Compression tests of unidirectional composite laminates with two delaminations

Compression tests are conducted on composite laminates consisting of 16 unidirectional carbon/epoxy layers with two through-width delaminations. Two types of delamination length and location are considered. One is that a short delamination is located at the middle surface along the thickness direction and a long delamination is positioned between the second layer and the third layer. The other is that a long delamination is located at the middle surface and the position of the short delamination is between the second layer and the third layer. The results indicate that if the long delamination is close to the surface of the laminate, the inner, short delamination has no effect on the critical buckling stresses. However, the presence of inner, short delamination may significantly change the critical delamination growth stresses. If the short delamination is above the long delamination that is located on the middle surface, the presence of the short delamination may significantly reduce the critical buckling stresses. But its effects on the critical delamination growth stresses are minor.