The needs
Laminated fibrous composite materials (fiber-reinforced composite laminates) have seen an increasing number of applications, not only in military applications but also in commercial ones. The performance evaluation of laminated fibrous composites is mostly an open-ended solution that states how a given design performs -not what the design should be to meet a target performance. Automated design optimization techniques are needed in conjunction with finite element simulation and dedicated pre-/post-processing programs, to explore the full range of design alternatives for laminated fibrous composites – enabling the designer to find a design that meets all the requirements.
The design problem
During the design process of fibrous composite laminates, one of the most important factors affecting the function and performance of components is the fiber direction in each lamina (layer) of the composite.
With complex shapes (such as a F1 chassis,see Figure 1) each lamina has to follow several curvatures and the fiber lay-up will have to accommodate these accordingly. As a consequence,fiber direction changes with respect to the global orientation as the fiber wraps around the object.
In building finite element models for laminated fibrous composites,three steps are usually involved:
- Orientation of fibers in each lamina from a global starting point
- Introduction of necessary “cuts ” (scissoring)
- Calculation of fiber directions along the part (draping)
Legacy simulation tools (e.g.MSC.NASTRAN ™) can solve for the performance (stress, dynamic properties, etc) of a part (or system) made of laminated fibrous composites, if each lamina is completely specified. Thus, the input to such a simulation tool needs to define the directions of the fibers in each lamina according to a global coordinate system. In providing this input, pre-processing programs (e.g.MSC.PATRAN ™ Laminate Modeler ™) are used to calculate fiber directions along the part (or system). In determining the most appropriate fiber directions, an optimization capability fully integrated within the simulation tool is insufficient, since the fiber directions along the part will change with each step in the optimization process and since the draping operation needs to be repeated at every step.
In this application note, an external optimization methodology is presented, using design space exploration techniques to optimize the performance of laminated fibrous composites.
The process
A simulation process appropriate for laminated fibrous composite modeling is built on the following sequence:
- performing the pre-processing operation of scissoring and draping
- running the simulation (static,dynamics,…)
- post-processing the simulation results with a specialized post-processor
In the example discussed in this application note, the pre- processing operation is performed with MSC.PATRAN ™ Laminate Modeler, the simulation with MSC.NASTRAN ™ while calculated results are post-processed with MSC.PATRAN ™ Laminate Modeler ™. This entire process can be automated by using LMS OPTIMUS, which not only integrates nearly any type of simulation software, but can also automatically drive them to explore the design space and search for the optimum design within given constraints. This automation and monitoring of the whole process eliminates one of the most tedious tasks in design engineering. OPTIMUS is unique in the sense that it can address simulation sequences that involve many simulation programs -an absolute pre- requisite for laminated fibrous composites.
