TITLE:
Controllable Crack Propagation in Off-Axis Crushing of Stitched Composite Absorbers
AUTHORS:
N. Ghafari-Namini, H. Ghasemnejad
KEYWORDS:
Composite, Mechanism, Stitched, Crush, Off-Axis
JOURNAL NAME:
Open Journal of Composite Materials,
Vol.5 No.4,
September
16,
2015
ABSTRACT: Crack growth resistance plays a different role in crashworthiness analysis since the progressive
energy absorption is based on controllable fracture mechanisms. In this regard, the present paper
studies the efficient crack growth resistance in off-axis crushing of composite tubular structures
by implementing natural fiber yarns. One of the through-to-thickness reinforcement methods
known as stitching has been chosen to influence the axial and off-axis crushing process. Improving
the crack growth resistance and appropriate fiber breakage at different stages of crushing process
can significantly improve the resistance force and consequently the energy absorption capability
of composite absorbers in axial and off-axis crushing. This analysis will be applied to non-stitched
and stitched CFRP composite boxes which showed brittle fracture and transverse shearing crushing
modes under off-axis loading of 10 degrees. The analytical methods are also implemented to
analysze the effect of various failure mechanisms such as bending, friction, bundle fracture, and
interlaminar crack growth for the observed crushing modes. The proposed model is able to predict
the crushing load and crush force efficiency in close agreement from experimental studies.