Discrete Bonding of Bio-Based Adherends

该项目使用新的3D打印和激光蚀刻技术来模拟和模拟不同液滴阵列对链粘附物之间粘合强度的影响。像木材这样非常不均匀的材料的困难在于强度和韧性的高变异系数测量需要大量的样品进行测试。金属基板将满足均匀材料的要求。第一部分使用3D打印将“粘合剂”液滴以固定形状和大小的热熔胶的形式沉积到均匀的表面上，即铝板。液滴可以预先打印在一个或两个板上，并通过在热板上加热形成粘合，直到粘合剂融化，然后让它们冷却到室温。将测量键的强度和韧性，并将其与液滴大小和间距相关，并确定最佳目标分布。然后，这些将在非均匀木树脂粘合剂（热熔和热固性）链基复合材料系统上进行测试，以验证模型。第2部分将使用激光蚀刻生产具有控制尺寸和间距的凸起粘合表面的木制附着物。Kamke等人（1996年）、Conrad等人（2003年）和Smith（2003年）过去曾研究过两种木材粘附体界面上胶滴大小的分散以及该界面的强度，但对胶滴大小和放置的严格控制是有限的。Smith（2005）能够使用改进的柔版印刷技术对打印到链表面的树脂液滴的大小进行一定的控制，但可重复沉积的液滴尺寸范围很小。3D打印机没有这种限制，这应该允许更大范围的液滴尺寸被快速和容易地检查。液滴大小和液滴间距的范围在木股在工业搅拌机是大的，与这种新的方法，液滴的大小和间距可以仔细控制。这将允许从简单的单分散液滴大小分布（每个液滴具有相同的大小和与相邻液滴的距离）到模拟工业搅拌器中发生的复杂随机分布的分布。该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，并测量这些粘合物的强度和断裂韧性。实际的方法，修改目前的实验室喷雾系统，以产生最佳树脂分布也将进行研究。可以预期的是，模型粘结样品与实验室规模搅拌器中涂层的粘结强度的差异将决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.