Prediction method for normalized fatigue delamination propagation rate of CFRP (carbon fiber-reinforced plastic) multi-directional laminated plate

Abstract

The invention discloses a prediction method for a normalized fatigue delamination propagation rate of a CFRP (carbon fiber-reinforced plastic) multi-directional laminated plate. The method comprises steps as follows: (1) fatigue delamination tests are performed on the CFRP multi-directional laminated plate under I / II mixed type static force and in different stress ratios; (2) fatigue delamination propagation resistance Gcf(a) changing with the delamination length is determined with a flexibility method; (3) a ratio of energy release rate variation amplitude deltaG and the fatigue delamination propagation resistance Gcf(a) is used as a normalized fatigue delamination propagation rate control parameter, and an expression of the normalized fatigue delamination propagation rate da / dN is corrected and established on the basis of a Paris formula; fitting parameters in the expression are obtained through linear fitting of fatigue delamination test data in a known stress ratio; (4) the fatigue delamination propagation rate in an unknown stress ratio is predicted by the aid of the expression of the fatigue delamination propagation rate in the known stress ratio. According to the method, the fatigue delamination propagation rate in the unknown stress ratio is predicted by the aid of the expression of the normalized fatigue delamination propagation rate of the CFRP multi-directional laminated plate in the known stress ratio, the test cycle can be significantly shortened, and the test cost can be reduced.

Description

technical field [0001] The invention relates to the field of prediction of fatigue delamination expansion rate of CFRP multidirectional laminates, in particular to a normalized fatigue delamination expansion rate prediction method based on Pairs formula correction. Background technique [0002] Carbon fiber reinforced composites are gradually used in the main load-bearing structures of aircraft due to their good mechanical properties. Delamination is one of the most common damage forms of composite laminates, and delamination damage leads to a significant decrease in the strength and stiffness of the laminate structure, and even leads to catastrophic accidents, which seriously restricts the application of composite materials in the main structure of aircraft. Aircraft structural components must not only meet the static strength design requirements, but also meet the service life requirements under a given reliability, which means that the structure must be able to withstand ...

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Problems solved by technology

[0003] The fatigue delamination growth rate is related to the corresponding strain energy release rate. Most of the current literatures express the composite fatigue delamination growth rate as a function of the strain energy release rate based on the modification of the Paris formula. However, the existing research has a major deficiency In the expression of the fatigue delamination growth rate of composite multi-directional laminates, the experimental undetermined constants related to its materials change with the change of stress ratio, and the fatigue delamination growth rate of composite material laminates under the known stress ratio R The expression of the fatigue delamination growth rate under the unknown stress ratio R cannot be speculated, and the general expression of the fatigue delamination growth rate that can remove the influence of the stress ratio R has not been proposed. In order to determine the fatigue delamination growth rate under different stress ratios R The rate needs to carry out the fatigue delamination expansion test under different stress ratio R separately, the test period is long and the cost is high

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