Composite Laminate Surface Layer for Coating Microcrack Resistance
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Solution Overview
Problem
Existing composite laminate structures 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 where a surface layer with modified thermal and moisture expansion coefficients and modulus is applied to match the secondary coating, providing stress relief and integrated damping to enhance microcracking resistance and minimize structural degradation during thermal and moisture cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a secondary coating is applied to a composite laminate structure with different CTE, CME, and modulus, then the secondary coating provides protective and aesthetic functions, but thermal moisture cycling causes strain mismatch leading to cracking and microcracking in the coating and underlying structure
Solution Approach 1:
The patent introduces a surface layer as an intermediary component between the composite laminate structure and the secondary coating. This surface layer has engineered CTE, CME, and modulus values that are intermediate between those of the composite structure and the secondary coating, thereby reducing the strain mismatch and preventing cracking while maintaining coating integrity
Solution Approach 2:
The patent modifies the physical parameters (CTE, CME, modulus) of the surface layer to create a gradient transition. By carefully selecting these parameters, the surface layer accommodates thermal and moisture expansion differences, reducing stress concentration and preventing crack formation during thermal moisture cycling
2Strength
If surface modification is applied to increase adhesion of secondary coating, then coating adhesion is improved, but the flexibility of the coating is not sufficient to address modulus mismatch and prevent internal cracking
Solution Approach 1:
The patent changes the modulus parameter of the surface layer to be closer to that of the secondary coating. This parameter adjustment allows the surface layer to flex with the coating during thermal moisture cycling, preventing internal cracking while maintaining strong adhesion between the coating and the modified surface
3Object-affected harmful factors
If strain isolation pad is used between two materials, then thermal expansion mismatch is reduced, but this solution is not effective for thermoset composite materials and secondary coatings
Solution Approach 1:
The patent employs a composite surface layer that is specifically designed for compatibility with thermoset composite materials and secondary coatings. This composite surface layer integrates the benefits of strain isolation while being chemically and physically compatible with the specific material system, unlike conventional strain isolation pads used with ceramic and metal materials
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 effectively reduces cracking and microcracking, improving the structural integrity and reducing maintenance costs by matching the modulus of the surface layer with the secondary coating, thus enhancing the composite laminate's performance under thermal and moisture exposure.
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... when the modified modulus composite laminate system is subjected to one or more of, a thermal exposure, and a moisture exposure, in a thermal moisture cycling
Data Source
AI summary
There is provided a modified modulus composite laminate system including a composite laminate assembly having structural ply layers preimpregnated with a structural resin. The system includes a surface layer applied to the composite laminate assembly, and having a modified modulus less than, or equal to, a ply modulus, a surface layer coefficient of thermal expansion different from a ply coefficient of thermal expansion, and a surface layer coefficient of moisture expansion different from a ply coefficient of moisture expansion. The system has at least one secondary coating applied to the surface layer. The modified modulus of the surface layer is modified to be greater than, or equal to, a secondary coating modulus. The surface layer creates a stress relief and an integrated dampening between the secondary coating and the structural ply layers, to provide an increased microcracking resistance and a minimized structural degradation of the modified modulus composite laminate system.