Compressive Behavior of a Thermoplastic Composite (GR/PEEK)

Abstract

The compressive properties of a graphite/thermoplastic composite (IM6/APC-2) were experimentally determined using unidirectional and multidirectional laminates. The notch sensitivity and damage tolerance of multidirectional laminates were also investigated by comparing the behavior of notched and impacted specimens with unflawed specimens. Whitney's average stress criterion was used to characterize the reduc tion in the compressive strength due to the presence of notches, while damage tolerance of impacted panels was compared directly using strength reduction. Resistance to low velocity impact was compared using a proposed empirical damage resistance parameter, γ, which was determined experimentally. The observed failure mechanisms were typical for a tough-resin composite. In general, the damage was limited to a small region immediately surrounding the source of the stress concentration and only minor delamination was observed. The unidirectional specimens failed due to a band of fiber kinking at a large angle to the applied load, while delamina tion was the dominant failure mechanism in the multidirectional laminates. C-scans of im pacted specimens indicated minimal damage compared with other thermoplastic and un toughened graphite-epoxy composites. The compressive properties of IM6/APC-2 compare favorably with similar commer cially available materials. The compressive longitudinal modulus (146 GPa) and strength (1062 MPa) are high and the notch sensitivity as measured by the characteristic length ( ao = 2.37 mm) is good. In particular, resistance to the initial impact was excellent when compared with untoughened graphite/epoxy systems [1].