Fundamental Investigations on the Incremental Forming of Nonwoven-Reinforced Organo Sheets
Topic(s) : Manufacturing
Co-authors :
Doran NETTIG (GERMANY), Jan-Erik RATH (GERMANY), Thorsten SCHÜPPSTUHLAbstract :
Introduction
Fibre-reinforced plastics (FRP) represent a steadily growing market segment, within which thermoplastic-based FRP have become increasingly important in recent years.
Pre-impregnated and pre-consolidated thermoplastic FRP sheets, so-called organo sheets, enable new manufacturing, integration, and joining strategies compared to classic thermosets. Furthermore, they offer significantly higher recycling potential. In this context, nonwoven reinforcements can facilitate the reusability of recycled carbon fibres (rCF).
Parts production from organo sheets is usually realized in the thermoforming process using complex and expensive moulds. However, a more flexible alternative for prototype and small batch production would be desirable.
In sheet metal forming, incremental forming has been commercialized in recent years. In this process, the desired target geometry is created using small standard tools guided in paths along the sheet surface, locally deforming the material.
Up to now, there has been only little research into the incremental forming of organo sheets, with no studies on nonwoven reinforcements. Therefore, the aim of this work is to gain fundamental insights into the behaviour of organo sheets with nonwoven reinforcement in the context of incremental forming.
Materials and Methods
To investigate the deformation behaviour of nonwoven organo sheets in an incremental process, an incremental punch test was developed. Experiments were conducted using a nonwoven rCF organo sheet with PA6 matrix, 30% fibre-volume content and 1 mm thickness. Samples of size 10x10 mm were securely clamped at the edge. A robot-guided tool with hemispherical tip was used to penetrate and deform the material in a reciprocating motion. To allow the deformation of the FRP, hot air blowers were used to heat the matrix in a defined area, varying heating conditions in the experiments. A camera was used to record the deformation process, a thermal camera and thermocouples to measure the temperature, and a force-torque sensor to measure the forming forces. Afterward, the geometry of the deformed samples was recorded in 3D-scans.
Results and Discussion
Samples showed a good localization of the heating, but also a high through-thickness temperature gradient, which made double-sided heating necessary to avoid exceeding the decomposition temperature of the matrix. Still, deconsolidation of the material occurred at a temperature of 200-210 °C, which was locally reversed by the punch but needs to be considered in a future forming process. Controlling the heated area, a good localization of the introduced deformation was achieved and no wrinkling occurred. The predominating deformation mechanism appears to be the thinning of the material in the peripheral surface of the formed cone. Overall, the fundamental experiments show promising results for developing an incremental forming process for nonwoven organo sheets.
Fibre-reinforced plastics (FRP) represent a steadily growing market segment, within which thermoplastic-based FRP have become increasingly important in recent years.
Pre-impregnated and pre-consolidated thermoplastic FRP sheets, so-called organo sheets, enable new manufacturing, integration, and joining strategies compared to classic thermosets. Furthermore, they offer significantly higher recycling potential. In this context, nonwoven reinforcements can facilitate the reusability of recycled carbon fibres (rCF).
Parts production from organo sheets is usually realized in the thermoforming process using complex and expensive moulds. However, a more flexible alternative for prototype and small batch production would be desirable.
In sheet metal forming, incremental forming has been commercialized in recent years. In this process, the desired target geometry is created using small standard tools guided in paths along the sheet surface, locally deforming the material.
Up to now, there has been only little research into the incremental forming of organo sheets, with no studies on nonwoven reinforcements. Therefore, the aim of this work is to gain fundamental insights into the behaviour of organo sheets with nonwoven reinforcement in the context of incremental forming.
Materials and Methods
To investigate the deformation behaviour of nonwoven organo sheets in an incremental process, an incremental punch test was developed. Experiments were conducted using a nonwoven rCF organo sheet with PA6 matrix, 30% fibre-volume content and 1 mm thickness. Samples of size 10x10 mm were securely clamped at the edge. A robot-guided tool with hemispherical tip was used to penetrate and deform the material in a reciprocating motion. To allow the deformation of the FRP, hot air blowers were used to heat the matrix in a defined area, varying heating conditions in the experiments. A camera was used to record the deformation process, a thermal camera and thermocouples to measure the temperature, and a force-torque sensor to measure the forming forces. Afterward, the geometry of the deformed samples was recorded in 3D-scans.
Results and Discussion
Samples showed a good localization of the heating, but also a high through-thickness temperature gradient, which made double-sided heating necessary to avoid exceeding the decomposition temperature of the matrix. Still, deconsolidation of the material occurred at a temperature of 200-210 °C, which was locally reversed by the punch but needs to be considered in a future forming process. Controlling the heated area, a good localization of the introduced deformation was achieved and no wrinkling occurred. The predominating deformation mechanism appears to be the thinning of the material in the peripheral surface of the formed cone. Overall, the fundamental experiments show promising results for developing an incremental forming process for nonwoven organo sheets.