This project was conducted to quantify the performance of adhesives bond lines under shear load subject to elevated temperature. The results add to the understanding of the performance of polyurethane adhesive bond lines under elevated temperatures to address areas of fire safety concern under the current building codes. The project focused on studying the shear bond capacity of three wood species by using 3 types of adhesives with/without nanoclay treatment at 4 temperature levels. The three wood species are Douglas-Fir, Hemlock and SPF. The adhesives are polyurethane (PU), Phenol-Resorcinol-Formaldehyde (PRF) and Epoxy. PU and PRF specimens were also tested with nanoclay treatment and without nanoclay treatment. Epoxy specimens were tested without nanoclay treatment only. The temperature levels considered were room temperature (about 20 °C), 60°C, 80°C and 100°C. The results indicate that the influence of elevated temperature on the shear bond strength of PU and PRF adhesive was in the range of 20 to 30% regardless of nanoclay treatment. Regardless of species, PU or PRF, with or without nanoclay, the average shear strength for 100°C oven temperature treatment ranged from 6.0 to 7.5 MPa. In the case of SPF PU specimens treatment with nanoclay reduced the variability of shear strength significantly from 12% at room temperature to 5% after 100°C oven treatment. This is an important aspect that needs further verification for enhancement of performance. Finally the data in this study can be used to support modeling of timber component subjected to elevated temperature.
This thesis describes a series of 5 tests that were conducted at Carleton University Fire Research Laboratory to assess the contribution of Cross Laminated Timber (CLT) panels to the development, duration and intensity of room fires. The tests were conducted in rooms constructed from 105 mm thick 3-Ply CLT panels and measured 3.5m wide by 4.5 m long by 2.5 m high. Propane and furniture fires were used with the CLT panels in protected and unprotected configurations. Data was collected on Heat Release Rate (HRR), room temperatures and charring rates. In protected configurations, no noticeable contribution was observed from the CLT panels, however in unprotected configurations, the CLT panels contributed to the fire load and increased fire growth rates and energy release rates. When charring advanced to the interface between the CLT layers, the polyurethane based adhesive failed resulting in delamination. Delaminated members contributed to the fire load and exposed uncharred timber which increased the intensity and duration of the fire. When delamination occurred, the fire in unprotected rooms continued to burn at high intensity well after the combustible contents in the room were consumed by the fire. These fires were extinguished as they could have resulted in structural failure of the test rooms.
This paper presents a study on evaluating rolling shear (RS) strength properties of cross laminated timber (CLT) using torsional shear tests and bending tests. The CLT plates were manufactured with Spruce-Pine-Fir boards and glued with polyurethane adhesive. Two types of layups (3-layer and 5-layer) and two clamping pressures (0.1 MPa and 0.4 MPa) were studied. For the torsional shear tests, small shear block specimens were sampled from the CLT plates and the cross layers were processed to have an annular cross section. Strip specimens were simply sampled from the CLT plates for the bending tests. Based on the failure loads, RS strength properties were evaluated by torsional shear formula, composite beam formulae as well as detailed finite element models, respectively. It was found that the two different test methods yielded different average RS strength value for the same type of CLT specimens. The test results showed that the CLT specimens pressed with the higher clamping pressure had slightly higher average RS strength. The specimens with thinner cross layers also had higher RS strength than the specimens with thicker cross layers.
Effective preservative treatments for Canadian glulam products are needed to maintain markets for mass timber on building facades, access markets with significant termite hazards, and expand markets for wood bridges. For all three applications, borate-treatment of lamina before gluing would be preferred as it would lead to maximum preservative penetration. However, the need to plane after treatment and prior to gluing removes the best-treated part of the wood, and creates a disposal issue for treated planer shavings. The present research evaluates the block shear resistance of glulam prepared from untreated and borate-treated lamina with a polyurethane adhesive. Borate treatment was associated with a small but statistically significant loss in median shear strength when evaluated dry; however, there was no difference between the performance of untreated and borate-treated samples when exposed to the vacuum-pressure soak/dry or the boil-dry-freeze/dry procedures. Further work is needed to modify the composition or application of the resin to improve shear strength for glulam applications and ensure consistent performance. However, overall, these data indicate that samples prepared from borate-treated lamina perform similarly in terms of block shear resistance to those prepared from untreated lamina.
This paper addresses the quality of the interface- and edge-bonded joints in layers of cross-laminated timber (CLT) panels. The shear performance was studied to assess the suitability of two different adhesives, polyurethane (PUR) and phenol–resorcinol–formaldehyde (PRF), and to determine the optimum clamping pressure. Since there is no established testing procedure to determine the shear strength of the surface bonds between layers in a CLT panel, block shear tests of specimens in two different configurations were carried out, and further shear tests of edge-bonded specimen in two configurations were performed. Delamination tests were performed on samples which were subjected to accelerated aging to assess the durability of bonds in severe environmental conditions. Both tested adhesives produced boards with shear strength values within the edge-bonding requirements of prEN 16351 for all manufacturing pressures. While the PUR specimens had higher shear strength values, the PRF specimens demonstrated superior durability characteristics in the delamination tests. It seems that the test protocol introduced in this study for crosslam-bonded specimens, cut from a CLT panel, and placed in the shearing tool horizontally, accurately reflects the shearing strength of glue lines in CLT.
Cross-Laminated Timber (CLT) is a relatively new construction material that has not gained popularity in Hungary yet. Producing such building elements using Hungarian raw materials may help to establish this technique. The purpose of our research was to examine the possibility of producing CLT using Hungarian I-214 hybrid poplar. One three-layer panel was produced using Hungarian hybrid polar and polyurethane resin, and tested in bending. The MOR of the poplar CLT was found to be comparable to low-grade softwood CLT, but the MOE was lower than the requirement. Poplar raw material may be suitable for CLT production by selecting higher grade raw material using nondestructive testing, or as a secondary raw material mixed in with softwood.
Process parameters of cross-laminated timber (CLT) fabricated with Japanese larch were evaluated. The process parameters were designed by using an orthogonal test including pressure, glue consumption, and adhesive. Both delamination and block shear tests were conducted on CLT in accordance with GB/T 26899 (2011). The results showed that the optimum process parameters were A2B3C2 including pressure (1.2 MPa), glue consumption (200g/m2), and amount of sdhesive (one-component plyurethane). The weight loss and moisture absoption increased when the temperature increased, but the block shear strength decreased as the temperature was raised from 20C to 230C.
In this study , torque loading tests on small shear blocks were performed to evaluate the rolling shear strength of cross-laminated timber (CLT). The CLT plates in the tests were manufactured with Mountain Pine Beetle-afflicted lumber boards and glued with polyurethane adhesive; two types of layups (five-layer and three-layer) with a clamping pressure 0.4 MPa were studied. The small block specimens were sampled from full-size CLT plates and the cross layers were processed to have an annular cross section. These specimens were tested under torque loading until brittle shear failure occurred in the middle cross layers. Based on the test results, the brittle shear failure in the specimens was evaluated by detailed finite element models to confirm the observed failure mode was rolling shear. Furthermore, a Monte Carlo simulation procedure was performed to investigate the occurrence probability of different shear failure modes in the tests considering the randomness of the rolling shear strength and longitudinal shear strength properties in the wood material. The result also suggested the probability of rolling shear failure is very high, which gives more confident proof that the specimens failed dominantly in rolling shear. It was also found that the torque loading test method yielded different rolling shear strength values compared to the previous research from short-span beam bending tests; such a difference may mainly be due to the different stressed volumes of material under different testing methods, which can be further investigated using the size effect theory in the future.
Massive timber panels (MTPs) has shown a great potential in construction of tall buildings. Evaluation of the face-bond strength of MTPs is of an interest to use of this kind of products. This study was aimed at developing an appropriate test procedure for evaluating the adhesive bond strength of cross-laminated laminated strand lumber (LSL). Short span bending tests were conducted on two-layer asymmetric cross-laminated LSL specimens, which were adhesively bonded using two-component polyurethane (PUR) and polyvinyl acetate (PVAc). For comparison, block shear specimens were tested as well. It was found that the 2-layer asymmetric cross-laminated specimen assembly under the short span bending could be used to differentiate between good and poor bond quality.
Thirteen Southern pine cross-laminated timber panels were tested in the intermediate scale horizontal furnace at the Forest Products Laboratory to determine the effects different adhesives and ply configuration had on fire performance. Four different adhesives were tested: melamine formaldehyde (MF), phenol resorcinol formaldehyde (PRF), polyurethane reactive (PUR), and emulsion polymer isocyanate (EPI). There were two ply configurations: Long-Cross-Long (LCL) or Long-Long-Cross (LLC) where “long” indicates the wood was parallel to the longer edge of the panel. The MF and the PRF prevented delamination and associated problems while the LLC configuration resulted in uneven charring patterns.
