Influence of laminate characteristics on properties of single-layer and cross laminated timber (CLT) panels

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University of New Brunswick


Cross laminated timber (CLT) has gained a lot of popularity within the construction sector. The reasons for this are due to its favourable dimensions for prefabrication and modular construction, its structural performance and dimensional stability, as well as people’s growing environmental awareness and desire to build with a lower carbon footprint. As the name suggests, cross laminated timber is an engineered wood based structure made from layers of lumber elements that are arranged perpendicular to each other. These layers are commonly face glued to each other. Naturally, the properties of CLT are driven by the material that is used to form these large dimensional panels. Besides the materials used, other factors can potentially influence the performance of CLT panels. The influence of three parameters on several characteristics of single-layer and CLT panels were investigated in this study, the influence of edge-gluing, the aspect ratio of the laminates and the effects of the growth ring orientation of the laminates. The so called edge-gluing refers to an adhesive bond between adjacent laminates within a layer. The laminate aspect ratio is the ratio between the width of the laminates to its thickness. The growth ring orientation of the laminates is determined by sawing pattern on the cross section of the wooden log and the location a laminate was cut from. The influence of these parameters on the moduli of elasticity in the major and minor strength direction, as well as in-plane and planar shear moduli and planar shear strength in the two panel directions of single-layer and multi-layer CLT panels were investigated. “Homogeneous” single-layer and scaled 3- and 5-layer CLT panels were formed. Modal and static test procedures were employed to determine the effects of the different parameters on the stated panel characteristics. The results showed that especially the single-layer and CLT panel properties associated with the minor strength directions were affected by the investigated parameters. While the single-layer panel properties were influenced by all three parameters, the properties of CLT panels were mainly influenced by the edge-gluing and aspect ratio only. Generally, the influence of the aspect ratio was linked to the absence of edge-gluing within a layer. Statistical models were developed for predicting the properties of several single-layer and CLT panels. The results from this study could help to increase the structural performance of CLT by choosing the right material and manufacturing processes. Nevertheless, the test results should be confirmed by full-scale CLT tests.