In this paper, the fatigue behavior of polylactic acid (PLA) material with bamboo filler printed by 3D additive printing using fused deposition modelling (FDM) technology at different infill densities and print nozzle diameters is investigated. The mechanical test results are supported by the findings from SEM image analysis. The fatigue behavior was tested at four consecutive 250 cycles at loads ranging from 5 to 20, 30, 40, and 50% based on the limits found in the static tensile test. The results of the static tensile and low-cycle fatigue tests confirmed significant effects of infill density of 60%, 80%, and 100% on the tensile strength of the tested specimens. In particular, the research results show a significant effect of infill density on the fatigue properties of the tested materials. The influence of cyclic tests resulted in the strengthening of the tested material, and at the same time, its viscoelastic behavior was manifested. SEM analysis of the fracture surface confirmed a good interaction between the PLA matrix and the bamboo-based filler using nozzle diameters of 0.4 and 0.6 mm and infill densities of 60%, 80%, and 100%. Low-cycle testing showed no reductions in the mechanical properties and fatigue lives of the 3D printed samples.

The paper deals with research focused on the use of fillers in the field of polymeric materials produced by additive technology SLA (stereolithography). The aim of the research is to evaluate 3D printing parameters, the mechanical properties (tensile strength, hardness), and the interaction of individual phases (polymer matrix and filler) in composite materials using SEM analysis. The tested fillers were cotton flakes and ground carbon fibres in different proportions. For the photosensitive resins, the use of cotton flakes as filler was found to have a positive effect on the mechanical properties not only under static but also under cyclic loading, which is a common cause of material failure in practice. The cyclic stress reference value was set at an amplitude of 5–50% of the maximum force required to break the pure resin in a static tensile test. A positive effect of fillers on the cyclic stress life of materials was demonstrated. The service life of pure resin was only 168 ± 29 cycles. The service life of materials with fillers increased to approximately 400 to 540 cycles for carbon fibre-based fillers and nearly 1000 cycles for cotton flake-based fillers, respectively. In this paper, new composite materials suitable for the use of SLA additive manufacturing techniques are presented. Research demonstrated the possibilities of adding cotton-based fillers in low-cost, commercially available resins. Furthermore, the importance of material research under cyclic loading was demonstrated.

Current research deals with thermoplastic polyamide (PA6)-based composites reinforced with basalt and Kevlar fabrics. Hybrid composites were developed by altering the stacking sequence of basalt and two kinds of Kevlar fabrics. Pure-basalt- and pure-Kevlar-based samples were also developed for comparison purposes. The developed samples were evaluated with respect to mechanical and thermomechanical properties. Mechanical tests, e.g., tensile, flexural, and impact strength, were conducted along with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) to ascertain the load-bearing and high-temperature stability of the hybrid composite samples vis-à-vis pure-basalt- and Kevlar-based samples. Scanning electron microscopy (SEM) was carried out to study the nature of fracture and failure of the composite samples. The pure-basalt-based PA6 thermoplastic composites exhibited the best mechanical performance. Hybridization with basalt proved to be beneficial for improving the mechanical performance of the composites using Kevlar fabrics. However, a proper stacking sequence and density of Kevlar fabric has to be selected. The thermogravimetric analysis showed minimal weight loss for basalt-based composites. Furthermore, the thermal stability of the composites using Kevlar fabric was improved by hybridization with basalt fabric. The thermomechanical characteristics of hybrid composites may be altered by changing the stacking order of the reinforcements. Differential scanning calorimetry further established that the hybrid composites with alternate layers of basalt and Kevlar can improve the heat flow rate and enable survivability at extreme temperatures. Such novel hybrid composites can be used for high-load-bearing and high-temperature applications, e.g., defense, aerospace, automotives, and energy applications.

This article focuses on the possibility of using biodegradable polymer-composite materials in additive manufacturing via fused deposition modelling (FDM) 3D printing. The main objective was to experimentally verify the technical feasibility of the repeated use of recycled PLA and PLA composites containing 10% natural coffee-ground (CG) filler in a print–degradation–recycling–print cycle. Special attention was paid to simulated ultraviolet radiation as a degradation factor affecting the materials’ mechanical properties. Pure PLA and PLA_CG were compared at four levels of degradation time and after subsequent recycling. The results show that the inclusion of coffee-ground filler slightly reduces the initial strength but enhances the 3D-printed material’s resistance to UV degradation and thus extends its functional service life. Unlike pure PLA, which loses its processability after 12 weeks, PLA_CG retains structural integrity and mechanical functionality. The research confirms the potential of recycled PLA composites with natural fillers for sustainable manufacturing and supports their use within a circular economy framework.

This paper investigates the development of fabric materials using several blends of inherently fire-resistant (FR) fibers and various knitted structures. The samples are evaluated with respect to their performance and comfort-related properties. Inherently fire-resistant fibers, e.g., Nomex, Protex, carbon and FR viscose, were used to develop different structures of knitted fabrics. Cross-miss, cross-relief, and vertical tubular structures were knitted by using optimum fiber blend proportions and combinations of stitches. Several important aspects of the fabric samples were investigated, e.g., their physical, mechanical and serviceability performance. Thermo-physiological and tactile/touch-related comfort properties were evaluated in addition to flame resistance performance. An analysis of mechanical performance indicated that the knitted structure has a significant influence on the tensile strength, bursting strength and pilling resistance. The cross-relief structure proved to be the strongest followed by the cross-miss and vertical tubular structures. The FR station suits made from 70:30 Protex/Nomex exhibited the best combination of tensile and bursting strength; therefore, this material is recommended for making a stable and durable station suit. Interestingly, it was also concluded from the experimental study that knitted samples with a cross-relief structure exhibit the best fire-resistance performance. Fiber blends of 70:30 Protex/Nomex and 70:30 Nomex/carbon were found to be optimum in terms of overall performance. The best flame resistance was achieved with Nomex:carbon fiber blends. These results were confirmed with vertical flammability tests, TGA, DTGA and cone calorimetry analysis. The optimization of blend composition as well as knitting structure/architecture is a crucial finding toward designing the best FR station suit in terms of mechanical, dimensional, thermal, thermo-physiological and flame resistance performance.

The current work is focused on numerical and experimental studies of woven fabric composites modified by hybridisation with biological (cellulosic) filler materials. The mechanical performance of the composites is characterized under tensile, bending and impact loads and the effect of hybridisation is observed with respect to pure and nonhybrid composites. Numerical models are developed using computational tools to predict mechanical performance under tensile loading. The computational prediction results are compared and validated with relevant experimental results. This research is aimed at understanding the mechanical performance of basalt–epoxy composites partially reinforced with micro-/nano-sized bio-fillers from cellulose and intended for various application areas. Different weave structures, e.g., plain, twill, matt, etc., were investigated with respect to the mechanical properties of the hybrid composites. The effects of hybridizing with cellulose particles and different weave patterns of the basalt fabric are studied. In general, the use of high-strength fibres such as basalt along with cellulosic fillers representing up to 3% of the total weight improves the mechanical performance of the hybrid structures. The thermomechanical performance of the hybrid composites improved significantly by using basalt fabric as well as by addition of 3% weight of cellulosic fillers. Results reveal the advantages of hybridisation and the inclusion of natural cellulosic fillers in the hybrid composite structures. The material developed is suitable for high-end applications in components for construction that demand advanced mechanical and thermomechanical performance. Furthermore, the inclusion of biodegradable fillers fulfills the objectives of sustainable and ecological construction materials.