Graduate Thesis Or Dissertation
 

Effects of Temperature and Moisture Content on Bonding Performance of Mass Plywood Panels

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/h128nn05g

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  • As a new product patented by Freres Lumber Company in 2018, little information exists for manu-facturing procedures of mass plywood panels (MPP). At first glance, MPP may appear to be ply-wood, laminated veneer lumber (LVL), or similar to conventional cross-laminated timber (CLT). Often manufacturers, as well as users, of MPP must infer from experiences with plywood, LVL, and CLT in regard to manufacturing operating parameters and in-service performance. As is the situation with all adhesive bonded wood products, moisture content and temperature conditions should be considered during its manufacturing and end-use applications. The main objective of this thesis was the creation of an operational envelope regarding temperature and moisture con-tent of materials in the factory environment, with particular attention to melamine-formaldehyde adhesive bonds in MPP. Small-scale and full-scale test procedures were utilized on MPP speci-mens produced at 5 different surface temperatures (13 to 39 °C) and 3 different surface moisture contents (2 to 11%). Small­scale mechanical lap­shear tests were performed on dry specimens and specimens after accelerated weathering according to ASTM D3434­18. Degradation of the melamine­formaldehyde (MF) bondline performance was observed throughout accelerated weathering. The short-span bending and block-shear tests on full-scale MPP did not discover significant differences amongst different manufacturing conditions in the dry and wet conditions. Seventeen months of monitoring environmental conditions inside the MPP manufacturing facility showed daily average temperate range from 21 to 27 °C and relative humidity 20 to 59%. Calcu-lated equilibrium moisture content conditions varied from 4.6 to 10.6%. Measured wood substrate temperature ranged from 23 to 30 °C and MC ranged from 5 to 8%. Therefore, actual manufac-turing conditions were within the parameters of this study. High variation in the data restrains the author from identifying statistically significant effects of surface temperature or moisture content on the bond performance of MPP. However, the melamine-formaldehyde adhesive bond per-formed consistently under all test conditions, with failure of test specimens occurring most often in the wood substrate. While some differences in bond performance were observed between sur-face temperature and surface moisture contents, the differences were small. Therefore, the tem-perature range of 13 to 39 °C (at 7% MC) and moisture content range from 2 to 11% (at 26 °C) is a satisfactory operating envelope. In regard to bond strength after accelerated weathering, small-scale tests showed a similar trend as full-scale tests. Furthermore, small-scale adhesive bond strength retention after 20 cycles (total of 24 hours) of accelerated weathering, according to ASTM D3434, was roughly equivalent to short-span shear strength retention of full-scale MPP specimens after 6 weeks of constant water soaking. However, the failure mode of the short-span shear specimens was rolling shear of the adjacent crossband veneer and not shear failure of the MF bondline.
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  • Pending Publication
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  • 2021-06-11 to 2022-07-11

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