Thermoplastic Composite Shell Manufacturing with Inflatable Bag Molding
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Solution Overview
Problem
Existing methods for manufacturing composite shells with complex geometries, such as helmets, are inefficient due to the difficulty in molding parts with high curvature and tightly closed geometries, particularly when using thermoplastic matrices, which result in long curing times, high volatile organic compound emissions, and limited recyclability.
Innovation Solution
A method involving cutting preimpregnated LFRTP fabrics into portions, arranging them in a mold with a multilayer structure, applying pressure and heat to replicate the geometry, and then cooling to extract the solidified body, overcoming the challenges of thermoplastic matrix impregnation and curing issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermoplastic matrix composite materials are used for manufacturing composite shells, then mechanical properties and recyclability are improved, but curing time and manufacturing complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-impregnating the reinforcement fibers with thermoplastic matrix material before molding. This pre-impregnation step prepares the composite material in advance with optimal resin distribution, eliminating the need for lengthy curing processes after molding and reducing overall manufacturing time while maintaining mechanical properties.
Solution Approach 2:
The patent utilizes parameter changes by controlling the temperature and pressure conditions during the molding process. By heating the pre-impregnated composite to specific temperatures and applying controlled pressure, the thermoplastic matrix is shaped and then rapidly cooled to solidify, replacing traditional lengthy curing processes with a faster thermal cycling approach.
2Ease of manufacture
If traditional thermoforming processes are used for manufacturing composite shells, then manufacturing simplicity is maintained, but mechanical properties and adaptability to complex geometries are limited
Solution Approach 1:
The patent employs composite materials by combining reinforcement fibers (such as glass, carbon, or aramid) with thermoplastic matrix material in a pre-impregnated state. This composite structure provides superior mechanical properties compared to traditional thermoforming of plain thermoplastics, while the thermoplastic nature maintains ease of manufacturing through melting and reshaping capabilities.
3Productivity
If thermosetting matrices are used for manufacturing composite shells, then manufacturing time is reduced, but recyclability and mechanical performance are compromised
Solution Approach 1:
The patent uses parameter changes by exploiting the thermoplastic material's ability to transition between solid and molten states through temperature control. The composite is heated above the melting point of the thermoplastic matrix during molding, then rapidly cooled to solidify the shape. This thermal cycling enables both rapid manufacturing and recyclability, as the material can be re-melted and re-formed multiple times without chemical degradation.
4Shape
If complex geometries with high curvature are molded using traditional methods, then design flexibility is achieved, but manufacturing difficulty and time increase
Solution Approach 1:
The patent applies preliminary action by pre-impregnating flat or slightly curved fiber reinforcement with thermoplastic matrix material before molding. This pre-impregnated material can then be easily formed into complex high-curvature geometries during the molding process, as the thermoplastic matrix becomes pliable when heated and conforms to the mold cavity, reducing manufacturing difficulty compared to attempting to pre-form complex shapes.
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 enables rapid, economical production of composite shells with improved mechanical properties, reduced weight, and enhanced recyclability, while maintaining the necessary mechanical performance and ergonomics, specifically addressing the limitations of thermosetting matrices and traditional thermoforming processes.
Implementation Method 1
causes the melting of the thermoplastic resin present in the fabrics and its flow to reproduce the geometry of the mold
Implementation Method 2
cooling the half-molds to a temperature such that it allows extracting the solidified molded body from the mold
Implementation Method 3
applying pressure inside the bag causing the bag to inflate and expand to such a volume causing the contact and pressure of the surface of the bag against the portions of fabrics
Data Source
AI summary
The present invention relates to a method of manufacturing a body made of composite material such as a shell of a helmet. Said body constitutes a multilayer structure where each layer is formed by superposed strata comprising portions of fabrics preimpregnated with thermoplastic resin in which at least some of said layers are formed by woven or non-woven LFRTP-type preimpregnated fabrics. The outer layer is formed by strata of portions of “veil” type or “felt” type fabrics, with non-woven and non-oriented fibers of lengths comprised between 5 and 20 mm. In the method, the multilayer structure arranged in a mold is subjected to the action exerted by a bag that is inflated due to pressure occupying the cavity of the mold.