This paper describes the development of the Composite Procedure (CTP) which both simplifies and improves the accuracy of side impact test procedures. The CTP test introduces a new type of compliance testing, computer aided compliance, and it was first introduced in May 1987 by Volkswagen as a means of designing car side structure for effective occupant protection. In April 1988, the method was put forward as an alternative procedure for side impact testing. At this stage the procedure consisted of the exterior barrier loading, the door to occupant contact (step 1), a single interior loading device which examined the interior door response (step 2), followed by continued deformation with the external barriers until the chosen crash severity was reached (step 3). Step 4 then consisted of the calculation of the "computer based" dummy model to give biomechanical output such as thoracic accelerations. In April 1989 this model of the occupant was improved to include additional outputs such as rib accelerations, chest deflection, viscous anterior and pelvic load against time. A two stage model was also introduced. This included separate thoracic and pelvic interior loading devices (ILDS) together with an additional segment below the thorax to assess abdominal loads. Later models replaced the 4 step by step stage with continuous measurement and calculation, controlled by one computer. With this model, the calculation determines what data is measured within the loop process, between the hardware inputs of the test, the structure and ILD responses, and the occupant dummy model at any particular moment, and controls the test rig accordingly. Validation of the procedure indicates that accuracy and repeatability of the results are excellent. A standard test rig is developed which can accommodate any barrier type, various ILDs, and vehicles whose size varies from a mini up to a medium sized van.
Abstract