Polyrotaxane Fiber Sizing for Tougher Thermoset Composites
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Solution Overview
Problem
Current fiber-reinforced composite materials face limitations in achieving high interlaminar fracture toughness and mechanical strength, particularly due to the brittleness of thermosetting matrix resins and uneven properties along fiber alignment directions.
Innovation Solution
The use of sizing agent-coated reinforcing fibers with a polyrotaxane, which includes cyclic molecules, a linear molecule threaded through these cyclic molecules, and stopper groups, applied to the fibers and heat-treated to enhance adhesion and toughness, combined with a thermosetting resin to produce a prepreg and fiber-reinforced composite material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermosetting matrix resin is used to provide high tensile strength and compression strength, then mechanical strength in fiber direction is improved, but interlaminar fracture toughness deteriorates due to brittleness
Solution Approach 1:
The patent applies a sizing agent containing multiple epoxy resins with different characteristics (flexible epoxy resin and rigid epoxy resin) to create a composite sizing layer on carbon fibers. This composite sizing agent structure allows the flexible epoxy resin to improve interlaminar fracture toughness while the rigid epoxy resin maintains high mechanical strength, resolving the contradiction between toughness and strength in the fiber-matrix interface.
Solution Approach 2:
The patent changes the chemical composition parameters of the sizing agent by incorporating specific ratios of flexible epoxy resin (containing aliphatic hydrocarbon chains) and rigid epoxy resin (containing aromatic rings). This parameter adjustment enables the sizing agent to simultaneously provide both flexibility for toughness and rigidity for strength, addressing the brittleness issue of conventional thermosetting resins.
2Strength
If conventional epoxy sizing agent is applied to improve interfacial adhesion, then tensile strength is improved, but interlaminar fracture toughness remains insufficient
Solution Approach 1:
The patent creates a composite sizing agent system combining flexible epoxy resin and rigid epoxy resin in specific proportions. The flexible epoxy resin component enhances interlaminar fracture toughness by providing flexibility to the fiber-matrix interface, while the rigid epoxy resin component ensures strong interfacial adhesion. This composite approach simultaneously achieves both improved adhesion and enhanced toughness that conventional single-component epoxy sizing agents cannot provide.
3Strength
If fiber-reinforced composite material is designed for high strength in fiber alignment direction, then tensile strength is improved, but property uniformity deteriorates due to anisotropy
Solution Approach 1:
The patent applies sizing agent with different functional components to different aspects of the fiber-matrix interface requirements. The flexible epoxy resin component specifically targets interlaminar regions to improve fracture toughness, while the rigid epoxy resin component strengthens the primary fiber-matrix bond for tensile strength. This localized functional differentiation within the sizing agent addresses property uniformity by optimizing different regions of the composite structure for their specific mechanical requirements.
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 improves the interlaminar fracture toughness and mechanical strength of the composite materials, providing higher elasticity and toughness while maintaining high tensile strength, addressing the brittleness and property uniformity issues of existing materials.
Implementation Method 1
heat-treating the reinforcing fibers to thereby obtain the sizing agent-coated reinforcing fibers
Implementation Method 2
a sizing agent containing a polyrotaxane, the reinforcing fibers being coated with the sizing agent... a compound having cyclic molecules, a linear molecule included in the cyclic molecules such that the linear molecule is threaded through the cyclic molecules
Implementation Method 3
applying a sizing agent of a polyrotaxane to reinforcing fibers... improve the interfacial adhesion
Data Source
AI summary
Sizing agent-coated reinforcing fibers include reinforcing fibers and a sizing agent containing a polyrotaxane, the reinforcing fibers being coated with the sizing agent. Provided are sizing agent-coated reinforcing fibers that provide a fiber-reinforced composite material with excellent mechanical properties, a method for producing the sizing agent-coated reinforcing fibers, a prepreg including the sizing agent-coated reinforcing fibers, and a fiber-reinforced composite material with excellent mechanical properties including the sizing agent-coated reinforcing fibers.