Evaluation of the bonding quality of E. grandis cross-laminated timber made with a one-component polyurethane adhesive

Dugmore, Michael Keith (2018-03)

Thesis (MScFor)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: Eucalyptus grandis is South Africa‘s most important commercial hardwood species. The availability of E. grandis and its fast growth rate creates the opportunity to explore its uses further. Cross-laminated timber (CLT) is a prefabricated multilayer engineered panel product made of at least three layers, with the grain direction of some or all of the consecutive layers orthogonally orientated. In order to add value to E. grandis, reduce the export of low-cost chips, increase the profit margins of local plantation owners and create jobs, the development of E. grandis CLT in South Africa may be an option. There is concern among some researchers that the bonding quality evaluation tests proposed by CLT standards have been developed for glulam and are too severe for CLT. These researchers proposed that further analysis and possibly even revision of the test methods should be considered. There is also a need to evaluate the mechanical properties of CLT panels made of E. grandis to completely understand the structural performance of these panels, including their bond quality and durability, and therefore be able to rely on E. grandis CLT as a construction material. The objectives of this study were: . To evaluate the face-bonding quality of CLT panels from E. grandis timber bonded with a one component polyurethane resin; . To determine the influence of material and processing parameters on the face-bonding quality of CLT manufactured from E. grandis timber bonded with a one component polyurethane resin; . To analyse different testing methods for evaluating the face-bonding quality of CLT. The design for this experiment consisted of eight groups with different combinations of parameters for density, grooves and pressure per group. Four different testing methods were used to evaluate the face-bonding quality of CLT panels from E. grandis and to determine the effect of parameters on face-bonding quality: A delamination test on 100 x 100 mm block specimens (Test A), a shear test on 40 x 40 mm specimens (Test B), a shear test on 40 x 40 mm specimens with grain direction 45° to load direction (Test C) and a combined delamination and shear test on 70 x 70 mm specimens with grain direction 45° to load direction (Test D). Results of the statistical analysis indicated that E. grandis CLT made with 1C-PUR adhesive can obtain excellent face-bonding quality using a clamping pressure of 0.7 MPa and with no stress relief grooves present. All samples passed the shear test (Test B) which is the reference test method proposed by EN 16351 (2015). It was found that a strength component and durability component will be an advantage when testing the bond quality of CLT. Shear tests at 45° to the load direction did not completely eliminate the rolling shear effect. The combined delamination and shear test (Test D), seems to have potential as a good test for bond quality since it is a combination of a durability and shear strength test. There are still questions about the relative advantages of specific test methods for bond quality, especially on the effect of rolling shear. Further work should focus on this aspect and the use of stress models might be a way of gaining further insights.

AFRIKAANSE OPSOMMING: Eucalyptus grandis is Suid-Afrika se belangrikste kommersiële loofhoutspesie. Die beskikbaarheid van E. grandis en sy vinnige groeitempo skep die geleentheid om sy gebruike verder te ondersoek. Kruis-gelamineerde hout (KGH) is 'n voorafvervaardigde, multilaag verwerkte paneelproduk van ten minste drie lae, met die greinrigting van sommige of al die opeenvolgende lae ortogonaal georiënteer. Ten einde waarde toe te voeg tot E. grandis, die uitvoer van lae-koste spaanders te verminder, winsmarges te verbeter van plaaslike plantasie-eienaars en vir die skepping van werksgeleenthede, het die ontwikkeling van E. grandis KGH in Suid-Afrika potensiaal. Daar is kommer onder sommige navorsers dat die lasgehaltetoetse voorgestel deur KGH standaarde ontwikkel is vir gelamineerde balke en te streng is vir KGH. Hierdie navorsers het voorgestel dat verdere analise en moontlik selfs hersiening van die toetsmetodes oorweeg moet word. Daar is ook 'n behoefte om die meganiese eienskappe van KGH panele, gemaak van E. grandis, te evalueer en die strukturele vermoë van hierdie panele, insluitend hul laskwaliteit -en duursaamheid, volledig te verstaan en dus te kan staatmaak op E. grandis KGH as 'n konstruksiemateriaal. Die doelwitte van hierdie studie was die volgende: . Evalueer die laskwaliteit op die platkante van KGH panele van E. grandis hout gelym met 'n een-komponent poliuretaan hars; . Bepaal die invloed van materiaal -en verwerkingsparameters op die laskwaliteit van KGH, vervaardig uit E. grandis hout, gelym met 'n een-komponent poliuretaan hars; . Ontleed verskillende toetsmetodes om die laskwaliteit op die platkante van KGH te evalueer. Die ontwerp van hierdie eksperiment het uit agt groepe met verskillende kombinasies van parameters vir digtheid, spanningsverligtinggroewe en klampdruk per groep bestaan. Vier verskillende toetsmetodes is gebruik om die laskwaliteit van KGH panele van E. grandis te evalueer en om die uitwerking van verskillende parameters te bepaal. Die vier toetse was: 'n delamineringtoets op 100 x 100 mm blokmonsters (toets A), 'n skuiftoets op 40 x 40 mm monsters (toets B), 'n skuiftoets op 40 x 40 mm monsters met greinrigting 45° met lasrigting (toets C) en 'n gesamentlike delaminering -en skuiftoets op 70 x 70 mm monsters met greinrigting 45° met lasrigting (toets D). Resultate van die statistiese analise het aangedui dat E. grandis KGH gemaak met 1C-PUR kleefmiddel uitstekende lasgehalte kan verkry met behulp van 'n klampdruk van 0.7 MPa en met geen spanningsverligtinggroewe teenwoordig nie. Alle monsters slaag die skuiftoets (toets B) wat die verwysingstoetsmetode in EN 16351 (2015). Daar is gevind dat 'n sterktekomponent en duursaamheidskomponent 'n voordeel sal wees wanneer die laskwaliteit van KGH getoets word. Skuiftoetse teen 45° met die lasrigting het nie die rolskuifeffek heeltemal uitgeskakel nie. Die gekombineerde delaminering -en skuiftoets (toets D), het oënskynlik potensiaal as 'n goeie toets vir laskwaliteit omdat dit 'n kombinasie van 'n duursaamheid -en skuiftoets is. Vrae bestaan nog oor die relatiewe voordele van spesifieke toetsmetodes vir laskwaliteit, veral op die effek van rolskuif. Verdere navorsing moet fokus op hierdie aspek en die gebruik van spanningsmodelle sal dalk 'n manier wees om verdere insigte daaroor te verkry.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103473
This item appears in the following collections: