STUDY OF NUMERICAL AND PHYSICAL FRACTURE WITH SPH METHOD

Two kinds of fractures can be observed in the SPH （smoothed particle hydrodynamics） simulations, which are the physical fracture and the numerical fracture. The physical one exists in reality, while the numerical one is fictitious. This paper presents the effects of both fractures and proposes a simple adding particle technique to avoid the numerical fracture. The real physical fracture is then figured out by using an applicable fracture criterion. Firstly, the effect of the numerical fracture on the computational accuracy is investigated by introducing the artificial fracture in a model of wave propagation. Secondly, a simple adding particle technique is proposed and validated by a three dimensional bending test. Finally, the experiments of penetration on the skin of aircrafts are simulated by both the initial SPH method and the improved method with the adding particle technique. The results show that the improved SPH method can describe the physical fracture very well with better accuracy.

Cross-linked polyelectrolyte reinforced SnO_(2)electron transport layer for robust flexible perovskite solar cells

SnO_(2)electron transport layer(ETL)is a vital component in perovskite solar cells(PSCs),due to its excellent photoelectric properties and facile fabrication process.In this study,we synthesized a water-soluble and adhesive polyelectrolyte with ethanolamine(EA)and poly-acrylic acid(PAA).The linear PAA was crosslinked by EA,forming a 3D network that stabilized the SnO_(2)nanoparticle dispersion.An organic–inorganic hybrid ETL is developed by introducing the cross-linked PAA-EA into SnO_(2)ETL,which prevents nano particle agglomeration and facilitates uniform SnO_(2)film formation with fewer defects.Additionally,the PAA-EA-modified SnO_(2)facilitated a uniform and compact perovskite film,enhancing the interface contact and carrier transport.Consequently,the PAA-EA-modified PSCs exhibited excellent PCE of 24.34%and 22.88%with high reproducibility for areas of 0.045 and 1.00 cm~2,respectively.Notably,owing to structure reinforce effect of PAA-EA in SnO_(2)ETL,flexible device demonstrated an impressive PCE of 23.34%while maintaining 90.1%of the initial PCE after 10,000 bending cycles with a bending radius of 5 mm.This successful approach of polyelectrolyte reinforced hybrid organic–inorganic ETL displays great potential for flexible,large-area PSCs application.

Theoretical prediction for effective properties and progressive failure of textile composites:a generalized multi-scale approach

A generalized analytical model is developed to predict progressive failure behavior of several types of textile composites,including plain weave composites,twill weave composites,two-dimensional tri-axially braided composites and warpreinforced 2.5-dimensional braided composites.In this model,the unit cell(UC)of composite is firstly identified and reconstructed into a refined lamina structure with multiple equivalent lamina elements(ELEs)based on apt geometrical approximation and assumptions.Secondly,two-way coupled stress-strain responses within the UC(macro-scale)and ELE(meso-scale)are established through a universal series-parallel model(SPM).Finally,a progressive damage model,which consists of damage initiation criteria and a stiffness evolution strategy,is employed to predict damage behavior of the ELE.The analytical results including mechanical properties and progressive failure process are validated against the existing numerical and experimental ones in literature.The validated analytical model is then used to study the effects of global fiber volume fraction,braided angle,shear failure coefficient and selected failure criteria on stiffness,strength and failure process.The present results demonstrate the efficiency and generic capability of the present analytical model for predicting the mechanical responses of a range of textile composites.

Highly efficient computation method for hazard quantification of uncontained rotor failure

Uncontained Engine Rotor Failure(UERF)can cause a catastrophic failure of an aircraft,and the quantitative assessment of the hazards related to UERF is a very important part of safety analysis.However,the procedure for hazard quantification of UERF recommended by the Federal Aviation Administration in advisory circular AC20-128A is cumbersome,as it involves building auxiliary lines and curve projections.To improve the efficiency and general applicability of the risk angle calculation,a boundary discretization method is developed that involves discretizing the geometry of the target part/structure into node points and calculating the risk angles numerically by iterating a particular algorithm over each node point.The improved efficiency and excellent accuracy for the developed algorithm was validated through a comparison with manual solutions for the hazard quantification of the engine nacelle structures of a passenger aircraft using the guidance in AC20-128A.To further demonstrate the applicability of the boundary discretization method,the proposed algorithm was used to examine the influence of the target size and the distance between the target and rotor on the hazard probability.