Predicting layer cracks in cross-laminated timber with evaluations of strategies for suppressing them

Nairn, John A.

doi:10.1007/s00107-019-01399-7

Cited by 16 publications

(12 citation statements)

References 30 publications

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“…Two compressed gel-phase (conjoined) films cured to glass phase had distinctive fracture mechanics; that is, the conjoined films had greater cohesive strength than comparable double thickness or stacked films. Although the mechanism is unclear, we speculate that this fracture resistance or toughness is a cross-grain effect [26,27]. In this interpretation, the mechanical stress produced a crack that spanned one layer, but the propagation of the crack was constrained by the conjoined layer.…”

Section: Discussionmentioning

confidence: 88%

Water-Dependent Blending of Pectin Films: The Mechanics of Conjoined Biopolymers

et al. 2020

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Biodegradable pectin polymers have been recommended for a variety of biomedical applications, ranging from the delivery of oral drugs to the repair of injured visceral organs. A promising approach to regulate pectin biostability is the blending of pectin films. To investigate the development of conjoined films, we examined the physical properties of high-methoxyl pectin polymer-polymer (homopolymer) interactions at the adhesive interface. Pectin polymers were tested in glass phase (10–13% w/w water content) and gel phase (38–41% w/w water content). The tensile strength of polymer-polymer adhesion was measured after variable development time and compressive force. Regardless of pretest parameters, the adhesive strength of two glass phase films was negligible. In contrast, adhesion testing of two gel phase films resulted in significant tensile adhesion strength (p < 0.01). Adhesion was also observed between glass phase and gel phase films—likely reflecting the diffusion of water from the gel phase to the glass phase films. In studies of the interaction between two gel phase films, the polymer-polymer adhesive strength increased linearly with increasing compressive force (range 10–80 N) (R2 = 0.956). In contrast, adhesive strength increased logarithmically with time (range 10–10,000 s) (R2 = 0.913); most of the adhesive strength was observed within minutes of contact. Fracture mechanics demonstrated that the adhesion of two gel phase films resulted in a conjoined film with distinctive physical properties including increased extensibility, decreased stiffness and a 30% increase in the work of cohesion relative to native polymers (p < 0.01). Scanning electron microscopy of the conjoined films demonstrated cross-grain adhesion at the interface between the adhesive homopolymers. These structural and functional data suggest that blended pectin films have emergent physical properties resulting from the cross-grain intermingling of interfacial pectin chains.

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Section: Discussionmentioning

confidence: 88%

Water-Dependent Blending of Pectin Films: The Mechanics of Conjoined Biopolymers

et al. 2020

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“…In terms of simulating the in-plane response of CLT panels, research performed in Gsell et al (2007) indicated that the behavior of the panels can be modeled using a homogenized linear elastic orthotropic material. In Gsell et al (2007), the elastic moduli of CLT panels are determined using the method proposed in Blaß and Fellmoser (2004), but there are other analytical approaches in the literature that allow the computation of in-plane shear modulus of CLT panels (Flaig and Blaß 2013;Bogensperger et al 2010;Dröscher 2014;Brandner et al 2017;Nairn 2019). To simulate the response of connections, a lumped springs modeling approach was developed in Breneman et al (2016) to capture the shear transfer between panels.…”

Section: Introductionmentioning

confidence: 99%

Analytical and Numerical Models for Wind and Seismic Design and Assessment of Mass Timber Diaphragms

Rodrigues,

Barbosa,

Sinha

et al. 2024

J. Struct. Eng.

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While the use of cross-laminated timber (CLT) panels for building construction has increased over the last several decades, current standards and existing literature provide limited information regarding the design of CLT diaphragms or the prediction of their deflections when subjected to wind and strong earthquake motions. This paper presents the design and assessment of a CLT diaphragm that was part of a full-scale two-story structure subjected to shake-table testing. An analytical model is proposed for diaphragm deflection accounting for in-plane shear and bending stiffness, as well as the stiffness of various connections. Moreover, a refined numerical modeling strategy is proposed in order to consider phenomena such as panel-to-panel gap closure. Results indicate that the analytical model yields conservative results both in terms of deflections and forces, when compared to the numerical model that simulates similar sources of strength and stiffness. The analytical model is suitable for the design of symmetric diaphragms with regular shapes, whereas the numerical model can also be used to model asymmetric diaphragms with an irregular shape.

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“…Adhesive-based engineered wood products (ABEWPs) are commonly used in residential and commercial construction due to their numerous benefits, such as ease of construction, carbon sequestration and low grade feedstock utilisation (Kremer et al, 2018;McGavin et al, 2020). In terms of structural engineering, they provide an alternative to large cross-sections rarely found in sawn material and have reduced mechanical property variability (Nairn, 2019;Sandak et al, 2020). These benefits have led to over 65% of the globally used wood products being ABEWPs (Pizzi, 2016).…”

Section: Introductionmentioning

confidence: 99%

Understanding the Adhesion Performance of Glued Laminated Timber Manufactured with Australian Softwood and High-Density Hardwood Species

Faircloth,

Gilbert,

Kumar

et al. 2024

Preprint

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To be commercialised, glued laminated timber must typically conform to a strict bond integrity assessment. While the associated testing protocols vary slightly from country to country, the general method consists of a series of swelling (water immersion) and shrinkage (drying) cycles. The approach is independent of the species and adhesive type. Those cycles strain the gluelines to a level depending on the species’ moisture uptake, timber dimensional movement and modulus of elasticity, as well as adhesive layer elasticity. High density and high modulus of elasticity materials frequently fail within the glueline regions rather than within the timber and therefore fail the bond integrity assessment. To better understand the mechanisms that lead to glueline failure, glulam samples were manufactured using three prominent Australian commercial timbers of various densities (Radiata pine – Pinus radiata, Southern pine – Pinus caribaea/Pinus elliottii, and Spotted gum – Corymbia citriodora) and two structural adhesive types (resorcinol formaldehyde and polyurethane). Using advanced measurement techniques (digital image correlation and strain gauges), the response of the different species and adhesive types to moisture swelling and shrinkage, as well as times at which glueline separation occurs, were captured. A relationship was observed between moisture uptake and delamination percentages with spotted gum producing significantly higher levels of delamination and significantly lower moisture uptake values, compared to both radiata pine and southern. While the polyurethane glued samples on average produced higher levels of delamination, the digital image correlation data indicates that the time at which this delamination occurs is later than the samples glued with resorcinol formaldehyde. No relationship exists between the block shear strength, wood fibre amounts, and delamination percentages.

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Predicting layer cracks in cross-laminated timber with evaluations of strategies for suppressing them

Cited by 16 publications

References 30 publications

Water-Dependent Blending of Pectin Films: The Mechanics of Conjoined Biopolymers

Water-Dependent Blending of Pectin Films: The Mechanics of Conjoined Biopolymers

Analytical and Numerical Models for Wind and Seismic Design and Assessment of Mass Timber Diaphragms

Understanding the Adhesion Performance of Glued Laminated Timber Manufactured with Australian Softwood and High-Density Hardwood Species

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