Estimation of transverse shear force during slamming impacts on a simply supported composite panel using a strain derivative method

Use of sandwich constructions in slamming regions of high speed marine craft has led to increased consideration of the applied transverse shear force. Low shear strength core materials can lead to transverse shear failure becoming a high risk failure mode. Direct measurement of transverse shear force is difficult without altering the structure of the hull panels. This work utilises a non-invasive strain derivative method to estimate the applied transverse shear force. The basis of this method is the correlation between applied bending moment, determined from surface mounted strain gauges, and transverse shear force. A simply supported 1000 × 500 mm instrumented sandwich panel has been tested in the Servo-hydraulic Slam Testing System. Impacts have been undertaken at 10° with vertical velocities from 1.0 to 3.5 m/s. The shear force to bending moment ratio has been compared with the ratio based on a uniformly distributed load, as frequently used in design. An increase of up to 68% for the slamming experiments is observed. This significant difference illustrates a greater applied transverse shear force in slamming regions than would be predicted through the application of a uniformly distributed load.