Properties of Wood/recycled Textile Composite Panels

This study evaluated the potential to use recycled cotton textiles as filler and possibly reinforcement in the core of oriented strandboard (OSB) panels. Nominal 11.1-mm-thick, 686 x 686-mm OSB/textile fiber composite panels (50% surface and 50% core layers) were fabricated. Recycled textile material (0, 5, 15, 25, and 50% of the total weight percentage in the panel) was blended with mixed hardwood core strands. For each combination of wood and textile material, 10 panels were produced for a total of 50 panels. Internal bond strength, static bending strength and stiffness, water absorption, thickness swell, and nail withdrawal strength properties were evaluated. The major finding of the study indicated that compared with controls (ie panels with 0% textile material), panels with 5% recycled textiles did not have a statistically significant difference in bending strength (modulus of rupture) and elasticity (modulus of elasticity) or nail withdrawal strength. Additionally, although the controls had the greatest average thickness swell, none of the groups tested showed a statistically significant difference (p = 0.064). The study indicated that there is potential for adding 5% recycled textiles to the core of OSB panels without significantly decreasing physical or mechanical properties

Influence of veneer roughness, lathe check, and annual ring characteristics on glue-bond performance of Douglas-fir plywood

Current lathe technology, smaller diameter logs, smaller core diameters, and the sale of higher grade veneer for use in engineered wood products are all factors contributing to plywood manufacturers using rougher veneer with different lathe check characteristics. When rough veneer is encountered, plywood manufacturers typically increase the adhesive spread rate in an attempt to achieve sufficient bonds between veneer surfaces. However, the effectiveness of this practice has not been clearly established. Little is known about how veneer roughness and lathe check characteristics interact to determine glue-bond quality or how lathe checks propagate under load while contributing to glue-bond failure. It was hypothesized that veneer roughness, lathe check, and annual ring characteristics interact to determine plywood glue-bond quality (i.e., wood failure percentage and load at failure). This study investigated the influence of veneer roughness, lathe check, and annual ring characteristics on Douglas-fir Pseudotsuga menziesii) plywood glue-bond performance. The study also investigated the differences in glue-bond quality when samples were tested in a dry and wet (PS 1 boil method) state and prepared such that lathe checks were pulled open or closed. To evaluate differences in test conditions on standard glue-bond samples, 120 blanks were cut from a Douglas-fir plywood panel and kerfed accordingly to produce 60 open and 60 closed specimens. Out of these specimens, half of the open samples and half of the closed samples were tested in a wet condition and the other half in a dry condition. On each sample, ultimate failure load and percent wood failure were recorded. A two-way analysis of variance (ANOVA) test performed on the load at failure results indicated that each factor (wet or dry conditioning and open or closed lathe checks) had a statistically significant influence in load at failure, as did the interactions of factors. Further analysis of the interactions using multiple range testing indicated a statistically significant difference between all four groups (dry open, dry closed, wet open, and wet closed). In terms of load at failure, dry closed exhibited the highest average load value, followed by dry open, wet closed, and wet open, respectively. A two-way ANOVA test indicated that each factor (i.e., wet or dry conditioning and open or closed lathe checks) did not have any statistically significant influence on percent wood failure nor did the interactions. In addition, multiple range testing indicated no statistically significant difference between all four groups. To investigate the influence of veneer characteristics on glue-bond quality, ninety veneer sheets, 12-inches by 12-inches, were separated into three visual roughness categories; smooth, intermediate and rough. Using a laser scatter/optical imaging system, fifteen mathematical roughness measurements were determined for five randomly selected 1-inch by 1-inch areas per sheet. The scanned veneers were placed as center plies in 3-piy, 3-layer plywood panels and pressed using typical mill lay-up procedures. Glue-bond specimens were prepared and tested in accordance to PS 1-95 to evaluate adhesive bonding of the 1-inch² Results from an ANOVA test showed that there was a statistically significant difference (p-value < 0.000 1) for average load at failure between visual roughness categories. Two sample t-tests indicated a statistically significant difference between average load at failure between smooth and intermediate (p-value < 0.000 1), smooth and rough (p-value <0.0001), and intermediate and rough (p-value = 0.043). Analysis of multiple range tests indicated a statistically significant difference for load at failure between smooth and intermediate, and smooth and rough, but found no significant difference between load at failure for intermediate and rough. Intermediate samples had the highest average load, followed by the rough and smooth, respectively, indicating that visual veneer roughness may not be a primary factor in determination of load at failure. Results from an ANOVA test showed that there was a significant statistical difference (p-value < 0.000 1) for average percent wood failure between visual roughness categories. Multiple range tests indicated a statistically significant difference between all three visual roughness groups for average percent wood failure. In addition, two sample t-tests showed a statistically significant difference for average percent wood failure between smooth and intermediate (p-value < 0.000 1), smooth and rough (p-value <0.0001), and intermediate and rough (p-value 0.01). Smooth samples had the highest average percent wood failure, followed by intermediate and rough, respectively. Using stepwise and all possible combination best-fit regression techniques, load at failure was found to decrease as lathe check frequency increased. In addition, load at failure was influenced by the number of growth rings per inch, percent latewood in the test area, earlywood/latewood ratio, distance of second lathe check to the saw kerf, and two distinct mathematical veneer roughness measures. Stepwise and best-fit regression analysis showed that percent wood failure was influenced mainly by mathematical veneer roughness measures, but was also affected by the number of growth rings per inch, percent latewood in the test area, and percent latewood at the tight-side glue-line. Specimen failure typically occurred by lathe checks propagating in a tangential-radial mode, radial-tangential mode or by glue-line failure attributed to peeling forces and/or severe surface roughness at the glue-line. In addition, both mathematical veneer roughness measures and veneer characteristics of latewood angle, percent latewood, lathe check frequency, growth rings per inch, number of latewood bands, average lathe check depth, and earlywood/latewood width ratio were found to influence elastic properties of glue-bond samples. These results suggest that plywood manufacturers can improve glue-bond quality by monitoring and adjusting for the key veneer characteristics of roughness, lathe check occurrence, and annual ring orientation that were found significant in the study. In particular, by reducing the frequency of lathe checks, higher loads at failure can be obtained and by reducing veneer roughness, percent wood failure can be increased

Non-destructive evaluation of veneer using optical scanning and ultrasonic stress wave analysis systems

Non-destructive commercial ultrasonic grading provides laminated veneer lumber (LVL) manufacturers a means for sorting veneer based on average ultrasonic propagation time (UPT) and/or average dynamic modulus of elasticity (MOEd). While this may provide reliable estimations of modulus of elasticity (MOE), little is known about the influence of veneer defects on strength properties of veneer and LVL. It was hypothesized that inclusion of veneer defect and growth ring pattern measures, obtained via optical scanning, would improve veneer and LVL static tensile MOE and strength (Ft) property predictions. Non-destructive and destructive testing on Douglas-fir (Pseudotsuga menziesii) veneer and LVL was performed to evaluate improvements in veneer and LVL tensile MOE and Ft property predictions. Various models based solely on density, optical, and ultrasonic system measures, as well as various combinations of systems measures, were developed for individual veneer and LVL property predictions. The integration of optical and ultrasonic measures (i.e., combined system model) best explained the variation in veneer static tensile MOE and Ft. The combined system model best predicted average LVL static tensile MOE. LVL static Ft was best predicted by using overall average veneer measures comprising the entire LVL material, rather than the average of individually predicted veneer Ft used in assembling the LVL. Specifically, the combined system model, which included various specific average defect, growth ring pattern, and MOEd measures comprising the LVL material, best explained the variation in LVL static Ft values (R2 = 0.65) as compared to all other models. Results from this study suggest improved veneer and LVL Ft predictions can be achieved by integrating the existing ultrasonic and optical systems already existing in many manufacturing facilities. Additionally, the optical model which included average defect, growth ring, and density measurements within the LVL material better explained the variation in LVL static Ft values (R2 = 0.58), as compared to the MOEd (R2 = 0.52) and UPT (R2 = 0.31) models. As a result, the developed optical system showed promise as a suitable veneer grading system. A need was identified for future research on optically grading full-size veneer sheets and manufacturing and testing full-size LVL billets

Evaluation of Laminated Veneer Lumber Tensile Strength Using Optical Scanning and Combined Optical-Ultrasonic Techniques

Nondestructive commercial ultrasonic grading provides laminated veneer lumber (LVL) manufacturers a means for sorting veneer based on average ultrasonic propagation time (UPT) and/or average dynamic modulus of elasticity (MOEd). However, little is known about the influence of veneer defects on strength properties of veneer and LVL. Including veneer defect and growth ring pattern measurements, obtained via optical scanning, was hypothesized to improve LVL static tensile strength (Ft) property predictions. Nondestructive and destructive testing of Douglas-fir (Pseudotsuga menziesii) veneer and LVL was performed to evaluate improvements in LVL Ft property predictions. Various models based solely on density, optical, ultrasonic, and combined system measurements were developed for LVL property predictions. LVL static Ft was best predicted (R2 1/4 0.65) with integrated optical and ultrasonic measurements (ie combined system model), which included average defect, growth ring pattern, and MOEd measurements from the LVL material. Results suggested improved LVL Ft predictions could be achieved by integrating ultrasonic and optical systems. Additionally, the optical model, which included average defect, growth ring, and density measurements, better explained the variation in LVL static Ft values (R2 = 0.58) compared with the MOEd (R2 = 0.51) and UPT (R2 = 0.31) models

Effect of Biochar Addition on Mechanical Properties, Thermal Stability, and Water Resistance of Hemp-Polylactic Acid (PLA) Composites

The present study investigated the effect of biochar (BC) addition on mechanical, thermal, and water resistance properties of PLA and hemp-PLA-based composites. BC was combined with variable concentration to PLA (5 wt%, 10 wt%, and 20 wt%) and hemp (30 wt%)-PLA (5 wt% and 10 wt%); then, composites were blended and injection molded. Samples were characterized by color measurements, tensile tests, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and water contact angle analysis. Experimental results showed that adding 5 wt% of BC enhanced the composite’s tensile modulus of elasticity and strength. Hence, the use of optimized loading of BC improved the mechanical strength of the composites. However, after BC addition, thermal stability slightly decreased compared with that of neat PLA due to the catalytic effect of BC particles. Moreover, the water-repelling ability decreased as BC content increased due to the specific hydrophilic characteristics of the BC used and its great porosity