Discovering new materials for the automotive industry

A deeper look into SMC and BMC materials

by Alfredo de Gregorio
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In recent years, the automotive industry has placed its bet on lighter materials to replace traditional metallic materials and their alloys, without compromising the increase in cost or the cadence of production. In turn, sheet molding compound (SMC) or bulk molding compound (BMC) material manufacturing processes have gained popularity for composite materials design. The main challenge is to size the components and orient the manufacturing process to the mechanical requirements of the component.

A new solution for evolving technological challenges 

New technological challenges led to the search for new materials. The use of composites is constantly growing, and according to recent trends, it will only continue to grow in the coming years.

In this search to find materials that replace metallic materials, compounds for BMC and SMC appear, which are formulated from multiple components. The acronyms refer to both the material and the manufacturing process and the products derived from them such as TMC (Thick Molding Compound), HPC (High-Performance Compound), CIC (Continuous Impregnation Compounds), and AMC (Advanced Molding Compounds). All these materials and processes are based on a mixture of discontinuous fibers with the resin or matrix to then be formed by the flow of this material within the mold thanks to the compression of the material charge.

Thanks to this relatively simple, inexpensive, and quick manufacturing process, industries obtain mass production components with excellent properties in terms of rigidity, mechanical strength, and durability. These materials:

  • resist high temperatures (e.g., in cases of fire)
  • exhibit excellent electrical insulation and tightness
  • prove to be lighter in weight compared to other materials

In their infancy, composites were mainly used in the aeronautic and aerospace industries. But over the years, their application has become widespread from the automotive, construction, and transportation sectors to sanitary and medical equipment, just to name a few.

Pitfalls in optimizing the design and manufacturing of SMC and BMC materials

Unfortunately, engineers working with this new type of material typically face many challenges. These challenges are mainly due to the initial randomness of the fibers and the difficult prediction of their orientation and fiber content after manufacturing. Engineers struggle with a great deal of uncertainty regarding the design and how to adjust manufacturing parameters to meet functional and design requirements. Adding to this is the lack of knowledge about the mechanical behavior of the manufactured part; the mechanical behavior is difficult to predict and will not be constant throughout the manufactured part, since the fiber distribution and orientation will not be uniform. Therefore, it is impossible to physically know the mechanical properties unless the simulation solutions are used. Additionally, to ensure the correct distribution of the fibers and a complete filling of all areas during the manufacturing process, engineers need to adjust a number of additional parameters (initial placement of the loads, speed, lowering force of the tool and, mold design). And if that weren’t enough, they must do all of this in the shortest time and with the least force to reduce the manufacturing time and energy consumption of this process.

SMC/BMC are quite new materials and knowledge and experience about the material behavior and manufacturing process is limited. Combining this with the fact that designers and manufacturers must quickly modify and tune their designs and manufacturing process, makes creating and optimizing designs and reliable structural parts very difficult.

In a nutshell, the lack of experience causes uncertainty which translates directly into higher safety margins for both, prototype cost and time. The goal is to build up early confidence by predicting the performance of new materials, especially in structural applications.

Accurately predict composite performance with numerical BMC & SMC simulation and virtual testing

What is the most efficient way to increase knowledge and confidence about BMC and SMC components and optimize both the part design and its manufacturing process? Numerical composite simulation based on finite element analysis. These unique simulation tools allow engineers across industries to adjust and optimize the parameters of the process while understanding the mechanical behavior of the manufactured part.

On the left, you see an exemplary visualization of a manufacturing chain for a sheet molding compound in ESI PAM-COMPOSITES simulation software.

Here’s my list of the two most important features and functionalities that a composite simulation software should offer to engineers: 

1. Make sure the software allows an intuitive entry into the work with FEM simulation even for beginners

  • A pre-configured set of standard parameters frees engineers from the need to create an exhaustive characterization of the material properties used in the manufacturing
  • To optimize parameters such as the optimal placement of the number and place the initial loads, download speed, and mold design, make sure you can quickly find:
    • the right pattern and time of filling
    • the force applied to the mold
    • the orientation and content of the fibers 

2. Create a seamless interface to ESI Virtual Performance Solution to run the structural analysis of new designs early 

  • By directly coupling a composite simulation software with a proven structural analysis tool you will be able to:
    • accurately predict the mechanical behavior of these types of materials in our component (based on the Mori-Tanaka and Voigt models)
    • account for the distribution of the orientations and fiber content previously calculated, without having to use intermediate software for homogenization and characterization of material
  • automate and adjust the model building and simulation to the customer´s process easily with the use of Visual GUI

In this way, you will be able to make a reliable and accurate structural calculation of your component. You will be able to iterate quickly and easily, changing parameters of the manufacturing process and, ultimately, achieving the highest efficiency in the design of your part. This supports both manufacturers and molders, or any industry that uses this type of materials for their products, to know and optimize the manufacturing, operation and behavior of the product and its integrity with the rest of the components. 

If you are interested in lightweight ideas and other ways to begin or continue your digital transformation to zero prototypes and innovative designs, join us for our biggest digital event of the year: ESI Live 2022! You will get to hear from your peers at Volvo, Diamler, and Renault (just to name a few) and you will also be able to ask questions to them and our own Virtual Prototyping experts. 

We look forward to seeing you there! 

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