Flexible Silicone Mat for Smooth FRP Surface Quality

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Solution Overview

Problem

The production of fiber-reinforced plastic (FRP) components often results in surfaces with waviness, fiber markings, and micro-porosities, making them difficult to coat uniformly, leading to increased material and labor costs, and limitations in achieving a smooth surface necessary for automotive body parts.

Innovation Solution

A method involving a flexible silicone mat in a single tool mold where a fiber semi-finished product is impregnated with a free-flowing plastic matrix, followed by the application of a surface coating, allowing both the fiber composite layer and surface coating to bond and cure together, ensuring a smooth, even surface without fiber markings or porosities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional RTM process is used to produce FRP components, then fiber reinforcement and structural strength are achieved, but the surface quality deteriorates with waviness, fiber markings, and micro-porosities

Engineering Contradiction:
Improvestructural strengthVSAvoidsurface quality
Core Design Contradiction:
StrengthVSManufacturing precision

Solution Approach 1:

The molding process is segmented into two distinct stages: first forming the fiber-reinforced structural layer with adequate strength, then separately forming the surface coating layer with smooth finish. This segmentation allows each layer to optimize its specific function without compromising the other.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention uses a composite structure consisting of a fiber-reinforced plastic layer combined with a separate surface coating layer. The fiber layer provides structural strength while the coating layer provides smooth surface quality, achieving both requirements simultaneously.

Inventive Principle:
Principle #40Composite materials

2Manufacturing precision

If additional grinding work is performed to eliminate surface defects, then surface quality is improved, but production time and labor costs increase

Engineering Contradiction:
Improvesurface qualityVSAvoidproduction time
Core Design Contradiction:
Manufacturing precisionVSProductivity

Solution Approach 1:

The smooth surface is created during the molding process itself through the surface coating layer, rather than requiring post-production grinding. This preliminary action eliminates the need for subsequent surface treatment operations.

Inventive Principle:
Principle #10Preliminary action

3Manufacturing precision

If high paint layer thickness is applied to cover surface defects, then surface appearance is improved, but material consumption and costs increase

Engineering Contradiction:
Improvesurface appearanceVSAvoidmaterial consumption
Core Design Contradiction:
Manufacturing precisionVSLoss of substance

Solution Approach 1:

The surface defects are eliminated at the source by using a smooth-flowing coating material that forms a defect-free surface layer, rather than attempting to cover defects with thick paint. This extracts the problem of surface quality from the painting stage.

Inventive Principle:
Principle #2Taking out (Extraction)

4Manufacturing precision

If in-mould coating process is used with movable slides, then coating application is achieved, but markings and flags are formed at transitions, requiring additional rework

Engineering Contradiction:
Improvecoating distributionVSAvoidprocess complexity
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The invention changes the key parameter of coating material viscosity to a low-viscosity state, allowing the material to flow smoothly into all mold cavities including transition areas without forming markings or flags, eliminating the need for complex slide mechanisms.

Inventive Principle:
Principle #35Parameter changes

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 produces high-quality, paintable FRP components with improved surface quality, reduced material and labor costs, and increased process reliability, enabling large-scale production with minimal post-processing requirements, and achieving a surface finish identical to sheet metal components.

Implementation Method 1

the mold cavity of the tool is filled with a free-flowing plastic matrix

Methodology Applied
Scientific EffectFlow:

Implementation Method 2

the semi-finished fiber product and the plastic matrix harden to at least partially form the fiber composite plastic layer

Methodology Applied
Scientific EffectCuring:

Implementation Method 3

a free-flowing plastic molding compound is filled into the mold cavity of the tool in such a way that a plastic layer is formed

Methodology Applied
Scientific EffectFlow:

Implementation Method 4

the surface coating being in full contact with the mat and at least partially bonding to the fiber-reinforced plastic layer

Methodology Applied
Scientific EffectAdhesion: Adhesive

Data Source

PatentEP2730396B1Process for manufacturing a molded part comprising a layer made of a fibre composite plastic layer and a surface coating consisting of a moulded plastic component
Publication Date: 2018.01.17 VOLKSWAGEN AG
  • EP2730396B1 patent drawingFigure 1
  • EP2730396B1 patent drawingFigure 2~3
  • EP2730396B1 patent drawingFigure 4~5

AI summary

The method involves arranging (a) flexible mat on a surface of a tool portion, which covers the surface of the tool part in an area defining the mold cavity. A fibrous half-finished product of reinforcing fibers is introduced in the mold cavity of the tool such that the fibrous half-finished product is arranged between the flexible mat and another tool portion. The mold cavity of the tool is filled (c) with a flowable plastic matrix. The plastic matrix is filled in a region between the flexible mat and the latter tool portion. The fibrous half-finished product and the plastic matrix are partially hardened (d) to form the fiber composite plastic layer in the mold cavity. The flexible mat is formed of silicone.