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.
Highlights
Many of composite absorbers are designed to dissipate large amounts of impact energy under axial crushing, bending or combined loading with controllable collapse manner in the collision event
In this paper experimental analysis was performed to study the effect of stitching on controllable crack growth in off-axis crushing behaviour and energy absorption of carbon/epoxy twill-weave composite box composite
Two fracture mechanisms of bundle fracture and interlaminar crack propagation in MixedMode I/II were found for all composite boxes at off-axis crushing process
Summary
Many of composite absorbers are designed to dissipate large amounts of impact energy under axial crushing, bending or combined loading with controllable collapse manner in the collision event. In their work an off-axis angle load dynamic effects in front of crash were examined at an angle of 0, 5, 10, 15 and 20 degrees Their results showed that the energy absorption capacity had significantly affected tube with various oblique angle, impact velocity and wall thickness. Due to crack propagation in Mixed-Mode I/II and more friction and bending resistance at one side of composite box which firstly contacted the crushing platen, the amount of SEA at off-axis loading of 10 ̊ was the maximum in comparison with other off-axis crushing loadings They showed that natural flax fibers had the main advantage over the synthetic fibers (e.g. carbon and glass) of providing both resistance and progressive failure (effective crack growth resistance) in the wall of composite box absorbers (see Figure 1). This research studied a controlling process to reinforce the laminate through the thickness using natural fibre yarns to improve the crack resistance during the crushing process known as effective crack growth
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