Layered Moulding Material for Pin-Hole-Free Surface Finish
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Solution Overview
Problem
Existing composite materials often cure to form poor surface finishes, characterized by rough, wavy, or pin-holed surfaces due to the coarseness of the reinforcement, particularly when coarse reinforcement is used for structural rigidity, which is undesirable in applications requiring a smooth surface finish like automobile body panels or wind turbine blades.
Innovation Solution
A moulding material comprising a primary non-woven fibre layer, a secondary non-woven fibre layer, and a resin layer, where the resin layer is exposed on the surface, bonded to the primary layer, providing excellent surface quality and preventing print-through of underlying fibre reinforcement layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If coarse reinforcement is used for structural rigidity, then structural strength is improved, but surface finish quality deteriorates
Solution Approach 1:
The moulding material is divided into distinct functional layers: a surface layer (5-20 micrometres thick) providing smooth finish, and a structural reinforcement layer providing rigidity. This segmentation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
Different regions of the moulding material have different properties: the surface layer has fine, uniform fibres for smooth finish, while the reinforcement layer has coarser, high-strength fibres for structural rigidity. Each layer's local quality is optimized for its specific role.
2Strength
If conventional moulding materials are used, then structural requirements are met, but surface finish requires extensive post-processing
Solution Approach 1:
The surface layer is pre-applied to the reinforcement layer before final curing, creating a smooth surface finish in advance. This preliminary action eliminates the need for extensive post-processing operations like sanding or filling.
Solution Approach 2:
The invention uses a composite structure combining a resin-impregnated surface layer with a fibrous reinforcement layer. This composite material provides both structural integrity and smooth surface finish in a single integrated component.
3Manufacturing precision
If surface layers are added to improve finish, then surface quality is improved, but material cost and complexity increase
Solution Approach 1:
The surface layer uses inexpensive, fine fibres (such as cellulose or short synthetic fibres) that are sacrificial in nature, primarily serving to provide surface finish rather than structural function. This keeps the added complexity and cost minimal.
Solution Approach 2:
The surface layer thickness is optimized to 5-20 micrometres - thin enough to maintain cost-effectiveness and simplicity, yet sufficient to provide the desired surface finish quality. This parameter optimization balances performance with complexity.
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 moulding material achieves an excellent surface finish with no pin-holes and avoids cosmetic defects, allowing prepreg reinforcement layers with a resin content of 30-45% without adverse impact on surface quality, and can be used with standard prepreg materials.
Implementation Method 1
a resin layer; wherein the resin layer bonds the secondary non-woven fibre layer to a first surface of the primary non-woven fibre layer
Implementation Method 2
the resin layer is exposed on the second surface of the primary non-woven layer... achieves an excellent surface finish with no pin-holes and avoids cosmetic defects
Data Source
AI summary
The present invention is concerned with a moulding material comprising: a) A primary non-woven fibre layer; b) A secondary non-woven fibre layer, and c) A resin layer; wherein the resin layer bonds the secondary non-woven fibre layer to a first surface of the primary non-woven fibre layer, and the resin layer is exposed on the second surface of the primary non-woven layer.