Stitching Yarn Linear Expansion Coefficient for Composite Microcrack Suppression
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Solution Overview
Problem
Fiber reinforced composite materials produced using stitched fiber-reinforced substrates often suffer from microcrack formation at the interface between stitching yarn and matrix resin, leading to reduced mechanical properties.
Innovation Solution
The use of stitching yarns with a linear expansion coefficient between -1×10^-6 and 70×10^-6/K after heating at 180°C for 2 hours and cooling, which reduces internal stress and interfacial delamination, thereby suppressing microcrack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If stitching yarn is used to integrate reinforcement fiber sheets, then the fiber-reinforced substrate material can be formed with high mechanical properties, but microcracks are generated around the stitching yarn which lowers the mechanical properties
Solution Approach 1:
The patent changes the physical-chemical parameters of the stitching yarn by controlling its linear expansion coefficient to be within -50 to 50×10^-6/K after heating at 180°C for 2 hours. This parameter change ensures that the stitching yarn's thermal expansion behavior matches the matrix resin, preventing differential expansion stresses that would otherwise cause microcracks during curing and cooling processes.
Solution Approach 2:
The patent converts the potentially harmful effect of thermal expansion differences into a beneficial outcome by selecting stitching yarns with specifically controlled linear expansion coefficients. The stitching yarn's thermal expansion behavior is matched to the matrix resin, transforming what would be a source of stress and microcracking into a compatible thermal response that maintains interfacial integrity.
2Object-affected harmful factors
If a stitching yarn with small yarn count (30 dTex or less) is used, then microcrack formation can be suppressed, but the interfacial adhesiveness between stitching yarn and matrix resin is still insufficient
Solution Approach 1:
The patent changes the critical parameter of linear expansion coefficient control for stitching yarns, specifying a range of -50 to 50×10^-6/K after heating at 180°C for 2 hours. This parameter change addresses the root cause of microcrack formation (thermal expansion mismatch) without being limited by yarn count restrictions, thereby enabling both microcrack suppression and adequate interfacial adhesiveness.
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 significantly reduces microcrack formation in the fiber reinforced composite material, maintaining high mechanical properties and improving interfacial adhesiveness between the stitching yarn and matrix resin.
Implementation Method 1
the stitching yarn has a linear expansion coefficient in the fiber axial direction of -1×10^-6 to 70×10^-6/K after heated at 180°C for 2 hours and cooled
Data Source
AI summary
An object of the present invention is to provide a stitched fiber-reinforced substrate material capable of suppressing the formation of microcracks in a fiber reinforced composite material. The stitched fiber-reinforced substrate material of the present invention is a fiber-reinforced substrate material formed by stitching reinforcement fiber sheets made of reinforcement fibers using stitching yarns, and the stitching yarn has a linear expansion coefficient in the fiber axial direction of -1×10-6 to 70×10-6/K after heated at 180°C for 2 hours and then cooled. The stitching yarn is preferably a stitching yarn to which an organic compound having a polar group is adhered.