Prepreg Composition for Automated Lay-up Processability
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Solution Overview
Problem
Existing prepregs face challenges in automated lay-up processes due to insufficient reduction in tackiness, leading to decreased productivity and adhesiveness between layers.
Innovation Solution
A prepreg composition comprising carbon fibers and a specific epoxy resin composition with a thermoplastic resin and particles, optimized to achieve high storage elastic modulus and peel strength, ensuring good processability and interlayer adhesiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the tackiness of the prepreg is reduced by using a matrix resin having a high viscosity, then the processability in automated lay-up device is improved, but the adhesiveness between prepreg layers becomes insufficient
Solution Approach 1:
The patent applies local quality by creating a dual-epoxy resin system where the first epoxy resin (lower viscosity) provides good adhesiveness and interlayer bonding, while the second epoxy resin (higher viscosity) provides reduced tackiness and improved processability. Each resin component is strategically positioned to fulfill specific local requirements within the prepreg structure.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the viscosity parameters of different epoxy resin components. The first epoxy resin has a viscosity of 50-500 Pa·s at 25°C for good adhesiveness, while the second epoxy resin has a viscosity of 500-5000 Pa·s at 25°C for reduced tackiness. The balance between these parameters is controlled to achieve both processability and bonding performance.
2Ease of operation
If the viscosity of the epoxy resin composition is increased to reduce tackiness, then the handling properties are improved, but the ability to achieve strong adhesion to reinforcing fibers deteriorates
Solution Approach 1:
The patent applies local quality by assigning different viscosity characteristics to different epoxy resin components based on their functional requirements. The first epoxy resin with lower viscosity (50-500 Pa·s) is optimized for fiber adhesion, while the second epoxy resin with higher viscosity (500-5000 Pa·s) is optimized for handling and tackiness control.
Solution Approach 2:
The patent uses composite materials by combining two different epoxy resin systems with complementary properties. This composite resin formulation allows the lower viscosity component to wet and adhere to fibers effectively, while the higher viscosity component provides the desired handling characteristics and reduced tackiness during automated processing.
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 proposed prepreg composition enhances slit tape processability, splicing properties, and interlayer toughness, resulting in a fiber-reinforced composite material with improved impact resistance and high peel strength.
Implementation Method 1
the second epoxy resin composition has a storage elastic modulus G' in the range of 1.0 × 10^4 to 1.0 × 10^6 Pa at 25°C
Data Source
Figure 1
AI summary
The problem is solved by the present invention, which aims to provide a prepreg that allows continuous laying-up of prepreg layers while preventing the reinforcing fibers or the matrix resin from being partly deposited on the automated lay-up device, when such a device is used with the aim of producing a fiber-reinforced composite material having a high toughness and impact resistance. A prepreg comprising the components [A] to [E] given below, meeting the requirements (i) to (iii) given below, and serving to produce a cured product having a reinforcing fiber layer defined as the region ranging from 8% to 92% depth from the surface in the thickness direction that contains a first epoxy resin composition in which 90 mass% or more of the component [A] exists, and two surface resin layers each defined as the region ranging from either surface to a depth of 8% exclusive in the thickness direction that contain a second epoxy resin composition in which 85 mass% or more of the component [E] exists, (i) the second epoxy resin composition includes the components [B] to [E] of which the component [C] accounts for 8 to 24 parts by mass relative to 100 parts by mass of the second epoxy resin composition, (ii) the second epoxy resin composition has a storage elastic modulus G' in the range of 1.0 × 104 to 3.0 × 106 Pa when measured at 25°C and an angular frequency of 3.14 rad/s, and (iii) plies of the prepreg laid up after being left to stand for 24 hours at room temperature show a peel strength of 0.1 N/mm or more at 35°C, [A] a carbon fiber, [B] an epoxy resin containing the components [b1] and [b2] specified below, [b1] a di- or less- functional epoxy resin containing, in a molecule, at least one ring structure having four- or more- membered ring and a glycidyl amine group bonded to a ring structure, [b2] a tri- or more- functional epoxy resin, [C] a thermoplastic resin with a weight-average molecular weight of 2,000 to 30,000 g/mol, [D] diaminodiphenyl sulfone, [E] particles having a volume-average particle size of 5 to 50 µm and insoluble in the component [B].