Paper number 445

FAILURE ANALYSIS OF THICK COMPOSITE RINGS UNDER DIAMETRAL COMPRESSION

Hassan Mahfuz, Aloke Pal, Mojibur Rahman, Shaik Jeelani, Leif Carlsson^* and Peter Davies^**

Tuskegee University's Center for Advanced Materials
Tuskegee, AL 36088
*Mechanical Engg. Dept., Florida Atlantic University, Boca Raton, FL 33431
**IFREMER Center de Brest, BP 70, 29280 Plouzane, France

Summary

Ring specimens extracted from thick composite cylinders with nominal thicknesses of 6 to 12 mm have been tested under diametral compression. Rings with three winding angles were tested to examine the effect of orientation on the structural integrity of the cylinder. The objective of this investigation was to determine the failure modes of ring specimens under the given compressive load. To enhance delamination, some of the specimens were fabricated with embedded teflon sheets to simulate delamination in the wall. Two sets of tests were conducted; one was with the implanted delamination and the other without the teflon inserts. Rings with teflon inserts were of particular interest to visualize the growth of delamination crack at various stages of loading. It was observed that ring failure occurred by an extension of the implanted delamination around the periphery of the ring. The cracks opened at the initial stage of loading but closed quickly as the load and delamination increased. The crack continued to grow almost symmetrically towards the top side of the ring, and final failure occurred due to massive fiber fracture at locations perpendicular to the loading axis. Finite element analysis using layered elements was performed to analyze the compressive testing of the ring specimens. Details of the experimental and finite element studies are presented in this paper.

Keywords

composite structures, blucking, Finite Element Method (FEM).