Library material was added

StructureHelperLogics/Models/Materials/IElasticMaterial.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace StructureHelperLogics.Models.Materials
+{
+    public interface IElasticMaterial : IHelperMaterial
+    {
+        double Modulus { get; set; }
+    }
+}