Research associate and manager, Hercules Advanced Materials and Systems Co. (HAMSCO), Magna, UT
In this work, the static and dynamic Mode II fracture properties of several thermosetting resin-based composite laminates are presented. Two classes of materials are explored. These are homogeneous thermosetting resins and toughened, multiphase, thermosetting resin systems. A new dynamic Mode II test is presented for composite laminates based on an end-notched flexure (ENF) specimen geometry. The specimen is impacted in three-point bending with an instrumented impact tower. Fracture initiation and propagation energies under static and dynamic conditions are determined analytically and experimentally. The test results show that the toughened systems provide superior fracture initiation and higher resistance to propagation under dynamic conditions. The results indicate that static fracture testing is inadequate for determining the fracture performance of composite laminates subjected to conditions such as low velocity impact. A good correlation between the basic Mode II dynamic fracture properties and the performance in a combined material/structural compression after impact (CAI) test is found. The results underscore the importance of examining rate-dependent behavior for determining the longevity of structures manufactured from composite materials.
Paper ID: CTR10081J