Chevron Step-Lap Splice for Wrinkle-Resistant Composite Structures
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Solution Overview
Problem
Fabricating composite structures with complex geometries, such as those found in aircraft fuselages, is challenging due to issues like wrinkling and ply bridging, which existing methods fail to fully address, especially when using automated equipment.
Innovation Solution
A method involving the formation of step lap splices with chevron and counterpart shapes in composite structures to reduce stress and inconsistencies, where each layer of a first section overlaps with a corresponding layer in a second section, forming a chevron and counterpart pattern to create a lap splice joint that mitigates wrinkling and crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high contour fabrication is performed through layer by layer hand draping, then complex geometries can be fabricated, but the process is labor-intensive and utilizes large amounts of space
Solution Approach 1:
The fuselage is divided into multiple sections with splice locations where chevrons are formed in each layer. This segmentation allows automated equipment to fabricate complex geometries by assembling multiple sections rather than requiring continuous hand draping, thereby reducing labor intensity and space requirements while maintaining the ability to create complex shapes.
2Productivity
If automated equipment is used to fabricate composite structures, then productivity increases, but undesired inconsistencies such as wrinkling and ply bridging occur
Solution Approach 1:
Chevron shapes are formed locally at splice locations within the composite layers. This local modification of the laminate structure at critical splice areas prevents wrinkling and ply bridging that typically occur during automated fabrication, while allowing the rest of the structure to be manufactured with high productivity using automated equipment.
Solution Approach 2:
The chevron patterns are pre-formed in each layer before final assembly and curing. This preliminary action at the splice locations prepares the structure to accommodate automated fabrication processes without developing surface defects, thereby maintaining both high productivity and manufacturing precision.
3Device complexity
If splices are formed in composite structures, then sections can be assembled to reduce manufacturing complexity, but stress concentration and crack propagation occur at splice locations
Solution Approach 1:
Chevron shapes with asymmetric geometry are formed at splice locations, creating a tapered transition that distributes stress more evenly across the splice area compared to traditional symmetric lap joints. This asymmetric design reduces stress concentration and mitigates crack propagation while maintaining simplified section assembly.
Data Source
AI summary
A method for fabricating a composite structure. A first section for the composite structure is formed in which the first section has a first end with a chevron shape, wherein first composite layers in the first section has a first step pattern at the first end. A second section for the composite structure is formed in which the second section has a second end with a counterpart shape to the chevron shape and in which second composite layers in the second section have a second step pattern at the second end. The first end the second end are positioned such that a first composite layer in the first composite layers in the first step pattern overlap the second composite layers in the second step pattern at a splice location.