In the previous article - Software Tools for Composites Structural Designers, we focused on structural design tools used at different stages of the design process. In this blog, we will deep dive into the next step i.e. production simulation of composites.
The application of virtual manufacturing simulation tools ensures that composite manufacturing processes lead to high-quality and cost-effective components. The simulation tools are used over a wide range of processes to validate the design and predict material behavior at each step of the processing. A wide gamut of virtual manufacturing simulations is available for different process simulations.
Design of tooling
Programming and simulation of automated placement processes
Program generation
Simulation of liquid composite molding processes such as Resin Transfer Molding (RTM) and Resin Infusion
Short-fiber injection and compression molding process modeling
Curing, Defects, and Residual Stresses
Residual stress and distortion assessments for structural analysis, process optimization, and tool compensation
Effect of defects studies (voids, waviness, bridging, tape paths, etc.)
Automated Deposition
Automated depositing of fiber tapes using Automated Fiber Placement (AFP) is increasingly being adopted by the industry. After the FEA analysis, the main outcome is fiber orientation and other selective reinforcements. In order to convert the ply data from the FEA model into an AFP program, the general flow of steps is outlined below:
Design of tooling
FEA model is exported into a CAD format such as .step or .igs. The CAD model shape provides the surface geometry of the tool. The tooling will be used for the layup with compaction force and the curing of parts all occurring on the tool itself. Typical mold design considerations e.g. sufficient draft angles, complex geometries, or multi-piece/sacrificial tooling might be required and taken into consideration. Additionally, tension and part shrinkage can contribute to a condition known as ‘spring-in’ with cured parts, requiring an angular compensation in the tool design.
Tooling and mandrels for automated fiber placement and tape-laying processes typically are designed to provide the appropriate inner-most-loft or outer-most-loft surface. Tools and mandrels of this type may be designed to index on an automated machine-bed platform for use with AFP or ATL equipment. Any modern CAD software can be used to draw the tool CAD model with the above considerations.
A detailed article on the tool design can be found here Things to consider when Designing for ATL/AFP Manufacturing
The tooling design step from the CAD model is shown in the figure below. The tool has extended boundaries for the AFP tool runways and vacuum bagging operations. The hole has been filled up to create a continuous surface for runways within the part. The mounting feature should be considered in the tooling design e.g. in the example shown below the tooling is mounted on the rotary chuck, so an extended shaft is added for mounting onto the rotary axis. Depending on the mold manufacturing method, the rest of the details can be created accordingly.
Programming and simulation of automated placement processes
The tooling CAD model is imported into the offline programming software (OLP) to create layup definitions in two steps i.e. Planning and Simulation.
Planning
OLP software used for AFP process workflow is presented in the figure below. The OLP Software takes the tooling CAD models as input. The first step is to define the layup area and boundary. Next, the processing parameters such as fiber orientations, runway, approach, clearance, speed, and heating intensity, are input based on your needs. Based on this information, the OLP can create motion paths for the fiber placement tool with multiple strategies.
In addition to the motion paths, there are multiple parameters e.g. tape weight (GSM), gaps, and staggering, that the engineer can choose from to configure the motion path. Typical OLP is capable of:
Path Planning: Generate desired fiber orientation paths on 2D & 3D surfaces (open) automatically
Custom Path Planning: Import your own fiber paths to create the layup you require, This is particularly helpful for any custom path trajectories, around the holes, along with the load direction fiber placement, etc.
Path modification: Modify generated paths i.e. shorten, suppress, edit motion frames, edit individual plies, etc. to optimize your placement strategy
Resource estimator: Estimate material and time utilized to conduct the layup, optimize process parameters to optimize resource utilization
Simulation
The generated paths will be followed by the AFP robot. While the AFP head is trying to follow the motion paths, there arise possibilities that it might hit the tooling or pass the robot singularities. In order to visualize these occurrences, robot motion simulation is evaluated either by automated analysis or by the operator to eliminate such problems. The key benefit of running the simulation in the virtual environment is avoiding costly collision and damage to the AFP head, robot, part, or tooling!