The buckling mode of failure is very common in case of plates, especially when their aspect ratio is large. In the present study, an endeavour has been made to carry out the hygro-thermal-induced buckling-based study of sandwich functionally graded (FG) plates made up of different material variation laws. A comparative study has been carried out between FGM plates made up of power, exponential and sigmoidal law using higher order zigzag theory. Nine-noded C-0 finite element has been used. It has been observed that the buckling behaviour of sandwich FGM plates under hygrothermal conditions is widely influenced by the geometry of the plate and the value of the law coefficient.Also, the nature of boundary condition widely affects the behavior of the plate.

This study aims to investigate the effect of incorporating waste glass powder (WGP) and quarry waste sand (QWS) on the properties of eco-friendly self-compacting mortar (SCM). Ordinary cement was replaced with WGP at rates of 0%, 10%, 20% and 30% by weight and the properties of the QWS-based SCM are compared to those of natural sand (NS)-based SCM. In this study, slump flow, superplasticizer requirement, mechanical strength, rheological parameters and hydration heat were investigated. The results obtained show that the use of WGP with different types of sand mixtures increases the fluidity of the SCM. After curing, SCM with 10% WGP exhibited higher compressive and flexural strengths after 28 days for both type of sand. The best performance was obtained with SCM mixes prepared with QWS sand compared to that of NS sand. Adequate relationships have been established to predict slump flow and mechanical strengths as a function of test parameters with high correlation coefficient and low root mean square error.

A modified Shear-lag model and variational approach were used to predict the effect of the crack density on stiffness degradation for [β_m/θ_n]_s composite laminates under different environmental conditions by the temperature variation and transient moisture concentration distribution in desorption case. Good agreement is obtained between the prediction models and experimental data published by Joffe and Katerelos, one reason for disagreement is damage in 40° layer and interface delamination that are not included in analysis. When the uncracked angle-ply laminate is submitted to hygrothermal conditions, the transient non-uniform moisture concentration distribution gives rise to relative reduction of the longitudinal Young's modulus. The results indicate that plies with a high orientation angle are more significantly affected by hygrothermal conditions, leading to greater degradation of mechanical properties, particularly Young's modulus. Furthermore, for cracked laminate [β/90₃]_s with transverse crack, the total stiffness is significantly reduced as transverse crack density and fiber angle orientation increase in the outer layer, coupled with rising temperature and moisture concentration. However, the relative stiffness for [0/θ₃]_s cracked laminate, decreases more substantially when the fiber angle orientation is less than 90° in cracked plies with transverse crack and under various environmental conditions. The present study underscores the significance of comprehending the degradation of stiffness in the aged and cracked laminates, particularly with different fiber orientation angle.

In this study, the performance of polyvinyl butyral interlayered friction stir welded (PVBFSWed) and ultrasonic vibration-assisted friction stir welded (UVaFSWed) AA7075-T651 joints are investigated, considering the effect of tool rotation and welding speed. The joints' tensile strength, microhardness, microstructure, and fracture behavior are evaluated. The UVaFSWed joints showed better performance compared to the PVBFSWed joints. The highest tensile strength of 322.8 MPa and microhardness of 157 Hv in weld nugget is observed for the UVaFSWed joint at a tool rotation of 2000 rpm and welding speed of 40 mm/min. However, the lowest surface roughness of 7.98 ㎛ was observed for the UVaFSWed joint at a tool rotation of 1400 rpm and welding speed of 40 mm/min. Comparatively lower tensile strength and microhardness were observed for the PVBFSWed joints compared to UVaFSWed joints. The fracture for the UVaFSWed and PVBFSWed joints mainly occurred in the heat-affected zone during the tensile test. The scanning electron microscopy (SEM) images show the more uniform, equiaxed grain distribution in the UVaFSWed joint.

The adhesive bonding technique has become widely prevalent in recent years, especially in fields such as engineering, aerospace, and sports. During operational service, adhesives are subjected to severe environmental conditions, including temperature variations, humidity, and UV radiation, which can impact their performance. In this study, we utilized the mechanical properties of the aged epoxy adhesive Adekit A140 in a finite element model to assess the impact of temperature and water absorption on the degradation of mechanical properties in metal-metal adhesive joints used in aeronautical structures. Our primary objective was to analyze, using the finite element method, the influence of these environmental factors on the joint's strength by evaluating the distribution of Von Mises stresses. The adhesive's mechanical properties, such as Young's modulus (E), were measured at different immersion periods and then integrated into the numerical modeling. The results revealed that water absorption leads to a significant degradation of the adhesive's mechanical properties, primarily manifested as a reduction in Young's modulus. Despite this degradation, an increase in plasticity was observed, which surprisingly improved the overall strength of the bonded assembly under certain conditions. Notably, after 90 days of immersion, the joint's strength demonstrated a 15% reduction in stiffness but exhibited enhanced durability due to plastic deformation, indicating a potential tradeoff between stiffness and durability in long-term service. This provides valuable insight into the design of adhesive joints under varying environmental conditions.