Datapoint Newsletter: Summer 2025, Vol. 31.2
Applus+ DatapointLabs staff celebrates 30th anniversary; expanded support for thermoset materials; 2025 events
Read full postMaterial Testing and Calibration Strategies for Material Models of Polymers, Foams, and Composite Materials
The accurate calibration of materials models is crucial for simulating the behavior of materials across various industries, including automotive, aerospace, and consumer goods. With the increasing complexity of modern materials, particularly polymers, foams, and composite materials, developing reliable and efficient calibration strategies is more important than ever. This paper presents a comprehensive comparative analysis of calibration strategies for material models applied to these materials, focusing on the challenges and best practices for each material class.
Read full postDatapoint Newsletter: Spring 2025, Vol. 31.1
Applus+ DatapointLabs marks 30th anniversary; latest research; 2025 events
Read full postComparison of Calibration Strategies for Material Models of Polymers, Foam, and Composite Materials
The accurate calibration of materials models is crucial for simulating the behavior of materials across various industries, including automotive, aerospace, and consumer goods. With the increasing complexity of modern materials, particularly polymers, foams, and composite materials, developing reliable and efficient calibration strategies is more important than ever. This paper presents a comprehensive comparative analysis of calibration strategies for material models applied to these materials, focusing on the challenges and best practices for each material class.
Read full postDatapoint Newsletter: Spring 2023, Vol. 29.1
DatapointLabs Founders Retire; Company Continues Focus on Materials in Simulation
Read full postBeyond Standards: Material Testing and Processing for Successful Simulations of Foam Materials (LAW90)
Simulations play a crucial role in engineering and material science, and their success heavily relies on the accuracy of input data. Material testing, data conversion, fitting, and formatting are essential steps in the simulation process. This conference will highlight the importance of material testing requirements that extend beyond ISO and ASTM standards to obtain reliable data for input into various common material models, such as Elastic-Plastic, Hyperelastic, and Rate Dependent models. The complexity of foam materials is shown through a case study of successful validation of polyurethane (PU) foam ball drop impact test using LAW 90. PU foams exhibit high deformation with rate dependency in compressive loading, as well as viscoelastic unloading behavior. Proper handling of input test data and critical settings in simulation setup are crucial for accurate results. The case study will showcase our streamlined approach to successful simulation of foam materials, including challenges and limitations of current material models.
Read full postDetermination and Use of Material Properties for Finite Element Analysis: Book Review
This book is intended to be a companion to the NAFEMS book, "An Introduction to the Use of Material Models in FE". It informs Finite Element Analysis users of the manner and methodologies by which materials are tested in order to calibrate material models currently implemented in various FEA programs. While the authors seek first to satisfy the basic material models outlined in the companion book, they make important extensions to FEA used in currently active areas including explicit simulation.
Read full postA Systematic Approach to Model Metals, Compact Polymers and Structural Foams in Crash Simulations with a Modular User Material
"Today the automotive industry is faced with the demand to build light fuel-efficient vehicles while optimizing its crashworthiness and stiffness. A wide variety of new metallic and polymeric materials have been introduced to account for these increased requirements. Numerical analysis can significantly support this process if the analysis is really predictive. Within the numerical model a correct characterization of the material behaviour – including elasto-viscoplastic behaviour and failure - is substantial. The particular behaviour of each material group must be covered by the material model. The user material model MF GenYld+CrachFEM allows for a modular combination of phenomenological models (yield locus, strain hardening, damage evolution, criteria for fracture initiation) to give an adequate representation of technical materials. This material model can be linked to LS-DYNA when using the explicit-dynamic time integration scheme. This paper gives an overview on the material characterization of ultra high strength steels (with focus on failure prediction), non-reinforced polymers (with focus on anisotropic hardening of polymers), and structural foams (with focus on compressibility and stress dependent damage evolution) with respect to crash simulation. It will be shown that a comprehensive material model - including damage and failure behaviour - enables a predictive simulation without iterative calibration of material parameters. A testing programme has been done for each material group in order to allow a fitting of the parameters of the material model first. In a second step different component tests have been carried out, which were part of a systematic procedure to validate the appropriate predictions of the crash behaviour with LS-Dyna and user material MF_GenYld+CrachFEM for each material group."
Read full postA Material Model for Transversely Anisotropic Crushable Foams in LS-DYNA
"Recently new materials were introduced to enhance different aspects of automotive safety while minimizing the weight added to the vehicle. Such foams are no longer isotropic but typically show a preferred strong direction due to their manufacturing process. Different stress/ strain curves are obtained from material testing in different directions. A new material model was added to the LS-DYNA code in order to allow a correct numerical simulation of such materials. Ease-of-use was a primary concern in the development of this user-subroutine: we required stress/ strain curves from material testing to be directly usable as input parameters for the numerical model without conversion. The user-subroutine is implemented as MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM, Mat law 142 in LS-DYNA Version 960-1106. In this paper we summarize the background of the material law and illustrate some applications in the field of interior head-impact. The obvious advantage of incorporating such detail in the simulation lies in the numerical assessment of impacts that are slightly offset with respect to the foam’s primary strength direction."
Read full postNonlinear viscoelastic modeling for foams
Lightweight design is one of the major principles in automotive engineering and has made polymer materials to inherent parts of modern cars. In addition to their lightweight thermoplastics, elastomers, fabric and composites also incur important functions in passive safety. In the age of virtual prototyping, assuring these functions requires the accurate modeling of the mechanical behavior of each component. Due to their molecular structure, polymer materials often show viscoelastic characteristics such as creep, relaxation and recovery. However, considering the general state of the art in crash simulation, the viscoelastic characteristics are mainly neglected or replaced by viscoplastic or hyperelastic and strain rate dependent material models. This is either due to the available material models that are often restricted to linear viscoelasticity and thus cannot model the experimental data or due to the time consuming parameter identification. In this study, a nonlinear viscoelastic material model for foams is developed and implemented as a user material subroutine in LS-DYNA. The material response consists of an equilibrium and a non-equilibrium part. The first one is modeled with a hyperelastic formulation based on the work of Chang [8] and formerly implemented as *MAT_FU_CHANG_FOAM in LS-DYNA (*MAT_083). The second one includes the nonlinear viscoelastic behavior following the multiple integral theory by Green and Rivlin [9]. The polyurethane foam Confor CF-45 used as part of the legform impactor in pedestrian safety was chosen for its highly nonlinear viscoelastic properties to test the presented approach. The investigation shows the ability of the method to reliably simulate some important nonlinear viscoelastic phenomena such as saturation.
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