# A Numerical Approach for the Efficient Concept Design of Laser-Based Hybrid Joints
## 4 Summary and Outlook  
In this paper, a computer-aided approach for the automated development of optimized microstructure concepts for laser-based hybrid joints was presented. To achieve this, a new numerical model for the automated positioning of cavities and new models for strength calculation and cost calculation were presented. The models were linked in an optimization approach to automatically generate cost- and strength-optimized concepts that optimally met the requirements. The approach was validated on a demonstration example and optimized microstructure concepts were identified for various benchmarks with classical structuring. The outcomes can be summarized as follows:  
* The stress-based numerical cluster approach was able to automatically identify regions with the same stress and load angles while still ensuring laser manufacturability. For each region, the cavities could be placed automatically, and thus microstructure concepts could be efficiently generated.
* To efficiently determine the quasi-static strength of the laser-based joint, the cohesive-zone-modeling (CZM) approach is suitable. The comparison of the predicted strength with an experiment showed an error of \(\sim\)3%.
* Supplying the CZM with only the FE-RVE data is possible and leads to sufficient prediction quality of the joint strength. The effort for simulation and implementation of the CZM was significantly lower than for the micromodel.
* The laser cost model is extended to calculate the laser production time and costs for arbitrary microstructure concepts.
* Linking the models in a genetic optimization procedure enabled the automated identification of optimized microstructure concepts, which had up to 67% lower costs than benchmarks with the classical microstructure but the same strength.  
Figure 17: Optimization history of the benchmark (b).  
In conclusion, a fully model-based design approach for laser-based hybrids was developed, which showed high potential for reducing the development time of laser-based plastic-metal hybrid joints. Furthermore, it is possible to efficiently develop tailored and load-optimized microstructure concepts without requiring iterative experiments, thus saving production time and costs as well as experimental effort. Thus, the full potential of the joining technology can be exploited and the industrial application is enhanced.  
The number of clusters was selected manually for the given parts. To improve the approach in future work, a method to automate this step is still required. Currently, the cavities of all clusters are independent of each other. The connection of some cavities over the clusters in post-processing holds further potential to reduce the total number of cavities and thus the laser production time and laser costs. The applicability and validity of the CZM approach were demonstrated in this paper for the quasi-static load case on a small example. Additional experimental validation of the CZM approach on different components, materials, and microstructures (e.g., crossed, under angle) will be carried out. Furthermore, the approach will be extended to dynamic load cases and also be able to consider temperature-dependent material behavior. In future work, further investigations will be carried out to also consider the influence of possibly uncertain parameters in the optimization approach.  
Conceptualization, J.B., G.J. and J.M.B.; methodology, J.B.; software, J.B.; writing--original draft preparation, J.B.; writing--review and editing, G.J. and J.M.B.; visualization, J.B.; supervision, G.J. and J.M.B.; All authors have read and agreed to the published version of the manuscript.  
This research has been carried out as part of the project \"TailoredJoints\", funding code 03 XP0277F which is funded by the German Federal Ministry of Education and Research (BMBF).  
Not applicable.  
The authors declare no conflict of interest.