Prepreg and method for manufacturing same
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Solution Overview
Problem
Existing prepregs using thermosetting resins have low impact resistance and storage stability due to issues with resin impregnation and curing reactions, leading to defects like voids and reduced mechanical properties.
Innovation Solution
A prepreg design where a primary prepreg with an epoxy resin composition is impregnated into a reinforcing fiber layer, and a surface layer with a higher curing agent content is formed, localizing the curing agent to maintain tackiness and draping properties over time, while allowing for high impact resistance and interlaminar toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a thermosetting resin is used to achieve high tackiness and moldability, then the prepreg shows good initial handling properties, but the impact resistance and toughness of the composite material are reduced
Solution Approach 1:
The patent uses a composite resin system combining thermosetting resin (for tackiness and moldability) with thermoplastic resin particles (for toughness and impact resistance). The thermoplastic particles are dispersed in the thermosetting resin matrix, creating a composite material that exhibits both the initial handling properties of thermosetting resins and the impact resistance of thermoplastic materials.
2Strength
If a large amount of thermoplastic resin is dissolved in thermosetting resin to improve toughness, then the impact resistance increases, but the viscosity becomes very high making resin impregnation difficult
Solution Approach 1:
Instead of uniformly dissolving thermoplastic resin throughout the thermosetting resin (which would increase overall viscosity), the patent localizes the thermoplastic resin as discrete particles distributed within the thermosetting resin matrix. This local quality approach allows the bulk resin to maintain low viscosity for easy impregnation while the localized thermoplastic particles provide toughness enhancement.
3Reliability
If the curing reaction of thermosetting resin composition proceeds with time, then the resin sets and forms the composite material, but the tackiness and draping property decrease making the prepreg unusable
Solution Approach 1:
The patent incorporates a curing inhibitor that preliminarily prevents the curing reaction from proceeding during storage. This preliminary action maintains the prepreg in an uncured, tacky state for extended periods. The inhibitor is subsequently removed or deactivated during the curing process, allowing the resin to then cure completely and form the final composite material.
4Duration of action of stationary object
If a prepreg is stored for an extended period, then the curing reaction progresses reducing tackiness, but storage stability is required for long-term availability
Solution Approach 1:
The patent introduces a curing inhibitor as an intermediary substance that mediates between the epoxy resin and curing agent, preventing their reaction during storage. This inhibitor acts as a temporary barrier, allowing the prepreg to be stored for extended periods without curing. The inhibitor is then removed or deactivated during processing, allowing the curing reaction to proceed to completion.
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 and impact resistance by preventing premature curing reactions, resulting in a composite material with reduced structural defects and enhanced mechanical properties.
Implementation Method 1
dissolution of a thermoplastic resin in a thermosetting resin
Implementation Method 2
the curing reaction of thermosetting resin composition proceeds with time
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.