Carbon Fiber Random Mat Structure for Low-Pressure Composite Molding

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Solution Overview

Problem

Fiber-reinforced composite materials with thermoplastic resin matrices face challenges in achieving high mechanical strength and fiber volume content ratios while minimizing molding pressure and springback, particularly with random mats containing carbon fibers, which often require high pressure and result in low bulk density and increased equipment costs for large-area molding.

Innovation Solution

A random mat comprising carbon fibers with specific fiber constitution, including an average fiber length of 3 mm to 100 mm, a fiber areal weight of 25 to 10,000 g/m², and a proportion of carbon fiber bundles defined by specific formulas, allowing for reduced molding pressure and increased bulk density, resulting in high fiber volume content ratios and mechanical strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If reinforcing fibers are opened up to single filament form to increase dispersion property, then dispersion property is improved, but bulk density becomes very low and molding pressure increases

Engineering Contradiction:

Improvedispersion propertyVSAvoidmolding pressure

Core Design Contradiction:

Quantity of substanceVSStress or pressure

Solution Approach 1:

The patent applies local quality by creating a non-uniform fiber structure where single filaments and bundles coexist in specific proportions. The single filaments provide dispersion and impregnation ability, while the bundles maintain bulk density and reduce molding pressure. This localized differentiation of fiber forms resolves the contradiction between dispersion property and molding pressure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses a composite fiber structure combining single filaments and bundles in a controlled ratio. This composite approach allows the material to simultaneously exhibit properties of both single filaments (good dispersion) and bundles (high bulk density, low molding pressure), effectively resolving the technical contradiction.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If reinforcing fibers are made into single filament form to improve impregnation ability, then impregnation ability is improved, but bulk density becomes very low

Engineering Contradiction:

Improveimpregnation abilityVSAvoidbulk density

Core Design Contradiction:

Quantity of substanceVSVolume of stationary object

Solution Approach 1:

The patent creates a non-uniform fiber structure where single filaments and bundles coexist in specific proportions. The single filaments provide dispersion and impregnation ability, while the bundles maintain bulk density. This localized differentiation of fiber forms resolves the contradiction between impregnation ability and bulk density.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses a composite fiber structure combining single filaments and bundles in a controlled ratio. This composite approach allows the material to simultaneously exhibit properties of both single filaments (good impregnation) and bundles (high bulk density), effectively resolving the technical contradiction.

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If high molding pressure is applied to mold large area shaped products, then molding is achieved, but equipment investment is remarkably increased

Engineering Contradiction:

Improvemolding capabilityVSAvoidequipment investment

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent changes the physical parameters of the fiber structure by controlling the proportion of single filaments and bundles. This parameter change results in altered material properties (higher bulk density, lower molding pressure requirement), which indirectly reduces equipment investment for large-area molding by enabling molding at lower pressures.

Inventive Principle:

Principle #35Parameter changes

4Volume of moving object

If non-woven material is compressed to reduce thickness, then thickness is reduced, but reinforcing fibers return to original bulky state and sheet expands (springback)

Engineering Contradiction:

ImprovethicknessVSAvoidspringback ratio

Core Design Contradiction:

Volume of moving objectVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary action by pre-forming the fiber structure with a specific combination of single filaments and bundles before molding. This pre-structured fiber arrangement resists springback during and after compression, maintaining thickness reduction and preventing expansion. The bundled structure provides structural memory that counteracts the springback tendency.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9909253B2Random mat, shaped product of fiber reinforced composite material, and carbon fiber mat

Publication Date: 2018.03.06 TEIJIN LTD

AI summary

There is provided a random mat including carbon fibers having an average fiber length of from 3 mm to 100 mm and a thermoplastic resin, wherein a fiber areal weight of the carbon fibers is from 25 to 10,000 g/m2, a proportion of carbon fiber bundles (A) constituted by single carbon filaments of a critical single fiber number or more defined by the formula (1) to the total amount of fibers in the random mat is from 40 to 99 Vol %, and an average number (N) of fibers in the carbon fiber bundles (A) satisfies the formula (2):critical single fiber number=600/D (1)2.0×105/D2≦N<8.0×105/D2 (2)wherein D is an average fiber diameter (μm) of carbon fibers.