Wood and Fiber Science

The effects of wooden dowel species and the end distance of miniflex fasteners on the shear strength capacity of H-Type furniture joints

ABDURRAHMAN KARAMAN — 2024-03-19

Effects of the wooden dowel species and edge distances were studied relative to the shear force capacities of H-type furniture joints with minifix fastener under loadings. Melamine coated medium density fiberboard (MDF-Lam), minifix fasteners, and wooden dowels were used for specimen as used in the furniture industry. H-type joint specimens were tested in shear force. This compression tests were applied on 60 pieces of test samples prepared for this study based on the principles of ASTM D 1037-06 (2010). According to the results, the highest shear force capacities were obtained for beech dowel. According to edge distances from end distances, the highest shear force capacities were obtained with 72 mm distance from the edge. In manufacturing of wood composite based H type furniture, the highest shear force capacity values were obtained with the edge distance of 72 mm with oak dowel combination (1649 N), while the edge distance of 90 mm with beech dowel combination (1405 N) gave the lowest shear force capacity values. Furthermore, it was concluded that oak dowel as a substance and the distance 72 mm from the edge as distance could be recommended.

Keywords: Shear force capacity, H-ype joint, end distance, minifix fastener, wooden dowel

Evaluation of withdrawal strength of self-tapping screw inserted into cross-laminated timber with different anatomical aspects

Sarah Amira — 2024-04-02

The use of cross-laminated timber (CLT) technology is witnessing an upsurge in Japan because of its satisfactory performance under seismic conditions. The withdrawal strength (f_ax) of a single self-tapping screw (STS) inserted into the CLT was observed using a withdrawal test. The experimental results showed that f_ax of the partially threaded STS was higher than that of the fully threaded STS when inserted perpendicular to the grain. The empirical model used to predict f_ax provided in the European standard for the design of timber structures was evaluated by comparing the predicted values with the experimental results, which showed that the empirical model was only suitable for predicting the withdrawal strength of specimens with STSs inserted perpendicular to the grain. Therefore, a new probabilistic model was proposed for specimens inserted with STSs inserted parallel to the grain. The failure modes with respect to the orthotropic anatomy of wood materials were observed.

Keywords: withdrawal strength, probabilistic model, failure mode.

Engineered Flooring from Low-Density Plantation Hardwood: Evaluation of Long-Term In-Service Trials

Kuluni Piumika Millaniyage — 2024-03-19

The use of short-rotation hardwood plantation species has been perceived to be unsuitable for flooring until recently, due to the lower densities. This study assesses the performance of a low-density plantation hardwood species, Eucalyptus nitens in engineered flooring applications. The selection of a suitable timber species for flooring has conventionally been based on its market acceptance or value and on its hardness to ensure minimal indentations or damages. While both of these reasons have determined flooring species selection, this is becoming more difficult as popular species are less available due to increasing flooring demand and the diminishing supply of native timbers due to government regulations on harvesting and conservation. Typically, the species hardness is determined by static tests in the laboratory. Although these tests can compare species hardness, they might not reliably indicate an end product’s performance, especially with engineered flooring. Despite the global interest on timber flooring manufacturing, investigations on the assessment of alternative testing methods to static hardness, methods to replicate in-service behaviour, timber flooring quality determination and characterisation of timber properties for flooring applications are still scarce. In this study, in-service trials were conducted on solid E. nitens boards and engineered flooring prototypes with E. nitens top layers to better understand the products’ behaviour when exposed to moderate traffic with distinct temperature and relative humidity variations. Dynamic impact hardness tests using the falling ball indentation method adapted from ASTM D 2394 were conducted to assess the surface hardness of the tested prototypes. The results showed E. nitens engineered prototypes’ performance to be comparable with the existing market products used as controls. This demonstrates the potential to use plantation grown E. nitens in engineered flooring applications in domestic dwellings.

Evaluation of flame retardant impregnation in perforated Hinoki (Chamaecyparis obtusa) plywood

Eun-Suk Jang — 2024-03-19

Recently, perforated plywood has become widely used as an indoor sound absorber. Flame retardant treatment is essential for utilization of wood materials as indoor building materials. Among the various flame retardant treatment methods, we focused on pressure impregnation of water-soluble phosphate flame retardant (WPFR) on commercial Hinoki (Chamaecyparis obtusa) plywood. Perforation rates were 0.06, 0.1, 0.3, and 1.7%, and impregnation times were 30, 60, and 90 min. Then, we evaluated the impregnation effect according to the plywood perforation frequency and impregnation time using Pearson's coefficient correlation analysis and multi-linear regression analysis. The higher were the perforation frequency and impregnation time, the greater was the impregnation effect.

Comparison of genetic algorithm optimized and PLS regression density models for Acacia auriculiformis

Laurence R Schimleck — 2024-03-19

Partial least squares (PLS) regression models based on genetic algorithm (GA) representative near infrared (NIR) wavelengths for estimating wood properties provide improved calibration and prediction statistics compared to PLS models based on all available NIR wavelengths. However, the utilization of predicted data, obtained from full NIR wavelength and GA selected NIR wavelength models, in a practical application, has not been explored. Our application was to examine radial density variation in Acacia auriculiformis Cunn. Ex Benth. clones at a resolution of 10 mm. One hundred and forty A. auriculiformis samples representing seven clones and two radial positions (adjacent to pith and bark respectively) had NIR hyperspectral images (wavelength range 931-1718 nm) collected from their transverse surface. Two PLS density models (all NIR wavelengths and GA representative NIR wavelengths) were developed using 134 NIR spectra extracted from the images. The models were then used to predict density in 10 mm increments of 144 radial samples from the same clones. A PLS density model using only 15 representative NIR wavelengths provided a mean (0.506 g/cm³) which was not statistically significantly different to measured density (0.503 g/cm³), whereas the mean for PLS model using all wavelengths was 0.522 g/cm³. However, the PLS model with 15 representative NIR wavelengths had greater variation (standard deviation of 0.060) compared with measured data (0.052) and the full NIR wavelengths PLS model (0.047). Radial density variation was less than 0.09 g/cm³ for six of the seven clones examined.