Development and evaluation of the combined loading modification to the V-notched rail shear test method for composite laminates

The objective of this research was to determine what modifications would be most effective in improving the loading capacity of the V-Notched Rail Shear test method. The new test method that was developed as a result of this research is known as the Combined Loading Modification to the V-Notched Rail Shear test method, or the Combined Loading test method. The Combined Loading test method modifies the current V-Notched Rail Shear test method by increasing the gripping region and the adding edge loaders similar to those used in the Iosipescu test fixture. To determine what modifications are most effective in increasing the loading capacity of the test method, finite element analyses were performed on v-notched shear specimens of different lengths and with different constraints. The dimensions in the gage section of the v-notched specimens of different length were maintained the same as the dimensions of the V-Notched Rail Shear specimens. These dimensions remained unchanged so that the highly uniform state of stress that exist in the V-Notched Rail Shear test method would still exist in any modifications. Finite element analyses showed that the Combined Loading test produced uniform states of stress for three different composite laminates. Finite element models also predicted that Combined Loading test would produce a more uniform state of inplane shear stress through the thickness of the specimen than the existing V-Notched test. V-notched specimens of multiple lay-ups and thickness were tested in the current V-Notched test fixture as well as the Combined Loading test fixture. Two different lengths of specimens were tested using the Combined Loading test method. Results showed that the Combined Loading test using the longer specimens produced the most consistent shear strengths for similar laminates of different thickness.