This research examines the impact of self-polymerized polydopamine (PDA) coating on the mechanical properties and microstructural behavior of polylactic acid (PLA)/kenaf fiber (KF) composites in fused deposition modeling (FDM). A biodegradable FDM model of natural fiber-reinforced composite (NFRC) filaments, coated with dopamine and reinforced with 5 to 20 wt.% bast kenaf fibers, was developed for 3D printing applications. Tensile, compression, and flexural test specimens were 3D printed, and the influence of kenaf fiber content on their mechanical properties was assessed. A comprehensive characterization of the blended pellets and printed composite materials was performed, encompassing chemical, physical, and microscopic analyses. The results demonstrate that the self-polymerized polydopamine coating acted as a coupling agent, enhancing the interfacial adhesion between kenaf fibers and the PLA matrix and leading to improved mechanical properties. An increase in density and porosity was observed in the FDM specimens of the PLA–PDA–KF composites, proportional to their kenaf fiber content. The enhanced bonding between kenaf fiber particles and the PLA matrix contributed to an increase of up to 13.4% for tensile and 15.3% for flexural in the Young’s modulus of PLA–PDA–KF composites and an increase of up to 30% in compressive stress. The incorporation of polydopamine as a coupling agent in the FDM filament composite led to an improvement in tensile, compressive, and flexural stresses and strain at break, surpassing that of pure PLA, while the reinforcement provided by kenaf fibers was enhanced more by delayed crack growth, resulting in a higher strain at break. The self-polymerized polydopamine coatings exhibit remarkable mechanical properties, suggesting their potential as a sustainable material for diverse applications in FDM.

This paper details a finite element analysis of the behaviour of Si-Al geopolymer concrete beam reinforced steel bar under an impulsive load and hyper velocity speed up to 1 km/s created by an air blast explosion. The initial torsion stiffness and ultimate torsion strength of the beam increased with increasing compressive strength and decreasing stirrup ratio. The study involves building a finite element model to detail the stress distribution and compute the level of damage, displacement, and cracks development on the geopolymer concrete reinforcement beam. This was done in ABAQUS, where a computational model of the finite element was used to determine the elasticity, plasticity, concrete tension damages, concrete damage plasticity, and the viability of the Johnson-Cook Damage method on the Si-Al geopolymer concrete. The results from the numerical simulation show that an increase in the load magnitude at the midspan of the beam leads to a percentage increase in the ultimate damage of the reinforced geopolymer beams failing in shear plastic deformation. The correlation between the numerical and experimental blasting results confirmed that the damage pattern accurately predicts the response of the steel reinforcement Si-Al geopolymer concrete beams, concluded that decreasing the scaled distance from 0.298 kg/m3 to 0.149 kg/m3 increased the deformation percentage.

Polylactic acid (PLA), a biodegradable and biocompatible thermoplastic commonly utilized in 3D Printing filaments, undergoes changes in properties upon recycling. The objective was to elucidate the role of extrusion temperature and screw speed in modulating the quality of recycled PLA filament, as well as in controlling its dimensional attributes. Recycled PLA pellets (3D850D) were extruded using a single filament extruder machine within an extrusion temperature range of 145°C to 165°C and a screw speed varying from 2 rpm to 6 rpm. The extruded filaments were subsequently 3D printed into specimens adopting a 0° raster angle, line infill pattern, and a 100 percent infill density, then tested as per ASTM D638 mechanical standards. The study revealed a profound influence of extrusion parameters on the filament's ultimate tensile strength, yield strength, and diameter. Optimal extrusion conditions - 155°C and 5 rpm - resulted in maximum mechanical strengths, while the parameters yielding filament diameters closest to commercial standards were identified as 5 rpm and 155°C. These results under-score the possibility of optimizing the recycled PLA filament's properties through adept control of extrusion parameters. Consequently, this investigation supports the potential use of recycled PLA filament in the 3D printing industry as a sustainable and performance-efficient material, offering a tangible step towards environmentally friendly additive manufacturing practices.

As know Polylactic acid (PLA) is a popular and widely used thermoplastic material used in fused filament fabrication (FDM) due to its biodegradability and As know Polylactic acid (PLA) is a popular and widely used thermoplastic material used in fused filament fabrication (FDM) due to its biodegradability and