Examination of a micromechanics based failure criterion for non-crimp fiber reinforced composite laminates

Official URL: http://192.168.1.20/record=b1225685 (Table of Contents)

Warp-knit non-crimp fabric (NCF) reinforced polymer matrix composites manufactured by vacuum infusion (VI) have become appealing for structural applications, particularly in automotive parts, wind turbine blade production and marine industry. Their efficient and optimal use in structural design relies on the accuracy of the selected failure criterion typically specific to fiber reinforced composites. Experimental studies are conducted in order to measure the accuracy of the methodology of the applied failure criterion. This thesis focuses on a failure criterion via finite element based micromechanics, typically referred as micromechanics of failure (MMF) and its experimental assessment for NCF reinforced polymer matrix composites. Glass fiber NCF/Vinyl ester unidirectional (UD) and multidirectional (MD) laminates are produced by VI. The mechanical properties of laminates with their constituent materials, i.e. the glass fiber and cured vinyl ester, are also measured to be used in micromechanics computations. Representative Volume Element (RVE) of a single fiber embedded in the polymer matrix at measured fiber volume fraction is modeled in MSC. PATRAN and solved in MD. NASTRAN for elastic constants. This RVE is also used for calculating the stress amplification factors within the RVE at several nodes. Back calculations of the glass fiber and cured resin strength by multiplying the ply average stresses at failure (experimental) with the maximum stress amplification factor are compared with the tested strength of constituents. They match well indicating the efficiency and accuracy of MMF in predicting the failure of NCF laminated composites and suggest that MMF can be implemented in design optimization of laminated composites against failure.