Thermoplastic Stitching Yards for Composite Microcrack Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fiber-Reinforced Polymer (FRP) composites used in applications like aviation and marine industries face issues with microcrack formation due to thermal cycles and hygrothermal stresses, leading to reduced strength and toughness, which existing strategies have not adequately addressed.
Innovation Solution
A process involving a curable composition with unidirectionally oriented multifilament carbon yarns and a multifilament stitching yarn made of thermoplastic polymer with a linear density of less than or equal to 80 dtex, heated to a temperature greater than the stitching yarn's melting point with controlled conversion, to reduce microcrack formation by enabling interdiffusion between the stitching yarn and matrix resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If stitching yarn is used to consolidate noncrimped fabric layers, then the layers are secured together, but microcracks form in the matrix around the stitching yarn due to thermal expansion stress
Solution Approach 1:
The patent changes the physical-chemical parameters of the stitching yarn by selecting thermoplastic polymers with specific melting temperatures (Tm) and glass transition temperatures (Tg) that are lower than the matrix resin's Tg. This temperature parameter differentiation enables the stitching yarn to soften and interdiffuse with the matrix resin during curing, reducing stress concentration and preventing microcrack formation while maintaining layer consolidation
Solution Approach 2:
The patent utilizes the phase transition of the thermoplastic stitching yarn from solid to softened state at temperatures between its Tm and Tg. This phase transition allows the stitching yarn to become more compliant and interdiffuse with the matrix resin, accommodating thermal expansion stresses without creating microcracks, while still maintaining the consolidated structure of the noncrimped fabric layers
2Stability of the object's composition
If conventional stitching yarn with higher linear density is used, then layer consolidation is achieved, but resin-rich zones form and mechanical properties deteriorate
Solution Approach 1:
The patent changes the linear density parameter of the stitching yarn to ≤80 dtex, which is significantly lower than conventional stitching yarns. This parameter reduction minimizes the volume of resin-rich zones formed around the stitching yarn during consolidation, thereby preserving the mechanical properties of the composite while still achieving effective layer consolidation
Solution Approach 2:
The patent employs a composite approach by combining thermoplastic stitching yarn with specific polymer matrix resins, where the thermoplastic yarn provides consolidation function while the matrix resin provides structural strength. The synergistic interaction between these materials allows for effective layer bonding without compromising mechanical properties
3Object-affected harmful factors
If thermoplastic stitching yarn with low linear density is used, then microcrack formation is reduced, but the ability to secure layers may be compromised
Solution Approach 1:
The patent utilizes the phase transition of the thermoplastic stitching yarn from solid to softened state at temperatures between its Tm and Tg. This phase transition allows the stitching yarn to become more compliant and interdiffuse with the matrix resin, accommodating thermal expansion stresses without creating microcracks, while still maintaining the consolidated structure of the noncrimped fabric layers
Solution Approach 2:
The thermoplastic stitching yarn acts as an intermediary between the rigid carbon fiber layers and the matrix resin. By softening at processing temperatures, it mediates the stress distribution and enables better interfacial bonding between layers, securing the structure without transferring excessive stress that would cause microcracks
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 microcracking in composite articles, enhancing their mechanical properties and resistance to thermal and humidity-induced stresses, resulting in improved durability and performance.
Implementation Method 1
heating the curable composition to a temperature T1, wherein T1 is greater than the melting temperature (Tm) of the stitching yarn
Implementation Method 2
maintaining the temperature T1 or heating to a temperature T2 for a time sufficient for the curable composition to be cured
Data Source
AI summary
The present disclosure relates to a process for manufacturing composite articles. and composite articles made thereby. The processes described herein make use of curable compositions containing NCF fabrics having certain types of stitching yarns. The curable compositions and composite articles made according to the present disclosure are particularly suited to the production of composite parts for use in many applications, such as in aviation, automotive, and marine applications.