Prepreg Production Using Elastic Edge Constraints
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Solution Overview
Problem
The production of fiber-reinforced composite materials using pressure impregnation methods often results in matrix resin bulging beyond the reinforcing fiber sheet edges, leading to reduced handling ease and strength, and uneven basis weight distribution due to fiber spreading.
Innovation Solution
The method involves using continuous elastic members with controlled tension, made of foamed materials, and lubricated release sheets to prevent resin bulging and fiber spreading, ensuring uniform impregnation and basis weight by encapsulating the edges during compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure impregnation method is used to produce prepreg, then matrix resin composition is impregnated into reinforcing fiber sheet, but matrix resin composition bulges out beyond the width of reinforcing fiber sheet
Solution Approach 1:
The patent uses a flexible sheet-like pressing member that can elastically deform under pressure to conform to the reinforcing fiber sheet and prevent resin bulging. The pressing member acts as a flexible constraint that maintains the width boundaries while allowing the resin to be impregnated uniformly into the fiber sheet.
Solution Approach 2:
The patent changes the physical state and properties of the pressing member by controlling its temperature and elastic modulus. By heating the pressing member to a temperature higher than the glass transition temperature of the resin, the resin becomes more fluid and easier to impregnate. The elastic modulus of the pressing member is controlled to provide appropriate flexibility and pressure distribution.
2Manufacturing precision
If pressure rolls compress the reinforcing fiber sheet, then matrix resin composition is impregnated, but reinforcing fiber bundles are moved sideways at both edges causing reduction in basis weight
Solution Approach 1:
The flexible sheet-like pressing member conformally contacts the reinforcing fiber sheet and distributes pressure evenly across the width, preventing fiber bundles at the edges from being pushed sideways. The flexibility of the pressing member allows it to adapt to the fiber sheet contours and maintain uniform pressure without causing lateral fiber displacement.
Solution Approach 2:
The pressing member provides locally adapted pressure distribution, with higher pressure concentration at the edges where fiber spreading is most likely to occur. This local quality adjustment ensures that fiber bundles remain in position at the critical edge regions while still allowing complete resin impregnation throughout the fiber sheet.
3Shape
If tape material with affinity to matrix resin composition is arranged at side edges to prevent bulging, then resin bulging is removed, but excessive matrix resin composition is adsorbed on the sheet
Solution Approach 1:
The flexible pressing member physically constrains the resin within the desired width boundaries through mechanical pressure and elastic deformation, rather than relying on chemical affinity like the tape material. This physical constraint method prevents resin bulging without causing excessive resin adsorption, as the pressing member does not chemically interact with the resin in the same way the affinity-based tape material does.
Solution Approach 2:
The pressing member acts as an intermediary between the pressure rolls and the reinforcing fiber sheet, distributing the compressive force in a controlled manner. It mediates the pressure application to achieve resin impregnation while preventing edge bulging, without the need for additional tape materials that would adsorb excess resin.
4Manufacturing precision
If pressure rolls are used for compression, then impregnation is achieved, but handling ease of prepreg decreases due to resin bulging
Solution Approach 1:
The flexible pressing member prevents resin bulging at the edges during compression, producing a prepreg with uniform width and smooth edges. This uniform geometry significantly improves handling ease during subsequent processing operations, while still achieving complete resin impregnation into the fiber sheet through the distributed pressure provided by the flexible member.
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
This approach prevents resin bulging and maintains uniform basis weight, enhancing the handling and strength of the prepreg while reducing material waste and production costs.
Implementation Method 1
a pair of elastic members is provided on one of the pressure rolls, one continuous in a longitudinal direction of the prepreg precursor
Implementation Method 2
lubricated release sheets to prevent resin bulging and fiber spreading
Data Source
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AI summary
A method for producing a prepreg, includes: preparing a reinforcing fiber sheet containing multiple reinforcing fiber bundles, a matrix resin composition, first and second release sheets, and elastic members; forming a prepreg precursor by providing the matrix resin composition on the reinforcing fiber sheet; sandwiching the prepreg precursor between the first and second release sheets so that first surfaces of the first and second release sheets make contact with the prepreg precursor and that the first and second release sheets respectively include extended portions that protrude outward from both edges of the prepreg precursor in a width direction; positioning the elastic members to face the extended portions of the second release sheet and to make contact with the second surface of the second release sheet; and compressing the prepreg precursor, first and second release sheets and the elastic members all at once in a thickness direction of the prepreg precursor.