Comparisons of Various Configurations of the Edge Delamination Test for Interlaminar Fracture Toughness.
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CENTER
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Various configurations of Edge Delamination Tension EDT test specimens, of both brittle and toughened-matrix graphite epoxy reinforced composite laminates, were manufactured and tested. The mixed-mode interlaminar fracture toughness, G sub c, was measured using layups designed to delaminations would form naturally between the central 90 deg. plies and the adjacent angle piles. Laminates were also made with Teflon inserts implanted between the 90 deg. plies and the adjacent angle theta plies at the straight edge to obtain a planar fracture surface. In addition, interlaminar tension fracture toughness, GIC, was measured from laminates with the same layups but with inserts in the midplane, between the central 90 deg. piles, at the straight edge. All of the EDT configurations were useful for ranking the delamination resistance of composites with different matrix resins. Furthermore, the variety of layups and configurations available yield interlaminar fracture toughness measurement needed to generate delamination failure criteria. The influence of insert thickness and location, and coupon size on Gc values were evaluated.
- Laminates and Composite Materials