Thermoplastic Prepreg Press Molding With Maintained Fiber Isotropy
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Solution Overview
Problem
Existing methods for manufacturing fiber-reinforced composite materials often result in isotropy issues and require trimming, leading to material waste and increased costs, especially when press-molded with a prepreg charge ratio of 100% or less.
Innovation Solution
A method involving a prepreg preparation step where a random mat with reinforcing fibers is impregnated with a thermoplastic resin and molded under specific temperature conditions, followed by arranging the prepreg in a mold with a controlled temperature and charge ratio, and then pressurized to maintain fiber isotropy and reduce material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a preform is arranged in a wider range than a total mold cavity area and press-molded, then the shaped product can be obtained, but the outer periphery portion requires trimming producing a large amount of offcuts
Solution Approach 1:
The patent changes the charge ratio parameter from the conventional 100% or more to 50% to 100%, and adjusts the prepreg temperature parameter to maintain it between the melting point and thermal decomposition temperature of the thermoplastic resin. These parameter changes enable the prepreg to flow and fill the mold cavity completely without requiring excess material that would need trimming, thus eliminating offcuts while maintaining fiber isotropy through the controlled temperature conditions.
2Manufacturing precision
If symmetrically layering is always made to obtain an integrated shaped product that substantially exhibits isotropy, then fiber isotropy is maintained, but the discretion degree of the time for preparing perform and the arrangement method in molding is low
Solution Approach 1:
The patent applies preliminary action by pre-heating the prepreg to a temperature between the melting point and thermal decomposition temperature of the thermoplastic resin before molding. This preliminary temperature treatment enables the resin to become sufficiently fluid, allowing the prepreg to automatically flow and distribute fibers uniformly throughout the mold cavity when pressed, thereby achieving fiber isotropy without requiring complex symmetric layering arrangements or extensive preparation time discretion.
3Productivity
If long fiber composite pellets with average fiber length of 5 mm to 15 mm are used for injection molding, then the shaped product can be manufactured, but the length of the reinforcing fibers is largely reduced
Solution Approach 1:
The patent replaces the injection molding mechanical system with a thermal processing system. Instead of using injection molding that subjects fibers to high shear forces and mechanical disruption, the patent uses controlled heating to melt the thermoplastic resin and pressing to consolidate the prepreg. This substitution of the processing mechanism preserves the long fiber length (5 mm to 100 mm) while maintaining manufacturing efficiency, as the thermal-pressing process is equally effective for consolidation without the fiber-damaging mechanical action of injection molding.
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 method allows for the production of lightweight, rigid, and thin fiber-reinforced composite products with excellent surface appearance and productivity, eliminating the need for trimming and reducing material waste, while maintaining fiber isotropy even at low prepreg charge ratios.
Implementation Method 1
a prepreg preparation step of obtaining a prepreg in which a random mat including reinforcing fibers with an average fiber length of 5 mm to 100 mm and a thermoplastic resin is heated up to a temperature of a melting point or more and less than a thermal decomposition temperature
Implementation Method 2
up to a temperature of a glass transition temperature or more and less than a thermal decomposition temperature in a case where the thermoplastic resin is amorphous
Implementation Method 3
a prepreg arranging step in which the prepreg that is set at the temperature of the melting point or more and less than the thermal decomposition temperature is arranged in a mold which is controlled to a temperature less than the melting point temperature in the case where the thermoplastic resin is crystalline or a temperature less than the glass transition temperature in the case where the thermoplastic resin is amorphous
Data Source
AI summary
The present invention provides a method for manufacturing a shaped product constituted by a fiber-reinforced composite material including reinforcing fibers and a thermoplastic resin. The shaped product maintains isotropy of the fibers to the end thereof even if press-molded under conditions in which charge ratio of a prepreg to a die is low. Specifically, the method includes using a specific prepreg obtained by impregnating the reinforcing fibers with thermoplastic resin, and molding-processing the prepreg under specific conditions.