Prepreg and method for manufacturing same
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Solution Overview
Problem
Existing prepregs composed of thermosetting resins suffer from low impact resistance and interlaminar toughness due to low toughness of thermosetting resins, and attempts to improve toughness by adding thermoplastic resins often result in high viscosity, making it difficult to impregnate resin into fiber substrates, leading to structural defects like voids and reduced mechanical properties.
Innovation Solution
A prepreg design where a primary prepreg with an epoxy resin composition containing a curing agent is impregnated into a reinforcing fiber layer, and a surface layer with an epoxy resin-soluble thermoplastic resin is formed, with the curing agent localized in the primary prepreg to maintain tackiness and draping properties over time, while allowing for high impact resistance and interlaminar toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a large amount of thermoplastic resin is dissolved in thermosetting resin to improve toughness, then impact resistance is improved, but viscosity becomes very high making it difficult to impregnate resin into reinforcing fiber substrate
Solution Approach 1:
The invention divides the prepreg structure into two distinct layers: a core layer containing thermosetting resin with dispersed thermoplastic resin particles for impact resistance, and surface layers containing thermosetting resin with dissolved thermoplastic resin for toughness. This segmentation allows each layer to have optimized properties - the core layer maintains lower viscosity for good impregnation while the surface layers provide the necessary toughness without compromising overall manufacturability.
Solution Approach 2:
The invention applies different resin compositions to different regions of the prepreg. The core layer uses a composition optimized for impact resistance with dispersed particles, while the surface layers use a composition optimized for toughness with dissolved thermoplastic resin. This local quality approach ensures that each region performs its specific function optimally without the entire prepreg suffering from high viscosity.
2Reliability
If curing reaction of thermosetting resin composition proceeds with time, then structural integrity is improved, but tackiness and draping property decrease with time
Solution Approach 1:
The invention incorporates a curing inhibitor that delays the curing reaction during storage, preserving tackiness and draping properties for extended periods. The inhibitor is consumed or deactivated during the molding process, allowing the curing reaction to proceed to completion and achieve full structural integrity. This preliminary action of delaying curing ensures the prepreg remains workable when needed.
Solution Approach 2:
The curing inhibitor acts as an intermediary substance that temporarily blocks the curing reaction between the thermosetting resin and its hardener. This intermediary control allows the prepreg to maintain its desirable handling properties during storage and transport, while enabling complete curing and structural integrity during the molding process when the inhibitor is no longer present.
3Strength
If thermoplastic resin is added to thermosetting resin to improve toughness, then interlaminar toughness is improved, but the prepreg loses tackiness and draping property
Solution Approach 1:
The invention segments the thermoplastic resin into two forms distributed across different layers: dispersed particles in the core layer for impact resistance and dissolved resin in the surface layers for toughness. This segmentation allows the dissolved thermoplastic resin in the surface layers to provide interlaminar toughness while the overall composition maintains adequate tackiness and draping properties for manufacturing.
Solution Approach 2:
The invention creates a composite structure combining thermosetting resin as the base matrix with thermoplastic resin in two different forms (dispersed particles and dissolved resin). This composite approach allows the thermoplastic resin to enhance interlaminar toughness and impact resistance while the thermosetting resin maintains the necessary tackiness and draping properties for 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 prepreg achieves excellent storage stability, reduced structural defects, and enhanced mechanical properties by maintaining tackiness and draping properties, and provides a composite material with improved impact resistance and interlaminar toughness.
Implementation Method 1
a first epoxy resin composition [A]... containing at least an epoxy resin, 30 to 100 parts by mass of a curing agent for epoxy resin relative to 100 parts by mass of the epoxy resin contained in the first epoxy resin composition, and 5 to 60 parts by mass of at least one epoxy resin-soluble thermoplastic resin selected from polyethersulfone, polysulfone, polyetherimide and polycarbonate
Implementation Method 2
only the epoxy resin composition of the primary prepreg contains a curing agent for epoxy resin
Data Source
Figure 1~2(c)
Figure 3~4(c)
Figure 5
AI summary
The present invention provides a prepreg comprising: a primary pre-pregnant made of a reinforced fiber substrate and an epoxy resin composition containing at least epoxy resin and thermoplastic resin impregnated into the reinforcing fiber that forms the reinforced fiber substrate; and a surface layer made of epoxy resin composition containing at least an epoxy resin and an epoxy resin-soluble thermoplastic resin that dissolves in the epoxy resin, the surface layer being formed on one or both surfaces of the primary prepreg; the prepreg being characterized in that only one of either the epoxy resin composition of the primary prepreg or the epoxy resin composition of the surface layer contains a hardening agent for an epoxy resin.