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Sustainable manufacturing technology is one of the requirements of the current industrial fields to reduce the weight and energy used. Friction stir welding (FSW) can be considered a quantum leap in the development of welding technology. A solid-state process utilizes a non-consumable tool and less electrical energy. Friction stir spot welding (FSSW) is a particular case of FSW that began to spread rapidly, especially for similar and dissimilar metals, which has extended to weld the polymers. The increase of FSSW use in different fields needs to simplify the equipment. This study used a portable drilling machine to construct an FSSW apparatus with a rotational speed between 1500 and 3000 rpm with a pin diameter of 2, 3 and 4 mm. The results indicated that the joints welded by the developed apparatus have good strength and hardness. Furthermore, many specimens succeeded in the bending test, especially when the rotational speed was set at 2250 rpm and the pin diameter was 3 mm. In addition, it was found that the mechanical properties increased with the rotational speed and pin diameter, then gradually decreased. Finally, the Response Surface Methodology (RSM), besides the analysis of variation (ANOVA), was utilized to maximize the lap-shear fracture load. The results indicated that the maximum lap-shear fracture load can be achieved at a tool speed N of {2300>N>1600} rpm with a pin diameter (d) of {2.75>N>3.75 mm}.

One major problem with concrete is high brittleness with low tensile strength and strain capacity, which can cause sudden failure. Structural Health Monitoring (SHM) is thus very important to detect cracks in initial stages to avoid catastrophic failure. In this research, an acoustic emissions (AE) technique was applied to enable SHM to detect cracks and predict the failure of composite concrete. This physical non-destructive testing process utilises transient elastic waves caused by the rapid release of energy from a localised source within a structure. A low-frequency acoustic emission system was thus tested for economical monitoring of the damage to reinforced composite cubic concrete under compression. Specimens of standard size (150 x 150 x 150 mm) were produced without and with polyamide reinforcement bars. The compression strength of the cubic concrete was then tested according to BS EN 12390-1. Prior to testing, a low-cost single piezoelectric wafer active sensor was applied to the centre of one side of each specimen, which was then connected to a PC’s sound card. Data was successfully recorded using sensors and the real-time of the applied load was recorded using a separate data logger. Traditional AE signal parameters were extracted and used for damage evaluation. The results indicated that the AE system was capable of detecting cracks in representative structures to final failure. Signal amplitude with load versus time showed an increase in AE activity and energy approaching the end of the test, while commutative hits could be used to distinguish between stable and unstable loading stages. The system also detected the initiation of the final failure stage at 72.6% and 83% of the failure load of specimens without and with polyamide reinforcement bars, respectively.

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