Variable-Weight Yarns for Composite Fiber Density Control
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Solution Overview
Problem
In the production of composite material parts with fiber reinforcement structures, maintaining minimal fiber density variation is challenging, especially in areas with decreasing thickness, where withdrawing yarns significantly affects density when few layers remain.
Innovation Solution
The use of variable-weight yarns, composed of separable assemblies of individual yarns, allows for weight adjustment during multilayer weaving to minimize fiber density variations in areas of reduced thickness, achieved by progressively extracting yarns or replacing them with adjacent variable-weight yarns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If yarns are withdrawn to match reductions in part thickness, then the quasi-final shape and dimensions of the part are achieved, but fiber density varies significantly when few layers remain
Solution Approach 1:
The yarns are divided into separable assemblies of individual yarns (e.g., 4 individual yarns making up one variable-weight yarn). This segmentation allows selective withdrawal of individual yarns rather than entire layers, enabling fine-grained control over fiber density in regions of reduced thickness while maintaining the overall quasi-final shape of the part.
Solution Approach 2:
The structure uses variable-weight yarns that can dynamically adjust their composition by progressively extracting individual yarns from the assembly. This dynamic reconfiguration allows the fiber density to be adapted locally in real-time during the weaving process, particularly in areas where thickness is reduced, thereby maintaining density uniformity while achieving the target shape.
2Volume of moving object
If the number of yarn layers is reduced in portions of small thickness, then the shape matches the final part dimensions, but fiber density variation becomes too great
Solution Approach 1:
The patent applies different yarn configurations to different regions of the structure. In portions of small thickness, variable-weight yarns with separable assemblies are used instead of uniform yarns throughout. This allows local adjustment of fiber density by selectively withdrawing individual yarns from the assembly only in the regions where thickness is reduced, thereby maintaining density uniformity locally while achieving the required thin profile.
Solution Approach 2:
The weight parameter of the yarns is made variable through the use of separable assemblies. By changing the number of individual yarns remaining in the assembly (from 4 down to fewer), the effective yarn weight and thus the fiber density can be adjusted to compensate for the reduced number of layers in thin portions, maintaining consistent density despite volume reduction.
3Manufacturing precision
If variable-weight yarns with separable assemblies are used, then fiber density variation is minimized in reduced thickness portions, but yarn structure complexity increases
Solution Approach 1:
While segmentation into individual yarns does increase structural complexity, it enables the withdrawal mechanism to operate at a finer scale. Instead of withdrawing entire layers of uniform yarns, individual yarns can be selectively removed from the assembly, providing precise control over fiber density with minimal variation, thus justifying the increased complexity through significant gains in manufacturing precision.
Data Source
AI summary
A fiber structure for reinforcing a composite material part, the structure being woven as a single piece by multilayer weaving between a first plurality of layers of yarns extending in a first direction and a second plurality of layers of yarns extending in a second direction. The second plurality of layers of yarns includes at least one layer of variable-weight yarns, each variable-weight yarn including a separable assembly of individual yarns, each having a determined weight. The fiber structure includes at least one portion of reduced thickness in which the variable-weight yarn presents a weight that is less than the weight that it presents prior to the reduced thickness portion.