Fatigue-Based Concept Design and Optimization
A recent development in optimization simulations codes is the ability to use stress-life and strain-life fatigue analysis as design criteria. This allows concept optimization analysis to generate designs which are more robust and more mature earlier in the development process as the early freeform optimization results take further real world loading and use conditions into account. Optimizing designs in using this technology ensures that the effort to reduce mass and weight out of products does not mean that performance and use life has to be affected and in many cases, can actually be enhanced.
The design of composite structures involves the definition of the ply angles, numbers of plies, and stacking sequence for the given laminate. Given the large number of potential variables, designs are usually limited to standard sets of design configurations based on experience and available test data. There is potential for laminated composite structures that have increased performance and reduced weight by utilizing optimization methods to find the best combination of variables for a given application.
Composite Optimisation Process
The virtual simulation process to design optimized composite materials includes a number of defined stages. Firstly, topology or freeform optimization is conducted to define the concept geometry. Secondly the ply shape of the composite component is studied to identify ideal ply drop-off zones. The thickness of each ply shape is then analysed to remove any unrequired material from the ply stack. Lastly the ply order within the stack is optimized to find the ideal order that multi-directional plies should be laid up. As with all optimisation processes, design performance criteria and manufacturing constraints are maintained from concept through to final design.
Composite Optimization Benefits
The composite optimization design process has a range of benefits including:
- Cuts development time and cost by providing high performance designs in the initial stages of the product development process
- Reduces product design time by eliminating the “trial and error” process of typical design iterations
- Automates calculation of the number of plies needed for each ply fiber orientation
- Automates composite laminate stacking sequence determination
- Automates incorporation of manufacturing constraints and Ply Book Rules for certified designs
Optimization applied to composite materials
Equivalent Static Load Method (ESLM)
The equivalent static load method, originally published by Dr. Park, Hanyang University, is a technique suitable for optimization of designs undergoing dynamic loads. The equivalent static load is that load which creates the same response field as that of the dynamic/nonlinear analysis at a given time step. The method has been implemented for the optimization of the following solutions:
- Multi-body dynamics problems including flexible bodies.
- Non-linear responses from implicit static analysis, implicit dynamic analysis and explicit dynamic analysis.
The calculated equivalent static loads from the analysis (as explained above) are considered as separate load cases, and these multiple load cases are used in the linear response optimization loop. An updated design from the optimization loop is then passed back to the analysis for validation and overall convergence. The design is validated against the original dynamic/non-linear analysis. Based on the outcome of this validation, the solution converges or an updated set of equivalent static loads is calculated for the updated geometry, and the entire process is repeated till convergence.
Apart from others, the equivalent static load method offers the following benefits:
- It can be applied at the concept design phase as well as design fine tuning phase, i.e. it can be used with topology, free sizing, topography, size, shape and free shape optimization.
- A design is optimized for updated loads due to an updated design during the optimization process.
Technical Paper - Optimization of Composite: Recent Advances and Application
Technical Paper - Force India – Composite Optimisation of a Formula One Front Wing
Technical Paper - Optimization of Blended Composite Wing Panels
Technical Paper - Composite Design Optimization: from Concept to Ply-Book Details
Technical Paper - Structural Optimization Considering Fatigue Requirements