Effects of delamination failure in crashworthiness of laminated composite box structures

Ghasemnejad, Hessammaddin (2009) Effects of delamination failure in crashworthiness of laminated composite box structures. (PhD thesis), Kingston University, .


The brittle nature of the most of fibre reinforced polymer (FRP) composites causes they show high capability in. absorbing the impact energy in vehicular structures. This energy absorption is introduced by various fracture mechanisms. In this regard, the fracture study is one of the most important areas to be considered in investigating the energy absorption capability of composite box structures. Various fracture mechanisms such as fibre breakage and buckling, matrix cracking and crushing, debonding at the fibre-matrix interface and especially plies delamination play important roles in progressive failure mode and energy absorption of composite tubes. Delamination occurs as results of shear and tensile separation between fronds. The main objective of this research is to study the effects of interlaminar fracture toughness on the progressive energy absorption of composite structures under quasi-static loading. In this regard, Mode-I, Mode-II and mixed-Mode I/II interlaminar fracture toughness of various types of FRP composites with various laminate designs are studied experimentally to investigate the relationship between interlaminar crack propagation and the energy absorption capability and crushing modes of composite structural elements. Plan view of crushed CFRP and GFRP composite box struts The combination of brittle fracture, lamina bending, local buckling and transverse shearing crushing modes was found from experimental studies. New analytical solutions based on friction, bending and fracture mechanisms were proposed to predict the mean crushing force for each of these failure modes. The crushing process of composite boxes was also simulated by finite element software LS-DYNA and the results were verified with the relevant experimental and analytical results.

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