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[Display omitted] • The complex fiber structure of 3D needled preform was reproduced using virtual fibers. • A fiber-level VFE (virtual fiber embedded) method was proposed to model 3D needled composite. • Stiffness correction method of the VFE element was proposed to achieve a reasonable stiffness of the model. • Damage constitutive models of virtual fiber and matrix were developed for failure simulation of the composite. The objective of this paper is to propose a fiber-level modeling method for simulating tensile fracture of 3D needled composite. The complex fiber structure of 3D needled nonwoven preform is reproduced using virtual fibers. Micro-scale model of the composite is established by embedding virtual fiber structure into the voxel meshes of matrix material. The novel stiffness correction method is developed to solve the problems of volume redundancy and loss of reinforcing effect in transverse and shearing directions of the virtual fiber embedded element. The stiffness of the virtual fiber is not changed by the stiffness correction, ensuring that the stress of the virtual fibers is accurate. Damage initiation and evolution for fiber and matrix materials are characterized by the development of damage constitutive models. The tensile behavior of 3D needled composite is simulated. Influence of modeling parameters, including virtual fiber diameter and voxel mesh density on calculation accuracy is analyzed. Experimental tests are conducted to verify the simulation results. It is indicated that the predicted stress–strain response, strength, and fracture mode all agree well with the experimental results. [ABSTRACT FROM AUTHOR]

Lambda wing, as a commonly used configuration for modern combat aircraft, tend to reduce stability margin known as Pitch-Break before the wing completely stalls. This phenomenon greatly affected the safety of aircraft at high angles of attack. In this paper, the characteristics of Pitch-Break are clarified and it is found that the initial airflow separation position of the outer wing is the principal reason for generating nonlinear moment of lambda wing. The airflow separation position is generally affected by leading edge vortex and the trailing edge spanwise airflow. Furthermore, the following conclusions are obtained: 1. The distribution of the absolute value of the leading edge radius is a decisive parameter of the initial position of leading edge vortex at the beginning of Pitch-Break zone; 2. The difference of trailing edge pressure gradient brings difference of trailing edge spanwise airflow at the end of Pitch-Break zone. To solve the aerodynamic problem of Pitch-Break, this paper adopts an all moving wingtip (AMT) as auxiliary aileron which has minor fluctuations during the Pitch-Break zone compared with conventional aileron. The result shows the defect of the conventional aileron pitch control at high angle of attack and presents the engineering feasibility of the all moving wingtip auxiliary aileron. [ABSTRACT FROM AUTHOR]

• This paper studies the debonding problem in the Eshelby's elliptical inclusion with remote stresses. • If one increases the remote loading gradually, the normal stress along interface will be changing from negative to positive. • This limit loading for the remote stresses becomes the debonding loading. • Two particular cases for debonding problem are solved in the present paper. • Complex variable method is used in the study. This technical note studies the debonding problem in the Eshelby's elliptical inclusion with remote stresses. Usually, if one inserts eigenstrains in the inclusion, the normal stress along the interface of matrix and inclusion is negative. In addition, if one increases the remote loading gradually, the normal negative stress along interface will be becoming vanishing. This limit loading for the remote stresses becomes the debonding loading. Two particular cases for debonding problem are solved in the present note. [ABSTRACT FROM AUTHOR]