SEDL / STP / STP864-EB / STP32782S

First-Ply Failure of Graphite/Epoxy Laminates

Kistner, MD
Materials research engineers, Materials Laboratory, Air Force Wright Aeronautical Laboratories, Wright-Patterson Air Force Base, OH

Whitney, JM
Materials research engineers, Materials Laboratory, Air Force Wright Aeronautical Laboratories, Wright-Patterson Air Force Base, OH

Browning, CE
Materials research engineers, Materials Laboratory, Air Force Wright Aeronautical Laboratories, Wright-Patterson Air Force Base, OH

Pages: 18    Published: Jan 1985

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Abstract

In situ transverse-ply failure in AS-4/3502 graphite/epoxy laminates is investigated by determining crack density as a function of laminate axial strain. These results are then related to laminate stress-strain response. Results show that plateaus in either the longitudinal or transverse stress-strain curve are associated with a significant increase in transverse-ply crack density. Stress analysis reveals a departure of inplane stresses from classical lamination theory near free edges. These stresses are found to be a function of laminate-ply orientations and stacking sequence. Thus, the onset of transverse-ply cracking may be influenced by the free edge in a standard tensile coupon.