Fatigue evaluation of composite bolted and bonded joints

This study evaluates the static and fatigue behavior of composite bolted and bonded joints made from PEKK (polyether-ketone-ketone) thermoplastic composite matrix. Specimens used in this investigation were long discontinuous fiber (LDF) AS4/PEKK graphite/thermoplastic composite laminates. Bonded joints were made by either adhesive bonding or fusion welding. In some cases, specimens were bonded without any surface pretreatment. In other cases, the surfaces were either grit blast or corona treated prior to bonding. Fusion bonded joints were prepared by either induction welding or thermabonding. Bolted joints were made using either thermoplastic or titanium fasteners with two different clamp-up levels. All bonded joints evaluated gave comparable static strengths. For the bolted joints, while no significant change in static strength with clamp-up was observed, clamp-up did have a significant effect on fatigue performance.