Microcracking in Cross-Ply Laminates due to Biaxial and Thermal Loading

Abstract

DOI: 10.2514/1.20798 This paper presents a methodology to predict microcracking and microcrack density in both surface and internal plies ofa symmetriccross-ply laminateunder biaxial mechanical andthermal loadingconditions. Thethermoelastic properties of the microcracked laminates at different crack densities were determined by finite element analysis of the unit cells bounded by the microcracks. Analytical expressions for the stiffness and coefficients of thermal expansion as functions of crack densities were obtained in the form of response surface approximations. These analytical expressions were then used to predict the formation of a new set of microcracks by equating the change in strainenergyintheunitcellbeforeandaftertheformationofthemicrocrackstothecriticalfractureenergyrequired for their formation. Analytical expressions obtained as response surface approximations were also used to predict progressive microcracking. Both displacement and load control cases were considered along with thermal loading. Results from the current methodology agree very well with published data. Nomenclature