The Development of a Modified Bi-Axial Composite Test Specimen

Classic bi-axial test specimens have typically been a cruciform design with a tapered thickness gage section. A gage section is created using a computer numeric controlled (CNC) milling machine. This milling process inflicts initial damage to the specimen which can cause inaccurate failure data. A new bi-axial cruciform test specimen has been developed using Finite Element Analysis (FEA). The new specimen was fabricated without milling the gage section. Aluminum shims have been incorporated into the design of the specimen to allow bi-axial stress to control the failure of the specimen. Uni-axial tests have been completed to accurately determine material property values. These values were then used in the Finite Element Model (FEM) developed to design the new specimen. Results from the FEM indicate that this new cruciform specimen can yield more accurate results than that of the classic bi-axial specimen.