The groundwork of this discussion is based on two peer-reviewed research papers, Structural Performance Characterization of Mass Plywood Panels by Soti et al. and In-Plane Shear Properties of Mass Ply Panels in Long-Ply Direction by Ho et al, and an externally reviewed life cycle assessment (LCA) of MPP.

The research papers have the objective of developing material statistics for structural use of MPP in civil engineering applications. The latter research paper focuses specifically on the in-plane shear properties of the MPP.

The LCA performs a cradle-to-gate life-cycle assessment of MPP production that could assist with the development of an Environmental Product Declaration (EPD) for MPP.

Methods
In both research papers the researchers conducted several empirical tests to determine the mechanical properties of the MPP. In the study conducted by Soti et al. these were tension and compression tests, both parallel to the long- and cross-ply, and several bending tests. Furthermore, in the study conducted by Ho et al. two tests were conducted, a center-point bending Test and a large scale shear test to determine the MPP’s in-plane shear properties.

Findings
The study conducted by Soti et al. indicated that tensile strength is significantly higher in the long-ply direction than in the cross-ply direction. The presence of butt joints affected the tensile strength significantly. The strength of the MPP without a butt joint was two times higher than that of the MPP with one butt joint. Compressive strength is almost five times higher in the long-ply direction than in the cross-ply direction.

Furthermore, we see that the study has a clear focus on determining the flexural properties of the MPP. It found that the bending strength is slightly higher in the edgewise orientation than in the flatwise direction.

One should note that also the study by Soti et al. considered shear strength of the MPP, however as the shear strength for the full-scale panels considered in the study by Ho et al. are lower than those in the study by Soti et al. Thus, these are considered as the appropriate values for the MPP’s in-plane shear properties.

It is important to note that the values for the mechanical properties of the MPP should only be considered as initial indication of design values, as the number of tested specimens does not meet the minimum requirement of ASTM D5456.

Methods
The LCA considered the cradle-to-gate life cycle stages (A1-A3 stages), where the A1 stage  included cradle-to-gate analysis for the laminated veneer lumber (LVL) and resin production. As a whole, an analysis of the total emissions from the forestry operations (cradle) through the manufacturing of MPP ready to be shipped (gate) was conducted.

Findings
The LCA quantified many environmental impacts, including the global warming potential (GWP) of the MPPs A1-A3 life-cyle stages. The total GWP was found to be 259 kg CO2e, most of which came from the raw material supply (A1) stage.

Discussion
A clear strength of MPP is its high tensile, compressive and flexural bending strength in the long-ply direction. However, a weakness is the material parameters' high dependency on the existence of butt joints intra panel. Furthermore, one need to be aware when discussing MPP material parameters that full-scale panels has lower shear strengths than that of smaller test specimens.

Potential use as a sustainable material for building construction
MPP is being considered for sustainable construction due to its highly customizable product design sizes, light weight and low embodied carbon. In terms of use in building construction, the LCA mentioned that MPP is “Strong, with superior acoustic, fire, seismic, and thermal performance”.