Discrete Bonding of Bio-Based Adherends

该项目使用新的3D打印和激光刻蚀技术来模拟和建模不同液滴阵列对链粘附物之间结合强度的影响。对于像木材这样的异质材料来说，困难在于强度和韧性测量的高变异系数需要测试大量的样品。金属衬底将满足均匀、均匀材料的要求。第一部分使用3D打印技术，将形状和大小固定的热熔胶形式的“粘性”液滴沉积到均匀的表面，即铝板上。液滴可以预印在一个或两个印版和粘合剂上，方法是将它们加热到热版上，直到粘合剂融化，然后让它们冷却到室温。将测量粘结的强度和韧性，并与液滴大小和间距相关，确定最佳目标分布。然后，将在不均匀的木材-树脂粘合剂(包括热熔胶和热固性胶粘剂)系统上进行测试，以验证模型。第二部分将使用激光蚀刻来生产具有凸起的粘合表面的木质粘合剂，其尺寸和间距可控。在过去，Kamke等人曾研究过两种木材粘合剂之间界面上的胶滴尺寸分散性以及界面的强度。(1996)，Conrad et al.(2003)和Smith(2003)，但对液滴大小和放置的密切控制是有限的。Smith(2005)能够使用改进的柔版印刷技术对打印到原丝表面上的树脂液滴的大小进行一些控制，但可重复沉积的液滴大小范围很小。3D打印机没有这一限制，这应该允许更大范围的液滴大小被快速和轻松地检查。在工业搅拌机中，木股上的液滴大小和液滴间距范围很大，使用这种新方法，液滴大小和间距可以仔细控制。这将允许创建从简单的单分散液滴尺寸分布到复杂的随机分布，其中每个液滴具有相同的大小和相邻液滴之间的距离。这一过程的下一步将是将具有相同或不同液滴阵列的粘附物粘合在一起，并测量这些粘结物的强度和断裂韧性。还将研究如何改进现有的实验室喷雾系统以产生最佳树脂分布的实用方法。预计模型粘结样品和在实验室规模的搅拌器中涂布的粘结强度的差异将确定通过更有效地沉积树脂可以获得多少额外的强度。

This project uses new 3D printing and laser etching technologies to simulate and model the effect of different droplet arrays on the bond strength between strand adherends. The difficulty with a very heterogeneous material like wood is the high coefficient of variation in strength and toughness measurements requires a large number of samples to be tested. A metal substrate would meet the requirements of a uniform, homogeneous material. Part 1 uses 3D printing to deposit `adhesive' droplets in the form of hot melt glue of fixed shape and size onto a uniform surface, i.e. aluminium plates. Droplets can be pre-printed onto one or both of the plates and bonds formed by heating them on a hot plate until the adhesive melts and then letting them cool to room temperature. The strength and toughness of the bonds will be measured and related to the droplet size and spacing, and optimal target distributions identified. These will then be tested on the non-uniform wood-resin adhesive (both hot melt and  a thermoset) system of strand-based composites to validate the model. Part 2 will use laser etching to produce wooden adherends with raised bonding surfaces of controlled size and spacing. Adhesive droplet size dispersion at the interface between two wood adherends and the strength of that interface has been examined in the past by Kamke et al. (1996), Conrad et al. (2003) and Smith (2003), but the close control over droplet size and placement was limited. Smith (2005) was able to have some control over the size of the resin droplets that were printed onto a strand surface using the modified flexographic printing technique but the range of droplet sizes that could be reproducibly deposited was small. The 3D printer does not have this limitation and that should permit a much wider range of droplet sizes to be examined quickly and easily. The range of droplet sizes and inter-droplet spacing on wood strands in an industrial blender is large and with this new approach the droplet size and spacing can be carefully controlled. This will permit distributions from simple, monodisperse droplet size distributions where every droplet has the same size and distance from its neighbor to complex, random distributions that mimic those occurring in an industrial blender to be created. The next step in this process will be to bond adherends with the same or different droplet arrays together and measure the strength and fracture toughness of those bonds. Practical means of modifying the current lab spray system to produce optimal resin distributions will also be investigated. It is expected that the difference in bond strength obtained for the model bond samples and those coated in the lab-scale blender will define how much additional strength could be obtained by depositing the resin more effectively.