diff --git a/fem_2d.py b/fem_2d.py
index 22831efc05b5e5b8a4feae751af4c81914b8a5dc..07f2264f1a00acfddfabac7f06b148a189b34ade 100644
--- a/fem_2d.py
+++ b/fem_2d.py
@@ -173,7 +173,16 @@ class Structure2DPlaneStress:
 
         # Assembles stiffness matrix
         for element_id in range(self.num_elements):
-            k_e = self.elements[element_id].get_k_mat(self.c_mat)
+            node_ids = self.elements[element_id].node_ids
+            k_e = self.elements[element_id].get_k_mat(self.thickness,
+                                                      self.c_mat)
+            indexes = ((node_ids[0], node_ids[0]),
+                       (node_ids[0], node_ids[1]),
+                       (node_ids[1], node_ids[0]),
+                       (node_ids[1], node_ids[1]))
+
+            
+    
 
 
 '''