Lightweight Composite Racket Frames With Expanding PMI/EPP Cores
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Solution Overview
Problem
Conventional racket frames, both with netted and solid faces, face issues of increased weight, complexity in manufacturing, high costs, and difficulty in controlling ball direction due to excessive shock absorption or rigidity, making them unsuitable for various user groups.
Innovation Solution
A manufacturing method using a core mold made of polymethacrylimide (PMI) or expanded polypropylene (EPP) particles, which expands under heat to create internal pressure, forming a composite material racket frame with fewer layers, reducing weight and complexity while maintaining rigidity and shock absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-layer core layer structure with honeycomb structure is used to enhance shock absorption, then shock absorption effect is improved, but racket weight increases and manufacturing complexity increases
Solution Approach 1:
The patent removes the honeycomb structure from the core layer, extracting only the essential shock absorption function through material selection (PMI or EPP particles) rather than complex geometric structures. This simplifies the overall structure while maintaining the core functionality of impact mitigation.
Solution Approach 2:
The patent utilizes porous expanded particles (PMI or EPP) as the core layer material. These materials inherently provide shock absorption through their cellular structure and energy-dissipating characteristics during compression, eliminating the need for additional honeycomb structures while maintaining lightweight properties.
2Reliability
If a multi-layer core layer structure with honeycomb structure is used to enhance shock absorption, then shock absorption effect is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent removes the honeycomb structure from the core layer, extracting only the essential shock absorption function through material selection (PMI or EPP particles) rather than complex geometric structures. This simplifies the overall structure while maintaining the core functionality of impact mitigation.
Solution Approach 2:
The patent utilizes porous expanded particles (PMI or EPP) as the core layer material. These materials inherently provide shock absorption through their cellular structure and energy-dissipating characteristics during compression, eliminating the need for additional honeycomb structures while maintaining lightweight properties.
3Reliability
If the racket face has better shock absorption, then impact force is absorbed better, but rebound sensitivity decreases and ball control becomes poorer
Solution Approach 1:
The patent applies different material properties to different layers: the core layer uses soft PMI/EPP particles for shock absorption, while the outer shell uses hard composite materials (carbon fiber, glass fiber) for rebound sensitivity. This local differentiation allows each layer to optimize its function without compromising the other.
Solution Approach 2:
The patent employs a composite structure combining soft porous particles (PMI/EPP) in the core layer with hard composite materials (carbon fiber, glass fiber, resin) in the shell layer. This composite approach enables the racket to simultaneously achieve shock absorption and rebound sensitivity by leveraging the complementary properties of different materials.
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 method results in a lightweight racket frame with improved control feel and reduced manufacturing costs, suitable for diverse user groups, including children and the elderly, by integrating a core mold and composite material layer for enhanced rebound elasticity and support.
Implementation Method 1
a core mold in the shape of a racket, made of polymethacrylimide (PMI) or expanded polypropylene (EPP) particles; then wrap the composite material around the core mold... heat the mold to a preset temperature. After heating, the core mold expands due to heat, forming internal pressure within the semi-finished product
Data Source
AI summary
A manufacturing method and structure for a composite material racket frame includes the following steps:(a) Resin impregnation: Impregnate a composite material with resin;(b) Wrapping the core mold with composite material: Use a core mold in the shape of a racket, made of polymethacrylimide (PMI) or expanded polypropylene (EPP) material; then wrap the composite material around the core mold to form a composite material layer. The mutually wrapped composite material layers and core mold together form a semi-finished product;(c) Heating and pressurizing: Place the semi-finished product into a mold with a cavity, and heat the mold to a preset temperature. After heating, the core mold expands due to heat, forming internal pressure within the semi-finished product;(d) Cooling and curing: Stop heating and allow the semi-finished product to cool until it reaches a cured state, and(e) Finished product formation: Remove a finished racket frame from the mold.