ABSTRACT

Glued-in Rods (GiR) connections are widely used in timber engineering as a connector between individual load-bearing members. Typically, GiR consist of a rod, e.g. rebars or threaded rods, glued into timber-based elements. However, rods made of new materials, as Glass-Fibre Reinforced Polymers (G-FRP) are increasingly being used due to their advantageous material properties like high tensile strength and good resistance against corrosion or chemical media. The cure of usually used and commercially available adhesives for GiR applications, mostly cold-curing 2 K-epoxies (2 K-EPX) and 2 K-polyurethanes (2 K-PUR), is time consuming. After adhesive application, the components must be fixed and maintained in position from several hours to days before the connection can be stressed. This process, depending on the connection type, can be significantly time, and cost, consuming for contractors, which makes the process difficult on-site. In order to overcome these restrictions, the present study investigated accelerated curing with the help of Curie-Particles (CP) exposed to a high-frequency (HF) alternating electromagnetic field (EMF). The CP are added to the 2 K adhesives, the resulting mix is then exposed to the EMF, generating thermal energy, which in turn accelerates the chemical reaction and associated adhesive curing. Due to the very nature of the CP, heating proceeds until their Curie temperature is reached, at which point the heating automatically stops. As a result, accelerated curing is achieved independently of external monitoring. In the present study, G-FRP rods were glued into blocks of spruce Glued Laminated Timber (GLT), and inductively cured through the addition of 33.3 w/w-% of CP. In total, four commercially available adhesives (three 2 K-EPX, and one 2 K-PUR) were investigated. The authors demonstrated on a total of 67 large-scale GiR specimens that inductively heated specimens achieved almost identical failure loads, and fracture patterns (wood failure), compared to cold-cured references accompanied by a reduction of curing time from as long as 1–10 days down to 10 min.

摘要

胶合杆 (GiR) 连接在木材工程中广泛用作单个承重构件之间的连接器。通常，GiR 由粘在木基元件中的杆组成，例如钢筋或螺纹杆。然而，由于玻璃纤维增​​强聚合物 (G-FRP) 具有优异的材料特性，如高拉伸强度和良好的耐腐蚀性或耐化学介质性，由新材料制成的杆越来越多地被使用。用于 GiR 应用的常用和市售粘合剂的固化非常耗时，主要是冷固化 2 K-环氧树脂 (2 K-EPX) 和 2 K-聚氨酯 (2 K-PUR)。涂上粘合剂后，组件必须在几个小时到几天内固定并保持就位，然后才能对连接施加压力。这个过程，取决于连接类型，承包商可能会花费大量时间和成本，这使得现场的过程变得困难。为了克服这些限制，本研究调查了在暴露于高频 (HF) 交变电磁场 (EMF) 的居里粒子 (CP) 的帮助下加速固化。将 CP 添加到 2 K 粘合剂中，然后将所得混合物暴露于 EMF 中，产生热能，进而加速化学反应和相关的粘合剂固化。由于 CP 的性质，加热会一直进行，直到达到它们的居里温度，此时加热会自动停止。因此，可以独立于外部监测实现加速固化。在本研究中，G-FRP 棒被胶合到云杉胶合层压木材 (GLT) 块中，并通过添加 33.3 w/w-% 的 CP 进行感应固化。总共研究了四种市售粘合剂（三种 2 K-EPX 和一种 2 K-PUR）。作者在总共 67 个大型 GiR 试样上证明，与冷固化参考相比，感应加热试样实现了几乎相同的破坏载荷和断裂模式（木材破坏），同时固化时间从 1– 10 天缩短到 10 分钟。