Carbon Fiber Prepreg Interface for Impact and Through-Thickness Conductivity
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Solution Overview
Problem
Carbon fiber reinforced composite materials face challenges in achieving both excellent impact resistance and electrical conductivity while maintaining long-term storage stability, as existing sizing agents fail to provide adequate adhesiveness between carbon fibers and the matrix resin and suffer from mechanical characteristic degradation over time.
Innovation Solution
A prepreg is developed with a sizing agent containing a specific ratio of aliphatic and aromatic epoxy compounds, applied to carbon fibers and impregnated with a thermosetting resin composition that includes thermoplastic or conductive particles, forming an interlayer to enhance adhesion and prevent reaction with the matrix resin, thereby maintaining mechanical properties and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a resin layer with dispersed particles is added to improve impact resistance, then impact resistance is improved, but electrical conductivity in the thickness direction remarkably decreases
Solution Approach 1:
The invention uses a composite sizing agent containing both aliphatic epoxy compound and aromatic epoxy compound to create an interfacial layer that simultaneously provides impact resistance and maintains electrical conductivity. This composite approach allows the sizing agent to exhibit dual functionality: improving interlayer strength while preserving conductive pathways through the interface between carbon fiber layers.
Solution Approach 2:
The sizing agent creates a localized interfacial layer with specific chemical composition (aliphatic and aromatic epoxy compounds) at the carbon fiber surface. This local modification of the interface provides enhanced adhesion and impact resistance without requiring a bulk resin layer that would block electrical conductivity paths.
2Strength
If conventional sizing agents are used to improve adhesiveness between carbon fibers and matrix resin, then adhesiveness is improved, but mechanical characteristics deteriorate during long-term storage
Solution Approach 1:
The invention changes the chemical composition parameters of the sizing agent by incorporating both aliphatic epoxy compound (30-70 mass%) and aromatic epoxy compound (30-70 mass%). This specific compositional parameter range optimizes the balance between initial adhesiveness and long-term storage stability, preventing mechanical characteristic degradation while maintaining strong carbon fiber-matrix bonding.
Solution Approach 2:
The sizing agent itself is a composite material combining aliphatic and aromatic epoxy compounds. This composite composition provides synergistic effects: the aliphatic component contributes to flexibility and adhesion, while the aromatic component provides structural stability and resistance to degradation during storage.
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 solution provides a carbon fiber reinforced composite material with improved adhesiveness, impact resistance, and electrical conductivity in the thickness direction, while minimizing changes during long-term storage, ensuring both mechanical integrity and stability.
Implementation Method 1
the sizing agent contains an aliphatic epoxy compound (A) and an aromatic epoxy compound (B1)... improved adhesiveness between carbon fibers and the matrix resin
Implementation Method 2
conductive particles or fibers (G)... interlayer formative layer containing (F) and (G) and/or (H)... electrical conductivity in the thickness direction
Data Source
Figure 1~2
Figure 3
AI summary
Provided are a prepreg that is excellent in adhesiveness between carbon fibers and a matrix resin and long-term storage stability and achieves both excellent impact resistance and electrical conductivity in the thickness direction and a carbon fiber reinforced composite material. The present invention provides a prepreg formed by impregnating sizing agent-coated carbon fibers coated with a sizing agent containing an aliphatic epoxy compound (A) and an aromatic epoxy compound (B1) with a thermosetting resin composition containing thermoplastic resin particles (F) and conductive particles (G) in a mass ratio of 1:1 to 1,000 or conductive particles (H) in which a thermoplastic resin is covered with a conductive substance. An (a)/(b) ratio is within a predetermined range where (a) is a height of a component at a binding energy assigned to CHx, C-C, and C=C and (b) is a height of a component at a binding energy assigned to C-O in a C1s core spectrum of surfaces of the sizing agent-coated carbon fibers analyzed by X-ray photoelectron spectroscopy.