Energy absorption of composite plates and tubes

A total of 28 graphite/epoxy nat-plate specimens and six graphite/epoxy tube specimens ere crushed under quasi-static conditions to provide a basis far comparison of the measured energy absorbency of these two geometries. The energy absorbency of each specimen was measured, and the specific sustained crushing stress (SSCS) was determined. All plate and tube specimens were manufactured from AS4/3501-6 graphite/epoxy with the same layup and thickness. thus providing a common laminate for comparison. Flat-plate specimens of two different widths were tested to determine the effect of the testing fixture on the observed energy absorbency. The flat-plate results indicate that the specific energy absorbency per unit thickness is nearly independent of the specimen width, with a small contribution to the energy absorbency by the testing fixture. However, this calculated value of measured energy absorption due to the test fixture is within the scatter of the data. The results also indicate that specimen geometry affects specimen stability and therefore the failure modes exhibited by the specimen during crushing. Similar failure modes were observed in the tube and flat-plate specimens with the flat plates absorbing 12% less energy per unit mass. Consequently, flat-plate specimens can be used as a lower-cost alternative to tube specimens or in test programs requiring simpler geometries.