This research investigates the development of sound-absorbing composites using areca nut shells fibers (ANS) bonded with polyvinyl alcohol glue, aiming to create an environmentally friendly and sustainable alternative to conventional synthetic materials. The research explores the effects of varying thicknesses (10, 20, and 30 mm) and fiber lengths (10, 20, and 30 mm) on the sound absorption performance of the composites. The sound absorption coefficient (SAC) was measured using the impedance tube method to determine the composites' effectiveness across different frequency ranges. The results indicate that the thickness of the composite significantly enhances sound absorption, particularly in the low-frequency range (1,500-2,500 Hz). Composites with a fiber length of 30 mm demonstrated the most effective sound absorption properties at 0.90 above 1,600 Hz (ANS-T30-L30). Additionally, blending fibers of different lengths led to SAC changed behavior. This study contributes to the growing body of knowledge on sustainable materials by utilizing agricultural waste to produce functional and eco-friendly sound-absorbing composites.

This study investigated the fire performance of cross-laminated timber (CLT) manufactured from the densified laminas of Paraserianthes falcataria, a fast-growing timber species. The aim of the study was to provide insights into the influence of short-duration densification on the thermal behavior of CLT during open burning, where compression ratios (40%, 50%, 60%) were applied. The outcomes indicated that higher compression ratios resulted in the formation of an insulating char layer that delayed the charring rate and enhanced the fire resistance of CLT. Notably, a 50% compression ratio was found to be optimal to achieve the desirable charring rate. The study further investigated the temperature-profile dynamics, emphasizing the impact of densification on the dynamic temperature changes in the CLT during a fire. The findings also highlighted the influence of the adhesive characteristics on the charring rate and temperature dynamics of the CLT, contributing to a deeper understanding of ways to produce CLT with desirable physicomechanical properties and excellent structural integrity.

Rattan is a vital organic biomaterial alongside wood and bamboo and is used in furniture, handicrafts, and construction. The industry necessitates a rapid, noninvasive assessment of rattan quality for optimal efficiency. This study aims to identify an optimal prediction model for estimating rattan density using near-infrared (NIR) spectroscopy. The rattan laboratory data included measurements of green and air-dry densities. A prediction model was constructed using NIR spectra obtained from the transverse and bark surfaces. Multivariate data analysis of cross-validation partial least squares regression was applied with many pretreatment choices for the spectra. This study yielded the most accurate prediction model for rattan density, with a coefficient of determination for cross-validation (R²CV) of 0.51. This was achieved by analyzing the air-dry density and spectra acquired on the bark with a pretreatment using the first derivative with 25 smoothing points. Distinct events were observed in the original NIR spectra of both surfaces. The bark spectra exhibited prominent peaks at 1,728 and 1,762 nm, followed by additional peaks at 2,308 and 2,348 nm, which were absent in the spectra of the transverse surface. The best density prediction model for rattan derived from the bark has considerable industrial applicability.

Studies on tropical wood formation using the pinning method in fast-growing species, such as red jabon [Anthocephalus macrophyllus (Roxb.) Havil], remain limited. In this study, we aimed to investigate wood formation over a certain period to determine the effect of climate (rainfall and temperature) on xylem formation. Wood formation in red jabon is understood by examining the anatomical structure of wood and new cell formation after pinning. The anatomical structure was observed from day 30 to 360 days after pinning, with sampling conducted at 30-day intervals. All samples show signs of pinning during all observation periods. The pinning canal remained open in the 30- and 60-day periods. The canal began to close in the 90- and 360-day sampling periods. Newly formed cells were first observed between 30 and 60 days at the sides of the canal, and their presence was visible until 360 days. New cells, including vessels, fiber, parenchyma, and ray cells were observed during the observation period. The width of the newly formed xylem was more than 2 cm after 360 days. In conclusion, pinning method is highly effective for monitoring the width of newly formed wood. Rainfall and temperature at the study location supported red jabon wood formation during observation.

One of the most effective ways to use wood-based products in terms of carbon neutrality is as structural materials for wooden buildings. This can enhance the carbon storage effect by extending its service life. To increase wood usage through building expansion, it is essential to implement supportive policies and conduct foundational research on the factors that ensure structural safety and predict building performance. Nail joints are among the most frequently used joints in wooden construction. In Korea, the shear performance of nail joints is evaluated by one- or two-sided lateral load resistance tests, according to KS F 2153. However, it is difficult to apply the standard to calculate the yield performance of the nail joint because the calculation method from the load-displacement results obtained through the test is not clearly presented. This study was conducted to propose a method for deriving the undefined yield properties during lateral resistance tests of timber structural joints in KS F 2153 by analyzing the error and difference between the predicted lateral yield load resistance, the average load-displacement curve obtained from actual experiments, and the bilinear curve derived from the yield properties. It was concluded that the method presented in EN 12512 was appropriate.

Wood plastic composites (WPC) were formed with wood waste and recycled polymer matrices to address the environmental concerns from the overuse of plastic materials and natural wood products. This study aimed to examine the mechanical and physical properties of WPC produced from two different types of native Indonesian wood before and after immersion in freshwater and seawater. The effects of employing various polymer matrix types of recycled and virgin polypropylene (r-PP and v-PP) produced through two distinct processes, compression moulding (CM) and injection moulding (IM), were examined. An extruder combined the WPC pellets, which were subsequently put into an IM process to fabricate tensile specimens. Statistics indicated that the IM specimens exhibited superior tensile strength and reduced water absorption compared to those produced with CM. The two-way analysis of variance indicated substantial variations in the tensile strength of the WPC based on the type of polymer matrix and wood waste utilised. In IM specimens, the teak wood-based WPC demonstrated superior tensile strength compared to the iron wood-based composites. Conversely, the v-PP matrix exhibited superior mechanical strength in CM specimens compared to r-PP. The tensile strength of v-PP/teakwood and v-PP/ironwood was 20.8 MPa and 21.8 MPa, respectively, while r-PP/teakwood and r-PP/ironwood achieved 17.0 MPa and 16.96 MPa. The types of polymer matrix and wood waste considerably influence the water absorption of the composites, particularly in CM specimens. The results underscore the significant effect of the processing method and the type of composite materials on the performance of WPC.

Several non-edible plants, including kepuh (Sterculia foetida), are used as feedstock for biodiesel production in Indonesia. This study aimed to evaluate site-specific variations in biodiesel yield, characteristics, and chemical composition from seeds of S. foetida from 25 locations on Java Island and select superior seed sources for renewable energy development based on the quality of the produced biodiesel. The biodiesel yields ranged from 23.6% to 26%. The biodiesel quality parameters, such as density (839.00 to 889.74 kg/m³), kinematic viscosity (2.58 to 4.53 cSt), acid value (0.039 to 0.502 mgKOH/g), saponification value (195.51 to 253.27), iodine number (59.71 to 110.0 mgI₂/100 g), cetane number (46.47 to 60.03), total glycerol (0.013% to 0.052%), and methyl ester content (99.28% to 99.79%), were within acceptable ranges. Gas chromatography-mass spectrometry analysis revealed that the five major fatty acid methyl esters in the biodiesel were sterculic acid (57.5% to 69.16%) as the dominant compound, followed by palmitic acid (11.95% to 18.81%), linoleic acid (4.47% to 9.52%), oleic acid (3.99% to 7.12%), and 10-octadecynoic acid (2.30% to 5.81%). Using Ward's hierarchical clustering method, biodiesel samples were grouped into three distinct clusters. Cluster II, particularly biodiesel from site K24 (Majalengka), demonstrated the most optimal results with a high cetane number, making it a promising planting material for biodiesel production.

Cellulose-chitosan-silk fibroin (CCF) composite films were fabricated using a 60% lithium bromide solution, and their physicochemical properties were analyzed. The CCF films exhibited a light yellowish-beige color with high transparency, and no distinct differences were observed in their cross-sectional structures. Throughout the dissolution and regeneration processes, cellulose was converted from cellulose I to cellulose II, with chitosan and silk fibroin (SF) influencing the crystalline structure of the film. High concentrations of cellulose and chitosan inhibited the formation of well-defined β-sheet structures, resulting in a composite with mixed silk I and II conformations and hydrogen bonding among the polymers. In the dry film, the tensile strength and elongation increased with increasing SF content; however, excessive SF led to a decrease in the elastic modulus. In the wet film, both tensile strength and elongation increased with increasing SF content, with CCF9 exhibiting the highest tensile strength owing to enhanced hydrogen bonding, partial β-sheet formation in SF, and physical entanglement between polymers. The swelling ratio of the CCF films increased with SF content, particularly in physiological fluids, owing to enhanced interactions between water molecules, ions, and the hydrophilic functional groups of SF. When the SF content exceeded 60%, partial β-sheet formation and strengthened hydrogen bonding significantly improved the swelling and mechanical properties. These results demonstrate the potential of CCF films in cosmetics, food packaging, and biomaterials, particularly for tissue engineering, wound dressings, and drug delivery systems in biomedical applications.