Delamination Testing of AlSi10Mg Sandwich Structures with Pyramidal Lattice Truss Core made by Laser Powder Bed Fusion

Sandwich structures possess a high bending stiffness compared to monolithic structures with a similar weight.This makes them very suitable for lightweight applications,where high stiffness to weight ratios are needed.Most common manufacturing methods of sandwich structures involve adhesive bonding of the core material with the sheets.However,adhesive bonding is prone to delamination,a failure mode that is often difficult to detect.This paper presents the results of delamination testing of fully additive manufactured(AM)AlSi10Mg sandwich structures with pyramidal lattice truss core using Laser Powder Bed Fusion(LPBF).The faces and struts are 0.5 mm thick,while the core is 2 mm thick.The inclination of the struts is 45°.To characterise the bonding strength,climbing drum peel tests and out-of-plane tensile tests are performed.Analytical formulas are derived to predict the expected failure loads and modes.The analytics and tests are supported by finite element(FE)calculations.From the analytic approach,design guidelines to avoid delamination in AM sandwich structures are derived.The study presents a critical face sheet thickness to strut diameter ratio for which the structure can delaminate.This ratio is mainly influenced by the inclination of the struts.The peel tests resulted in face yielding,which can also be inferred from the analytics and numerics.The out-of-plane tensile tests didn’t damage the structure.

AEROELASTIC PROPERTIES OF SANDWICH BEAM WITH PYRAMIDAL LATTICE CORE CONSIDERING GEOMETRIC NONLINEARITY IN THE SUPERSONIC AIRFLOW

The equation of motion of sandwich beam with pyramidal lattice core in the supersonic flow considering geometric nonlinearity is formulated using Hamilton＇s principle. The piston theory is used to evaluate aerodynamic pressure. The structural aeroelastic properties are analyzed using frequency- and time-domain methods, and some interesting phenomena are observed. It is noted that the flutter of sandwich beam occurs under the coupling effect of low order modes. The critical flutter aerodynamic pressure of the sandwich beam is higher than that of the isotropic beam with the same weight, length and width. The influence of inclination angle of core truss on flutter characteristic is analyzed.

Cantilever sandwich beams with pyramidal truss cores subjected to tip impact

Experiments were conducted to investigate the deformation of cantilever sandwich beams with pyramidal truss cores subjected to impact by a projectile at their tips.A new technique was employed to the fabrication of sandwich beams with pyramidal truss cores.For a better observation of large deformation of specimens during impact process,a high-speed digital video camera was successfully used to capture the instant shapes of the deformed beams.A projectile collection device was designed and installed to avoid the projectile flying away from the beam tips after impact and thus the kinetic energy imparted to the beams was measurable.The experiments show that the sandwich beams have a superior shock resistance compared to the monolithic beams of the same material and mass.Further,finite element simulations were performed to gain insight into the deformations and plastic energy absorptions in the sandwich beams.

Sound Insulation Performance of Pyramidal Truss Core Cylindrical Sandwich Structure

Recently,cylindrical structures have been exploited in various fields due to their excellent mechanical properties.With the increase in the application of cylindrical shell structures,researchers are paying more and more attention to its acoustic performance and sound insulation applications.By inserting the pyramidal truss lattice into the cylindrical shell structure,a cylindrical sandwich structure is obtained and the sound insulation performance of the structure is investigated.The space-harmonic expansion method and the principle of virtual work are employed to establish a theoretical model for the acoustic analysis of cylindrical sandwich structures.The vibro-acoustic coupling is taken into account by imposing the velocity continuity condition at the fluid-solid interface.The sound transmission loss(STL)performance of the structure is examined by establishing both theoretical and finite element models.Subsequently,the influence of various parameters on sound transmission loss is researched and analyzed.