strain at midplane test

tests/Test_laminate_strain.py

@@ -0,0 +1,45 @@
+'''
+Test of strains of LaminateStrength
+===================================
+
+Test LaminateStrength class using examples from reference 1
+
+References
+----------
+1 - https://ntrs.nasa.gov/api/citations/19950009349/downloads/19950009349.pdf
+'''
+
+import pytest
+import numpy as np
+import pandas as pd
+
+from composipy import OrthotropicMaterial, LaminateProperty, LaminateStrength
+
+
+@pytest.fixture
+def laminateconfig():
+    '''
+    Material configuration from Example 1 in page 31.
+    Laminate configuration from Example 4 in page 46
+    This laminate is used in all tests
+    '''
+    E1 = 2.01e7 #lb/in2
+    E2 = 1.301e6 #lb/in2
+    v12 = 0.3
+    G12 = 1.001e6 #lb/in2
+    t = 0.005 #in
+    material = OrthotropicMaterial(E1, E2, v12, G12, t)
+    stacking = [0, 45, 45, 0]
+    return LaminateProperty(stacking, material)
+
+
+def test_example_3_midplane(laminateconfig):
+    '''
+    Example 3 in page 46
+    This test check the stains at the midplane
+    '''  
+    Nxx = 500 #lb/in
+    strain_analysis = LaminateStrength(dproperty=laminateconfig, Nxx=Nxx)
+    calculated_strains = strain_analysis.epsilon0()
+    reference_result = np.array([0.00221, -0.0007, -0.00115, 0, 0, 0])
+    np.testing.assert_allclose(calculated_strains, reference_result, rtol=1e-2, atol=1e-4)