In this study, nonlinear buckling response of composite sandwich semi-ellipsoidal shell subjected to uniform hydrostatic external pressure is investigated numerically and experimentally. The face sheet of the sandwich shell is made up of laminated composite layers and the honeycomb core is considered as reinforced with and without strips. The various honeycomb core configurations with strip reinforcements are employed in the sandwich semi-ellipsoidal shell. The numerical buckling analysis of the sandwich shell is performed using the commercially available software ANSYS (R). The geometric nonlinearity and material nonlinearity of the shell structures are included through the arc length method while solving the nonlinear differential equations and identifying the critical pressure of the structure. The efficacy of the numerical modeling and analysis are verified by comparing the critical pressure obtained through the experimental investigations performed on a composite semi-ellipsoidal sandwich shell and results available in the literature. The various parametric investigations are performed on the composite sandwich shell to study the effect of honeycomb configurations, ply orientation of face sheets, aspect ratio and slenderness of the structure, geometric imperfections on the critical pressure. It was seen that the semi-ellipsoidal sandwich shell having double strip reinforcement core yields higher critical pressure among the various configurations of honeycomb cores. However, the semi-ellipsoidal sandwich shell with the single strip reinforcement in between the core having [0 degrees](6s) face sheet composite ply configuration yields higher stiffness to weight ratio which leads to the highest critical pressure among the various configurations of sandwich shell.

The present study focuses on the numerical and experimental investigation of a hat-stiffened composite inverted conical structure to identify its strength and stability under axial compressive loading conditions. A new design for the 3rd stage adapter with few changes in the present polar satellite launch vehicles launch vehicle is considered. An inverted conical structure with a hat-stiffened type of construction is used to obtain the higher bending stiffness. Both high-modulus and low-modulus uni-directional carbon prepreg are considered for the inverted conical structure. The experimental and numerical study is carried out on a hat-stiffened panel with a low-modulus carbon fiber prepreg material. Using the commercial software CATIA (R), the geometry of the inverted conical structure and hat-stiffened panel is generated. The structural analysis is carried out using MSC NASTRAN/PATRAN (R) to determine the maximum load-carrying capacity, maximum stress and displacement values. It was observed that the strain obtained experimentally on the surface of the stiffened panel at twenty-six points using the 26-strain gauges shows good correlations with those obtained numerically.

The present study examines the vibration characteristics of GFRP sandwich beams incorporated with cellular co-continuous architected periodic gyroidal bio-inspired cores. Using the higher-order shear deformation theory (HSDT), free vibration analysis was performed analytically on the designed sandwich beam. Four distinct configurations of bio-inspired cores are considered and 3D printed using Poly-lactic Acid (PLA) material. Subsequently, alternative dynamic approach (ADA) and ASTM E1876 is used to determine the properties of core and laminate. Amongst various bio-inspired beam configurations, GM02 yield better stiffness and prominent shear modulus for its structural weight proportions and parametric studies were performed for all the core models.

The present study involves the numerical and experimental buckling response of MWCNT reinforced composite sandwich semi-ellipsoidal dome subjected to uniform hydrostatic external pressure. The skin of the composite sandwich dome is made up of MWCNT-GFRP composite layers and the PLA honeycomb core, which is reinforced with and without strips. Various honeycomb core configurations, such as SRHC-1 to SRHC-3, are formulated in such a way that the strips are reinforced between the regular honeycomb core in longitudinal and transverse directions to enhance the stiffness characteristics of the structure. The nonlinear buckling analysis of the MWCNT reinforced composite sandwich dome is formulated and solved through the commercially available software ANSYS (R). The geometry and material non-linearity of the MWCNT reinforced sandwich dome structures are incorporated in the numerical model while solving the non-linear differential equations and identifying the critical pressure of the sandwich structures using arc length method. The testings were performed to obtain the various mechanical properties, the non-linear behavior of yield stress with a plastic strain of the MWCNT-reinforced GFRP skin and the transverse shear modulus of the various honeycomb core patterns. The efficiency of the present numerical modeling and buckling analysis is confirmed by comparing the critical pressure obtained through the experimental buckling analysis performed on the MWCNT-reinforced prototype sandwich dome and the results available in the literature. Various parametric studies are performed on the MWCNT-reinforced composite sandwich dome to examine the influence of MWCNT reinforcement on the skin, honeycomb core patterns, stacking sequence of skins, aspect ratio and slenderness of the shells and geometric imperfections on the critical pressure.

This research concentrates on the exploration of the free vibration of a multi-walled carbon nanotube (MWCNT)-reinforced semi-ellipsoidal composite dome. A glass fiber-reinforced composite laminated dome without and with MWCNT reinforcement is considered for numerical analysis. Free vibration analysis is carried out numerically using ANSYS (R) to determine the natural frequencies and mode shapes at various boundary conditions. In addition, the efficiency of the numerical analysis has been proven by conducting an experimental examination on a prototype dome with and without MWCNT reinforcement and comparing the results with those obtained numerically and experimentally. Parametric studies such as the influence of MWCNT wt.%, the aspect ratio of the dome, slenderness ratio of the dome, etc., with and without MWCNT reinforcement is performed to determine the dynamic behaviour. It was noted that the clamped end conditions of the hybrid composite domes provide the highest natural frequencies among the numerous end conditions considered. Also, the hybrid composite dome with 1.5 wt.% CNT reinforcement yields the highest natural frequencies at all the end conditions, beyond which the amalgamation of CNT content decreases the natural frequencies of the structures. Furthermore, composite dome "S-1" with 0 degrees orientation and "S-4" with 45 degrees orientation yields the highest and the lowest natural frequencies.

Abstract Bio-inspired structures have been commonly used in robotics, aerospace, and bioengineering because of their extraordinary qualities. The present study investigates compressive behavior for bioinspired cores. The experimental compression behavior of the bioinspired cores is supported with numerical analysis. As bioinspired structures are complex in nature, it is difficult to fabricate with the conventional technique. powder bed fusion (PBF) is employed to overcome this difficulty. Further specific energy absorption due to the compression behavior of the bioinspired cores and residual stress induced during the manufacturing process is investigated in detail, and the best-performing bioinspired core is reported in this study.

Combustor casing experiences the highest pressure and temperature of gas turbine thermodynamic cycle and its failure or rupture can lead to catastrophic failure of the engine and aircraft. This paper presents the structural analysis of combustor casing to establish its margin of safety. The combustor is tested at twice the maximum operating pressure and also subjected to cyclic pressure for 20,000 min–max-min cycles. Demonstration of adequate safety margin, capability of withstanding overload and cyclic pressure ensures structural safety and adequate life of the casing for a reliable operation in aero engine. Non-linear buckling analysis also has established adequate margin for safe operation in the intended engine.

In this paper, non-linear buckling performance of a semi-elliptical steel dome under uniform external pressure is investigated numerically and experimentally. Numerical buckling analysis is performed on an ellipsoidal dome with various nonlinearities including geometric (GN) and material non-linearity (MN) to obtain the critical pressure. The option ``Arc length method'' available in ANSYS is implemented to solve the nonlinear differential equations. Further, an experimental testing is performed on the prototype ellipsoidal dome subjected to external hydrostatic pressure to obtain the critical pressure. The effectiveness of the developed numerical modelling is demonstrated by comparing the critical buckling load evaluated using the present non-linear analysis with those available in literature and experimental analysis. Imperfections such as Force Induced Dimple (FID) and eigen affine imperfections are considered in the ellipsoidal dome to investigate their effects on collapse load. Non-linear (NL) buckling analysis of stringer reinforced semi-elliptical dome is performed to investigate the effect of stringers on critical buckling pressure. Various parametric studies are also performed to study the effect of the nature of imperfection, location of imperfection, aspect ratio on critical buckling pressure of the dome. It was observed that an increase in the amplitude of eigen affine imperfection significantly reduces the critical buckling pressure. FID at an apex of the dome causes a reduction in buckling pressure whereas FID located at the middle and bottom of dome do not affect the critical load significantly. It was also demonstrated that stringer reinforcement on semi-elliptical dome without modifying the mass of overall structure significantly increases the critical buckling pressure. The effect of geometric nonlinearity and material nonlinearity on the critical buckling pressure of the semi-elliptical dome is observed to be more significant in stringer reinforced domes.

In the present work, formulation for the nonlinear free vibrational behavior of laminated variable stiffness composite beams with curvilinear fibers is made incorporating sinusoidal function for representing the trans-verse shear flexibility, geometrical nonlinearity, and accounting for Poisson's effect through the constitutive equation for analyzing beams with general composite lay-up. Applying Hamilton's principle combining with a finite element approach based on three-noded C-1 beam element, the governing equations are formed through matrices. The solutions for the developed governing equations are evaluated iteratively by introducing eigenvalue analysis and the results are viewed through the frequency-amplitude relationship. A large number of design parameters like curvilinear fiber angles in a layer, number of layers, lay-up sequence, thickness ratio, etc. is assumed to visualize the nonlinear free vibration characteristics of VSCL beams. Also, for the practical situation, the influence of thermal environment and restraint elastically against beam ends rotation, to accommodate other than classical boundary conditions, hybrid beam (consisting of constant and variable stiffness layers) on the non-linear free vibrational behavior is presented.

European union end of life vehicle directive mandates the use of more sustainable/recyclable materials in automotive industries. Thermoplastics matrix-based composites allow recyclability of composites at the end of life; however, their processing technology is more challenging than thermoset composites. Manufacturing process and mechanical testing of sustainable sandwich composite made from sustainable materials: flax, recycled carbon fiber, polypropylene, and recycled PET foam are presented in this article. High pressure compression molding with adhesive thermoplastic polymer film was used for manufacturing sandwich composite skin. The recycled PET foam core was integrated/joined with the skin using a thermoplastics adhesive film. A three-point bending test was conducted to compare the flexural properties. The results show that such sustainable sandwich composites will be an excellent material for truck side panel to operate in adverse wind/storm conditions. The sustainable sandwich composite can potentially be an excellent candidate for the fabrication of light-duty, lightweight, and low-cost engineering structures in automotive industry to meet the EU end of life requirements.