Press Glued Connections – Research Results for Discussion and Standardization

It is important to realize that fastener distance,fastener type, used adhesive is not the completepart of the puzzle. Parameters like achieved glueline thickness, surface quality, production conditions,etc., are elements that are all important to guaranteethe final bond quality.A measurement setup was successfully developedwhich allowed the measurement of compression loadsgenerated by fasteners. The measured peak loadshould however not be used as reference to estimatethe average curing pressure. Instead, a load measuredafter this peak should be used. For nails and staples,the 10 seconds seems to be a reasonable point. Itcould be stretched a little for screws in the future.Press gluing with nails or staples is not popularamongst wood construction industry. The largespread in generated compression loads is a possibleexplanation. They do offer economical solutions, butadditional quality control is recommended.The variety of screws tested showed that somefasteners can provide high adhesive curing pressures.The head typology affects this curing load andfasteners could be optimised to achieve higher curingloads without much redesign of the fastener.The EN 14080:2013 provides a first evaluation ofthe remaining bond quality. It is believed to be tooconservative since the ductility of the fastener is notconsidered in the failure behaviour. A test setup couldbe redesigned to include this in future assessments ofthe bond quality.