Philipp Weißgraeber

Philipp Weißgraeber
University of Rostock · Faculty of Mechanical Engineering and Marine Technology

Full Professor
Chair of Lightweight Design, University of Rostock

About

44
Publications
6,456
Reads
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732
Citations
Additional affiliations
October 2009 - May 2015
Technische Universität Darmstadt
Position
  • Research Assistant

Publications

Publications (44)
Preprint
Full-text available
For a slab avalanche to release, the system, consisting of a weak layer below a cohesive slab, must facilitate crack propagation over large distances – a process we call dynamic crack propagation. Field measurements on crack propagation at this scale are very scarce. We therefore performed a series of propagation saw test experiments, up to ten met...
Article
The housing of automotive electrical components are commonly manufactured from polybutylene terephthalate with 30% of glass fiber (PBT-GF30). These housings can be subjected to severe conditions of temperature and humidity that can catalyze the degradation of their properties. In order to connect the different parts of the housing, a silicone adhes...
Preprint
Full-text available
With the aim of understanding failure modes in the peeling of silicone-based adhesive joints and, in particular, the occurrence of adhesive or cohesive failure, an experimental campaign has been conducted by considering plastic substrates with different surface roughness. A flexible strip has been bonded onto such substrates using a silicone adhesi...
Article
Full-text available
Short fiber reinforced polymers are widely used in the construction of electronic housings, where they are often exposed to harsh environmental conditions. The main purpose of this work is the in-depth study and characterization of the water uptake behavior of PBT-GF30 (polybutylene terephthalate with 30% of short glass fiber)as well as its consequ...
Chapter
This work describes why additive manufacturing is a key technology for efficient design iterations and rapid production ramp-up with large-scale manufacturing technologies. Laser cutting, injection moulding and folding were used to increase the production capacity of face shields for health care workers during the COVID-19 pandemic. We applied syst...
Article
The present contribution focuses on the effect of adherend surface roughness on the strength of adhesive joints, which are particularly cost-effective and extensively applied in a wide range of industrial applications. However, the reliability of such solutions is a critical concern for the integrity of commercial products. To gain a deeper underst...
Article
With the aim of understanding failure modes in the peeling of silicone-based adhesive joints and, in particular, the occurrence of adhesive or cohesive failure, an experimental campaign has been conducted by considering plastic substrates with different surface roughness. A flexible strip has been bonded onto such substrates using a silicone adhesi...
Article
In this paper, both location and energy of impacts on an anisotropic carbon fiber reinforced plate (CFRP) are detected with the help of deep learning. We introduce sparse low-cost sensor array integration in CFRP plates that allows for structural monitoring of lightweight structures. Using a resin transfer moulding process microelectromechanical sy...
Article
Adhesives play an important role in many key industrial sectors, such as the automotive industry, enabling the construction of lightweight, multi-material structures, combining polymers, composites and metals. However, adhesives are usually polymeric materials, which can be affected by environmental and working conditions, such as moisture and cont...
Preprint
The present contribution focuses on the effect of adherend surface roughness on the strength of adhesive joints, which are particularly cost-effective and extensively applied in a wide range of industrial applications. However, the reliability of such solutions is a critical concern for the integrity of commercial products. To gain a deeper underst...
Article
Full-text available
Using the analytical model presented in Part 1 of this two-part paper, a new conceptual understanding of anticrack nucleation in weak layers is proposed. To obtain a sufficient condition for onset of failure, two necessary conditions must be satisfied simultaneously: (i) the weak layer must be overloaded in terms of stress and (ii) the initiating c...
Article
Full-text available
Dry-snow slab avalanche release is preceded by a fracture process within the snowpack. Recognizing weak-layer collapse as an integral part of the fracture process is crucial and explains phenomena such as whumpf sounds and remote triggering of avalanches from low-angle terrain. In this two-part work we propose a novel closed-form analytical model f...
Article
Full-text available
Dry-snow slab avalanche release is preceded by a fracture process within the snowpack. Recognizing weak layer collapse as an integral part of the fracture process is crucial and explains phenomena such as whumpf sounds and remote triggering of avalanches from low-angle terrain. In this two-part work we propose a novel closed-form analytical model f...
Article
Full-text available
Using the analytical model presented in part I of this two-part paper, a new conceptual understanding of anticrack nucleation in weak layers is proposed. To obtain a sufficient condition for onset of failure two necessary conditions must be satisfied simultaneously: i) The weak layer must be overloaded in terms of stress and ii) the initiating crac...
Conference Paper
Full-text available
To improve modeling of slab avalanche release we propose a new mechanical snowpack model and a novel criterion for anticrack nucleation. The model allows to analyze skier-loaded slopes as well as PST experiments. We obtain closed-form analytical expressions for shear and normal stresses in the weak layer as well as for the energy release rate of cr...
Article
Full-text available
In this work, an enhanced eXtended finite element method (XFEM) implementation is outlined. It allows for modeling two-dimensional crack growth including potential crack deflection at significantly tougher constitutents of multi-material continua. At such material interfaces a user-defined crack deflection criterion is utilized that allows for crac...
Article
In this work, crack initiation in adhesive lap joints of arbitrary joint configuration is studied by means of a finite fracture mechanics approach. The analysis is based on a general stress solution for adhesive joints combined with a coupled stress and energy criterion. The instantaneous formation of a crack of finite size is predicted if a stress...
Article
Full-text available
An application of the finite fracture mechanics concept to open-hole plates subject to combined tensile and bending loading is presented. In finite fracture mechanics, the simultaneous satisfaction of both, a stress and an energy criterion, is enforced as a condition for crack initiation. Efficient modeling and closed-form expressions for the depen...
Article
Abstract Plates notched with open-holes that are subject to combined tensile and in-plane bending loading are studied in this analysis of crack onset. A finite fracture mechanics approach is employed to study the onset of asymmetric crack patterns in the notched structure. The stress field and the energy release rates required to solve the coupled...
Article
Full-text available
The present work provides a new model for the stress analysis of functionally graded adhesive lap joints with composite adherends. It is applicable to various joint configurations such as single lap joints, L-joints, T-joints, reinforcement patches, corner joints or balanced double lap joints. The modelling approach follows the concept of general s...
Conference Paper
Full-text available
Using an efficient numerical approach, a model rendering the initiation of asymmetric crack patterns in open-hole plates subject to combined tensile and in-plane bending loading is presented. In the framework of finite fracture mechanics a stress and an energy criterion are enforced simultaneously and used as a coupled condition for the formation o...
Conference Paper
Full-text available
In the present work a generally applicable failure model for the assessment of crack onset in adhesive lap joints which is based on finite fracture mechanics is presented. The approach combines a general sandwich-type model with a coupled stress and energy criterion that requires only two fundamental failure parameters: the strength and the toughne...
Article
The failure behaviour of structural situations depends on the shape of the energy release rate function of possible crack configurations. Depending on the structural situation, the energy release rate function can decrease (negative geometry) or increase (positive geometry) with increasing crack size. In this work, three structural situations exhib...
Article
Full-text available
Crack initiation in brittle materials is not covered by classical fracture mechanics that deals only with the growth of pre-existing cracks. In order to overcome this deficiency, the Finite Fracture Mechanics concept assumes the instantaneous formation of cracks of finite size at initiation. Within this framework, a coupled criterion was proposed a...
Article
Abstract In this work an efficient general Finite Fracture Mechanics model for crack initiation in adhesively bonded joints is presented which is applicable to various joint configurations with shear flexible laminate and metallic adherends. The mechanical behaviour of the adhesive joints is modeled by a general sandwich-type model for the analysis...
Article
In this work, crack initiation in elliptically notched plates under uniaxial tension is studied by means of a Finite Fracture Mechanics analysis. The stress concentration factor changes with the aspect ratio of the half axes: from unity for slender ellipses in loading direction to infinity for crack-like ellipses normal to the loading. The closed-f...
Article
In this work crack initiation at elliptical holes in plates under uniaxial tension is studied by means of a closed form analytical Finite Fracture Mechanics approach. To allow for a detailed study of crack initiation, stress intensity factors available in literature are discussed and compared to extensive numerical results. Based on physical ration...
Article
Brittle failure of adhesively bonded single lap joints is considered in this paper. A coupled stress and energy criterion in the framework of finite fracture mechanics is employed to study crack initiation by means of a numerical model presented by Hell et al. (Eng Fract Mech 117:112-126, 2014). Two different formulations of the coupled criterion a...
Article
Full-text available
To study crack initiation at weak stress singularities classical Fracture Mechanics approaches do not suffice. In this work weak singularities are discussed and the obstacles occurring in fracture analysis are outlined. The concept of Finite Fracture Mechanics and the use of coupled criteria is explained. A brief discussion of coupled criteria is g...
Article
Efficient analyses of adhesive joints are very important for pre-dimensioning or optimization processes. In this work a new model for adhesive joints is presented that can be applied to various joint configurations, as e.g. single lap joints, T-joints, L-joints or reinforcement patches. This is done by means of a two-dimensional, plane-strain model...
Article
In this work, a new approach for the prediction of the crack initiation loads of single lap joints (SLJ) is presented. The failure model for crack initiation in brittle adhesive layers is based on Finite Fracture Mechanics and makes use of a coupled stress and energy criterion. It requires only two fundamental material parameters: the tensile stren...
Article
Coupled stress and energy criteria in the framework of Finite Fracture Mechanics have been widely used to study crack initiation at stress concentrations. In many cases, the incremental energy release rates of the considered cracks of finite size increase monotonically with increasing crack sizes. But in certain structural situations, referred to a...
Article
Up to now the failure load assessment of bonded joints is still not fully understood. This work provides a new approach for assessing the crack initiation load of bonded joints. A failure model for single lap joints is proposed that is based on Finite Fracture Mechanics. Only two basic fracture parameters are required: the tensile strength and the...
Article
This work is concerned with the analysis of failure of adhesive joints. Typically adhesive joints fail due to cracking of the adhesive with cracks originating from the reentrant corner of the adherend and the adhesive. A failure model based on a coupled stress and energy criterion settled in the framework of Finite Fracture Mechanics (FFM) is propo...
Article
A deeper understanding of load transfer in the human hip joint is of great importance as there is strong evidence that the mechanical loading of the hip has a major effect on the onset and progression of osteoarthritis. In this work, a biomechanical model of the human hip joint is developed which takes the lateral rotators into account. On the basi...
Article
In this paper a linear, closed-form analysis of the buckling behavior of an orthotropic plate with elastic clamping and edge reinforcement under uniform compressive load is presented. This is a typical structural situation found in aerospace engineering for instance as stiffeners in wings or the fuselage. All governing equations are transformed in...
Conference Paper
In this paper a finite fracture mechanics approach for calculating failure loads of adhesively bonded joints is presented. The approach based on classical linear elasticity solutions for adhesively bonded single lap joints and uses a combined energy and stress criterion. Parameter studies are performed and it is shown, that the effects of the major...
Article
In this work, crack formation and the corresponding failure load of bonded lap joints is analyzed. The analysis is based on linear elasticity solutions for bonded lap joints and makes use of the finite fracture mechanics. A hybrid criterion is applied that states the spontaneous formation of a crack of finite size if a stress and an energy criterio...
Article
In this work the determination of the properties of an edge reinforcement of a composite plate stiffener is treated. A minimum stiffness criterion for the edge reinforcement on the basis of a closed-form buckling analysis of a composite plate with edge reinforcement and elastic clamping is given. The minimum stiffness criterion is given in explicit...
Article
For the widespread use of adhesive joints an exact and reliable prediction of the strength is mandatory. In this work, a new approach to assess the strength of single lap joints is presented. The approach is based on the hybrid criterion as postulated by Leguillon in the framework of finite fracture mechanics. It strictly combines a consideration o...
Article
In many structural situations, e.g. in aerospace engineering, composite plates with edge reinforcements are used, for example as stiffeners of a fuselage section of an airplane. Based on an explicit analysis of the buckling behavior of the laminate plate, a minimum stiffness criterion is presented in this contribution. A transformation of the gover...

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Projects

Projects (2)
Project
This project focuses on the roughness effect on the mechanical behavior of the adhesive joint. The surfaces roughness will be characterized by the confocal profilometry and then the mechanical response of adhesive joints will be assessed experimentally and numerically in the presence of the roughness.
Project
Have RG stop asking for a project