Optimizing Surface Micro Grooving to Reduce the Checking and Cupping of Douglas Fir, Western Hemlock and White Spruce Decking Exposed to Natural Weathering

Abstract

Machining grooves into the surface of pine and fir (Abies spp.) deckboards reduces undesirable checking that develops when “profiled” boards are exposed to the weather. We aim to develop improved profiles for Douglas fir, western hemlock and white spruce decking to reduce their susceptibility to checking, and understand how profile geometry influences the stresses that cause checking. We varied the width and depth of grooves in profiled deckboards, exposed deckboards to the weather, and measured checking and cupping of boards. A numerical model examined the effect of groove depth on the moisture-induced stresses in profiled spruce boards. Profiling significantly reduced checking, but increased cupping of deckboards made from all three species. Western hemlock checked more than the other two species. Profiles with narrow grooves (rib profiles) were better at restricting checking than profiles with wider grooves. A rib profile with deeper grooves developed smaller stresses than a rib profile with shallower grooves, and boards with the former profile checked less than boards with shallower grooves. We conclude that checking of profiled Douglas fir, western hemlock and white spruce decking is significantly reduced by changing profile geometry, and our results suggest the best profiles to reduce checking of all three species.

Finite Element Modelling of the Effect of Adhesive Z-Connections on the Swelling of a Laminated Wood Composite

“…Moisture diffusion in wood is governed by Fick's second law, which can be expressed using Equation (1) [25,27]:…”

“…However, there is a similarity between the governing equations for moisture diffusion and ther-mal diffusion [34]. Thermal diffusion (transient heat conduction) can be described using Equation ( 2) [25][26][27].…”

“…On the other hand, a finite element analysis (FEA) and computer simulation of the effects of adhesive Z-connections on the hygroscopic swelling of composites would make it possible to easily change the aforementioned design parameters and model their effects on thickness swelling. FEA has been used to model the hygroscopic swelling of wood and polymeric materials [22][23][24][25][26][27]. Hygroscopic swelling of wood is a physical phenomenon that couples moisture absorption and moisture-induced strain energy.…”

Assessment of color and contact angle change of weathered wood in relation to wood species and different coating types

“…However, even for wood species with high weather resistance, when exposed outdoors without surface protection, the color changes rapidly, and the extractive compounds are leached. Heshmati et al (2018) manufactured a wooden deck using Douglas fir, western hemlock, and white spruce, all which are commercial species used in Canada, and studied the checking and cupping of the wooden deck according to outdoor exposure. Kim et al (2017) compared the durability of wooden decks by species with tropical hardwoods such as lpe (Tabebuia ipe Standle), malas (Homalium foetidum Bth), and massaranduba (Manilkara huberi (Ducke.)…”

“…Standl), which distributed as wooden deck materials, and Douglas fir (Pseudotsuga menziesii) and Japanese larch (Larix leptolepis), which are softwoods in Republic of Korea. Investigation on wood color change under exposure to environmental outdoor conditions was conducted for commercial wood species (Heshmati et al 2018;Kim et al 2017). Various stain options include transparent, semi-transparent, and opaque stains.…”