OPEN-HOLE KENAF FIBER COMPOSITES UNDER ELEVATED TEMPERATURES: EXPERIMENTAL AND NUMERICAL APPROACHES

Abstract

AN EXPERIMENTAL PROGRAMME TO INVESTIGATE NOTCHED STRENGTH OF OPEN-HOLE WOVEN FABRIC KENAF FIBER REINFORCED POLYMER (WKRP) COMPOSITE PLATES UNDER QUASI-STATIC TENSILE LOADING. TESTING SERIES INCLUDES VARIATION OF LAY-UP TYPES, NUMBER OF HOLES IN SINGLE ROW AND DIFFERENT ELEVATED TEMPERATURES. IT WAS FOUND THAT ALL TESTING COUPONS WERE FAILED IN NET-SECTION, FRACTURE AND FAILURES INITIATED AT THE HOLE EDGE DUE TO STRESS CONCENTRATIONS AND PROPAGATED TO THE PLATE EDGE. WKRP PLATES EXPOSED TO ELEVATED TEMPERATURE WERE STRONGER THAN UNDER ROOM TEMPERATURE DUE TO MATRIX TOUGHENING MECHANISM. LATER, TWO-DIMENSIONAL NUMERICAL MODELLING FRAMEWORK WERE DEVELOPED FOLLOWING PREVIOUSLY EXPERIMENTAL SERIES. A CONSTITUTIVE MODEL OF TRACTION-SEPARATION RELATIONSHIP WERE INCORPORATED BY USING TWO MODELLING TECHNIQUES, I.E., EXTENDED FINITE ELEMENT MODEL (XFEM) AND COHESIVE ZONE MODEL (CZM). THESE PHYSICALLY-BASED MODEL USED INDEPENDENT MATERIAL PROPERTIES TAKEN FROM LITERATURES OF SIMILAR SUB-SETS WKRP LAY-UPS TESTED. MOREOVER, TO TAKE INTO ACCOUNT THE EFFECTS OF ELEVATED TEMPERATURES, ELEVATED TEMPERATURES AND THERMAL EXPANSION COEFFICIENT WAS INCORPORATED WITHIN THE MODELLING FRAMEWORK. BOTH MODELLING TECHNIQUES WERE EVALUATED AND COMPARED, ALBEIT TO INSIGNIFICANT DIFFERENCES OF MAXIMUM LOAD OUTPUT IN BOTH TECHNIQUES, XFEM DOES NOT REQUIRES APRIORI FAILURE PATH COMPARED TO CZM. GOOD AGREEMENT BETWEEN THE PREDICTED AND MEASURED NOTCHED STRENGTH WAS FOUND, BOTH DISPLAYED A CONSISTENCE OF NET-SECTION FAILURES.