This paper presents the experimental investigation on the progressive deformation behaviour of uni-directional pultruded composite tubes subjected to an axial impact load. Pultruded square and circular profiles with glass-polyester and glass-vinylester combinations were used for this study. Two types of triggering profiles were incorporated to investigate the effect of triggering on the energy absorption. All above combinations were investigated for three different impact velocities (9.3, 12.4 and 14m/s). The crushing peak and mean load characteristics of the composite tubes with different triggering profiles and their progressive failure modes are presented. To measure the impact velocity and the impact force, a contactless method using digital image correlation technique was adopted. The effects of the geometry profile, triggering, strain rate and the type of resin on energy absorption of the composite tubes were studied in detail.KEYWORDS: Specific energy absorption; Triggering mechanism; Crushing; Progressive failure; Composite tubes
IntroductionA great deal of research and development has been carried out in the past decades to design safer automobiles. Out of the factors considered for safety criteria, the crashworthiness has attracted significant attention due to its multiple functions. The functions of the crashworthiness structures are to (i) absorb energy, (ii) keep the occupant compartments intact and (iii) ensure tolerable deceleration levels for driver and passengers during the crash event. To meet the above functions, the automobile industry is focused on the design architecture and materials used to produce crashworthiness. As a result, different forms of the energy absorbers [1,2] and combinations of high strength metal alloys are used for crashworthiness structures. The focus on new innovative materials which yield superior strength to weight ratio [3] has been increased in order to meet the future stringent crashworthiness norms and to enhance the fuel economy target.On the other hand, there is a considerable amount of experiments [4][5][6][7] conducted on composite material to assess the energy absorption. It is a well-known fact that one can
This paper focuses on the quasi-static crushing characteristics and the corresponding energy absorption of nine different shapes of small-scale composite tubes. The idea is to choose suitable cross sections and geometrical shapes of the composite tubes which can yield progressive deformation and higher energy absorption; the finalized geometrical shapes will be studied further for the inner core of a sacrificial cladding structure against blast loading. All the composite tubes have been manufactured by a hand lay-up technique using E-glass fabric and polyester resin. Quasi-static axial crushing tests have been conducted to understand the deformation patterns and the corresponding load-deformation characteristics of each composite tube. The effect of dimensions (thickness to diameter ratio) on the specific energy absorption of each composite tube was studied. Finally, the quasi-static test parameters such as the peak crush load, mean crush load and the specific energy absorption of all these composite tubes were compared. From this unique study, it was found that the specific energy absorption of special geometrical shapes (hourglass type -A, hourglass type -B, conical circular type -X and conical circular type -Y) of the composite tubes is significantly higher than the standard and uniform profiles such as the square and the hexagonal cross sections.
This paper presents the quasi-static crushing performance of nine different geometrical shapes of small-scale composite tubes. The idea is to understand the effect of geometry, dimension and triggering mechanism on the progressive deformation of small-scale composite tubes. Different geometrical shapes of the composite tubes have been manufactured by hand lay-up technique using uni-directional E-glass fabric (with single and double plies) and polyester resin. Dedicated quasi-static tests (144 tests) have been conducted for all nine geometrical shapes with different t/D (thickness to diameter) ratios and two triggering profiles (45 ⁰ chamfering and tulip pattern with an included angle of 90 ⁰ ). From this unique study, it was found that the crushing characteristics and the corresponding energy absorption of the special geometrical shapes are better than the standard geometrical shapes such as square and hexagonal cross sections. Furthermore, the tulip triggering attributed to a lower peak crush load followed by a steady mean crush load compared to the 45 ⁰ chamfering triggering profile which resulted into a higher energy absorption in most of the geometrical shapes of the composite tubes.
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