Browse Articles

Fused Filament Fabrication (FFF) is the most popular and widely used additive manufacturing process for printing polymer and composite products. Various production factors influenced the strength and stiffness of the part manufactured by 3D printing. A comprehensive experimental analysis was conducted in this study to examine the effect of FFF process parameters (infill density, pattern, and layer thickness) on mechanical properties and failure mechanism. The tensile, flexural, and impact test specimens were printed using ABS and carbon fibre reinforced ABS filaments in accordance with ASTM standards. Furthermore, dynamic properties are studied using dynamic mechanical analysis to estimate the loss factor and glass transition temperature under the impact of temperature and frequency in addition to static properties. Further, the results showed the addition of carbon fiber in ABS increases the mechanical properties. The failure modes are studied using optical microscopy and Scanning Electron Microscopy images and it has been visualized that due to improper layer deposition, poor bonding between the previous layer and low infill density creates a void in the specimen which results in poor mechanical properties. The Dynamic Mechanical Analysis showed that at higher frequency the molecular movement decreases which in turn stabilizes the composite behavior and reduces the loss factor.

Epoxy based hybrid composites are extremely wide used materials in the polymer engineering field and always have a demand for their versatile applications. Nano clay is yet another trending substance handled by many researchers due to their enhanced abrasion characteristics. This research was performed to investigate the effect of dispersing nanoclay into epoxy matrix and further coupled with pineapple fibers to fabricate a hybrid composite of excellent mechanical property. 4 layers of Pineapple fiber mats were compression moulded with epoxy nanoclay blend to obtain composite specimens of 4mm thickness. Nanoclay was added into epoxy resin at four different weight ratios (2%, 4%, 6%, and 8%) to form four different combinations of matrix materials into which pineapple fiber mats were reinforced individually at a constant weight ratio of 25%. The enhancement of mechanical and abrasion rate of the hybrid composites were matched with those of the neat Epoxy/Pineapple fiber composites that are currently being developed as alternatives for brake pads. Moisture absorption rate of the composites were analysed to ASTM D570 and Morphology was inspected using Field Emission Scanning Electron Microscope (FESEM). The results depicted optimum mechanical performance at 4 wt% nanoclay infused epoxy/pineapple fiber composite that had a tensile strength of 166.75 MPa, flexural strength of 801.15 MPa and impact strength of 148.76 kg/sq. m. The least abrasion rate was detected in the composite with 8 wt% nanoclay content, resulting in an abrasion rate of 0.1064 g/m.

To give full play to the advantages of perforated plate backed by porous materials in low and medium frequency noise absorption, this study uses Johnson-Champoux-Allard method with the finite element model to describe the acoustic characteristics of this composite structure. The effects of structural parameters of perforated plate and characteristic parameters of melamine foam on sound absorption coefficient were systematically investigated by numerical simulation. Practical composite were prepared to verify the reliability of the numerical simulation method. The simulation and experimental data in this study are helpful to promote the design of porous material-perforated plate structure for noise control in life.

Fiber reinforced polymer composites (FRPCs) are considered as core structure in Multi layered armour systems (MAS) to take advantage of maximum energy absorption, mobility and cost criteria design. In this article, based on the problem defining attribute’s optimal material selection in FRPCs determined by Multiple criteria decisions making (MCDM) approach for considered alternative materials from polymer resin, synthetic and natural fiber. Attribute’s weightage and alternatives priority rank were determined through Fussy-Analytical hierarchy process (F-AHP) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method. Obtained rank was compared with Preference selection index (PSI) an another MCDM method, for better computational conformity. Selected materials from MCDM approach, simulated for energy absorption ability and damage after impact were studied by considering Cowper-Symonds constitutive materials model using 3D macro shell analysis. Various impact velocities were considered from 3 to 50 m/s for rigid steel impactor directed towards the deformable plate. Parameter like Residual kinetic energy, Residual velocity, Energy absorption ratio after impact were studied numerically. Simulation results in terms of specific energy absorption were compared with the rank obtained in MCDM approach. Among the polymers considered epoxy, polyurethane and polyester found better choice. In fibers hemp and basalt found better materials choice for heterogenous FRPCs design in ballistic armour.

Improving the crystallization performance of poly(L-lactide) (PLLA) is necessary to adapt for various applications. In the current work, N, N`-bis(isonicotinic acid) 1, 4-naphthalenedicarboxylic acid dihydrazide (NAIAH) was synthesized to be firstly aimed at promoting the crystallization of PLLA, and the NAIAH-nucleated PLLA materials were prepared using PLLA as a matrix material and NAIAH as a nucleating agent, and the crystalline nucleation, melting behavior, thermal decomposition and mechanical properties of PLLA/NAIAH samples were investigated by the relevant testing instruments. The results from the non-isothermal melt-crystallization from the melt of 190ºC indicated that the NAIHA could significantly accelerate PLLA’s crystallization, and played an efficient heterogeneous nucleation in PLLA’s crystallization. The effect of different final melting temperatures on PLLA’s melt-crystallization behavior showed that a relatively low final melting temperature was beneficial for the crystallization of PLLA, and the 170ºC was the optimum final melting temperature in this study. An increase of cooling rate could weaken PLLA/NAIAH’s crystallization ability, but the NAIAH was still able to promote PLLA’s crystallization upon the fast cooling at 50ºC/min, showing a powerful crystallization accelerating effect of NAIAH. PLLA/NAIAH’s melting behaviors after different crystallization conditions were affected by heating rate and crystallization temperature, and the double melting peaks appeared in melting DSC curves were assigned to melting-recrystallization. Thermal decomposition processes in air showed that the NAIAH decreased PLLA’s thermal stability, but the interaction of PLLA with NAIAH had an inhibition for a drop in onset decomposition temperature. Additionally, the introduction of NAIAH dramatically reduced PLLA’s tensile modulus and elongation at break.

The scope of this paper is to determine the evolution of the dimensional value of the part and to study if there is gas and particle emission produced by the plant-based resin in the 3D printing process with mask stereolithography. For dimensional measurement, a solution with digital calliper is used. For the measurement of emission, two devices are used for indoor air quality. In the vertical direction of part body printed, it is possible to observe a descending linear type of direction with a minimum value at the highest element 3D printed. The data taken into account in this study are mathematically studied using the EXCEL regression equation for dimension. The gases emitted are measured with the booth devices in parallel for formaldehyde and volatile organic compound gases. For CO2 and particles, one of these devices is used. The air quality index was determined in relation to CO2 and, respectively, particle emitted. In the printing process, an increase in CO2 emission of 500 ppm can be observed in the initial phase of the process and a lower value in the body area. It is possible to consider that the quality air in 3D printing with plant-based clear resin is in the good to medium level from all types of emission. These data were put in ac-cordance with the level value offered by the manufacturer of the measuring devices. In this study the dimensional aspects are evaluated in parallel for two types of part bodies and the dimensional equations are the same after three mount times.

Nowadays, the use of agricultural wastes is a high impact research area, due the fact that this kind of materials can provide some interesting properties to a polymer matrix. Among these materials, the seed shell are materials with no industrial applications, so it is necessary to find a use in the aim to avoid the pollution. The Styrene-butadiene copolymer (SBS) is a wide used material due it thermoplastic behavior. In present work, the inclusion of two different species of seed shell particles: (jatropha curcas seed particles (JCSP) and pistachio (PSP)) into a Styrene-butadiene copolymer (SBS) and their effect on the thermal behavior of the resulting composites have been studied. The composites were prepared by melting fussion process at different concentrations ranging from 2 to 10 phr (parts per hounded of resin). The obtained composites were characterized by means of Thermogravimetric analysis (TGA), Dynamic Mechanical Analysis (DMA) and infrared Spectroscopy (FTIR).

The purpose of this study was to investigate how well a polytetrafluoroethylene graft interposition works in limited situations to avoid the use of prosthetic venous access grafts or installing a permanent dialysis catheter. A retrospective examination of clinical data from a single institution was undertaken on a case series from January 2018 to September 2019. We included in our study 28 polytetrafluoroethylene interpositions, done using a mean prosthetic length of 3.5 cm and diameters of 5 and 6 mm. The patency at 24 months was 71.43%, higher than the literature percentages. We found that these interventions were successful and long-lasting, and the technique we used has a minimal risk of thrombosis, infection, or bleeding.

Electromagnetic compatibility issues and those generated by these radiations are a major concern for electrical and electronic products, mainly in the fields of communications, information technology, transportation, security and medical services. The paper presents the way to obtain nanostructured paint/plastic/nanopowder paint systems with electromagnetic shielding properties, as well as their characterization by FTIR analysis, DSC and dielectric tests. These systems have Electro-magnetic Interference (EMI)/Electromagnetic Compatibility (EMC) and Electrostatic Discharge (ESD) applications in the manufacture of enclosures for various electronic devices and for the automotive industry. At the laboratory level, 4 non-additive experimental models (EM) coded M1-M4 and 16 additive experimental models coded M5-M20 were obtained. Revolutionary to these materials is the fact that inside they are insulating and, on the outside, they behave like a shield. The results obtained from the dielectric tests performed on the 16 additive systems showed that the samples with a maximum percentage (20 %) of metal nanopowders show the highest values of electrical conductivity. Of the two nanopowders used, that of Fe from samples M11, M12, M19 and M20 which induces the composite higher conductivities than Al nanopowders. The ATR/FTIR spectra of the two paint samples analyzed showed that they were almost identical, suggesting that the paints tested had the same basic chemical structure. DSC analysis showed that pigment paint (V2) has low thermal oxidation stability and lower decomposition temperatures than pigment-free paint (V1), therefore, V2 is less stable under usage conditions, under the influence of normal environmental factors (temperature, humidity, natural or artificial light, etc.) compared to V1.

In this paper some mechanical characteristics of a composite made from a hybrid resin and reinforced with corn cob powder are presented. The hybrid resin was made with a combination between the natural dammar resin combined with a small percentage of acrylic one. The synthetic resin was inserted in order to increase the polymerization process which was produced in about 24 h. In the fist part of the investigation, from the compression test, some mechanical characteristics are determined, such as: breaking strength or maximum force obtained at breaking. Then, by using the SEM analysis and EDS spectrometry, some samples with 50% dammar and 60% dammar were investigated. The last hybrid resin test was Shore D hardness and it was found out that the hardness decreases with the increase of dammar percentage. In the last part of the study, some composites by using the poposed hybrid resin reinforced with corn cob powder were manufactured. It has been found out that the proposed composite reinforced with corn cob powder has increased compression mechanical properties compared other composites that have the same reinforcement.