Effects of delamination failure in crashworthiness of laminated composite box structures
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.
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.