Pengaruh posisi pengelasan chain straight dan zig-zag terhadap kekuatan produk struktur ringan longitudinal square honeycomb corrugated core sandwich panels pada pengelasan two-stage refilled micro friction stir spot welding (tfssw) = Effect of welding position at chain straight and zig-zag position on strength of lightweight structure longitudinal square honeycomb corrugated core sandwich panels product at two-stage refilled micro friction stir spot welding (tfssw)