| Composite materials are widely used in aerospace field due to their specific strength, high specific modulus and design advantages. Composite materials will be affected by various types of impact inevitably in the actual use process. This has a serious potential threat on its subsequent use. Therefore, damaged composite materials need to be repaired in time to restore its performance to guarantee the continuous use. Composites and their impact damage are studied in this paper. The repair technology to improve the using safety performance of composite materials has important value of theory and application.In this paper, carbon fiber/epoxy resin composite material was prepared with carbon fiber cloth and epoxy resin as raw materials according to [0/90] and [0/45] two layer direction, by hand lay- up molding method. The change laws of residual compression strength and compression ratio composites after 4 J impact was studied under the impact of different quality bullet(160 g, 250 g, 330 g), different shapes impact bullet(semicircle, plane, frustum of a cone shape) and different impact conditions(for support). Impact finite element model of composites was established based on finite element analysis software ABAQUS and the differences of the impact damage between the simulation and nondestructive testing(ultraso nic F) were compared. Burning method was used to measure the composite resin content, and the resin content for the compression after impact of composite materials was analyzed. Dig repair method was used to repair for the half thickness of the damage composite materials repair. The effect of recovery rate and quality increase rate of different repair layers was studied.In this paper, the research conclusions are as follows:1) Semicircle impact for decline rate of composites was maximum, because the contact area between impact bullet and composites was smallest, impact damage in composites was the most serious. The compression after impact is 125.67 MPa,117.67 MPa respectively whether composites placed in the bracket of the 12 cm span or not; the compression rate is 3.54%, 3.37 respectively. This indicates that impact damage to the overhead of the composite materials was smaller.2) Finite element model of composite impact materials was established based on finite element analysis software ABAQUS with combining the Hshin composite material failure criterion. Damage under certain energy was calculated. Simulation results showed that the composite internal delamination damage area was 265 mm2 and the damage area was 253.34mm2 by ultrasonic C scan detecting. The two differ by 4.40%. Composite materials subjected to impact, the simulation calculation of the maximum impact load of 11469 N and the experiment of measuring maximum impact load of 11828 N. The two differ by 3.04%. The relation between the composite materials in impact time of 0.057 seconds to absorb impact energy and impact time is: y = 2724 x2.4with using ABAQUS post-processing provide data and origin of fitting.3) Resin content of composite was 61.7%, 56.8% and 52.2% respectively containing 7, 8, 9 layer quality of fiber. The drop rate of compression after impact of the samples was 19.3%, 11.5% and 10.4% respectively. Impact resistance of composites was stronger with more carbon fiber layer4) The intensity recovery rate of composite materials was 58.63%, 67.67% and 73.00% respectively with 1, 2, 3 layer respectively of carbon fiber cloth after repair。The rate of qauality increases was 3.66%, 5.42% and 8.22% respectively. The repair of composites with 2 layer was the best. |
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