Developing a Methodology to Study the Effects of Adhesive Flow Penetration on Wood Adhesive Bond Performance by using Micro X-ray Computed Tomography (XCT) and Digital Volume Correlation (DVC)
Wood composites are an important renewable structural material which can be a net carbon sink when used in combination with sustainable forest management practices and high rates of log utilization. Adhesive bondlines are an essential part of composites, and for wood composites, they determine the moisture durability and mechanical performance of these products. This dissertation is part of a decades long effort to understand how the properties of the wood adhesive system influences the performance of wood composites. Specifically, the relative importance of the shape of the cured adhesive in situ is not well understood. Since adhesives are the most expensive part of wood products by mass, insights into the performance of the wood adhesive system could lead to cost savings of some kind. This dissertation describes the methods for in situ mechanical loading and moisture induced swelling experiments of wood composites using the combination of x-ray computed tomography and digital volume correlation to make full field strain measurements. Since this is the first time these methods have been applied to study the wood composite system many suggestions for improved methods are made. Software tools were also created to assist with segmentation of wood adhesive bondlines and to simulate x-ray computed tomography data acquisition. These tools may assist in making future experiments better. The influence of adhesive flow on the mechanical performance of wood adhesive bonds is inconclusive either because specimen variability was too high or metrics for measuring bond performance insufficient. The local influence of adhesive bondlines on moisture induced swelling was measured for adhesives of different precure molecular weights, and no effect of the precure molecular weight was observed. However, it was observed that the wood and adhesive influence the moisture induced swelling of one another, and adhesive fracture during swelling may limit the ability of the adhesive to constrain wood swelling.