P.F. Fuchs

Polymer Competence Center Leoben GmbH · Simulation and Modeling

Mechanical metamaterials have gained a lot of research interest over the last years due to their unusual mechanical properties and potential use for structural applications. However, the design and analysis of mechanical metamaterials remains challenging and time-consuming. Herein, we present a software framework for automated generation, finite el...

Metamaterials with their distinctive unit cell-based periodic architecture feature a wide range of possible properties with unusual characteristics and a high potential for optimization. Due to their complex interaction between unit cell geometry and material properties, as well as their inherent multi-scale nature, suitable optimization strategies...

Metamaterials are a class of materials with a distinctive unit cell-based periodic architecture, often resulting in unique mechanical properties. The potential of metamaterials can be further improved by using gradients of unit cell parameters and thereby creating a specific distribution of material properties in a part. This design freedom comes w...

Explains the predictability of permeation properties based on the orientation of regular filler patterns.

In this paper, the results of new investigations on the relationship between physical surface parameters of polymer-based coatings, skin hydration levels and tactile friction are presented. For this purpose, the chemical composition of the investigated coatings was varied on the basis of the curing and binding agent and also with respect to the add...

Mechanical metamaterials have gained a lot of research interest over the last years due to their unusual mechanical properties and potential use for structural applications. However, the design and analysis of mechanical metamaterials remains challenging and time consuming. Herein, we present a software framework for automated creation, finite elem...

Different designs for mechanical metamaterials with tunable normal-strain shear coupling effect have been demonstrated over the last years. Their adjustable shear deformation makes them suitable as building blocks for soft robotics applications or structures with a desired deformation behavior, such as shape morphing structures. Herein, we present...

Surface Mounted Devices (SMDs) are widely used throughout microelectronics and power electronics. They mostly employ epoxy molding compound (EMC) based encapsulations. Thus, enhanced lifetime assessment methods are necessary. To understand the stress situation in SMDs at the end of the production cycle, an improved model approach for the curing of...

Among several new module concepts and cell architectures, shingled solar cell interconnection is a promising technology to realize increased power output (higher power densities) by increased active cell area and low electrical losses. In shingled modules the pre-cut crystalline cells are placed like roof tiles on top of each other, resulting in a...

Power electronics are key-enablers of several industry trends, such as more efficient renewable energy harvesting, eco-friendly mobility and many more. With their uprising use and versatility the requirement for these packages is steadily increasing; thus leading to an evermore complex electro-thermo-mechanical loading situation. On the one side, e...

Mechanical metamaterials with zero or negative Poisson’s ratio were subject to increasing research interest over the last few years. Their energy absorption capabilities make them suitable for impact and dampening applications, such as personal protection equipment or packaging materials. The variable porosity and unusual mechanical properties also...

Photopolymerizations, in which the initiation of a chemical-physical reaction occurs by the exposure of photosensitive monomers to a high-intensity light source, have become a well-accepted technology for manufacturing polymers. Providing significant advantages over thermal-initiated polymerizations, including fast and controllable reaction rates,...

The photo imaging process is one of the most important advances in the production of printed circuit boards (PCBs). Especially, UV-curable resins are widely used in the semiconductor and microelectronics industries and are becoming increasingly popular due their options to modernize manufacturing processes, as the introduction of the Laser Direct I...

It is apparent from the literature that the matrix–fiber mechanical interaction, as a result of interfacial adhesive bonds at the interface, significantly contribute to the macroscopic constitutive response of hyperelastic fiber-reinforced materials. This study bridges the degradation of macroscopic mechanical properties to the microscopically visi...

Meeting financial and mechanical prerequisites, in this study, an epoxy/amine resin was filled with nano- and submicron-scaled alumina particles, yielding a gradient composite. While most types of polymers have a very low thermal conductivity, this shortcoming can be compensated for by the addition of fillers. The thermal conductivity of the consid...

Mechanical metamaterials with variable stiffness recently gained a lot of research interest, as they allow for structures with complex boundary and load conditions. Herein, we highlight the design, additive manufacturing, and mechanical testing of a new kind of bending-dominated metamaterial. By advancing from well-established mechanical metamateri...

Artificially structured materials, also called metamaterials, can achieve very unique properties due to the fact that their attributes are mainly derived from the design of the structures. This work gives an overview of the mechanical behavior of four differently designed and 3D‐printed metamaterial structures. For each structure, both, the printin...

This study identifies a unique performance benefit in flexible composite laminates through evaluation of the load-coupling potentials once an external stimulus triggers extensional loadings. A combination of soft elastomers with stiff fibers can be used to develop a composite with distinct direction-dependent properties. Unique exponential flexibil...

The Micro-Electro-Mechanical Semiconductor (MEMS) sensor packages are an advanced multi-material composite system. These packages comprise polymeric materials like prepregs, solder-mask, insulation, and conductive adhesives. Prepregs are glass fiber reinforced epoxy laminates. Only a low material sensitivity to environmental influences will ensure...

Micro Electro Mechanical Semiconductors (MEMS) functionalities have been continuously extended during the last years, and they are applied in a wide range of industrial sectors, including the automotive, consumer electronics, and Internet of Things (IoT) markets. These MEMS sensor packages are a multi-materials composite system. The composite mater...

Hyperelastic fiber-reinforced materials are commonly characterized and modeled in terms of the contributions of the constituent materials, while their matrix-fiber mechanical interactions have been received little attention. This work is an initial attempt to quantify the matrix-fiber mechanical interactions using a combined experimental, analytica...

The interface between the reinforcement and surrounding matrix in a fibrous composite is decisive and critical for maintaining component performance, durability, and mechanical structure properties for load coupling assessment, especially for highly flexible composite materials. The clear trend towards tailored solutions reveals that an in-depth kn...

The focus of this research is to quantify the effect of load-coupling mechanisms in anisotropic composites with distinct flexibility. In this context, the study aims to realize a novel testing device to investigate tension-twist coupling effects. This test setup includes a modified gripping system to handle composites with stiff fibers but hyperela...

The use of Micro-Electro-Mechanical Semiconductor (MEMS) sensor packages has revolutionized the automotive, home, and building applications (HABA) and Internet of Things (IoT) industries. However, increasing demands on their functionality and reliability necessitates an improved behavior of the packaging materials concerning thermal and hygroscopic...

The aim of this work was to analyze the influence of fibers on the mechanical behavior of fiber-reinforced elastomers under cyclic loading. Thus, the focus was on the characterization of structure-property interactions, in particular the dynamic mechanical and viscoelastic behavior. Endless twill-woven glass fibers were chosen as the reinforcement,...

Hyperelastic fiber-reinforced materials are conventionally modeled based on the contributions of their constituent materials. A unified invariant-base constitutive model, named Matrix-Fiber-Interaction (MFI) model, is proposed to take into account particularly the mechanical interaction contribution of the constituent materials in fiber-reinforced...

This research focuses on the investigation of endless fiber-reinforced elastomeric materials with special tailoring by different fiber orientations in the composite structure. Therefore, a modified testing device including a suitable specimen production was carried out and the comparability of tests conducted at different test scales (micro- to mac...

The focus of this paper is the realization and verification of a modified fiber bundle pull-out test setup to estimate the adhesion properties between threads and elastic matrix materials with a more realistic failure mode than single fiber debond techniques. This testing device including a modified specimen holder provides the basis for an adequat...

The focus of this study is the investigation of the adhesion properties of hyperelastic fiber-matrix composites as well as the comparability of tests conducted at micro-, meso- and macro-scale. A modified fiber bundle pull-out (FBPO) test was performed to estimate the adhesion properties between fiber bundles and a hyperelastic matrix material with...

Stator bars are the critical components in generators with respect to their lifespan. The winding insulation may be susceptible to damage under excessive alternating temperature loads incurred by a high number of start–stop cycles and heavy overloads. The differences in thermal expansion between the different components in the multi-layered winding...

Reliable material data, especially of the thermal conductivity as a function of temperature, are crucial for the virtual optimization of the rubber injection molding process. Due to the low thermal conductivity of rubber compounds, typically in the range from 0.15 to 0.4 W m⁻¹K⁻¹, and the fact that the molding of the rubber part takes place in a he...

In order to increase the productivity in the manufacturing of rubber components or reduce optimization cycles in mold making, injection molding simulations are intensely used in today’s polymer industry. Performing injection molding simulations of rubber parts, the thermal conductivity is a crucial material property for the precise calculation of t...

Modeling Moisture Diffusion Experimental Conclusion and Outlook Performance of materials used in MEM semiconductor packages for various environmental factors needs to accounted for. Hence, with the help of measured material properties a simulation process predicting the package under defined environmental loads is presented. A mathematical model fo...

Microelectromechanical systems (MEMS) and MEMS packaging solutions are gaining increased interests for electronic applications. These packages feature a variety of polymeric materials and composites e.g. fiber reinforced polymer laminates, insulating and conductive adhesives. Due to the sensitivity of MEMS devices to mechanical stress and environme...

For the design of the next generation of microelectronic packages, thermal management is one of the key aspects and must be met by the development of polymers with enhanced thermal conductivity. While all polymer classes show a very low thermal conductivity, this shortcoming can be compensated for by the addition of fillers, yielding polymer-based...

Stator insulations comprised of mica-filled epoxy glass composite materials are of paramount importance for the reliability of high-voltage rotating machines. The present work deals with the fracture mechanical characterization of the winding insulation under conditions of monotonic and cyclic loading. The identification and quantification of the w...

This work presents a compressible hyperelastic constitutive model for dry woven-fabrics with two families of inextensible fibers. In recent works it has been demonstrated that shear interaction of the fibers is the dominant deformation mode in state of the art shear characterization methods of woven fabrics as for example the bias-extension test. T...

A finite element method algorithm for epoxy curing degree simulation was developed in Abaqus by integrating the discretized analytical solution of the model free kinetics into its user subroutines. This method was verified by nonisothermal and isothermal DSC experiments of an epoxy resin. By means of this method, the real manufacturing press cycle...

Different Printed Circuit Board (PCB) designs were tested in an Interconnection Stress Test. In such a test, PCBs were subjected to temperature cycles alternating between two extremes (e.g. -40. °C to 160. °C). The electrical resistance was measured on-line during these tests. If the resistance rose by more than 10% of the initial value at the high...

In printed circuit boards, thin copper layers are used as current paths. During the thermal loading of printed circuit boards, stresses arise due to the different coefficients of thermal expansion of the used materials. To be able to model the mechanical behavior of printed circuit boards under cyclic thermal loads, cyclic mechanical tests of thin...

Purpose – The overall aim of this research work was the improvement of the failure behavior of printed circuit boards (PCBs). In order to describe the mechanical behavior of PCBs under cyclic thermal loads, thin copper layers were characterized. The mechanical properties of these copper layers were determined in cyclic four-point bend tests and in...

In this work a method was worked on that assesses the lifetime of printed circuit boards (PCBs) under low cycle fatigue conditions. The method was based on finite element models and low cycle fatigue experiments. Verifying it, two significantly different PCB designs and several different PCB built ups were analyzed. Doing so, for the numerical part...

The overall objective of this research work is the characterization of the mechanical behavior of Printed Circuit Boards (PCBs) under cyclic thermal loads. The conducting traces in PCBs are made from thin copper layers in an etching process. Hence, thin copper layers are characterized experimentally and subsequently cyclic material parameters are d...

Purpose The purpose of this paper is to analyse, in a finite element simulation, the failure of a multilayer printed circuit board (PCB), exposed to an impact load, to better evaluate the reliability and lifetime. Thereby the focus was set on failures in the outermost epoxy layer. Design/methodology/approach The fracture behaviour of the affected...

During manufacturing and use printed circuit boards (PCB) are subjected to different mechanical and thermal loads. These loads can cause the PCBs to develop a delamination between the insulating layers of pre-preg and conducting copper which can lead to failure of the entire electronic device. Therefore, it is critical to understand the delaminatio...

To improve the reliability of printed circuit boards (PCBs), occurring failure modes have to be studied and analysed. In order to reduce the expenses of experimental testing, finite element analysis (FEA) is used to describe the failure behaviour. Therefore, the availability of the proper material data is crucial. As the materials used in printed c...

In this work, a new test set-up was applied in order to determine cohesive zone models experimentally. A high speed camera in combination with a digital image correlation system was used to record the local displacements enabling the detailed determination of crack opening values. The J-Integral method was used to calculate the cohesive stresses. T...

The reliability of printed circuit boards under dynamic loads is a key issue in the handheld electronic products industry. In order to predict the performance of the boards in their application lifetime, different tests were developed. The current industry-wide standard testing method is a board level drop test. In this test, the boards are dropped...

Printed circuit boards (PCBs) are frequently exposed to a complex combination of external and internal thermo-mechanical loads (static, cyclic and impact loads superimposed by local and global temperature effects). In this study, instrumented impact tests of the PCBs were performed and characterized. In addition to the acceleration measurement of t...

Printed Circuit Boards (PCBs) are frequently exposed to a very complex combination of external and internal thermo-mechanical loads (static, cyclic and impact loads superimposed onto local and global temperature effects). Instrumented impact tests were performed in this study to characterize the failure behavior of these boards. In addition to the...

Printed Circuit Boards (PCBs) are frequently exposed to a very complex combination of external and internal thermo-mechanical loads (static, cyclic and impact loads superimposed onto local and global temperature effects). Instrumented impact tests were performed in this study to characterize the failure behavior of these boards. In addition to the...