Abstract
The design and development of composite structures requires precise and robust manufacturing processes. Composite materials such as fiber reinforced thermoplastics (FRTP) provide a good balance between manufacturing time, mechanical performance and weight. In this contribution, we investigate the process combination of thermoforming FRTP sheets (organo sheets) and injection overmolding of short FRTP for automotive structures. The limiting factor in those structures is the bond strength between the organo sheet and the overmolded thermoplastic. Within this process chain, even small deviations of the process settings (e.g., temperature) can lead to significant defects in the structure. A cyber physical production system based framework for a digital twin combining simulation and machine learning is presented. Based on parametric Finite-Element-Method (FEM) studies, training data for machine learning methods are generated and a FEM surrogate is developed. A comparison of different data-driven methods yields information on the estimation accuracy of task-specific data-driven methods. Finally, in accordance with experimental cross tension tests, the investigated FEM surrogate model is able to predict the interface bond strength quality in dependence of the process settings. The visualization into different quality domains qualifies the presented approach as decision support.
Highlights
In the field of automotive structures, lightweight materials such as high-strength steels, aluminum or fiber-reinforced plastics (FRP) are increasingly being used in the production of vehicles [1,2]
We have investigated an approach for designing a digital twin that enables both, a fast offline analysis of different process conditions and an inline quality gate for the interface bond strength between a thermoformed Fiber reinforced thermoplastics (FRTP) sheet and an injection overmolded thermoplastic polymer
The digital twin is based on a comprehensive numerical parametric study that serves as input data for machine learning to obtain a FEM surrogate model
Summary
In the field of automotive structures, lightweight materials such as high-strength steels, aluminum or fiber-reinforced plastics (FRP) are increasingly being used in the production of vehicles [1,2]. The combination of thermoforming of a continuous fiber-reinforced thermoplastic laminate (organo sheet) with injection overmolding of (short fiber reinforced) thermoplastics provides great potential for the economically efficient production of automotive lightweight structures. It allows the implementation of large scale production systems and the manufacturing of structures with high specific stiffness and strength due to the continuous fiber reinforcement in the organo sheet.
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