Tapered Drop-off Plies for Variable Gage Composite Structures
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Solution Overview
Problem
Existing composite structures with variable gages face issues such as large resin pockets, delamination, ply kinks, and reduced laminate strength due to blunt-end shaped drop-off plies arranged in clusters, which can lead to reduced interlaminar strength and increased risk of wrinkles under thermal and mechanical loads.
Innovation Solution
The use of tapered-shaped drop-off plies, arranged in a pattern that mirrors each other on either side of a central portion, with staggered and spaced positions to minimize resin pockets and enhance interlaminar strength, allowing for a smoother transition between different gages while reducing material handling costs and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If blunt-end shaped drop-off plies are arranged in clusters to achieve variable gage, then manufacturing simplicity is improved, but interlaminar strength deteriorates and resin pockets form
Solution Approach 1:
The patent applies local quality by transitioning from uniform blunt-end plies to tapered plies with varying thickness profiles. Each drop-off ply has a tapered shape that locally adapts to the variable gage requirement, with the thickness gradually reducing to zero at the drop-off point. This local geometric adaptation eliminates resin pockets and improves interlaminar strength while maintaining manufacturing feasibility through automated tape placement systems.
Solution Approach 2:
The patent implements parameter changes by modifying the geometric parameters of the drop-off plies from blunt-end shapes to tapered shapes. The tapered plies have controlled thickness variations along their length, with specific taper angles and transition zones that optimize both structural performance and manufacturability. This parameter optimization resolves the contradiction by enabling variable gage construction without the harmful effects of blunt-end ply clustering.
2Adaptability or versatility
If variable gage composite structures are formed with traditional methods, then adaptability to different structural requirements is improved, but manufacturing precision deteriorates due to ply kinks and wrinkles
Solution Approach 1:
The patent applies preliminary action by pre-forming the drop-off plies with tapered shapes and optimized geometric parameters before placement. The plies are designed with predetermined taper angles, transition zones, and drop-off locations that account for the variable gage requirements. This pre-planning and pre-forming approach ensures that when the plies are placed using automated systems, they maintain proper alignment and flatness without developing kinks or wrinkles, thus preserving manufacturing precision while achieving structural adaptability.
Solution Approach 2:
The patent implements dynamics by using automated tape placement systems that can dynamically adjust placement parameters during manufacturing. The system can vary ply orientation, tension, and positioning in real-time to accommodate the tapered geometry of drop-off plies. This dynamic control capability enables precise placement of variable gage plies without manual intervention, maintaining high manufacturing precision while achieving the adaptability needed for complex structural configurations.
3Strength
If more plies are used to increase laminate strength, then strength is improved, but weight increases
Solution Approach 1:
The patent applies local quality by implementing variable gage construction where the ply thickness and material density are locally optimized according to the structural requirements at each position. In high-stress regions, more plies or thicker sections are used to provide enhanced strength, while in low-stress regions, fewer plies or thinner sections are used to reduce weight. The tapered drop-off plies enable smooth transitions between these varying thickness zones, creating a weight-optimized structure that maintains necessary strength without unnecessary material.
Solution Approach 2:
The patent implements parameter changes by systematically varying the ply count, thickness, and material properties across the structure based on stress analysis and performance requirements. The tapered plies have controlled thickness parameters that transition from full thickness to zero over specific zones, allowing precise control over the weight-strength trade-off. This parametric optimization enables the structure to achieve maximum strength-to-weight ratio by placing material only where structurally necessary.
Data Source
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AI summary
A composite structure (300) includes a first end (310A) having a first gage (312A), a second end (310B) having a second gage (312B), which is less than the first gage, a plurality of continuous plies (318A), and a plurality of drop-off plies (318B). Each continuous ply extends from the first end to the second end. Each drop-off ply includes a tip having a tapered shape. Each drop-off ply extends from the first end to a respective position of the tip of the drop-off ply between the first end and the second end. The plurality of drop-off plies are separated from each other by at least one of the plurality of continuous plies.