Carbon Fiber Epoxy Sizing for Stronger Vinyl Ester Composites
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Solution Overview
Problem
Carbon fiber-vinyl ester resin composites fail to match the mechanical properties of carbon fiber-epoxy composites due to a weak fiber-matrix interface and high cure volume shrinkage in vinyl ester resin matrices, limiting their application in rugged industries.
Innovation Solution
Functionalized carbon fibers with covalently bound epoxy sizing agents containing crosslinking molecules are used, which form crosslinks between the sizing agent and the polymer matrix, enhancing the fiber-matrix interface strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If vinyl ester resin is used as matrix material, then cost is reduced and corrosion resistance is improved, but mechanical properties and fiber-matrix interface strength deteriorate
Solution Approach 1:
The patent introduces a coupling agent as an intermediary substance that chemically bonds to both the vinyl ester resin matrix and the carbon fiber surface. This coupling agent contains reactive groups that form covalent bonds with the fiber surface and compatible groups that bond with the resin, thereby mediating the interface between fiber and matrix to improve interfacial adhesion and mechanical properties while maintaining the cost advantages of vinyl ester resin
Solution Approach 2:
The patent modifies the chemical parameters of the fiber-matrix interface by applying surface treatments to carbon fibers and using coupling agents with specific chemical compositions. These parameter changes in surface chemistry and interfacial composition transform the weak physical interface into a strong chemical bond interface, enabling vinyl ester composites to achieve mechanical properties comparable to epoxy systems
2Ease of manufacture
If vinyl ester resin is used as matrix material, then cost is reduced, but fiber-matrix interface integrity deteriorates due to high cure volume shrinkage
Solution Approach 1:
The patent applies coupling agents and surface treatments to carbon fibers before composite manufacturing to pre-establish strong chemical bonds at the fiber-matrix interface. This beforehand cushioning creates a robust interfacial structure that can withstand the stresses induced by vinyl ester resin's high cure volume shrinkage, preventing interface degradation and maintaining composite integrity
3Strength
If epoxy resin is used as matrix material, then mechanical properties are improved, but cost increases
Solution Approach 1:
The patent replaces expensive epoxy resin with cheaper vinyl ester resin while maintaining performance through the use of coupling agents. Although vinyl ester resin has lower inherent mechanical properties and higher shrinkage, the coupling agent compensates for these deficiencies by creating a strong chemical interface, effectively making the cheaper resin perform as well as the expensive epoxy in terms of mechanical properties
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 approach significantly increases the interlaminar shear strength and mechanical properties of carbon fiber composites, making them suitable for high-strength applications previously reserved for epoxy-based composites.
Implementation Method 1
covalent bonds with crosslinking molecules. The crosslinking molecules possess reactive groups that function to crosslink between epoxy groups in the sizing agent and also function to crosslink between the sizing agent and a polymer matrix
Data Source
AI summary
A functionalized carbon fiber having covalently bound on its surface a sizing agent containing epoxy groups, at least some of which are engaged in covalent bonds with crosslinking molecules, wherein each of said crosslinking molecules possesses at least two epoxy-reactive groups and at least one free functional group reactive with functional groups of a polymer matrix in which the carbon fiber is to be incorporated, wherein at least a portion of said crosslinking molecules are engaged, via at least two of their epoxy-reactive groups, in crosslinking bonds between at least two epoxy groups of the sizing agent. Composites comprised of these functionalized carbon fibers embedded in a polymeric matrix are also described. Methods for producing the functionalized carbon fibers and composites thereof are also described.