Jute and banana fibers are biodegradable green fibers being increasingly used to replace synthetic fibers in fiber‐reinforced polymer composites. Integration of jute and banana distinct natural ...fibers has the potential to improve composite performance in secondary structural applications. In this study, an equal quantity of unidirectional jute and banana fibers with four different fiber orientations (0/0)3s, (0/45)3s, (0/90)3s, and (+45/−45)3s was embedded in phenol formaldehyde resin to make hybrid laminates using the hot press method. Tensile, flexural, impact, interlaminar shear strength (ILSS), and single‐end notch bend tests are performed in accordance with the ASTM standards to evaluate the effect of fiber orientation on natural fiber hybrid composites (NFHCs). Experimental results revealed that changing the fiber orientations (0/0)3s leads to a major impact on reducing the mechanical properties of NFHC laminates to the extent of 39%. Furthermore, the tensile strength, Young's modulus, impact and ILSSs, and fracture toughness were found to be 37% higher for the (0°/0°)3s composite. Additionally, tensile, flexural, and impact fractured specimens were examined by scanning electron microscopy to understand the fiber–matrix failure behavior due to inter‐ply orientation in NFHCs.
Core-shell structured particle contains Fe2O3 as core and amino phenol formaldehyde resin as shell (Fe2O3@APFS) has been synthesized. The results of SEM and TEM test indicate that the obtained ...Fe2O3@APFS particle is monodisperse and possesses uniform core-shell structure. Its diameter is about 100 nm and the thickness of APFS layer is about 30 nm. The effects of Fe2O3@APFS on the physicochemical properties of cured epoxy composites have been systematically investigated. The cured Fe2O3@APFS/epoxy composites demonstrated enhanced mechanical and thermal properties. A maximum tensile strength of 94.3 MPa was obtained when 4 wt% loading Fe2O3@APFS particles was added. The fracture toughness of epoxy composites with 5 wt% Fe2O3@APFS loading reaches a value of up to 1.71 MPa·m1/2, which is 80% higher than that of pure epoxy resin. The glass transition temperature (Tg) of cured Fe2O3@APFS/epoxy composites was increased by 13.9 °C than that of pure epoxy resin. TEM observation illustrates that Fe2O3@APFS was monodisperse in epoxy matrix. Monodispersion of Fe2O3@APFS, covalent bond linked interface between Fe2O3@APFS and epoxy matrix and synergistic effect of Fe2O3 and APFS were responsible for the enhanced mechanical and thermal properties of epoxy composites. This work provides a new insight into the combination of soft and rigid fillers used to modify polymer.
In the last decades, manufacturers attracted much attention to developing processes with competitivity, sustainability, and productivity. One of the most important developments was related to ...employing more efficient tools. CBN was developed to improve the performance of the abrasive materials by higher hardness, thermal conduction, and chemical stability. In this sense, not only abrasive grains’ properties are important for tool performance, but also bonds are essential for the consolidation of CBN abrasives in manufacturing industry. In order to contribute to findings about the performance of applied bonds in CBN grinding wheels, this work aims to compare CBN grinding wheels composed of vitrified bond and resinoid bond. The workpiece material was AISI D6 special steel which is widely used to manufacture stamping matrix, and this application requires parts with high geometrical and dimensional precision, also high-quality surface finish. For the results analysis and discussion, tangential grinding force and acoustic emission were monitored in order to analyze the process efficiency and surface roughness and
G
ratio was measured; besides scanning electron, confocal microscopy and optical microscopy were used for the analysis of the ground surface. The vitrified bond provided more efficient results in terms of surface roughness and
G
ratio in comparison with resinoid bond. However, acoustic emission and tangential grinding force were lower in grinding with CBN resinoid bond what indicated lower mechanical loads. Therefore, this paper presents relevant information to select the appropriate bond to CBN grinding wheel application.
In this study, thermal analysis, infrared spectroscopy (near and mid) in conjunction with low field NMR, have been used to characterize the crosslinking reaction involving phenol formaldehyde resin ...and a crosslinking agent, hexamethylenetetramine (HMTA) used as adhesive in organic-inorganic composites. The strong hydrogen bonds in the resin and the completely crystalline HMTA (Tm = 280°C) severely hamper the crosslinking process. Yet the addition of a small amount of plasticizer can induce an efficient (> 50% increase) crosslinking reaction as compared to the system without plasticizer. The infrared spectroscopy clarifies the dissolution process of the crystalline crosslinker and the specific interactions needed to achieve miscibility of the reactants. The thermal analysis enabled us to follow the reaction as a function of temperature. The low field NMR with the T1 inverse recovery technique allowed us to monitor the crosslinking process directly. For the first time, it is now possible to identify the functionality of the plasticizer and correlate the degree of crosslinking achieved in order to assess the macroscopic cohesive strength needed for high performance adhesives.
Plywood is an important engineered wood product manufactured by orthotropically bonding veneers together. Bonding strength plays a crucial role in the performance of plywood. However the interaction ...between bonding strength and strain distribution has not been fully understood yet. Therefore, in this study, relationships between bonding strength and shear strain distribution in six types of plywood were illustrated using digital image correlation (DIC) approach as performing the lap-shear tests. Both urea formaldehyde (UF) and phenol formaldehyde (PF) resin were used as the bonding adhesive. Fluorescence microscopy was adopted to visualize the resin distribution within the micro-structure of the specimens. Results showed that the failure load (FL) of plywood positively and negatively correlated to the quantity of UF and PF resin, respectively. Increased quantity of UF resin facilitated to form a consecutive bond line, while large quantity of PF resin made the specimens brittle. Large ratio between load and strain, and homogenous strain distribution contribute to the high FL. Strain starts in regions adjacent to the notches and transfers to the remaining areas in the region of interest (ROI) by smoothly crossing the bond line. The properties of wood veneers play an important role in the bonding strength as strain is more likely to be started from the veneers. Findings of this study can contribute to the improvement of design strategies aiming the enhancement of the mechanical properties of plywood with small amount of resin.
Phenol formaldehyde resin (PFR) based composites with multiwalled carbon nanotube (MWCNT) additives (2 and 5 wt.%) were prepared and their electromagnetic (EM) properties were investigated in Ka‐band ...frequency range (26–37 GHz). It was demonstrated that the combination of such materials in a double‐layered structure allows achievement of the significant attenuation of EM radiation. The electromagnetic response of considered double‐layered system was modeled by solving the electric field integral equation, utilizing the Green's function technique. Absorption up to 96% in the 26–37 GHz frequency band was both predicted and experimentally observed.
The microwave absorbing properties of a double‐layer system based on phenol formaldehyde resin (PFR) and multiwalled carbon nanotube (MWCNT) composite materials were modelled and analysed in Ka‐band (26–37 GHz) based on the electric field integral equation, utilizing the Green's function technique. Absorption up to 88–96% within the whole 26–37 GHz range was predicted and experimentally observed in considered sandwich structures.
Lignin is the most abundant aromatic biopolymer and is the sustainable feedstock most likely to supplant petroleum-derived aromatics and downstream products. Rich in functional groups, lignin is ...largely peerless in its potential for chemical modification towards attaining target properties. Lignin’s crosslinked network structure can be exploited in composites to endow them with remarkable strength, as exemplified in timber and other structural elements of plants. Yet lignin may also be depolymerized, modified, or blended with other polymers. This review focuses on substituting petrochemicals with lignin derivatives, with a particular focus on applications more significant in terms of potential commercialization volume, including polyurethane, phenol-formaldehyde resins, lignin-based carbon fibers, and emergent melt-processable waste-derived materials. This review will illuminate advances from the last eight years in the prospective utilization of such lignin-derived products in a range of application such as adhesives, plastics, automotive components, construction materials, and composites. Particular technical issues associated with lignin processing and emerging alternatives for future developments are discussed.
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