Research On The Effect Of Gap-Filling Parameters On Mechanical Behavior Of The Bolt Connected Composite Structure

Advanced composite materials are widely used in aircraft manufacturing due to the extraordinary performance in weight reduction,fatigue resistance,corrosion resistance and designability.However,there also exposes many problems during engineering application,one of which is gap-filling during the assembly of aircraft composite components The complex forming process of the composite material leads to the low manufacturing precision of the composite parts.Assembly gap will be created between the mating surfaces due to the geometric and dimensional deviation of composite parts.If the inappropriate compensation measures was adapted,the damage would be created inside the composite such as delamination,crack propagation.In order to achieve reasonable compensation for the assembly gap,the effects of compensation on assembly quality of composite structure must be understood first.This paper makes a research on the issue of gap-filling compensation for the assembly of composite components.In order to summarize the influence of the compensation parameters on the mechanical properties of the composite assembly structure,two aspects of related content are discussed: The effect of gap-filling parameters on the stress and strain of composite assembly structure and the effect of gap-filling parameters on the mechanical behavior of the composite to composite single lap joint.The main research contents are summarized as follows:(1)The research on the effect of gap-filling parameters on the stress and strain of composite assembly structure is based on the assembly experiment and the corresponding FEM analysis of composite components.Additional assembly stress and strain are primary concerned.In the part of strain analysis,the areas of composite affected relatively more seriously by the assembly gaps are identified by the characteristics of surface strain distribution.The function of liquid shim and peelable shim are compared based on the strain fluctuation before and after the gap-filling operation.The results showed that: The area close to the fixed end is affected by the assembly gaps relative more seriously;The introduce of liquid shim is helpful to make the strain distribution more uniform;The performance of the peelable shim is not as good as the liquid shim.In the part of stress analysis,the stress analysis is mainly based on the finite element simulation model,aiming at exploring t the variations of compensation effect of the liquid shim with the increase of assembly gap.The results showed that: The liquid shim achieves relatively good performance in the assembly gap interval within 0.2~0.7mm.(2)The research on the effect of gap-filling parameters on the mechanical behavior of the composite to composite single lap joint is implemented.The tensile stiffness and strength of the joints with or without the gap-filling operation are compared to analyze the effect of material and thickness of the shim on the tensile properties of the joint.The results showed that: The introduction of shim layer helps to improve the ultimate load;The tensile stiffness of the joint is relative more larger when adapting peelable shim;The load distribution of the inner wall of the bolt hole tends to be concentrated and the ultimate load of the joint is decreased with the increase of the thickness of the shim layer.