Modified Modulus Composite Laminate for Coating Microcrack Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Composite laminate structures in aircraft experience strain mismatch between secondary coatings and the underlying structure due to differences in thermal expansion, moisture expansion, and modulus, leading to cracking and microcracking, which increases repair costs and compromises structural integrity.
Innovation Solution
A modified modulus composite laminate system with a surface layer and secondary coating having tailored thermal and moisture expansion coefficients and moduli, integrated to provide stress relief and dampening, minimizing cracking and microcracking during thermal and moisture cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a secondary coating is applied to a composite laminate structure, then the appearance and protection are improved, but strain mismatch between the coating and structure causes cracking and microcracking
Solution Approach 1:
The patent applies an intermediate strain isolation pad layer between the secondary coating and the composite laminate structure. This intermediary layer has different mechanical properties (lower modulus of elasticity) than both the coating and the structure, allowing it to absorb and distribute strains, preventing direct stress transfer that causes cracking while maintaining coating adhesion and integrity
2Strength
If the modulus of the surface layer is increased to match the secondary coating, then adhesion is improved, but thermal and moisture cycling causes strain mismatch and cracking
Solution Approach 1:
The patent changes the modulus of elasticity parameter of the surface layer by introducing a strain isolation pad material with lower stiffness than both the composite laminate and the secondary coating. This parameter modification allows the surface layer to accommodate thermal and moisture expansion differences, reducing strain mismatch and preventing cracking while maintaining sufficient adhesion strength
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
The system enhances microcracking resistance and reduces structural degradation by matching the modulus of the surface layer with the secondary coating, improving thermal moisture cycling performance and reducing repair needs.
Implementation Method 1
The surface layer with the modified modulus creates a stress relief between the at least one secondary coating and the plurality of structural ply layers
Implementation Method 2
The surface layer with the modified modulus creates an integrated dampening between the at least one secondary coating and the plurality of structural ply layers
Implementation Method 3
provide an increased microcracking resistance and a minimized structural degradation... to minimize or prevent surface microcracking or cracking in the secondary coating to avoid repair or rework
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
There is provided a modified modulus composite laminate system (10) including a composite laminate assembly (16) having structural ply layers (22) preimpregnated with a structural resin (60). The system (10) includes a surface layer (12) applied to the composite laminate assembly (16), and having a modified modulus (25c) less than, or equal to, a ply modulus (25a), a surface layer coefficient of thermal expansion (26b) different from a ply coefficient of thermal expansion (26a), and a surface layer coefficient of moisture expansion (28b) different from a ply coefficient of moisture expansion (28a). The system (10) has at least one secondary coating (70) applied to the surface layer (12). The modified modulus (25c) of the surface layer (12) is modified to be greater than, or equal to, a secondary coating modulus (25d). The surface layer (12) creates a stress relief (31) and an integrated dampening (102) between the secondary coating (70) and the structural ply layers (22), to provide an increased microcracking resistance (106) and a minimized structural degradation (108) of the modified modulus composite laminate system (10).