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• Single shotgun pellet ricochet marks can imply their impact angles. • Pinch points/ nucleus ricochet marks can be seen following shotgun pellet ricochets. • Extents of impacting and ricocheting shot spreads have significant reconstructive values. Compared to popular handguns and rifle bullets, quantitative and empirical-based ricochet studies using shotgun pellet ricochets are observed to be far fewer. This empirical study examines the ricochet behaviour and impact evidence when shotgun pellets (Buckshot) ricochet off standard floor tiles, providing a series of novel findings related to the resultant ricochet marks. Among these findings, a novel and statistically significant relationship between the lengths and widths of individual ricochet marks and the shot impact angles is demonstrated, offering useful forensic application. Ricochet mark shapes and morphologies highlighted in this study at different impact angles demonstrate the interactions between the ricocheting spherical pellets and tile surfaces, and the effects of acting frictional forces and degree of energy transfer in the production of impact evidence on the tile surface. Relationships with high statistical significance were also reported between the shot spreads on the tile surfaces and the post-ricochet cardboard witness screens, with shot impact angles. Finally, this work reports on the first documented observations of 'Pinch Points' and 'Nucleus' ricochet marks with shotgun pellet ricochets as angle-specific phenomena. [ABSTRACT FROM AUTHOR]

This paper presents the first-ever investigation of Menger fractal cubes' quasi-static compression and impact behaviour. Menger cubes with different void ratios were 3D printed using polylactic acid (PLA) with dimensions of 40 mm x 40 mm x 40 mm. Three different orders of Menger cubes with different void ratios were considered, namely M1 with a void ratio of 0.26, M2 with a void ratio of 0.45, and M3 with a void ratio of 0.60. Quasi-static Compression tests were conducted using a universal testing machine, while the drop hammer was used to observe the behaviour under impact loading. The fracture mechanism, energy efficiency and force-time histories were studied. With the structured nature of the void formation and predictability of the failure modes, the Menger geometry showed some promise compared to other alternatives, such as foams and honeycombs. With the increasing void ratio, the Menger geometries show force-displacement behaviour similar to hyper-elastic materials such as rubber and polymers. The third-order Menger cubes showed the highest energy absorption efficiency compared to the other two geometries in this study. The findings of the present work reveal the possibility of using additively manufactured Menger geometries as an energy-efficient system capable of reducing the transmitting force in applications such as crash barriers. [ABSTRACT FROM AUTHOR]

Green construction materials developed using renewable resources have become the focus of concurrent research owing to increasing environmental considerations and legislations. However, most of the available literature focus only on load-bearing construction elements. Consequently, little attention has been paid towards non-load-bearing construction elements such as partitioning materials. The present work aims to address this gap by investigating the viability of using the biodegradable bioplastic PLA in combination with yarns spun using banana fibres to manufacture a composite panel intended for temporary partitioning materials used in the construction industry. Pre-tensioned banana yarns were used as the reinforcement while PLA was used as the matrix. The composite panels were manufactured using the compression moulding technique. The effect of process parameters such as moulding temperature and pressure, the effects of the degree of pre-tension and the amount of reinforcing yarn on the performance of the panels were investigated. The optimum moulding conditions were found to be 180oC moulding temperature and 15 tons of moulding pressure. Yarn pre-tensioning exhibited a positive effect on the performance of the composite panels. However, increasing the reinforcing yarn percentage caused a degradation of flexural performance of the composite. Finally, the performance was compared against the most widely used partitioning material currently, medium-density fibreboard (MDF). The novel composite panel manufactured at optimum conditions exhibited 52% higher impact strength and 55% higher flexural strength when compared to MDF. The composite panel presented herein has the potential to replace MDF as a better performing material manufactured using renewable resources. [ABSTRACT FROM AUTHOR]

This study elaborates on the effects of matrix rigidity on the high-velocity impact behaviour of UHMWPE textile composites using experimental and numerical methods. Textile composite samples were manufactured of a plain-weave fabric (comprising Spectra® 1000 fibres) and four different matrix materials. High-velocity impact tests were conducted by launching a spherical steel projectile to strike on the prepared samples via a gas gun. The experimental results showed that the textile composites gradually changed from a membrane stretching mode to a plate bending mode as the matrix rigidity and thickness increased. The composites deformed in the membrane stretching mode had higher impact resistance and energy absorption capacity, and it was found that the average energy absorption per ply was much higher in this mode, although the number of broken yarns was smaller in the perforated samples. Moreover, the flexible matrix composites always had higher perforation resistance but larger deformation than the rigid matrix counterparts in the tested thickness and velocity range. A novel numerical modelling approach with enhanced computational efficiency was proposed to simulate textile composites in mesoscale resolution. The simulation results revealed that stress and strain development in the more rigid matrix composite was localised in the vicinity of the impact location, leading to larger local deformation and inferior perforation resistance. [ABSTRACT FROM AUTHOR]