Abstract

Stiffness and strength are important structural design criteria. However, most contributions to Topology Optimization (TO) deal with the compliance minimization problem. Controlling stresses in a structure is very important to avoid material failure, but that raises complications in TO, such as: nonlinearity, singularity and high computational cost. The total weight of a structure is also another important criterion in optimal design. The multi-material setting is considered in the present work as it opens the possibility to improve structural performance even further allowing extra weight reduction. Recursive SIMP is used as the material interpolation scheme and design solutions are sought using the ground structure approach. This means that truss-like (lattice) designs are obtained here. The problem is relaxed to the continuum by introducing an artificial density variable and it is solved by a gradientbased algorithm (MMA). A stress-constraint relaxation technique (qp-approach) is applied to overcome the stress singularity phenomenon. A continuation approach is used to guarantee discrete solutions, i.e., only the presence or absence of bars is identified. Therefore, design uniformity in terms of bars cross section areas is ensured. Hence, this work proposes a methodology to perform Multi-Material Topology Optimization (MMTO) of truss structures, with density-based design variables, and subject to stress constraints. To discuss the differences between stiffness and strength-oriented optimal designs, a compliance minimization problem subject to mass constraint is also considered. The example chosen demonstrates the viability of the proposed design methodology and it also reveals differences between the strongest and the stiffest designs.

Abstract

The transport industry is dominated by the challenge on lightening the weight due to environmental restrictions and cost reduction. The use of different materials and multi-material designs provide a great opportunity to develop products capable of meeting this challenge. Critical aspects to be considered in multi-material manufacturing are surface preparation and dissimilar joining. The multi-material joining metal-composite thermoplastic (CTP) is critical for different aspects such as low adhesion due to a low chemical affinity or corrosion problems in the case of the use of carbon fiber reinforced composites. On the other hand, laser texturing is one of the most promising techniques to create surfaces with controlled roughness, manufacturing in a single step and improving metal-CTP adhesion, without the need to use adhesives.

This work, developed within the framework of the European COMMUNION project (GA680567), addresses the optimization of the direct joining process between different high-performance metals and thermoplastic composite cintas. The study deals with surface preparation using laser texturing, the study of different joining strategies and the characterization of joints using different techniques and Single-Lap Shear tests.

Depending on the texture, type of materials or manufacturing strategy, the strength of the joint is improved by 50-200%, achieving structural strength values (> 10MPa) in the optimized joints.

Abstract

The present work addresses different aspects of the manufacturing process optimization of structural components for the automotive sector. More precisley the development of a novel bumper beam is being pursued by combining steel and composite to achieve, ultimatly, a weight reduction of the current component. For this it has been fundamental to consider not only the requirements of the part, specially from the safety prespective, but also manufacturing criteria.

The study carried out has included everything from the design of the component up to the evaluation of a wide range of composite materials, both of thermostable and thermoplastic nature. Thus, different manufacturing technologies together with their process window and tooling desing has been accomplished in this work. In addition, several surface treatment technologies including cutting-edge ones such as laser texturing, have been combined with different strategies to ensure, in this way, the optimal performance of the solution.

Finally, the development of ad-hoc demonstrators has allowed identifying the most suitable design and materials. Also, it has been possible to quantify the performance of the components, process times and final cost. Finally, a 25% weight reduction has been achieved, maintaining the mechanical properties and cycle times down to 5 minutes.

Abstract

The transport sector has exerted and continue to be the driving force for the development of new materials and lightweigth solutions. The present study focuses on the work developed in a recently completed European project (CARBODIN https://carbodin.eu/) where one of the main objectives is to develop innovative and affordable solutions for advanced car body shells. Composite materials appear to be one of the most promising candidates to attain these ambitious targets. However, to overcome the cost barrier as well as meet additional railway requirements, new strategies such as process integration and novel manufacturing routes are needed, which will offer a cost-effective industrial solution. The case study corresponds to a C-Groove insert used as an anchoring point to hang passenger seats off the car body side walls, to fix Interior Panels or luggage racks. To improve this design, a trendsetting design was developed to integrate composite C-Grooves to Composite sidewalls. This work will display the details of such design as well as the optimal manufacturing strategy to achieve it. An out of autoclave (OoA) manufacturing process was assisted through different monitoring technologies such as resin arrival sensors and thermography to ensure high quality components. Additionally, a multi-material approach based on 3D printed technologies has been tackled. A thorough analysis of the joint has been performed and different integration approaches have been explored by designing co-cured and co-bonded manufacturing stages. Finally, several demonstrators have been made and tested to define the most promising integration approach and scaling up yet again to a larger demonstrator.

Abstract