Impact damage testing on composite marine sandwich panels. Part 2: Instrumented drop weight

Marine grade hybrid sandwich panels are designed in accordance with BS EN ISO 12215-5:2008 using a wet lay-up and cured under vacuum pressure. The high fibre content composite laminate skins use marine grade orthophthalic polyester, POLYLITE® 440-M850, resin and chopped strand mat (CSM)/woven E-glass; the core is DIVINYCELL® H100 closed cell linear polyvinyl chloride (PVC) foam. Impact damage testing followed American Society for Testing and Materials (ASTM) D7766-11 procedure C and ASTM D7136/D7136M-05. Impact damage was sustained by the default hemispherical indentor and further ‘standard’ geometrical indentor rocks – conical, pyramid and cylindrical. The investigation reviews the current state of affairs in impact sandwich testing procedures. A 50–80% through thickness penetration criteria is proposed following noted shortcomings in the standard originally intended for laminates. It is shown that the panel overall flexural rigidity to thickness ratio better describes the transition between ‘thin’ to ‘thick’ impact response; force measurements indicate that strain rate effects need to be considered; dent indentation can only be assessed through data acquistion; destructive damage observation sectioned specimen observations describe the impact damage sustained under the various indentor conditions, as well as the roles played by both the face composite skins and the core material.