Komposiittisen siipikaaren uuman ja laipan välisen nurkan lujuuden arviointi

The thesis focuses on composite ribs of an airliner wing. The sizing factor for the composite ribs is typically delamination of the rib foot corner caused by the out-of-plane stresses in the crash load case. The main purpose of the thesis is to find a strength prediction method for the composite rib foot corner. Related to this, new test methods providing more generic material data are developed. The strength of a composite rib foot corner is analyzed through an L-shaped carbon fiber reinforced specimen with a 90° angle. The specimen is bolted to a rigid steel plate. The L-shaped specimen studied is RTM-processed from the materials G0926/RTM6. The bolts are made of titanium. The typical loads and stress states of the composite rib foot corner are presented. The delamination of the corner is due to out-of-plane stresses. These stresses are calculated with a method developed by Lekhnitskii. The applied loads are estimated according to ESDU 84039. Five different failure criteria are considered in the work. The strength predictions from the analyses are compared with the test results. Several tests for generating more generic material data were considered. The ASTM D6415 standard test proved to be most suitable for the out-of-plane tensile strength testing. A new test method was introduced for testing the out-of-plane shear strength. The stress concentration caused by the bolt pull-through is accounted for in the test. Effects of parameters on the strength of the composite rib foot corner were studied through the tests and analyses. The final analysis results were calculated using material data measured with the described tests. The Puck's failure criterion provided the best failure load predictions in the final analysis. The analysis method used in the thesis provided good results in comparison to test results