Carbon Fiber Prepreg Composition for Adhesion and Microcrack Resistance
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Solution Overview
Problem
Carbon fiber reinforced composite materials face issues with adhesion between matrix resin and carbon fibers, microcrack resistance, and mechanical characteristic deterioration during long-term storage, particularly due to thermal distortion and environmental fatigue.
Innovation Solution
A prepreg comprising sizing agent-coated carbon fibers with an aliphatic epoxy compound and an aromatic epoxy compound, along with core-shell rubber particles and a thermoplastic resin, is used to enhance adhesion and microcrack resistance, while a metallic mesh is integrated for lightning strike resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermosetting resins are used as matrix resin for carbon fiber reinforced composite materials, then adhesion with carbon fibers is improved, but microcracks occur due to thermal distortion from temperature changes
Solution Approach 1:
The invention uses a hybrid resin system combining thermosetting resin (for adhesion) and thermoplastic resin particles (for toughness and microcrack resistance). The thermoplastic particles act as stress concentrators that prevent crack propagation, while the thermosetting matrix maintains strong fiber adhesion. This composite material approach resolves the contradiction by integrating the advantages of both resin types.
Solution Approach 2:
The invention modifies the matrix resin properties by controlling the glass transition temperature (Tg) of the thermoplastic resin particles to be lower than the service temperature, ensuring they remain rubbery and effective at absorbing thermal stress. The particle size (0.1-10 μm) and concentration (1-50 wt%) are optimized to balance adhesion and microcrack resistance.
2Temperature
If carbon fiber reinforced composite materials are exposed to repeated temperature cycles, then thermal distortion occurs due to coefficient of linear expansion difference, but mechanical characteristics deteriorate over time
Solution Approach 1:
The invention incorporates thermoplastic resin particles beforehand into the matrix to cushion against future thermal stress. These particles are distributed throughout the matrix before curing, creating a pre-configured stress absorption network that prevents microcrack formation during subsequent temperature cycling and long-term storage.
Solution Approach 2:
The invention creates local regions around thermoplastic particles with different mechanical properties. The particles themselves remain rubbery and flexible, while the surrounding thermosetting matrix maintains rigidity. This local quality differentiation allows the material to withstand thermal expansion differences without compromising overall structural strength.
3Strength
If epoxy resin composition is used as matrix resin, then adhesion with carbon fibers is excellent, but toughness is low and microcracks are likely to occur
Solution Approach 1:
The invention creates a composite resin system where epoxy resin (thermosetting) provides adhesion and structural integrity, while dispersed thermoplastic resin particles provide toughness. The thermoplastic particles act as stress concentrators and crack arrestors, preventing the propagation of microcracks that would otherwise occur in the brittle epoxy matrix under thermal stress.
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 excellent adhesion between carbon fibers and the matrix resin, maintains mechanical characteristics during long-term storage, and enhances microcrack resistance and lightning strike resistance in carbon fiber reinforced composite materials.
Implementation Method 1
excellent in adhesion between a matrix resin and carbon fibers
Implementation Method 2
increasing the elongation and toughness of thermosetting resins is an important issue
Implementation Method 3
the coefficient of linear expansion of carbon fibers is extremely small, and given this situation, a large difference in the coefficient of linear expansion is present between the carbon fibers and the matrix resin, and expansion and contraction caused by the temperature changes add distortion, that is, thermal distortion to the matrix resin
Data Source
AI summary
A prepreg includes; agent-coated carbon fibers coated with a sizing agent; and a thermosetting resin composition impregnated into the sizing agent-coated carbon fibers. The sizing agent includes an aliphatic epoxy compound (A) and an aromatic epoxy compound (B1). The sizing agent-coated carbon fibers are in a shape of woven fabric or braid. The thermosetting resin composition includes a thermosetting resin (D), a thermoplastic resin (F), and a latent hardener (G). The sizing agent-coated carbon fibers have an (a)/(b) ratio in a certain range where (a) is the height of a component at a binding energy assigned to CHx, C—C, and C═C and (b) is the height of a component at a binding energy assigned to C—O in a C1s core spectrum of the surfaces of the sizing agent-coated carbon fibers analyzed by X-ray photoelectron spectroscopy.