Abstract: Barium titanate/graphene oxide/polyurethane (BTO@GO@PU) composite membranes for microwave absorption were designed and fabricated by mechanical-blending of BTO and GO in PU medium, followed by mold formation. The cross section morphology of the BTO@GO@PU membrane indicated that the BTO nanoparticles with 450 nm average diameter are successfully incorporated into the PU matrix. Mechanical tensile measurement showed that, as the amount of BTO nanoparticles increased from 5 wt% to 20 wt%, the elastic modulus of the corresponding membrane increased up to 23.0 MPa elongation with the elongation above 450 %. Microwave absorption property of the BTO@GO@PU membranes were evaluated by measuring its reflection loss in the frequency range of 0.1-18 GHz. With the addition of BTO up to 20 wt%, the maximum absorptivity of the composite reached up to 51 %. This is attributed to the dielectric loss of BTO nanoparticles.
Abstract: Graphene has been proved to be an excellent enhancer in metal matrix composites. Core-shell structured SiC nanoparticles and graphene nanosheets (GNSs) were fabricated and incorporated into aluminum matrix using ball milling in the current study. Graphite powder was exfoliated into thin GNSs, which are flexible to wrap SiC nanoparticles. The ductile aluminum particles were firstly flattened and then repeatedly welded and fractured into equalized particles during the ball milling of Al alloy-SiC-GNSs composite powder, which were observed using scanning electron microscopy and X-Ray diffraction. SiC-GNSs were embedded and dispersed into the aluminum matrix during the milling process.
Abstract: The fire behaviour of Polymeric composite structures is one of the most critical aerospace research topics. Indeed, the exposure of Polymeric composite structures to high temperatures leads to material decomposition, associated to thermal and mechanical properties degradation. This degradation causes a reduction of the mechanical performances, which can be of main concern for safety reasons. In this paper, the tensile behaviour of Carbon Fibre Composite Polymer specimens, subjected to fire, has been experimentally and numerically investigated. The material properties degradation has been estimated according to an Arrhenius shape function, which relates the mechanical properties of the composite to the temperature. At first, static structural analyses have been carried out to assess the mechanical behaviour of the investigated specimen without fire effects. Then, a coupled thermo-structural analysis allowed evaluating the fire effect on the specimens’ mechanical and the thermal behaviour. In order to preliminary validate the proposed degradation model, the numerical results, in terms of Load versus Displacements curves, have been compared against data obtained from an ad-hoc experimental campaign where fire condition have been suitably replicated during the mechanical tests.
Abstract: Epoxy-glass fiber composite pipes were fabricated with filament winding machine. Full automation and precise control over the processing parameters are the major advantages of this manufacturing technique. Stacking sequence is one of the important processing parameters on which the properties of filament wound components depend to a large extent. This paper comes up with a comparative damage analysis of traditional composite pipes (TCPs) of stacking sequence [±55]6, and functionally graded composite pipes (FGCP) of stacking sequence [70-55-40-40-55-70]. The stacking sequence in FGCP was chosen such that the average stacking angle is retained the same as of TCPs, i.e. [±55]. An impact analysis of these pipes was carried out. Impact energy of 45 J was applied on both pipes and damage was quantified using back-lighting technique. It was observed that the damage occurred in FGCPs was 30% lesser compared to TCPs.
Abstract: The approach suggested in this analysis stems from basic material science laws and considers that any environmental degradation of polymer composites ultimately consists in chemical link and cohesion force alteration. Such alteration leads to the modification of material viscoelastic characteristics that can be measured through stress relaxation or creep. Then the analysis deals with the applicability of the time-temperature shift principle for prediction test in cases involving environmental degradation. It is demonstrated that the shift factor as determined from Arrhenius Law needs to incorporate an additional term to account for the variation of the activation energy of the chemical and physical degradation. The method leads to excellent prediction of the time and environment dependent material strength.
Abstract: Experimental work on tensile behaviour and failure mechanism of composite double lap bolted joint has been carried out. Chopped strand mat (CSM) coir, glass and coir-glass/epoxy composite plates were fabricated by hand lay-up method. The bolted joint specimens were of 155 mm length and 48 mm width. Steel bolts of 4 mm and 8 mm diameters were used. Effect of material type, number of layers and width to diameter ration (w/d) on tensile load, bearing strength and failure behaviour were examined. Results show that, the maximum load obtained from the glass/epoxy, coir/epoxy and coir-glass/epoxy specimens increased with the increase in the number of layers and (w/d) ratio. Maximum load obtained from the six layers glass/epoxy with w/d ratio of 12 is found higher respectively 15.2% and 50.14% than that obtained from hybrid coir-glass and coir/epoxy composite specimens. The percentages of difference were 14.2% and 42.97% for the specimens with w/d ratio of 6. It has been found that the maximum strength of the six layers glass/ epoxy specimens was found higher in the range between 17.5% to 18.46 % and 51.67% to 57.74 % than the hybrid coir-glass and coir/epoxy specimens respectively. Net tension failure and cleavage failure modes were observed for the two and four layers coir/ epoxy specimens with w/d ratios of 6 and 12. Bearing failure mode was observed for the six layers coir, glass and hybrid coir-glass/epoxy specimens.
Abstract: In this research work, polyethersulfone (PES) and polyethersulfone/polyvinyl acetate (PES/PVAc) blend were incorporated with 10 wt.% of TiO2 nanoparticles to form mixed matrix membranes (MMM). FESEM and TGA were utilized respectively to scrutinize the morphology and thermal stability of the developed membranes. Permeation tests of ideal CO2 and CH4 gases were also conducted to assess the separation performance of resultant membranes. The PES/PVAc/TiO2 polymer blend MMM was found to be the most thermally resistant and has the highest CO2 permeability and CO2/CH4 selectivity as compared to the other membranes.
Abstract: Many auto manufacturers such as Mercedes Benz, Toyota and DaimlerChrysler have already embraced natural fiber composites into both interior and exterior parts and are looking to expand the uses of this composites. They have to balance the changing public demands of greater comfort, better driving performances, and higher safety standards with the environmental requirements. Based on the preliminary study using 20 to 30 wt.% NaOH treated sugarcane bagasse fibers to make biocomposites with polypropylene matrix, the tensile strength obtained was variably, in the range between 8.31 to 20.59 MPa. A further study was required to improve the strength of the composites in comparison with the specified flexural strength required by the industry for automotive parcel tray. The sugarcane bagasse fibers obtained from the sugar mill were used and alkali treated with 10% v/v NaOH at various soaking time of 2, 4, and 6 hours. Biocomposite samples were prepared from 25/75 wt.% ratio sugarcane fibers/polypropylene (PP). The highest tensile strength of 14.35 MPa was obtained from the samples with sugarcane fibers receiving two-hour alkali treatment. However, the highest flexural strength (37.78 MPa) was gained on the samples made from sugarcane fibers with 4 hours alkali treatment. This value has met the strength specification of two materials for current parcel trays which were made from monomaterial of polypropylene and woodboard composite which their flexural strengths were 35.6 MPa and 37.57 MPa, respectively. Structural studies using scanning electron microscopy (SEM) on the fracture surface of tensile tested samples show two different orientations of bagasse fibres in PP matrix, i.e. a group was in longitudinal orientation and other in transversal orientation.
Abstract: In this study, whey protein concentrate (WPC) and poly (ε-caprolactone) (PCL) composite nanofibers were prepared by electrospinning in the diameter of 50-350nm. Characterization tests of the polymer solutions such as density, viscosity, conductivity was studied. Fourier-transformed infrared spectroscopy (IR) results confirmed that the processed fibers were composed of both PCL and WPC constituents. Morphology of nanofibers composite was observed using scanning electron microscopy (SEM). Moreover the PCL/WPC nanofibers with high WPC content exhibited the maximum tensile strength (about 1.40 MPa).