Low Velocity Impact Damage Tolerance Studies on Glass-Epoxy Laminates - Effects of Material,Process and Test Parameters

摘要

An effort has been made to study the effects of variable incident impact energy and laminate thickness (obtained by varying the number of fabric layers at constant moulding pressure and also by varying the pressure for a fixed number of fabric layers),on the low velocity impact damage tolerance of GFRP composite laminates (woven E-glass fabric in a room temperature cure epoxy system LY556/HY951).Repeated drop tests were conducted using an in-house built drop weight impact tester.Number of drops to failure (Nf),was considered as the impact damage tolerance index.Correlations between Nf and composite material parameters (fiber weight fraction -Wf,laminate thickness - t,number of fabric layers - L) and a test parameter (incident impact energy E) were found out and the bounding limits for these were defined.Critical values of impact energy (Ec) and laminate thickness (tc) were defined (for the particular resin - hardener system chosen for the study) which can quite possibly be used as designer's guidelines.A new ratio,(t/Wf},was introduced for the study of composite systems where both fiber weight fraction and laminate thickness get affected upon alteration of a process parameter (the pressure - P as in this case).