STP937

    Comparisons of Various Configurations of the Edge Delamination Test for Interlaminar Fracture Toughness

    Published: Jan 1987


      Format Pages Price  
    PDF Version (348K) 23 $25   ADD TO CART
    Complete Source PDF (8.2M) 23 $76   ADD TO CART


    Abstract

    Various configurations of edge delamination tension (EDT) test specimens were manufactured and tested to assess the usefulness of each configuration for measuring interlaminar fracture toughness. Tests were performed on both brittle (T300/5208) and toughened-matrix (T300/BP907) graphite reinforced composite laminates. The mixed-mode interlaminar fracture toughness Gc was measured during tension tests of (30/−302/30/90n)s, n = 1 or 2; (35/−35/0/90)s; and (35/0/−35/90)s layups designed to delaminate at low tensile strains. Laminates were made without inserts so that delaminations would form naturally between the central 90° plies and the adjacent angle plies. Laminates were also made with Teflon® inserts implanted between the 90° plies and the adjacent angle (θ) plies at the straight edge to obtain a planar fracture surface. In addition, Mode I interlaminar tension fracture toughness GIc was measured from laminates with the same layups but with inserts in the midplane, between the central 90° plies, 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 measurements, both pure Mode I and mixed mode, needed to generate delamination failure criteria.

    The influence of insert thickness and location, and coupon size on Gc values were evaluated. For toughened-matrix composites, laminates with 1.5-mil (38.1-μm) thick inserts yielded interlaminar fracture toughness numbers consistent with data generated from laminates without inserts. Coupons of various sizes yielded similar Gc values. The influence of residual thermal and moisture stresses on calculated strain energy release rate for edge delamination was also reviewed. Edge delamination data may be used to quantify the relative influence of residual thermal and moisture stresses on interlaminar fracture for different composite materials.

    Keywords:

    composite materials, delamination, fracture, toughness, graphite/epoxy


    Author Information:

    O'Brien, TK
    Senior research scientist, Aerostructures Directorate, U.S. Army Research and Technology Activity (AVSCOM), NASA Langley Research Center, Hampton, VA

    Johnston, NJ
    Senior research scientist, NASA Langley Research Center, Hampton, VA

    Raju, IS
    Senior scientist, Analytical Services and Materials, NASA Langley Research Center, Hampton, VA

    Morris, DH
    Professor and instructor, Virginia Polytechnic Institute, Blacksburg, VA

    Simonds, RA
    Professor and instructor, Virginia Polytechnic Institute, Blacksburg, VA


    Paper ID: STP24379S

    Committee/Subcommittee: D30.06

    DOI: 10.1520/STP24379S


    CrossRef ASTM International is a member of CrossRef.