Over the last few years, many classifications have been proposed for functionally graded materials (FGMs). In this Paper, critical review of different available classifications for FGM based on their physical, structural and manufacturing characteristics are presented. Advantages and limitations of each fabrication method for use in a given application is correspondingly considered. In addition, new classifications based on gradation control and accuracy, residual stresses, specific energy consumption, environmental impact evaluated throughout the complete life cycle and manufacturing costs are proposed. These classifications mainly reflect the needs of both FGM designers and industrial manufacturers. Based upon the presented classifications and the recent advances in analysis and production techniques, new major directions for FGMs research are proposed.

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Horizontal centrifugal casting machine was adopted to fabricate tubes of functionally graded materials (FGM) made of commercially pure aluminum reinforced with different weight fractions of SiC particles. Tubes with 2.5, 5 and 10%wt. SiCpwere produced in the speed range 800 to 1100 rpm. Wear experiments involving dry sliding under different loading conditions were conducted on samples taken from three consecutive layers across the wall of the FGM tubes. Analysis of variance (ANOVA) was used to determine the significant FGM production parameters and wear test parameters (normal load and test duration) affecting the wear resistance of the samples. Obtained wear test results have been used to build a regression model to predict the expected weight loss across the wall thickness of the tube depending on the production parameters and the loading conditions.

Composites made from food packaging waste are recently introduced to the industry as promising materials that aim to reduce the environmental waste and to develop cost effective products. They possess good physical properties, which makes them potential competitors to wood based composite structures such as commercial particleboard (PB), and medium density fiberboard (MDF). Despite the expected advantages, the mechanical and dynamic behaviour of this genuine structure still needs to be studied and tested to evaluate its suitability for light weight structure applications. Experimental modal analysis is conducted on specimens made of food packaging waste, sandwich structured packaging waste with woven glass-fiber skin, MDF and PB. The dynamic testing results show superior damping ratio for the food packaging waste composites compared to the wood-based specimens. Natural frequencies exhibit comparable dynamic stiffness with respect to MDF, and PB. Further investigation has been made to evaluate both the modulus of rapture and the static stiffness of the material by conducting flexural tests on all specimens. Sandwich structure produced from food packaging waste and veneered with woven glass-fiber fabric exhibit excellent magnitudes for the modulus of rupture in addition the highest damping ratio.

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