In this work a cycloaliphatic amine-cured epoxy (EP) resin was modified by micron-scale rubber particles (RP). Nominal RP, in sizes of 200 and 600 µm respectively, were produced using worn truck tires and ultra-high-pressure water jet cutting. The RP were dispersed into the EP resin using different mixing techniques (mechanical, magnetic, and ultrasonic stirring) prior to the introduction of the amine hardener. The dispersion of the RP was studied using optical light microscopy. A longer mixing time reduced the mean size of the particles in the EP compounds. Static (tensile and flexural), dynamic (unnotched Charpy impact), and fracture mechanical (fracture toughness and strain-energy release rate) properties were determined. The incorporation of the RP decreased the stiffness and strength values of the modified EPs. In contrast, the irregular and rough surface of the RP resulted in improved toughness. The fracture toughness and strain-energy release rate were enhanced up to 18% owing to the incorporation of 1% by weight (wt%) RP. This was traced to the effects of crack pinning and crack deflection. Considerably higher improvement (i.e., up to 130%) was found for the unnotched Charpy impact energy. This was attributed to multiple cracking associated with RP-bridging prior to final fracture.
A great deal of attention is currently paid to recycling or reusing carbon fibres, as it improves sustainability and the lifetime of carbon products. The applicability of recycled carbon fibre–reinforced polymer (rCFRP) composite materials is supported by the results of material scientists; however, the machinability of rCFRPs has not been analysed yet. The machinability of virgin and rCFRPs was compared by analysing cutting force and torque in drilling. Six different CFRPs (virgin and recycled CFRPs with different reinforcing structures) were drilled at three feed levels using two different solid carbide cutting tools. The cutting force and torque were measured with a KISTLER 9257BA dynamometer, processed, and analysed by fast Fourier transformation (FFT) and analysis of variance (ANOVA). The experimental results proved at a significance level of 0.05 that the recycled/virgin status of the applied CFRPs significantly influences both the thrust force and drilling torque of each CFRP. Furthermore, the cutting force and torque are higher in rCFRPs than in virgin CFRPs at each reinforcing structure. The present study suggests spreading rCFRP applications, as there are no essential barriers against them from the point of view of drilling force and torque.
Since governments encourage sustainability, industries are making great efforts to reuse or recycle carbon fibre–reinforced polymer (CFRP) composites. Despite the promising early results concerning the material properties of recycled CFRP, there is no published knowledge available about their machinability. In this study, drilling-induced micro and macro-sized geometrical defects were analysed and compared in virgin and recycled CFRP. A total of 180 drilling experiments were carried out using uncoated solid carbide cutting tools. Six different CFRP composites were tested at different feeds. The burr characteristics and microstructure were analysed by optical and scanning electron microscopy. The analysis of variance (ANOVA) results suggest that the formation of drilling-induced burrs in CFRP reinforced by recycled chopped and nonwoven mats is less pronounced than in virgin CFRP. Micro- and macro-sized geometrical defects in both recycled and virgin milled CFRP were negligible. This study found no relevant objection to using recycled CFRP from the point of view of drilling-induced burrs and microstructure damage.
This present study demonstrates the applicability of basalt fibre-reinforced polymer (BFRP) composite materials in thermal shielding. Basalt fibres are produced from natural, sustainable sources and obtain comparable mechanical performance to commercial glass fibres. In addition to their mechanical strength, BFRPs have excellent chemical and heat resistance. Basalt fibres tend to have a higher thermal stability than their competitor glass fibres. The heat resistance of basalt fibres derives from the volcanic origin of the raw material basalt gabbro. These favourable features make BFRP composites an attractive group of materials for application in several industries. To test the fire resistance of the materials, we produced mono and hybrid composite plates from different types of basalt reinforcement structures (milled fibres, chopped fibres and woven fabric) and epoxy resin. Surface treatment with silane coupling agents significantly improved the mechanical and thermomechanical properties of BFRPs by up to 70%. Three-point bending tests were performed to determine the flexural properties of the composite specimens, and their fire behaviour was evaluated with a horizontal burning test, and a novel jet fire test assisted with infrared thermal imaging. Higher fibre content in hybrid laminates decreased the linear burning rate by 8%, and the maximum surface temperature was approximately 80 °C lower after jet fire impingement compared to woven reinforcement structure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.