IMPACT DAMAGE ANALYSIS WITH STRESS CONTINUITY CONSTRAINTS FULFILMENT AT DAMAGED-UNDAMAGED REGIONS AND AT LAYER INTERFACES

Abstract

LOW-VELOCITY IMPACTS HAVE A RELEVANT IMPORTANCE FOR SAFETY OF HIGHLY SUSCEPTIBLE TO DAMAGE LAMINATED AND SANDWICH COMPOSITE STRUCTURES. IN ORDER TO EFFICIENTLY SIMULATE IMPACTS, A 3D COST EFFECTIVE ZIG-ZAG MODEL IS DEVELOPED THAT A PRIORI FULFILLS THE CONTINUITY OF OUT-OF-PLANE STRESSES AT THE LAYER INTERFACES, THE CONTINUITY OF STRESSES UNDER IN-PLANE VARIATION OF PROPERTIES ACROSS UNDAMAGED AND DAMAGED REGIONS AND GENERAL BOUNDARY CONDITIONS. DERIVED FROM A FORMER MODEL ABLE TO ACCURATELY PREDICT STRESSES FROM CONSTITUTIVE EQUATIONS AT A LOW COST, ITS ADVANTAGE LIES IN THE CAPABILITY OF BEING REFINED KEEPING FIXED THE NUMBER OF UNKNOWNS. A MODIFIED HERTZIAN CONTACT LAW THAT FORCES THE TARGET TO CONFORM TO THE SHAPE OF THE IMPACTOR AND THE NEWMARK’S IMPLICIT TIME INTEGRATION SCHEME ARE USED FOR COMPUTING THE CONTACT FORCE TIME HISTORY. THE PROGRESSIVE DAMAGE ANALYSIS IS CARRIED OUT USING STRESS-BASED CRITERIA. NON-CLASSICAL FEATURE, A CONTINUUM DAMAGE MESOMECHANIC MODEL IS EMPLOYED THAT ACCOUNTS FOR THE EFFECTS OF LOCAL FAILURES IN HOMOGENIZED FORM BY MODIFYING THE STRAIN ENERGY EXPRESSION. FIBER, MATRIX AND DELAMINATION FAILURES ARE PREDICTED USING STRESS-BASED CRITERIA, AND THEN THE MODIFIED STRAIN ENERGY EXPRESSION IS EMPLOYED FOR COMPUTING STRESSES. HENCE FROM THE ENERGY STANDPOINT, RESIDUAL PROPERTIES ARE ACCOUNTED FOR AS THEY ARE IN THE REALITY. AS SHOWN BY THE COMPARISON WITH EXPERIMENTS, A CLOSED-FORM SOLUTION BY THE GALERKIN’S METHOD, AS A SERIES EXPANSION OF TRIAL DISPLACEMENT FUNCTIONS, ACCURATELY SIMULATES THE CONTACT FORCE AND THE DAMAGE PROGRESSIVELY ACCUMULATED. THE RESULTS SHOW THE IMPORTANCE OF IN-PLANE STRESS CONTINUITY FOR OBTAINING ACCURATE PREDICTIONS.