Philippe Grönquist

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Grönquist

First Name

Philippe

ORCID

0000-0001-8432-1706

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Publications 1 - 10 of 29

Hygroscopicity of Waterlogged Archaeological Wood from Xiaobaijiao No.1 Shipwreck Related to Its Deterioration State
Han, Liuyang; Guo, Juan; Wang, Kun; et al. (2020)
Polymers
Waterlogged archaeological wood (WAW) artifacts, made of natural biodegradable polymers, are important parts of many precious cultural heritages. It is of great importance to understand the hygroscopic behavior of WAW in different deterioration states for the development of optimal drying processes and choices of safe storage in varying conditions. This was investigated in a case-study using two Hopea (Giam) and two Tectona (Teak) WAW samples collected from the Xiaobaijiao No.1 shipwreck. The deterioration state of WAW was evaluated by the maximum water content (MWC) method and by the cell morphological structure. Both Hopea and Tectona WAW could be classified into moderately and less decayed WAW. The hygroscopic behavior of moderately and less decayed WAW was then comparatively investigated using Dynamic Vapor Sorption (DVS) measurements alongside two sorption fitting models. Compositional analysis and hydroxyl accessibility measurements of WAW cell walls were shown to correlate with the hygroscopicity of WAW in different deterioration states. It was concluded that moderately decayed WAW possessed higher hygroscopicity and hysteresis than less decayed WAW because of the lower relative content of polysaccharides and the higher relative content of lignin, including the slow hydrolysis of O-acetyl groups of xylan and the partial breakage of β-O-4 interlinks, accompanied by an increased hydroxyl accessibility. This work helps in deciding on which consolidation measures are advised for shipwreck restauration, i.e., pretreatments with specific consolidates during wood drying, particularly for wooden artifacts displayed in museums.
High-performance timber-concrete-composites with polymer concrete and beech wood
Stucki, Sandro; Kelch, Steffen; Mamie, Tim; et al. (2024)
Construction and Building Materials
The performance of adhesive-bonded timber-concrete-composites (TCC) can be enhanced by using beech wood and polymer concrete (PC). In this work, two different PCs with an epoxy- and a polyurethane (PUR)-based matrix were investigated for application in TCCs. The mechanical performances were tested in dry and wet state by small-scale shear tests and flexural tests. Epoxy-PC showed high bond strength to beech with a shear strength of 16.7 ± 3.0 MPa compared to 3.2 ± 1.7 MPa observed with PUR-PC. Characterization of the swelling strain with digital image correlation (DIC) showed superior water stability of the epoxy-PC compared to PUR-PC. The results indicate that PCs, especially epoxy-PC, could be viable replacements for cement-based concrete in TCCs.
Biodegradable and Flexible Wood-Gelatin Composites for Soft Actuating Systems
Koch, Sophie; Dreimol, Christopher; Goldhahn, Christian; et al. (2024)
ACS Sustainable Chemistry & Engineering
Compliant materials are indispensable for many emerging soft robotics applications. Hence, concerns regarding sustainability and end-of-life options for these materials are growing, given that they are predominantly petroleum-based and non-recyclable. Despite efforts to explore alternative bio-derived soft materials like gelatin, they frequently fall short in delivering the mechanical performance required for soft actuating systems. To address this issue, we reinforced a compliant and transparent gelatin-glycerol matrix with structure-retained delignified wood, resulting in a flexible and entirely biobased composite (DW-flex). This DW-flex composite exhibits highly anisotropic mechanical behavior, possessing higher strength and stiffness in the fiber direction and high deformability perpendicular to it. Implementing a distinct anisotropy in otherwise isotropic soft materials unlocks new possibilities for more complex movement patterns. To demonstrate the capability and potential of DW-flex, we built and modeled a fin ray-inspired gripper finger, which deforms based on a twist-bending-coupled motion that is tailorable by adjusting the fiber direction. Moreover, we designed a demonstrator for a proof-of-concept suitable for gripping a soft object with a complex shape, i.e., a strawberry. We show that this composite is entirely biodegradable in soil, enabling more sustainable approaches for soft actuators in robotics applications.
The Impact of Cloud Processing on the Ice Nucleation Abilities of Soot Particles at Cirrus Temperatures
Mahrt, Fabian; Kilchhofer, Kevin; Marcolli, Claudia; et al. (2020)
Journal of Geophysical Research: Atmospheres
Soot particles are generally considered to be poor ice nucleating particles. Involvement of soot in clouds and their release back into the atmosphere can form residual particles with altered cloud forming potential. The impact and extent of such different cloud processing scenarios on ice nucleation is, however, not well understood. In this work, we present the impact of cloud processing of soot aerosols on subsequent ice nucleation cycles at T≤233 K. Coupling of two continuous flow diffusion chambers allows the simulation of different cloud processing scenarios and investigation of subsequent ice nucleation activity of the processed particles. The processing scenarios presented here encompass contrail, cirrus, and mixed‐phase cloud processing, mimicking typical pathways that soot particles can be exposed to in the atmosphere. For all scenarios tested, the processed particles showed an enhanced ice active fraction for T<233 K. The relative humidity with respect to water for the ice nucleation onset was observed to be on average approximately 10% (relative humidity with respect to ice, RHi≈16%) lower for the cloud‐processed particles compared to the unprocessed soot for which ice nucleation was observed close to or at homogeneous freezing conditions of solution droplets. We attribute the enhanced ice nucleation abilities of the cloud‐processed soot to a pore condensation and freezing mechanism and have identified key parameters governing these changes. Enhanced ice nucleation abilities of soot in cirrus clouds can have significant impacts, given the importance of the atmospheric ice phase for precipitation formation and global climate.
Self-camber of timber beams by swelling hardwood inlays for timber–concrete composite elements
Müller, Katharina; Grönquist, Philippe; Cao, Alex Sixie; et al. (2021)
Construction and Building Materials
Timber–concrete composites (TCC) are smart solutions for slabs in residential and office buildings regarding the sustainable and performance-optimized use of materials. However, a non-negligible disadvantage is the deflection of the timber elements caused by in-situ concrete casting during construction. This paper presents an approach to camber timber elements without external forces by using the innate swelling capacity of wood. Oven-dried hardwood inlays can be inserted transversally into cuts on the top side of a timber element. After an increase of the moisture content in the inlays, the swelling pressure will result in a self-camber of the timber element. In this study, a procedure for prediction of the self-camber is derived and the model is validated using an experimental test series. The results demonstrate that the self-camber of spruce elements using beech inlays is both feasible and predictable. On this basis, practical application scenarios for TCC elements in timber engineering are shown and discussed.
Modeling and design of thin bending wooden bilayers
Grönquist, Philippe; Wittel, Falk K.; Rüggeberg, Markus (2018)
PLoS ONE
In recent architectural research, thin wooden bilayer laminates capable of self-actuation in response to humidity changes have been proposed as sustainable, programmed, and fully autonomous elements for facades or roofs for shading and climate regulation. Switches, humidistats, or motor elements represent further promising applications. Proper wood-adapted prediction models for actuation, however, are still missing. Here, a simple model that can predict bending deformation as a function of moisture content change, wood material parameters, and geometry is presented. We consider material anisotropy and moisture-dependency of elastic mechanical parameters. The model is validated using experimental data collected on bilayers made out of European beech wood. Furthermore, we present essential design aspects in view of facilitated industrial applications. Layer thickness, thickness-ratio, and growth ring angle of the wood in single layers are assessed by their effect on curvature, stored elastic energy, and generated axial stress. A sensitivity analysis is conducted to identify primary curvature-impacting model input parameters.
Ice nucleation abilities of soot particles determined with the Horizontal Ice Nucleation Chamber
Mahrt, Fabian; Marcolli, Claudia; David, Robert O.; et al. (2018)
Atmospheric Chemistry and Physics Discussions
Analysis of hygroscopic self-shaping wood at large scale for curved mass timber structures
Grönquist, Philippe; Wood, Dylan; Hassani, Mohammad M.; et al. (2019)
Science Advances
The growing timber manufacturing industry faces challenges due to increasing geometric complexity of architectural designs. Complex and structurally efficient curved geometries are nowadays easily designed but still involve intensive manufacturing and excessive machining. We propose an efficient form-giving mechanism for large-scale curved mass timber by using bilayered wood structures capable of self-shaping by moisture content changes. The challenge lies in the requirement of profound material knowledge for analysis and prediction of the deformation in function of setup and boundary conditions. Using time- and moisture-dependent mechanical simulations, we demonstrate the contributions of different wood-specific deformation mechanisms on the self-shaping of large-scale elements. Our results outline how to address problems such as shape prediction, sharp moisture gradients, and natural variability in material parameters in light of an efficient industrial manufacturing.
Bonding of beech wood to mortar with a novel epoxy hybrid-adhesive: Performance in dry and wet conditions
Stucki, Sandro; Kelch, Steffen; Mamie, Tim; et al. (2025)
International Journal of Adhesion and Adhesives
Composites made of timber and cementitious materials require a rigid connection to exploit their full composite action, which can be achieved by using full-surface adhesive bonding. In this work, we investigated a novel hybrid-adhesive system consisting of a silane-terminated polyurethane (STP) and epoxy resin for the bonding of beech wood timber to fresh mortar for use in timber-mortar composites (TMC). The mechanical performance and the influence of moisture on TMC produced by the wet-in-wet process (fresh mortar) was investigated and compared to the bonding of prefabricated mortar (prefab process). The STP-epoxy hybrid-adhesive showed a suitable bonding performance of beech wood to both, fresh mortar and precured mortar with median compression shear strengths of 4.57 MPa and 6.07 MPa, respectively. The fracture pattern showed the strength of the near-surface layer in the mortar, close to the adhesive, being often decisive for the bond performance. The same failure mode predominated in TMC beams after 3-point bending tests. The stability of the composite upon the influence of moisture is especially challenging when using beech wood due to its low dimensional stability. Thus, the moisture stability of the bond was investigated by compression shear tests after water immersion. It showed an improved water stability compared to composites bonded with an epoxy resin. Nonetheless, a clear reduction in bond strength compared to the dry state was observed, with delamination of 25 % of the wet-in-wet and 17 % of the prefab specimens during water immersion. Furthermore, it was seen that the adhesive open laying time played a decisive role in the wet-in-wet produced specimens influencing both, dry and wet shear strength.
Residual stresses in adhesively bonded wood determined by a bilayer flexion reporter system
Maas, Jonas Matthias; Grönquist, Philippe; Furrer, Jennifer; et al. (2022)
Wood Science and Technology
The application of adhesives in modern timber engineering often introduces moisture into the wood, leading to permanent residual stresses after hardening. This paper proposes a novel approach to assess these residual stresses by using wooden bilayers as a reporter system. For thin bilayers, moisture-induced stresses lead to pronounced visible flexion that can be used to identify the stress-driving parameters of the adhesive’s gelation process. These parameters depend solely on the wood/adhesive combination and are inversely determined by fitting a finite element method model on the experimentally obtained flexion state. In a subsequent step, the determined parameters are used to calculate the residual stresses in the adhesive bondline of cross-laminated timber plates, emphasizing this approach’s scale independence and general applicability to larger scale structures. All combinations of European beech and Norway spruce with the adhesives Melamine–Urea–Formaldehyde (MUF), Phenol–Resorcinol–Formaldehyde (PRF), and Polyurethane (PUR) were investigated.

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Philippe Grönquist

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