THE NANOCLAY INFLUENCE ON IMPACT RESPONSE OF LAMINATED PLATES

Abstract

PROTECTION OF INDUSTRIAL, MILITARY AND CIVIL ENGINEERING STRUCTURES AGAINST IMPACT LOADINGS HAVE GAINED A LOT OF ATTENTION, SPECIALLY AFTER THE 9/11 TERRORIST ATTACKS. AN ECONOMICAL AND VIABLE OPTION TO CONVENTIONAL AND HIGH COST BALLISTIC MATERIALS IS THE USE OF FIBER GLASS/EPOXY COMPOSITES, BUT FOR IMPACT APPLICATIONS THEIR TOUGHNESS STILL HAS TO BE ENHANCED. STUDIES DEVELOPED BY YASMIN ET AL. AND ISIK ET AL. DEMONSTRATED THAT BY ADDING A SMALL AMOUNT OF NANOCLAYS INTO EPOXY SYSTEMS, A SENSIBLE INCREASE ON MECHANICAL PROPERTIES CAN BE OBTAINED. TO INVESTIGATE HOW THE PLATE IMPACT STRENGTH IS AFFECTED BY THE PRESENCE OF NANOCLAYS, A SET OF FIBER GLASS-EPOXY-NANOCLAY LAMINATE COMPOSITES WITH 16 LAYERS AND 65% ¯BER VOLUME FRACTION IS MANUFACTURED BY VACUUM ASSISTED WET LAY-UP. FIBERS HAVE A PLAIN-WEAVE CON¯GURATION WITH DENSITY OF 180 G/M2, WHILE THE EPOXY RESIN SYSTEM IS MADE OF DIGLYCIDYL ETHER OF BISPHENOL A RESIN WITH ALIPHATIC AMINE AS THE CURING AGENT. THE NANOCLAY (NANOMER I30E) IS AN ORGANICALLY MODI¯ED MONTMORILLONITE CERAMIC AND IT IS EXFOLIATED INTO THE EPOXY SYSTEM IN A 1%, 2%, 5% AND 10% RATIO IN WEIGHT WITH RESPECT TO THE MATRIX. THE SQUARE PLATES HAVE A 150 MM EDGE AND THICKNESS OF 2.4 MM. THE METHODOLOGY USED FOR THE IMPACT TEST IS BASED ON THE ASTM D5628-01 STANDARD. THE RESULTS HAVE SHOWN THAT FOR THE FOUR EDGES CLAMPED CONDITION NOT ONLY THE DELAMINATION PHENOMENON IS REDUCED BUT ALSO THE DAMPING IS INCREASED DURING THE REBOUNDS. HOWEVER, THE MOST FAVORABLE NANOCLAY CONCENTRATION SEEMS TO BE CLOSE TO 5%. THIS CAN BE DUE TO THE VIBRATION MODE SUPERPOSITION ASSOCIATED TO A STIFFNESS ENHANCEMENT.