A residual strength analysis method of an aircraft composite structure with large damage based on Mar-Lin model

Abstract

A residual strength analysis method of an aircraft composite structure with large damage based on a Mar-Lin model belongs to the field of damage tolerance design and conformity certification of an aircraft composite main structure. The fracture toughness and singularity exponent n of the composites are determined by a data fitting method based on the low-order fracture test data of the composites,and a composite residual strength Mar-Lin model is built, an extrapolation method is utilized to expand the Mar-Lin model, and thus the residual strength of large-scale cracks is determined. A special finite element simulation method is used to simulate the structure and crack type of composite material and the finite element solution is carried out, then the energy release rate of crack tip is obtained by solving the finite element analysis results with the energy method, and finally, the geometrical influence factors of the structure are obtained by using the energy release rate of different configurations. The geometrical influence factors and Mar-Lin model determines the residual strength of the structure to be analyzed, and then judges whether the residual strength meets the requirements, and completes the analysis of large damage tolerance. The design risk and reliability of composite structures can be evaluated.

Description

technical field [0001] The invention relates to a damage tolerance analysis method for a composite material structure of a large civil transport aircraft, and belongs to the fields of damage tolerance design and compliance certification of a main structure of an aircraft composite material. Background technique [0002] In the field of aeronautical design, based on economic and safety requirements, the main structure of modern large transport aircraft is mostly designed using the concept of damage tolerance design. The fuselage, wing, and spherical frame of large transport aircraft are mostly designed with reinforced structures, so the damage tolerance analysis of reinforced panels plays an extremely important role in the design of large transport aircraft. Moreover, in the Advisory Circular AC20-107B, the damage suffered by composite materials is classified, and the damage tolerance design requirements for various types of damage are also specified. One of the important co...

AI Technical Summary

Problems solved by technology

[0004] Since the composite material is a hybrid anisotropic material, the failure modes of the crack tip are complex and diverse, which leads to the fact that the residual strength of the composite material structure with damage is seriously affected by parameters such as material properties, interlayer toughness, layup sequence, and laminate thickness. , it is difficult to accurately evaluate, especially the residual strength of composite structures with more than 3 types of damage

Based on the above reasons, the classic linear elastic fracture mechanics formula cannot be blindly adopted Composite residual strength is calculated, and many studies have demonstrated that composite laminates are much less sensitive to large variations in notch size than would be expected using classical fracture mechanics

Images