Prepreg with Localized Un-impregnated Regions for Void Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional out-of-autoclave processes for producing fiber-reinforced composite materials face challenges such as long molding times, high failure rates, and the generation of voids due to volatile vaporization in epoxy resins, while semi-impregnated prepregs with large un-impregnated regions compromise handleability, and interlayer toughening techniques with solid thermoplastic resins hinder resin flow during molding.
Innovation Solution
A prepreg design featuring reinforced fibers with an epoxy resin composition and a thermoplastic resin insoluble in epoxy, where the un-impregnated regions are shifted to the surface, allowing efficient volatile removal and improved impact resistance, with a degree of impregnation between 30% to 95% and a shift parameter of 0.10<σ<0.45, enabling efficient void reduction and enhanced handleability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large un-impregnated regions are provided in semi-impregnated prepreg to ensure continuity for volatile removal, then void generation is reduced, but handleability deteriorates due to fiber fluffing and tearing
Solution Approach 1:
The patent applies local quality by creating un-impregnated regions with specific characteristics (larger size, positioned near surfaces) in localized areas of the prepreg rather than uniformly throughout. This allows continuous pathways for volatile removal at critical locations while maintaining impregnation in other areas to preserve overall handleability and structural integrity
Solution Approach 2:
The patent uses partial action by providing un-impregnated regions that are sufficient to ensure continuity for volatile removal but not excessive to the point of compromising handleability. The degree of un-impregnation is carefully controlled to achieve the minimum necessary for continuous pathways while avoiding fiber fluffing and tearing issues
2Ease of manufacture
If out-of-autoclave process is used to avoid expensive pressurizing equipment, then manufacturing cost is reduced, but molding time increases and voids remain due to volatile vaporization
Solution Approach 1:
The patent applies preliminary action by pre-forming continuous un-impregnated regions in the prepreg structure before molding. This preliminary preparation of volatile pathways enables efficient volatile removal during the out-of-autoclave molding process, allowing shorter molding times while maintaining low void generation and avoiding the need for expensive autoclave equipment
3Strength
If thermoplastic resin is shifted to space between fiber layers for interlayer toughening, then impact resistance is improved, but resin flow during molding is hindered
Solution Approach 1:
The patent applies local quality by positioning thermoplastic resin specifically at interfaces between fiber layers where impact resistance is needed, while maintaining epoxy resin impregnation in the bulk fiber regions to ensure proper resin flow and curing. This localized placement achieves toughening without significantly hindering overall molding process
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 solution enables the production of fiber-reinforced composite materials with reduced voids, improved impact resistance, and excellent handleability, suitable for vacuum molding without the need for autoclaves, while maintaining mechanical properties.
Implementation Method 1
a thermoplastic resin [D] that is insoluble in the epoxy resin [B] and is localized at surfaces on both sides of the prepreg
Implementation Method 2
allowing efficient volatile removal
Implementation Method 3
an epoxy resin composition containing an epoxy resin [B] and a hardener [C], the epoxy resin composition being partially impregnated into the reinforced fibers [A]
Data Source
AI summary
A prepreg which is suitable for producing a fiber-reinforced composite material in a short period of time without using an autoclave, can produce a fiber-reinforced composite material in which the occurrence of voids is suppressed and excellent impact resistance is achieved, and has excellent handling properties; and a fiber-reinforced composite material using the prepreg. This prepreg is a prepreg in which a reinforcing fiber [A] arranged in layers is partially impregnated with an epoxy resin composition containing an epoxy resin [B] and a curing agent [C], wherein the impregnation rate φ is 30-95%, and a thermoplastic resin [D] insoluble in the epoxy resin [B] is unevenly distributed on both surfaces of the prepreg. In addition, in the layers of the reinforcing fiber [A], epoxy resin composition-unimpregnated portions are localized on one surface of the prepreg, and the localization parameter a, which defines the degree of localization, is in the range of 0.10<σ<0.45.