25. Inertial Impact Method for the Through-Thickness Strength of Composites

This work presents the design of a novel inertial impact test for the determination of the through-thickness tensile strength of composite materials at high strain rates. The principle behind this new test method is as follows: A rectangular plate specimen is impacted by a projectile that imparts a short compressive stress wave. This compressive wave will then travel through the specimen and reflect off of the free end becoming a tensile wave. The strength of a laminate composite is significantly higher in compression than in tension thus, the test parameters (e.g. specimen or projectile dimensions, projectile speed) can be selected such that the reflected tensile wave will cause failure in the specimen without exceeding the compressive strength. Full-field measurements can then be taken throughout the test and stress-strain curves can be reconstructed using the Virtual Fields Method. The stress-strain curves can then be used to determine the tensile strength of the composite. A preliminary design of test has been optimised using explicit dynamics simulations. Future work will include experimental validation of the test principle.