Clay is a type of problematic soils that can cause problems such as swelling, settlement and significant deformation due to the absorption of water and moisture. Today, the use of available and waste materials to prevent environmental pollution to stabilize problematic soils is considered that one of these materials is sawdust ash. In the present study, the possibility of improving the properties of clay using sawdust ash has been assessed. For this purpose, sawdust ash with weight percentages of 3, 6, 9 was mixed with clay and then cured for 1, 7 and 14 days. In order to evaluate the geotechnical behavior of stabilized soil, Atterberg limits, standard compoaction, uniaxial compressive strength, direct shear, California bearing ratio (CBR) and consolidation tests have been performed. The results of the present study show that the optimum amount of sawdust ash is equal to 3% during the curing time of 14 days. In improved soil, the placticity index is 49%, the compression index is reduced by 40% and the maximum dry intensity is up to 14%, the uniaxial compressive strength is 65% and the shear strength at the moment of failure is on average 53.6% compared to not the stabilization state increased.

This study focuses on the mechanical characterization and application of the various Multiple Attribute Decision Making (MADM) approaches for the selection of composites fabricated using two natural fibers, kenaf, and sawdust. Mechanical characterization involves testing the physical properties of these materials, such as tensile strength, flexural strength, and impact strength along with density and water absorption, to determine their mechanical behavior and suitability for various applications. The MADM approaches namely VIKOR and PSI are used to evaluate the mechanical properties of kenaf and sawdust reinforced composites for different applications based on multiple criteria or attributes. The study analyzes the trade-offs between different attributes to identify the optimal composite configuration for a given application. MADM technique offers a helpful framework for assessing the mechanical attributes of fiber-reinforced composites thereby determining their possible uses in a variety of sectors. However, it is essential to use the MADM approach in conjunction with other methods of material characterization and testing to ensure that the final decision is based on a comprehensive understanding of the material's properties and performance. The outcomes of this feasibility study will benefit researchers, manufacturers, and decision-makers involved in the selection and development of composite materials. It can assist in optimizing the material selection process, promoting sustainable and environmentally friendly choices, and enhancing the overall performance and cost-effectiveness of composite materials in various applications.

The rising cost of concrete production due to the global recession in world economy caused by the COVID-19 pandemic and the greenhouse gases emitted in the production of cement has necessitated the need for alternative materials for cement. In this study, bamboo strips and steel rebars were used as reinforcements in a ternary blended concrete to determine their strength properties. In alignment with standard requirements for testing, concrete specimens were tested at curing ages of 7, 14 and 28 days for compressive, splitting tensile and flexural strengths. The morphological and bond characteristics of the bamboo were determined through the Scanning Electron Microscopy (SEM) and Fourier Transform Infra-Red Spectroscopy (FTIR), respectively; while its tensile strength was determined and compared with that of steel reinforcement. These results showed that bamboo is ductile and has stretching vibrational spectrum. The combinations of quarry dust, river sand, Rice Husk Ash (RHA) and Guinea Corn Husk Ash (GCHA) yielded compressive and split tensile strengths of 20.4 N/mm2 and 2.18 N/mm2, respectively. Concrete with 50 % river sand and 50 % quarry dust performed better in flexure for both Bamboo Reinforced Concrete (BRC) and Steel Reinforced Concrete (SRC) at 28 days with strengths of 12.75 N/mm2 and 22.49 N/mm2, respectively. Therefore, bamboo, quarry dust, rice husk and guinea corn husk ash can be used for reinforced concrete production.

To study the tensile properties and impact strength in Wood Plastic Composites (WPC) polypropylene as a matrix and teada pine sawdust as reinforcement / filler is used. Ethylene / propylene / Diane / monomer (EPDM) as modified impact resistance with 10, 20 and 30 percent improved impact resistance and maleic anhydride grafted polypropylene (MAPP) at a rate of 3 percent as a fasteners to improve response and polymers and fillers were added to the composite. To evaluate the fracture surface of a structure scanning electron microscope (SEM) was used. The apply of 10% elastomer and 3% coupling agent cause to improved of tensile properties and the use of higher levels of elastomer (20 and 30%) has shown a decreasing trend in these properties. The results showed that PP matrix by adding sawdust to a significant reduction in impact strength of composite than pure PP is observed. An EPDM additive used in all contents of composites PP / sawdust has improved impact strength. Simultaneous use of EPDM and MAPP used a positive effect in tensile properties and impact strength. The apply of EPDM (30%) and 3% (MAPP) has demonstrated the highest level of impact strength. SEM images show that the use of EPDM and MAPP composites will improve the connection of interface.

Nowadays, optimization is becoming one of the most important techniques in engineering and industry to provide competing products in design and manufacturing. Therefore, it is a necessity to search for optimum designs with productibility. In aerospace industry reducing weight and improving reliability of the products are major concerns. As regards the gearbox is one of the most important parts in the helicopter propulsion system, these objects should be more considered. However, most of the existing designs consider only one object, hence, it is vital to implement optimization techniques to include different objectives to improve the existing designs and provide optimum products. In this paper, optimum design parameters including module and face width of gears for the main gearbox of Sikorsky ASH-3D helicopter have been determined (modified) using single and multi-objective mixed discrete- continuous optimization method to minimize weight of the gearbox, increase the safety factor and reduce the difference between safety factors of different gears. The results show that the weight of the gears can be reduced by 27.24% comparing with the existing gearbox. The results of the multiobjective optimization have also been presented as Pareto front diagram wich can be used by the manufacturers to satisfy the prefered requiments.

Effects of temperature, cellulose Nano fibers and Nano clay particles on mechanical, physical and morphological properties of biodegradable composites made of recycled thermoplastic starch biopolymer and mixed industrial sawdust are investigated. Cellulose Nano Fibers and Nano Clay particles were selected at 0, 3 and 5 weight percent and were blended with biodegradable composites using internal mixer and then samples prepared by injection molding. Mechanical properties including tensile modulus and strength, flexural modulus and strength were measured under the temperatures ranging from 23 º C to 80 º C. Impact test and water absorption and thickness swelling were also determined according to relative methods. Results showed that elevating the temperature drastically reduce mechanical properties. Nano Clay addition results in increased mechanical properties except for impact strength. Water absorption and thickness swelling are reduced. Addition of 5% Cellulose Nano Fibers improves mechanical and morphological properties more than 3%. Dynamic mechanical thermal analysis revealed that Nano composites samples with 5% Nano Clay and Cellulose Nano Fibers has higher storage modulus and glass transition temperatures in compare to pure composite samples. Nano particles can be successfully used to improve properties and performance except for fracture resistance.

Insulated paper board saw dust waste from paper board industries is used to develop composite materials for its application as door shutter. Physical and mechanical analysis of the developed composite is carried out and presented along with optimized process parameters. Developed composite is analysed for its density, porosity, water absorption, compressive strength, tensile strength and screw withdrawal properties. Observed behavior is explained and it is found that this waste can be successfully used for the development of composites. This has its potential application as door shutter in building industry, and can be used as a substitute to natural wood.