The Application Of Adhesive Cured At Room Temperature In The Repair Of Helicopter Composites

In this paper, the repair scheme of surface scratch and internal delamination of carbon-fibre-reinforced composite laminate with stacking structure of [45/0/0/45],[45/0/45/0/45], [45/0/45/0/45/0/45] was formulated. Surface scratch was repaired by the methods of patch-bonded repair and internal delamination was repaired by replacing damaged parts. Two kinds of adhesives named as EI and JI were used in the repair. El was imported and JI was domestic and they both cured at room temperature.The finite element models were established by the Patran/Nastran software. The strength of intact composite laminates model and the repaired laminates model were calculated with Maximal stress criterions and Tsai-Wu criterions. The tensile models of three kinds of stacking layer structure were repaired by patch-bonded method with El and JI. The residual strength of laminate repaired by El was 86.67%, 85.59 and 83.16% which was greater than that of 85.68%, 84.67% and 80.25% by JI. The residual strength of laminate repaired by EI and JI were all greater than 80% and met the repair requirements. The compression models of three kinds of stacking layer structure were repaired by replacing damaged parts with EI and JI. The residual strength of 4 layers structure laminate repaired with El and JI respectively were 61.18% and 61.45%. They were both less than 80% which did not meet the repair requirements. The residual strength of laminate with 5 and 7 layers structures repaired by El was 84.77% and 88.03% of original strength which was better than that of 81.46% and 87.19% by JI. The residual strength of laminate with 5 and 7 layers structures repaired by El and JI could meet the rapair requirements of 80% strength recover. The shear models of three kinds of stacking layer structure were repaired by replacing damaged parts with El and JI.The residual strengths repaired with El were 81.57%, 81.65% and 81.77% which met the repair requirements of 80% strength recover. However, the residual strengths repaired with El were 77.87%, 77.93% and 79.44% which did not meet the repair requirements of 80%strength recover.The test samples were made and repaired according to the plan formulation. El and JI were tested by Fourier infrared tester in order to analyze the main functional groups and chemical reactions in curing. Then tensile, compression and shear experiments were done to test the strength of the repaired composite laminate by the Mechanical testing machine. The mechanical property testing showed that the diviation between experiment and simulation was less than 10%. It showed that the finite element numerical simulation had the guiding significance for the engineering practice.The fracture of the test samples were observed by SEM and failure mode and micro fracture mechanism were determinined. The research of the paper has provided theoretical basis for aircraft repair rapidly at room temperature.