Composite Laminate Wrinkle Reduction via Off-Angle Plies
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Solution Overview
Problem
Traditional laminate layups using 0°, 45°, and 90° plies often result in ply wrinkling during the forming of contoured composite laminate parts with high aspect ratios, such as stringers and spars, due to fiber compression along the part's length.
Innovation Solution
The method involves selecting a set of fiber angles (+θ1, +θ2, ±θ3) for unidirectional reinforcing fibers, where none of the angles are 0° relative to the major axis of loading, and determining the number of plies in each zone to achieve desired in-plane laminate properties. The plies are then laid up in a flat stack and formed into the contoured shape without using 0° plies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional laminate layups using 0°, 45°, and 90° plies are used, then the part can achieve desired stiffness and strength, but ply wrinkling occurs during secondary forming operation due to fiber compression
Solution Approach 1:
The invention changes the fiber orientation parameter from traditional 0°/45°/90° plies to a quasi-isotropic stacking sequence with specific angles (e.g., [0/6.7/13.3/20/26.7/33.3/40/46.7/53.3/60/66.7/73.3/80/86.7/90] degrees). This parameter change eliminates 0° plies that cause compression wrinkling while maintaining structural performance through distributed fiber orientations.
Solution Approach 2:
The continuous fiber orientation spectrum is segmented into discrete ply angles distributed across the stacking sequence. Instead of having concentrated 0° fibers that buckle, the load-carrying function is segmented across multiple angled plies, each contributing to both axial stiffness and wrinkle resistance.
2Manufacturing precision
If 0° plies are cut into segments to reduce wrinkling, then ply wrinkling is reduced, but load carrying ability decreases
Solution Approach 1:
Instead of segmenting 0° plies, the invention changes the fundamental parameter of fiber orientation to use distributed angled plies. This maintains continuous load paths through the laminate while eliminating the compression-induced wrinkling that occurs with 0° fibers during forming.
3Strength
If additional plies are added to compensate for reduced load carrying ability, then load carrying ability is restored, but material costs and part weight increase
Solution Approach 1:
The invention optimizes the stacking sequence parameters to achieve quasi-isotropic behavior with exactly 16 plies. This optimized configuration provides both the required load carrying ability and wrinkle resistance without adding excess weight, as each ply contributes efficiently to both axial stiffness and forming performance.
Solution Approach 2:
Each ply in the quasi-isotropic stacking sequence serves multiple functions: providing axial stiffness, resisting compression wrinkling, and contributing to overall laminate strength. This multi-functionality eliminates the need for additional plies to compensate for performance deficiencies.
4Quantity of substance
If traditional 0°, 45°, and 90° plies are used, then material costs are reduced, but production rate decreases due to rework needed to eliminate wrinkling
Solution Approach 1:
The wrinkle-prevention strategy is built into the laminate design from the beginning through the quasi-isotropic stacking sequence. This preliminary action eliminates the need for post-forming rework, maintaining material efficiency while improving production rate by preventing defects before they occur.
Data Source
Figure 1~3
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Figure 6~7
AI summary
Wrinkling of a contoured composite laminate part (30) during forming to contour is reduced by using laminate plies (44) having off-angle reinforcing fibers (48) that provide the part with primary axial strength along a major axis of loading (40).