Low Velocity Impact And Compression Properties After Impact Of Repaired Composite Laminates

Benzoxazine carbon fiber resin matrix composite material is a kind of new composite material,its high temperature characteristics,low porosity,easily prepared characteristics are very remarkable,which has been widely applied in the domaine of aerospace.But in the actual service environment,the composite material will be frequently subject to external damage,such as scraping,cutting,wear etc.That will produce stratification,cracks,scratches and other forms of damage,and these damageds are needed to be repaired,but the effect on the mechanical properties due to the repairing are not yet clear.Existing studies have shown that the impact of the composite material properties will cause extremely serious damage,exacerbating the material failure,reducing the structural life of the parts.Therefore,we use the experimental method,through the repair step,using the non-destructive testing method of repair quality evaluation,carried out a fixed energy low-speed impact test,analysed the ultrasonic C scan nondestructive testing,and took the final implementation of the after-impact compression strength test,combined with fracture morphology analysis and compression data processing to measure its impact resistance.The results show that the patch repair method we use,is technically qualified,and of reliable quality.In addition,the laminates of the bulk material have less cracks than the non-bulk materials,and the length is short,and the protrusion of the matrix,the peeling of the tows and the phenomenon of resin shedding are not obvious.And for the double-side repaired test pieces,the rebound rate is higher than the single-side repaired;the double-side repaired specimens' contact time is shorter,the maximum contact force is larger,the displacement is smaller;the bulk material repaired pieces' maximum contact force is larger than the non-bulk material repaired parts;the choice of repair materials will cause a wide range of changes in the area of delamination,the bulk material repaired plates performance better,especially in the repair ladder;single-side repaired laminates' repair effect will be significantly stronger than double-side repaired ones,showing a smaller area,a narrow penetration range.The compression experiment shows that the strength and modulus of the impact plate after repair can not reach the performance before repair,and the performance degradation is not particularly obvious compared with the unshaped impact plate.For the unidirectional belt laminates,the ratio of CAI strength of bulk single-side repaired ones,bulk double-side repaired ones,non-bulk single-side repaired ones,non-bulk double-side repaired ones on the CAI strength of unrepaired laminates are 96.93%,93.97%,95.61% and 88.82% respectively,and the ratio of compression modulus are 90.30%,81.58%,82.19% and 73.73% respectively.For the two-way fabric laminates,the ratio of CAI strength of bulk single-side repaired ones,bulk double-side repaired ones,non-bulk single-side repaired ones,non-bulk double-side repaired ones on the CAI strength of unrepaired laminates are 96.12 %,89.39%,92.16% and 86.88% respectively.The ratio of compression modulus was 88.20%,74.97%,82.49% and 67.51% respectively.This is related to the residual stress strain value of the material after repair,but also with the bonding and curing effect of the material.