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NUMERICAL MODELLING AND EXPERIMENTAL INVESTIGATION OF CFRP STRUCTURES FOR LARGE DEFORMATIONS
thesisposted on 13.08.2019 by ARCHIT MILIND DESHPANDE
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
The use of carbon-ﬁber reinforced composite materials is not novel in the ﬁeld of motorsports industry. Their use in collapsible structures for crashworthiness is however not fully understood and predicted. Due to the complex failure mechanisms occurring within the material, the energy absorbing capacity cannot be easily predicted. The need to understand their contributions in crashworthy structures is thus of great importance. Furthermore, failure of carbon-ﬁber composites is highly dependent on the geometry of structure. Problems arise in both experimental and numerical modelling of these structures. Although many explicit FEA codes exist, they often include experimental parameters that need to be calibrated through either coupon tests or actual crash tests. As composite structures become more commonly used in automotive industry, it is necessary to set some guidelines to successfully model and simulate composite crashworthy structures.
The numerical modelling was done in LS-DYNA Enhanced composite damage MAT54. The material properties were conﬁgured using experimental coupon tests. The tests were conducted on square composite tubes. The Speciﬁc Energy Absorption (SEA) of the tubes were calculated through several coupons. As SEA is a function of geometry, it was necessary to conduct tests with similar geometry as seen in nosecone. MAT54 was chosen to simulate both crush and crash simulations due to its capability to simulate element level crushing. Furthermore, various modiﬁcations within the material model, improve its accuracy to determine composite failure.
The research utilizes the characterization of material inputs in MAT54 by conducting quasi-static compression tests on simpler but similar geometry. By utilizing inputs, a zonal optimization was conducted on the nosecone geometry. The number of layers, layer orientations and ply thicknesses were varied to vary the energy absorbed per zone. The deceleration of the vehicle can thus be controlled, and the weight of the structure could be reduced.