| Carbon fiber reinforced composites have good mechanical properties and are widely used in aerospace,mechanical,electrical and other fields.However,there will be delamination damage,fiber fracture and matrix cracking in the process of use.At present,damaged parts need to be replaced after material damage,but in recent years,the repair and healing of damaged materials have gradually become a hot research direction in consideration of economic conditions and difficult replacement in local areas.In this paper,a numerical model was established to study the fracture toughening and healing properties of polyethylene-methacrylic acid(EMAA)suture braided composite,and the experimental method was used to verify the fracture toughening and healing properties,and the parameters affecting the healing properties were optimized.EMAA self-repairing carbon fiber composites were prepared by three-dimensional suture toughening and phased curing process.Based on the type I interlayer fracture toughness test,the crack growth behavior and fracture toughness properties of the composites under loading and repairing conditions were studied.The nonlinear spring model was used to study the discrete bridge mechanism,and the double-partition cohesive zone model and modified spring parameters were used to realize the numerical modeling and simulation calculation before and after repair.The experimental and simulation results show that the numerical model can accurately predict the type I crack growth resistance curve and fracture toughness of the original and repaired composites with three-dimensional self-healing network.The addition of EMAA improves the actual toughness of interlayer fractures.The interlayer toughness and repair efficiency are positively correlated with the content of EMAA.Secondly,based on the influence of parameters such as EMAA suture spacing,diameter,area fraction and content on the self-healing performance of interlaminar fracture,single-parameter optimization and multi-parameter optimization were carried out for the self-healing performance of interlaminar fracture.When EMAA suture spacing was 7.52 mm,diameter was 1.42 mm and area fraction was 13.3%,the optimal healing efficiency was 245%,which was 46.6% higher than that without optimization.The finite element model was used to verify the optimization results.Then,the influence of EMAA on the impact resistance and repair effect of plain braided carbon fiber composites was studied by experimental and numerical methods.The self-healing impact specimens were prepared by three-dimensional suture toughening and staged curing process.Based on low-speed impact tests,the peak impact force and impact resistance of the composites were studied under unrepaired and repaired conditions.The nonlinear spring model was used for numerical model modeling,numerical modeling and simulation calculation before and after repair.The experimental and simulation results show that the established finite element model can accurately predict the impact performance of EMAA repair agent.The addition of EMAA can improve the impact resistance of the structure before and after repair,and the impact resistance of the structure after repair is significantly improved.With the increase of EMAA repair agent content,impact peak value,impact time and impact performance were enhanced.Finally,based on the influence of EMAA suture parameters such as spacing,diameter,area fraction and content on the anti-impact damage performance,the anti-impact damage performance was optimized by single parameter and multi-parameter respectively.When the transverse and longitudinal spacing of EMAA suture was 5.25 mm,the diameter was 1.93 mm,and the area fraction content was9.81%,the minimum absorption energy was 3.716 J,which was 29.4% lower than that of 5.266 J without EMAA healing agent.The finite element model was used to verify the optimization results. |
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