Assessment of the residual strength of marine laminate panels

Abstract

Marine grade laminates are subjected to a wide variety of impacts from objects of all shapes and sizes and to different impact energy levels. The impacts considered here may be simulated by quasi-static indentation. The impact may range from between barely visible impact damage (BVID) to complete laminate penetration. The damage sustained will influence the residual properties of the composite material. The laminate panel configuration is designed in accordance to the Small Craft Standard BS EN ISO 12215-5 for CE certification, fabricated by the hand lay-up technique following ASTM D5687. Tensile, compressive and flexural properties characterisation in accordance with ISO 527-4, ASTM D3410 and ASTM D790 respectively were conducted. Impacted by quasistatic indentation, ASTM D7766M-11 and ASTM D6264M-04, when the load is applied slowly pressing an indentor on the 152 mm square laminate specimen surface. Two support configurations for QSI are possible - procedure A, rigid support and procedure B, simply supported on a 127 mm diameter circular opening, by two different shaped indentors. The indentors are the standard hemisphere of 12.7 mm diameter, a pyramid, having a 30o apex angle and 52.8 mm maximum dent depth and a 15 mm diameter cylinder. Following which, the damaged laminate is tested in a compressive after impact (CAI) apparatus, ASTM D7137M, for determining the compressive residual strength. The tensile and flexural residual strength were also assessed by testing the damaged specimens using the tensile and flexural standard testing procedures to obtain the strength-retention factor (SRF) of the laminate panel. A new concept of the Modulus retention Factor (MRF) is also introduced. Composite materials designer will benefit greatly from a means of predicting the post impact behaviour of the composite laminates.