Method for simulating a fiber orientation in an injection-molded part made of a fiber-reinforced plastic, and design method for designing an injection-molded part made of a fiber-reinforced plastic

1 . A method for simulating a fiber orientation in an injection-molded part made of a fiber-reinforced plastic, the method comprising:

determining an orientation of the fibers in the injection-molded part to be manufactured that is present after the injection molding via a macroscopic simulation of the injection molding, and the macroscopic simulation of the injection molding taking place using macroscopic physical parameters of the fiber-reinforced plastic, wherein in the macroscopic simulation:

determining a temporal development of a fiber orientation tensor via a combination of two macroscopic models, a first temporal development of the fiber orientation tensor being determined via a first macroscopic model of the two macroscopic models based on shear flows, and a second temporal development of the fiber orientation tensor being determined via a second macroscopic model of the two macroscopic models based on elongation flows; and

carrying out a weighting of an influence of the first macroscopic model and of the second macroscopic model on the temporal development of the fiber orientation tensor, determined in the simulation, based on a Manas-Zloczower number, limited to an upper value of 1 that corresponds to a pure elongation flow.

2 . The method as recited in claim 1 ,

wherein the Manas-Zloczower number is limited to a lower value of 0.5 that corresponds to a case of a pure shear flow.

3 . The method as recited in claim 1 , wherein first macroscopic physical parameters for the first macroscopic model and/or second macroscopic physical parameters for the second macroscopic model are determined via experimentally ascertained data.

4 . The method as recited claim 1 , wherein first macroscopic physical parameters for the first macroscopic model and/or second macroscopic physical parameters for the second macroscopic model are ascertained via a micromechanical simulation.

5 . The method as recited in claim 4 , wherein the micromechanical simulation is carried out using a discrete element method (DEM), or a smoothed particle methodology, or a moving particle semi-implicit (MPS) method.

6 . A method for simulating a fiber orientation in an injection-molded part made of a fiber-reinforced plastic, the method comprising:

determining an orientation of the fibers in the injection-molded part to be manufactured that is present after the injection molding via a macroscopic simulation of the injection molding, and the macroscopic simulation of the injection molding taking place using macroscopic physical parameters of the fiber-reinforced plastic, wherein in the macroscopic simulation:

determining a temporal development of a fiber orientation tensor via a combination of two macroscopic models, a first temporal development of the fiber orientation tensor being determined via a first macroscopic model of the two macroscopic models based on shear flows, and a second temporal development of the fiber orientation tensor being determined via a second macroscopic model of the two macroscopic models based on elongation flows;

wherein first macroscopic physical parameters for the first macroscopic model and/or second macroscopic physical parameters for the second macroscopic model are ascertained via a micromechanical simulation;

wherein the ascertainment of the first and/or second macroscopic physical parameters using the micromechanical simulation includes the following steps:

a) forming a material cell including an ensemble of individual fibers that are embedded in a matrix material, fiber volume content and fiber length being predefined as input values,

b) carrying out the micromechanical simulation in which the material cell is sheared at a predefined shear rate for a predefined period of time, or the material cell is stretched at a predefined elongation rate, at least the positions of the fibers of the ensemble being determined for each time increment of the simulation,

interaction forces between two fibers in each case being determined during the micromechanical simulation, for at least a portion of the fiber-fiber interactions a pure interaction force being determined via a trained machine learning model, using input parameters of interaction angle, fiber aspect ratio, and distance between the fibers, and an interaction force being determined from a pure interaction force, using a linear relationship between viscosity of the matrix material and a relative velocity between the fibers.

7 . The method as recited in claim 6 , wherein the interaction forces take into account lubrication forces between two fibers in each case.

8 . The method as recited in claim 7 , wherein for training the machine learning model, analytical solutions for the lubrication forces and/or numerical solutions for the lubrication forces are used as training data, the training data in each case assigning an interaction force to the input parameters of the interaction angle, the aspect ratio, and the distance between the fibers.

9 . The method as recited in claim 6 , wherein the machine learning model is an artificial neural network.

10 . A method for designing an injection-molded part made of a fiber-reinforced plastic, the method comprising:

carrying out a simulation of fiber orientation including:

determining an orientation of the fibers in the injection-molded part to be manufactured that is present after the injection molding via a macroscopic simulation of the injection molding, and the macroscopic simulation of the injection molding taking place using macroscopic physical parameters of the fiber-reinforced plastic, wherein in the macroscopic simulation:

determining a temporal development of a fiber orientation tensor via a combination of two macroscopic models, a first temporal development of the fiber orientation tensor being determined via a first macroscopic model of the two macroscopic models based on shear flows, and a second temporal development of the fiber orientation tensor being determined via a second macroscopic model of the two macroscopic models based on elongation flows; and

carrying out a weighting of an influence of the first macroscopic model and of the second macroscopic model on the temporal development of the fiber orientation tensor, determined in the simulation, based on a Manas-Zloczower number, limited to an upper value of 1 that corresponds to a pure elongation flow;

determining a load-bearing capacity of the injection-molded part; and

comparing the determined load-bearing capacity to a predefined load-bearing capacity.