Neurofuzzy modelling of moisture absorption kinetics and its effect on the mechanical properties of pineapple fibre-reinforced polypropylene composite

Abstract: The focus of this work was to analyze the influence of leaf treatments on mechanical, physical and chemical properties and thermal stability of the gelatin/lotus leaf composites. Lotus leaves were treated with drinking water at 95 °C for 5 min. The gelatin/untreated lotus leaf (referred to as GUL) and the gelatin/hot water treated lotus leaf (referred to as GHL) composites have been prepared by the compression molding technique. The composites have been investigated by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TAG), Scanning electron microscopy (SEM). Effect of the lotus leaf hand lay-up fiber orientation was studied for longitudinal, transverse and random orientation of the fibers. The tensile strength of gelatin/lotus leaf composites were influenced by the orientation of the fibers. It was found that longitudinal orientation delivered higher mechanical properties than that of the transverse and random orientation whether untreated or treated. The hot water modification of the lotus leaf was employed to improve the interfacial adhesion of the composites in order to improve the tensile properties. By using TGA analysis data and Ozawa-Flynn-Wall (OFW) method, the thermal stability and degradation temperature of the lotus leaves treated with hot water were higher than those of untreated leaves. In addition, the properties of the novel bio-composites were potential in further development of biodegradable packaging materials.

Abstract: The aim of this paper was to improve the performance of the adaptive neuro-fuzzy inference system (ANFIS) and to predict the flexural strength of the sandwich panels made with thin medium density fiberboard as surface layers, and polyurethane foam as a core layer, by applying metaheuristic optimization methods. For this purpose, various models, namely ant colony optimization for the continuous domain (ACOR), differential evolution (DE), genetic algorithm (GA), and particle swarm optimization (PSO) were applied and compared, as different efficient bio-inspired paradigms, to assess their suitability for training the adaptive neuro-fuzzy inference system model. The predicted values of the flexural strength resulting from applying adaptive neuro-fuzzy inference system trained by ACOR, DE, GA, and PSO, were compared with the values derived from adaptive neuro-fuzzy inference system classical model. The molar ratio of formaldehyde to melamine and urea, sandwich panel thickness, and the weight ratio of the modified starch to MUF resin (OS/MUF weight ratio) were used as an input variables and the modulus of rupture was used as an output one. The developed hybrid models were used to predict the values of the modulus of rupture obtained from experimental tests. In order to evaluate and compare the performance of the models, three performance criteria were employed namely, determination coefficient (R2), root mean square error, and mean absolute percentage error. It was found that ANFIS–ACOR, ANFIS–DE, ANFIS–GA, and ANFIS–PSO showed different performance ratios compared to the predicting model. In addition, the ANFIS–GA model is found to be by far more accurate than the other hybrid models.

Abstract: Environmentally beneficial composites can be made by replacing glass fibres with various types of cellulose fibres. Fibres from pine or eucalyptus wood and also one-year crops such as coir, sisal, etc. are all good candidates. The poor resistance towards water absorption is one of the drawbacks of natural fibres/polypropylene composites. New natural fibres/polypropylene composites were made and the water absorption in them was studied by immersion of the composites in water at three different temperatures, 23, 50 and 70 °C. The process of absorption of water was found to follow the kinetics and mechanisms described by Fick's theory. In addition, the diffusivity coefficient was dependent on the temperature as estimated by means of Arrhenius law. A decrease in tensile properties of the composites was demonstrated, showing a great loss in mechanical properties of the water-saturated samples compared to the dry samples. The morphology change was monitored by scanning electron microscopy studies of the samples before and after exposure to water and the devastating effect of water on the fibre structure was shown.

Abstract: The environmental degradation behaviour on the physical and mechanical properties of short sisal/PP composites has been studied with special reference to the influence of ageing conditions like treatment with water and UV radiation. The dependence of water uptake on the sorption characteristics of sisal/PP composites was evaluated by immersion in distilled water with respect to fibre loading, temperature and chemical treatment. It is found that water uptake increases with increase of fibre loading due to the increase in cellulose content. The raise of temperature up to 70 °C is accompanied by an increase of the rate and extent of sorption. Chemical treatments such as urethane derivative of PPG, PMPPIC and MAPP were given to sisal fibre. All chemically modified fibre composites showed lower uptake than the unmodified composites. This is because all chemical treatments given to sisal fibre reduce its hydrophilicity thereby favouring strong interfacial adhesion between the fibre and PP matrix. The influence of water uptake on the tensile properties of sisal/PP composites was studied. Tensile properties decreased with water uptake, time of immersion and fibre loading. The behaviour was strongly dependent on the chemical treatment and fibre orientation. The influence of the tensile properties of sisal/PP composites exposed to UV radiation was studied. The tensile properties were found to decrease with increase in the time of exposure to UV radiation. The reduction in properties is due to chain scission and degradation occurring to PP molecules as a result of photooxidation promoted by ultraviolet radiation. As a result of UV irradiation, surface cracks can be seen on neat PP and PP composites which can be evidenced from SEM photos. The retention of tensile properties increased with increase of fibre loading.

Abstract: The influence of water environment on the sorption characteristics of low-density polyethylene composites reinforced with short pineapple-leaf fibers (PALF/LDPE) has been studied by immersion in distilled water at 28, 50 and 70°C. The effects of fiber loading, temperature and chemical treatment on the sorption behavior are also evaluated. Water uptake is found to increase with fiber loading owing to the increased cellulose content. Weight change profiles for the composites at high temperature indicated that the diffusion is close to Fickian. All of the treated composites showed lower uptake than the unmodified composites. Parameters like diffusion, sorption and permeability coefficients were determined and activation energies were calculated. The thermodynamic constants such as entropy, enthalpy and first-order kinetic rate constant have been evaluated. A correlation between theoretical and experimental sorption results was evaluated. The effect of water uptake on uniaxial tensile properties has also been studied. Mechanical properties decreased after exposure to water, depending on time of immersion, fiber loading and chemical treatment. Finally, studies were carried out on the flexural properties of PALF/LDPE composites exposed to ultraviolet radiation.

Abstract: The tension–tension fatigue behaviour of different natural fibre reinforced plastics was investigated. The composites used were made of flax and jute yarns and wovens as reinforcements for epoxy resins, polyester resins and polypropylene. Fibre type, textile architecture, interphase properties, fibre properties and content were found to affect the fatigue behaviour strongly as illustrated with damping versus applied maximum load curves. It was found that natural fibre reinforced plastics with higher fibre strength and modulus, stronger fibre–matrix adhesion or higher fibre fractions possess higher critical loads for damage initiation and higher failure loads. In addition, damage propagation rates were reduced. Furthermore, unidirectional composites were less sensitive to fatigue induced damage than woven reinforced ones.

Abstract: The moisture absorption and mechanical properties of wood flour–filled polypropylene composites in a hydrothermal environment have been studied by immersing the composites in water at 23, 60, and 100°C. The degree of moisture absorption was found to be dependent on the modification of matrix, the weight percentage, mesh size, and surface treatment of wood flours. It increased with increasing the immersion temperature. The tensile strength of all composites with wood flours of different contents, mesh sizes, and surface treatments increased after immersion in water baths of various temperatures, to either greater or lesser extents. The flexural strength and modulus followed a similar trend when immersed in water at ambient temperature. However, the contrary was true for composites when immersed in 60 and 100°C water baths. The impact strength increased after immersion in water at each immersion temperature, and the extent of such increment decreased with increasing the immersion temperature. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2824–2832, 2002