Composite Structure Ply Configuration for Thermal Distortion
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Solution Overview
Problem
Composite structures face challenges in achieving optimal stiffness and minimizing thermal-induced distortion during manufacturing, particularly when using un-balanced ply sets which can introduce bending torsion coupling and distortion due to thermal expansion mismatches.
Innovation Solution
The structure comprises two regions with balanced and un-balanced ply sets, where the number of primary and cross plies are equal in one region and the number of positive-angled and negative-angled bias plies are equal in the other, with a quasi-isotropic region for smooth transition, to balance stiffness and reduce distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If un-balanced ply sets are used to increase stiffness in one bending direction, then the stiffness of the structure along the principal bending axis is improved, but thermal-induced distortion and bending torsion coupling occur during manufacturing
Solution Approach 1:
The structure is divided into multiple regions (first region, second region, and optional third region) with different ply configurations. The first region uses un-balanced primary and cross plies for high stiffness, the second region uses un-balanced bias plies for bending-torsion coupling, and the third region uses balanced plies for smooth transition and minimal distortion.
Solution Approach 2:
Different regions of the structure have different ply orientations and balance characteristics tailored to local requirements. The first region has N1>N4 for high bending stiffness, the second region has N2≠N3 for controlled torsion, and the third region has N1=N4 and N2=N3 for smooth transitions.
2Manufacturing precision
If balanced bias plies are used to prevent bending torsion coupling, then manufacturing distortion is reduced, but the ability to control torsional stiffness and achieve desired physical characteristics is limited
Solution Approach 1:
The structure is divided into multiple regions (first region, second region, and optional third region) with different ply configurations. The first region uses un-balanced primary and cross plies for high stiffness, the second region uses un-balanced bias plies for bending-torsion coupling, and the third region uses balanced plies for smooth transition and minimal distortion.
Solution Approach 2:
Different regions of the structure have different ply orientations and balance characteristics tailored to local requirements. The first region has N1>N4 for high bending stiffness, the second region has N2≠N3 for controlled torsion, and the third region has N1=N4 and N2=N3 for smooth transitions.
3Strength
If the proportion of primary plies is increased to increase stiffness, then the stiffness along the principal bending axis is improved, but the ply set becomes un-balanced causing thermal expansion mismatch
Solution Approach 1:
The structure is divided into multiple regions (first region, second region, and optional third region) with different ply configurations. The first region uses un-balanced primary and cross plies for high stiffness, the second region uses un-balanced bias plies for bending-torsion coupling, and the third region uses balanced plies for smooth transition and minimal distortion.
Solution Approach 2:
Different regions of the structure have different ply orientations and balance characteristics tailored to local requirements. The first region has N1>N4 for high bending stiffness, the second region has N2≠N3 for controlled torsion, and the third region has N1=N4 and N2=N3 for smooth transitions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a compromise between increased stiffness and reduced thermal distortion by maintaining balanced ply sets in critical regions and allowing un-balanced bias plies to introduce bending torsion, minimizing distortion while maintaining structural integrity.
Implementation Method 1
distortion due to the mismatch in thermal expansion between the positive and negative-angle bias plies
Implementation Method 2
each ply having a ply orientation defined by a principal stiffness direction of the ply
Data Source
AI summary
A structure comprising a plurality of plies of fibre-reinforced composite material, each ply having a ply orientation defined by a principal stiffness direction of the ply. The structure has a first region and a second region, each region comprising N1 primary plies, N4 cross plies with a ply orientation substantially perpendicular to the primary plies, N2 positive-angled bias plies with a ply orientation at a positive acute angle to the primary plies, and N3 negative-angled bias plies with a ply orientation substantially perpendicular to the positive-angled bias plies. The ply orientation of the primary plies in each region is more closely aligned with a primary axis of the structure than the cross plies or the bias plies. N1=N4 in the first region but not in the second region, and N2=N3 in the second region but not in the first region. In each of the two regions, one ply set is balanced and the other ply set is un-balanced. This provides a compromise between the advantages of using un-balanced ply sets, for instance to provide bending torsion coupling, and the disadvantage that un-balanced ply sets can introduce thermally induced distortion during manufacture.