Induction Heated Die for Thermoplastic Natural Fiber Composites
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Solution Overview
Problem
Current methods for producing composite parts with a thermoplastic matrix and continuous natural fiber reinforcement are inadequate due to issues such as flammability, moisture-induced defects, and inability to achieve tight non-developable shapes and high production rates, particularly in mass production of components like mobile phone casings and luggage.
Innovation Solution
A device comprising a die with induction heating and cooling mechanisms, allowing for localized and rapid heating of the thermoplastic polymer to the melting point while maintaining fiber tension, and subsequent cooling below the glass transition temperature, ensuring uniform temperature distribution and preventing fiber degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If preheating is performed at a temperature sufficient to allow fluidity of the resin for stamping, then the thermoplastic matrix becomes fluid enough to enable fiber sliding in non-developable zones, but this leads to burning of natural fibers
Solution Approach 1:
The patent applies local quality by differentiating temperature zones within the stamping process. The resin is heated to melting temperature (e.g., 180-220°C) in specific zones where fluidity is needed for fiber sliding, while other zones maintain temperatures below the fiber burning point (e.g., below 150°C). This spatial differentiation of temperature allows the process to achieve both resin fluidity for formability and fiber protection simultaneously.
Solution Approach 2:
The patent utilizes parameter changes by precisely controlling the temperature parameter throughout the stamping process. The temperature is raised to the resin's melting point to enable fluidity and fiber movement, then rapidly cooled below the glass transition temperature to fix the formed shape. This dynamic parameter control allows transient access to high-temperature benefits while avoiding permanent exposure that would damage fibers.
2Adaptability or versatility
If natural fiber reinforcement is used in thermoplastic composite, then the part becomes light and environmentally friendly with recyclability, but the continuous fibers prevent use of injection molding methods
Solution Approach 1:
The patent replaces the injection molding process with a stamping process. Instead of injecting molten material through molds, the method uses a preformed thermoplastic blank that is mechanically stamped into the desired shape. This substitution eliminates the incompatibility of injection molding with continuous natural fiber reinforcement while preserving mass production capabilities.
Solution Approach 2:
The patent applies preliminary action by pre-forming the thermoplastic matrix and fiber reinforcement into a blank structure before the stamping operation. The continuous natural fibers are embedded in the thermoplastic matrix in advance, creating a preconsolidated blank that maintains fiber integrity during subsequent stamping. This preliminary preparation enables the use of sustainable natural fiber composites in stamping processes.
3Object-affected harmful factors
If vacuum bag forming is used to prevent fiber flammability, then fiber burning is avoided, but tight non-developable shapes such as trunk corners cannot be achieved
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting temperature during the forming process. The thermoplastic matrix is heated to its melting temperature to increase polymer chain mobility and reduce viscosity, enabling the material to flow into tight non-developable zones and trihedral connections. This temporary parameter change allows precise shape formation without exceeding fiber burning temperatures, as the high temperature is maintained only briefly during forming.
Solution Approach 2:
The patent utilizes dynamics by implementing a time-dependent temperature profile. The process involves rapid heating to melting temperature, brief holding at high temperature for formability, followed by rapid cooling to lock in the precise shape. This dynamic temperature control enables the material properties to change temporarily for shape formation while maintaining fiber protection throughout the process.
4Adaptability or versatility
If natural fibers with moisture content greater than 10% are used, then the material is readily available and sustainable, but moisture turns into water vapor during hot stamping causing quality defects
Solution Approach 1:
The patent applies the skipping principle by rapidly passing through the temperature range where moisture evaporation occurs. The heating rate is controlled to quickly raise the temperature to the resin melting point while minimizing the time spent in the 100-150°C range where water vapor generation would cause defects. This rapid traversal through the critical temperature zone allows moisture-containing natural fibers to be processed without quality degradation.
Solution Approach 2:
The patent applies preliminary action by pre-drying or pre-conditioning the natural fibers before composite formation. The fibers are treated to reduce moisture content or adjust moisture distribution before being combined with the thermoplastic matrix. This preliminary moisture management prevents water vapor defects during subsequent stamping while preserving the sustainability benefits of natural fiber usage.
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
Enables the production of composite parts with enhanced mechanical strength, precision, and recyclability, while avoiding fiber burning and moisture-related defects, suitable for high-volume production of complex shapes like half-shells with trihedral connections.
Implementation Method 1
means for induction heating of the form comprising two inductors each forming at least one turn in planes of different heights
Implementation Method 2
heating the part of the blank located in the cavity by induction
Implementation Method 3
die cooling means
Data Source
Figure 1~3
Figure 4~6D
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AI summary
The invention relates to a device for forming and consolidating a textile preform (600) comprising continuous fibers impregnated with a thermoplastic resin, characterized in that it includes: i) a die (200) including a former (210) comprising a cavity (220) corresponding to the shape of the part, the depth of said former extending between an inlet plane and a bottom, and said former being inserted into a mold base (230); ii) means (241, 242) for the induction-heating of the former (210), including two inductors which extend into recesses of the former (210), and each of which forms a turn in a plane substantially parallel to the inlet plane of the cavity (220) and located between said inlet plane and the bottom of the former; and iii) a means (235) for cooling the die. The invention also relates to a method implemented by said device and to a part produced by such a method.