Moldex3D IARD

Fiber

Introduction to Fiber

Fiber Reinforced Plastics (FRP) have widely acted as a major material because of their superior mechanical

properties, high strength to weight ratio, high toughness to anticorrosion, and high creep resistance. FRP also has

many versatile mechanical characteristics due to different fibers, matrixes and producing processes. The factors are

fiber type, fiber content, and the original fiber length (before molding). The mechanical properties of FRP product

depend on its fiber length and orientation. For long fiber, the fiber length will be degraded during molding. In

addition, orientation determines the fiber-induced anisotropic mechanical properties. The fiber orientation will be

along the flow direction in skin layer while being perpendicular to flow direction in the core layer. The deformation,

fracture and ultimate strength owing to external loads of FRP product are hard to predict. Consequently, designers

conservatively employ FRP's capabilities with some limitations.

Fig. 1 Schematic diagram of fiber orientation

Function Overview of Moldex3D Fiber Module

Moldex3D Fiber module helps in predicting the fiber orientation, part warpage and the resultant anisotropic

mechanical properties of fiber-reinforced materials. This module is designed to:

1. Calculate the fiber orientation of short and long fiber reinforced thermoplastics (FRTP)

2. Correct the anisotropic shrinkage and mechanical properties for the injection molded FRTP parts.

3. Link with Moldex3D Warp module in calculating 3D warpage of FRTP parts.

Moldex3D incorporates fiber analysis into the modules of Flow, Pack, and Warp. The effect induced by fiber

orientation in filling stage will have a large impact on warpage results.

Note that a dedicated license is required to run fiber analysis. Besides, Moldex3D Fiber supports all solid, shell, and

eDesign mesh models.

Moldex3D Fiber calculates fiber orientation by applying the Folgar-Tucker model and its modification for long fiber

reinforcement. Moldex3D Material Wizard provides appropriate material parameters to generate legitimate analysis

results. In the hierarchical structure of material grades in Moldex3D Material Wizard, the sign next to the

material grade entry indicates that fiber related parameters are included. In addition, the fiber related parameters

can be modified by the user if the material is added to the User Bank.

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Fig. 2 Sign indicates that this material grade has fiber properties.

Pre-Processing

Moldex3D Fiber supports all mesh projects with fiber material application. The procedures in the pre-processing

stage for the Moldex3D Fiber module are similar to those for basic modules：

Step 1: Create a mesh model

Step 2: Create a new project

Step 3: Create a new run

Step 4: Run analysis

In the following, it lists special setup instructions in some specific steps.

Create a New Run

In Computation Parameter, specify all parameters in Fill/Pack/Cool/Warp or other tabs. The option of Run fiber

orientation analysis in the Fill/Pack tab will be checked by default as long as the fiber material is selected. The

Consider fiber orientation effect will also be checked in the Warp tab. There are three micro-mechanics models

that can be selected, traditional composite model, Halpin-Tsai model, and Mori-Tanaka model. The definitions and

descriptions of these models can be found in the chapter of Mathematical models: Fiber Orientation.

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Fig. 3 Fiber orientation analysis function setting in Fill/Pack and Warp tab of Computation Parameter

The Folgar-Tucker equation is used in calculating the fiber orientation in filling and packing processes. Therefore, it

is mandatory for Flow/Pack analyses to accurately simulate flow history of fiber orientation. Note that analyses with

the fiber-orientation calculation function will have a longer computation time.

Definition of Fiber Orientation

The orientation of a single fiber is defined by the orientation vector p. The probability function Ψ(θ, φ) is defined, and

the probability of a fiber existing between (θ, φ) and (θ+dθ, φ+dφ) can be given by Ψ(θ, φ)sin(θ)dθdφ. In addition, the

probability distribution function must satisfy two physical conditions which are listed as follows:

1. One end of the fiber is indistinguishable from the other, therefore,

Ψ(θ, φ) = Ψ(π−θ, φ+π).

2. Each fiber must have a definite direction, so the normalization requirement is

Fig. 4 Definition of orientation vector p

The second order fiber orientation tensor Aij

is described below.

,

where Aij is a symmetric tensor:

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Aij = A

ji,

A11

+ A22

+ A33

= 1 .

Because an orientation tensor matrix is real and symmetric, three orthogonal eigenvectors e1, e

2, and e

3, and three

eigenvalues λ1, λ

2, and λ

3 exist. Each eigenvalue ranges from 0 to 1. In the post-processing of fiber orientation,

fiber orientation phenomena can be described by the maximum eigenvalue and its corresponding eigenvector

plotted together. The orientation of the vector indicates the majority fiber orientated direction, and the magnitude

(displayed in color) shows its orientation in degree.

If fiber orientation is random, the maximum eigenvalue would be 1/3; likewise, if fiber orientation is unidirectional,

the maximum eigenvalue would be approximately 1.

Advanced Fiber Parameter setting

In Computation Parameter, fiber parameter settings can be found in Advanced Options under Flow/Pack tab.

There are three new approaches to improve the fiber orientation accuracy for short or long fiber-filled composites.

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Fig. 5 Fiber Parameter setting in Advanced Options for Fill/Pack tab of Computation Parameter.

The first approach is the 4th orientation tensor closure. It includes three methods: Hybrid (original Moldex3D fiber

orientation calculation solver model), ORE (orthotropic closure approximation model), and IBOF (modified

orthotropic closure approximation model). The properties of the three models are listed below.

The second approach is the Rotary Diffusion, It includes three methods: Folgar-Tucker (original Moldex3D fiber

orientation calculation solver model), ARD (Anisotropic Rotary Diffusion model) and iARD (Improved Anisotropic

Rotary Diffusion model). The properties of these models are listed below.

Hybrid

Short computation time

Fiber orientation tensor over-estimates at skin

Moderate fiber orientation prediction accuracy

ORE

Long computation time

Improvement of fiber orientation tensor over-estimating problem

High fiber orientation prediction accuracy

IBOF

Short computation time

Improvement of fiber orientation tensor over-estimating problem

High fiber orientation prediction accuracy

Folgar-Tucker

Accounts for fiber-fiber interactions with isotropic rotary diffusion

which helps to capture the short-fiber orientation distribution

profile.

ARD

Accounts for fiber-fiber interactions with anisotropic rotary

diffusion which helps to better capture the long-fiber orientation

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The third approach uses the Retard Principal Rate (RPR) to consider Fiber-Matrix Interaction, and hence

improves the original Folgar-Tucker model approach, which over-estimates the changing rate of the orientation

tensor in concentrated suspensions. The RPR model alpha factor is suggested to be from 0 to 1 (the larger factor

value is, the more obvious RPR effect will be).

Average fiber length

Moldex3D is capable of predicting fiber breakage inside the barrel and cavity at the filling stage. The screw

information can be set by Machine mode in Process Wizard. If CAE mode is chosen, the screw specification will be

set to default.

distribution profile. The drawback is there are five parameters

to set.

iARD

Accounts for fiber-fiber interactions with anisotropic rotary

diffusion which helps to better capture the long-fiber orientation

distribution profile. Only two parameters are needed.

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Under Filler Parameter tab, check the box of Consider fiber breakage calculation and click on Param… to open

Advanced calculation option window and enter the fiber information appropriately. Otherwise simply use default

settings. Click Considering screw-induced fiber breakage to predict fiber breakage by screw. To check if this

function is indeed involved within the calculation, the message of “Fiber breakage in Screw = on” in *.lgf file will be

shown. For internal calculation, the fiber breakage level is determined by the length.

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After setting up fiber breakage and finishing the analysis, Average Fiber Length and Screw-induced Fiber Breakage

result entries will be shown in the result tree in Project Workspace.

The following plot shows the Average Fiber Length from 8.5 to 5.6 mm reduced by screw.

And the fiber length of the initial condition (melt entrance) for calculation will be 5.6 mm instead of 8.5 mm.

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Click on the entry to display average fiber length distribution either by average number or average weight. This

result helps to examine fiber breakage phenomena near the gate region and fiber length distribution of the part after

injection. Note that fiber length distribution does not affect part mechanical properties in R13.0.

Fig. 6 Average Fiber Length(by Number)

Fig. 7 Average Fiber Length(by Weight)

Flake Orientation (as opposed to long/short fiber orientation)

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Some polymers are mixed with flake fillers instead of long thin fibers. Moldex3D now supports this special type of

material in Material Wizard.

In order to view a Flake Orientation result after the analysis, the selected material must contain the mechanical

property of flake-filled polymer. You can modify fiber property as flake by using the Modify function in Material

Wizard.This flake property in Material Wizard is shown as below.

Next, under the Flow/Pack tab in Computation Parameter, check the box of Run flake orientation analysis to enable

flake orientation calculation later in the analysis. For advanced settings of flake parameters, click on Advanced at

the bottom to enter the setting dialog. Note that the breakage calculation is not supported here due to the shape of

the flake filler.

The model is ready to be analyzed after these settings are completed. Return to Moldex3D Project, and click

Analysis sequence and select Full Analysis –CF/PCW for Fiber analysis. Note that analysis sequence is selected

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from the drop down menu per your need.

Post-processing

Shell

Output as Contour Demonstrated in Display Window

For shell models, fiber-orientation analysis will not affect Filling and Packing results, such as, melt front time,

temperature, pressure, etc. However, if fiber analysis is included, there will be additional results, such as

Fiber Orientation (Average), Fiber Orientation of Layer1 (Core), Fiber Orientation of Layer2,…, Fiber

Orientation of Layer6 and Fiber Orientation of Layer7 (Skin). The number of the layer is specified in

Computation Parameter. Number of thickness layer is n, so the total number of fiber orientation layers would

be n+1. The Layer1 corresponds to the orientation on the symmetric plane and Layer(n+1) corresponds to the

skin layer.

Fig. 8 A schematic representation of core layer and skin layer

Fiber Orientation (Average) is defined as follows.

,

where H is the thickness of the part, and z is the thickness direction. The eigenvalue of represents Fiber

Orientation (Average).

Solid/eDesign

Output as Contour Demonstrated in Display Window

The additional analysis outputs for Solid/eDesign models are Fiber Orientation (Skin) and Fiber Orientation.

Fiber Orientation (Skin) is the orientation on the part skin layer. Fiber Orientation is the three-dimensional fiber

orientation distribution across the part; the slicing function can help to display the results’ details.

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Fig. 9 Fiber Orientation (Skin)

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Fig. 10 Contour result of Fiber Orientation

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Fig. 11 Contour result of Fiber Orientation described by Dynamic Slicing Function

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Contour result of Fiber Orientation described by Multi-Plane Slicing FunctionExport to Other Software for Further

Analysis

Moldex3D can export the file of fiber orientation results in different formats for further analysis within other CAE

softwares. Basically, Moldex3D provides the injection molding processes, including post-simulation material

properties which can be directly forwarded to structure analysis via Moldex3D FEA Interface module. In addition,

Moldex3D also provides the data transformation from Moldex3D molding results to Digimat. For the instructions of

Moldex3D FEA Interface or Digimat, please refer to FEA Interface or Digimat.

Generate Report

After finishing analyses and evaluating results, click Report Wizard in Post or Toolbar on the right side of the

window.

The Wizard dialog pops up. Select the desired result items and export them as the report. For more information

about Report Wizard, you may refer to Project Visualization and Management.

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