Problem & Solution

We approach plastics product and process development with a strong background in material science. This is useful as plastics show complex material behavior that frequently complicates the development process. Over the years we have developed an approach this problem which is highlighted here.

Table of Contents

Problem

Material

Plastics show nonlinear material behavior, which always depends on temperature, time and the level and type of loading. Depending on material and application, other phenomena such as humidity or tribological behavior need to be regarded.

Forming

When material is brought into a shape, final material properties depend on the local composition and processing conditions. As a consequence, material properties vary spatially (heterogeneity) and depend on the direction of loading (anisotropy).

Loaded Structure

In a loaded structure, material and shape act together. Strain fields, stress fields and residual stress fields develop. Each component shows a characteristic tolerance for stress peaks, which may depend on size effects.

Managing Complexity

The better we know all these effects, the better we can take them into account. The more accurately we can measure and calculate these effects, the better we can optimize components for the occurring loads. However, testing and simulation consume time and money. Accordingly, models should be as simple as possible and only as detailed as necessary.

Solution

Modeling

We support by providing answers to questions:

  • Which phenomena should be considered or omitted?
  • In which ranges are the occurring quantities (stresses, strains, times, temperatures, …)
  • Which methods, programs and models should be used?
  • How can experience, thought experiment, test and computation be bundled into efficient solutions?

Giving answers to these questions, we conduct preliminary tests and make initial calculations.

Test Plan

As soon as the modeling approach model is clarified, a set of experiments for determining the model parameters needs to be found. Some questions then arise and need to be answered:

  • Which tests, with which test parameters, in what number are carried out?
  • Which specimen shapes are used?
  • How are the specimens manufactured?
  • Which test documentation is necessary?

Answering these questions, an efficient test plan, suitable for model parameter identification, is created.

Testing

Our laboratory is equipped for the thermo-mechanical characterization of plastic materials and plastic components.
We focus on:

  • Tests for model parameter identification
  • Characterization of heterogeneous and anisotropic materials
  • Component testing, specimens from components
  • Temperature dependent properties in the range -80 °C to 250 °C
  • Moisture-dependent properties (PA).

Our documentation is detailed and computerized. We report: tested components, specimens, experimental programs, test results and raw data.

This makes a comprehensive statistical evaluation and in-depth examination of the results possible. The provided data is uniform and fit for direct further computer processing (Excel format).

Identification of Model Parameters

After it has been clarified, which material model is used, and if suitable experimental data already exists, we calibrate model parameters. We mainly work with Abaqus and tools in this ecosystem. As a result we provide the material model input deck (e.g. Abaqus inp) and a model-experiment comparison for all regarded experiments.

Finite Element Analysis

Based on a clear specification of geometry, modeling, parameters and loads, we perform finite element analysis.
As software we use Abaqus with extensions for material modeling and fatigue life assessment.

Some of our strengths:

  • Prediction of time- and temperature dependent deformation and damage behavior (creep, cyclic deformation, …)
  • Fatigue life assessment for components made of short and long fiber reinforced polymers and SMCs