Posljednjih je godina aditivna proizvodnja postala redoviti proces u raznim industrijama, a posljedično se pojavila sve veća potreba za procjenom ekoloških aspekata te tehnologije i s njom povezanih ...materijala. U ovom su radu ispitane i uspoređene procjene životnog vijeka konvencionalnog proizvoda „od kolijevke do groba” te 3D isprintane alternative izrađene od polilaktične kiseline (PLA) i PLA-drvnog materijala na temelju standarda ISO 14044:2006. Utjecaj svakog proizvoda na okoliš kvantificiran je unutar 18 kategorija. Cilj procjene životnog vijeka takvih proizvoda (LCA) bio je utvrditi može li uporaba 3D printanih PLA/PLA-drvnih proizvoda
biti održiva alternativa tradicionalnim metalnim proizvodima. U radu je prikazana studija slučaja u kojoj je provedena komparativna procjena životnog vijeka – LCA. Rezultati pokazuju da metalni dio proizveden primjenom konvencionalnih subtraktivnih procesa (glodanja, bušenja, zavarivanja itd.) ima veći utjecaj na okoliš nego 3D isprintane alternative izrađene od obnovljivih materijala. Međutim, u vezi s tim postoje i mnoga potpitanja koja se moraju adekvatno riješiti.
The Environmental concern and awareness around the globe have led to the development of sustainable bio composites which are derived from renewable resources. Biodegradable polymers and natural ...fibers derived from different renewable resources have played a vital role in the manufacture of bio composites. Poly lactic acid or polylactide (PLA) is one of the versatile aliphatic linear thermoplastic biodegradable polymers obtained from fully renewable sources such as wheat, corn, rice and sweet potato, and it has unique characteristics like renewable, sustainable, biocompatible and compostable. PLA has distinct advantages like low energy consumption and emission of low greenhouse gas during production and suitable for 3D printing applications. It also has some demerits such as low gas and water barrier properties, poor toughness, low glass transition temperature and is hydrophilic in nature, which limit its use in commercial applications. To overcome this, PLA is blended with various natural fibers in order to improve the thermal, water barrier, crystallization, mechanical, antimicrobial and degradability properties. Moreover, inclusion of natural fibers not only decreases the cost of PLA products but also helps in producing good competitive commercial products which are used in different industries. Hence, this review focuses on the synthesis and degradation of PLA, its applications in various sectors and manufacturing methods involved in PLA composites. Moreover, this review discusses about the different types of natural fibers and their influence on the unique properties of PLA based natural fiber reinforced composites. The overall aim of this paper is to provide a holistic idea about PLA based bio composites to academicians, industry personnel and researchers.
•Comprehensive review on the natural fibers and its PLA composites.•Various manufacturing process available for producing natural fiber/PLA composites.•Focused on properties of natural fiber reinforced PLA composites.•Importance of natural fiber/PLA composites for various applications.
A cleaner production pattern for high-performance continuous carbon fiber reinforced thermoplastic composites (CFRTPCs) has been proposed on the base of recycling and remanufacturing of 3D printed ...continuous carbon fiber reinforced (CFR) PLA composites. Continuous carbon fiber and PLA matrix was recycled in the form of PLA impregnated carbon fiber filament from 3D printed composite components and reused as the raw material for further 3D printing process. The original printing trajectory is reversely applied, allowing for a 100% recycling of the continuous fiber without any effect on the mechanical properties. Tensile performance of recycled carbon fiber filaments was evaluated, which was higher than that of originally printed composites. Remanufactured CFRTPCs specimens also exhibited a 25% higher bending strength than that of original ones, which experimentally demonstrated the first non-downgrade recycling process for CFRTPCs. A material recovery rate of 100% for continuous carbon fiber and 73% for PLA matrix were achieved for a better environmental impact. Energy consumption of 67.7 and 66 MJ/kg respectively for recycling and remanufacturing processes was detected and compared with conventional methods. The proposed cleaner production pattern offered a potential strategy for the low-cost industrial application of fully recyclable composites.
•The high-yield MNLCs were prepared by simple DES swelling and mechanical treatment.•The presence of lactic acid could lead to esterification modification of MNLCs.•The diameter of as-prepared MNLCs ...with varying lignin content were below 100 nm.•Lignin improve the interfacial compatibility of esterified MNLCs and PLA.•Addition of MNLCs enhanced flexural property and thermal stability of composites.
It is important to improve the interface compatibility between lignocelluloses (LCs) and biodegradable polylactic acid (PLA) for the preparation of strong composite materials. In the current study, esterified lignocellulose nanofibers (LCNFs) with high yield were prepared from LCs with different lignin contents (0.83–17.45 %) by swelling with a lactic acid/choline chloride deep eutectic solvent (LA/ChCl DES) at 100 ℃ for 3 h followed by mechanical colloid milling. Esterification occurred along with nanofibrillation of the LCs to obtain LCNFs having ester bonds with diameters mostly less than 100 nm. Lignin remained in the LCNFs with various contents. Uniform LCNF/PLA composites were prepared by a direct blending method. Lignin in the esterified LCNFs acted as an interface adhesive and played a key role in increasing the LCNFs interface compatibility with PLA, as well as strengthening the mechanical properties of the composites. The optimized flexural properties of the composites reached a maximum value of 204.5 MPa when 20 % LCNF (containing 10.92 % lignin) was added, which was 120.6 % higher than that of pure PLA. The prepared high-strength biodegradable composites have broad application prospects and great potential to replace non-degradable plastics.
Fused filament fabrication (FFF) is a promising additive manufacturing (AM) technology due to its ability to build thermoplastics parts with advantages in the design and optimization of models with ...complex geometries, great design flexibility, recyclability and low material waste. This technique has been extensively used for the manufacturing of conceptual prototypes rather than functional components due to the limited mechanical properties of pure thermoplastics parts. In order to improve the mechanical performance of 3D printed parts based on polymeric materials, reinforcements including nanoparticles, short or continuous fibers and other additives have been adopted. The addition of graphene nanoplatelets (GNPs) to plastic and polymers is currently under investigation as a promising method to improve their working conditions due to the good mechanical, electrical and thermal performance exhibited by graphene. Although research shows particularly promising improvement in thermal and electrical conductivities of graphene-based nanocomposites, the aim of this study is to evaluate the effect of graphene nanoplatelet reinforcement on the mechanical properties, dimensional accuracy and surface texture of 3D printed polylactic acid (PLA) structures manufactured by a desktop 3D printer. The effect of build orientation was also analyzed. Scanning Electron Microscope (SEM) images of failure samples were evaluated to determine the effects of process parameters on failure modes. It was observed that PLA-Graphene composite samples showed, in general terms, the best performance in terms of tensile and flexural stress, particularly in the case of upright orientation (about 1.5 and 1.7 times higher than PLA and PLA 3D850 samples, respectively). In addition, PLA-Graphene composite samples showed the highest interlaminar shear strength (about 1.2 times higher than PLA and PLA 3D850 samples). However, the addition of GNPs tended to reduce the impact strength of the PLA-Graphene composite samples (PLA and PLA 3D850 samples exhibited an impact strength about 1.2-1.3 times higher than PLA-Graphene composites). Furthermore, the addition of graphene nanoplatelets did not affect, in general terms, the dimensional accuracy of the PLA-Graphene composite specimens. In addition, PLA-Graphene composite samples showed, in overall terms, the best performance in terms of surface texture, particularly when parts were printed in flat and on-edge orientations. The promising results in the present study prove the feasibility of 3D printed PLA-graphene composites for potential use in different applications such as biomedical engineering.
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•An experimental study on vibration amplitude control in additive manufactured PLA and PLA composites (PLA-SCF, PLA-CCF) structures was conducted.•The natural frequencies and mode ...shapes of each structure were determined using the Polytec 3D laser vibrometer.•The optimal phase and voltage amplitude for the MFC actuator (M8507-P2) was tuned for each structure to achieve maximum amplitude damping.•The proposed experimental scheme can be applied to a wide range of composite materials.
In this study, Macro Fiber Composite (MFC) as actuator has been used for open-loop active vibration control (AVC) in additive manufactured structures made of polylactic acid (PLA) and PLA composites, such as PLA with short carbon fibers (PLA-SCF composite) and PLA with continuous carbon fibers (PLA-CCF composite), when subjected to forced vibrations. The laser vibrometer has been used to find the natural frequencies and bending mode shapes of each beam structure. The MFC patch (M8507-P2), used here as an actuator, is very sensitive to supplied voltages. Thus, it is very crucial to find out the optimum phase and amplitude of the input voltage. The optimal phase angle and voltage for each structure (PLA, PLA-SCF, PLA-CCF) are estimated by a domain search in an incremental manner. Once tuned with the optimal input voltage values, the proposed technique shows exceptional performance in vibration suppression. The results confirmed that this technique can be used in a wide range of composite materials.
•Fracture properties of MEX-printed PLA-based composites were experimentally investigated.•Layer growth and material type significantly influence the mechanical behavior of the samples.•PLA material ...gives the best strength properties, while CF-PLA stands out as the stiffest material.•Distinct failure mechanisms associated with each test type, material and layer growth were identified.
Due to the continuous development of material extrusion-additive manufacturing (MEX-AM) technology, the fracture behavior of polymeric parts, and especially of their associated composites, presents some shortcomings and also a challenge in the field. In this paper, the fracture properties of non-reinforced (NR) and reinforced Polylactic Acid (PLA) samples manufactured by MEX-AM process are investigated through tensile, flexural and fracture mechanics tests. The samples are reinforced with glass fibers (GF-PLA), carbon fibers (CF-PLA) and bronze particles (BP-PLA), and tested parallel (named FLAT for all tests) and normal (named UPRIGHT for tensile test, and ON-EDGE for flexural and fracture mechanics tests) to the layer growth (LG). It was found that regardless of the type of test, the LG and the material significantly influence the mechanical properties and collapse modes of the MEX-printed samples. It was obtained that the parallel-LG load is favorable for the tensile and flexural tests, and the normal-LG for the fracture mechanics tests. Overall, the NR-PLA material gives the best strength, strain and energy absorption properties, CF-PLA stands out as the stiffest material, while BP-PLA presents the minimum performances for almost all properties. The macroscopic analyzes of the fractured samples clearly highlight distinct failure mechanisms associated with each type of test, material and LG. From the analysis of the mechanical behavior and macrostructural images, CF-PLA was identified as the most brittle material, and NR-PLA the most ductile.
To overcome the brittleness of poly (lactic acid) (PLA), worm-like helical carbon nanotubes (HCNTs) were selected as a novel additive to PLA in this work due to their unique morphology. To enhance ...the interfacial interaction with PLA matrix, a silane-coupling agent (3-aminopropyltriethoxysilane, KH550) is chemically grafted onto the HCNTs. Interestingly, a remarkable improvement in the ductility of poly (lactic acid) (PLA) composites is achieved by adding a small amount of KH550-treated HCNTs. The elongation at break and the impact strength of HCNT-KH550/PLA composite are 205% and 30% higher than those of pure PLA, respectively. The high orientation of PLA molecular chains and crystals is responsible for the remarkable enhancement in the tensile ductility. This strategy is believed to offer more possibilities for optimizing the mechanical properties of PLA composites.
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