M.B. Ioannidis

Crashworthy capability of composite material structures

Abstract Considerable research interest has been directed towards the use of composite materials for crashworthiness applications, because they can be designed to provide impact energy absorption capabilities which are superior to those of metals when compared on a weight basis. This review draws together information from a variety of sources to compare the findings of researchers in this field. The anisotropy of composite materials means that there are a great number of variables controlling mechanical behaviour and much of the investigative experimental work conducted in this area has concentrated on composite tubular specimens. The material, geometrical and experimental factors which have been shown to affect the energy absorption capability of such samples are related and a comparison is made of some of the specific energy absorption values which have been quoted in the literature. A selection of methods for predicting composite material energy absorption capability is presented and consideration is given to some of the more practical aspects of employing composite materials for crashworthiness purposes.

Crashworthy characteristics of axially statically compressed thin-walled square CFRP composite tubes: experimental

In this paper the results of experimental works pertaining to the crash behaviour, collapse modes and crashworthiness characteristics of carbon fibre reinforced plastic (CFRP) tubes that were subjected to static axial compressive loading are presented in detail. The tested specimens were featured by a material combination of carbon fibres in the form of reinforcing woven fabric in thermosetting epoxy resin, and they were cut at various lengths from three CFRP tubes of the same square cross-section but different thickness, laminate stacking sequence and fibre volume content. CFRP tubes were compressed in a hydraulic press of 1000 kN loading capacity at very low-strain rate typical for static testing. The influence of the most important specimen geometric features such as the tube axial length, aspect ratio and wall thickness on the compressive response and collapse modes of the tested tubes is thoroughly analysed. In addition, the effect of the laminate material properties such as the fibre volume content and stacking sequence on the energy absorbing capability of the thin-wall tubes is also examined. Particular attention is paid on the analysis of the mechanics of the tube axial collapse modes from macroscopic and microscopic point of view, emphasizing on the mechanisms related to the crash energy absorption during the compression of the composite tubes.

Finite element simulation of the axial collapse of metallic thin-walled tubes with octagonal cross-section

Abstract The present paper deals with the implementation of the explicit FE Code LS-DYNA to simulate the crash behaviour and energy absorption characteristics of steel thin-walled tubes of octagonal cross-section subjected to axial loading. The collapse procedure is successfully simulated and the obtained numerical results are compared with actual experimental data from small-scale models and useful concluding remarks pertaining to the design requirements of the crushing process are drawn.

The static and dynamic axial crumbling of thin-walled fibreglass composite square tubes

In the present paper we report on the behaviour and crashworthiness characteristics of square composite tubes subjected to static and dynamic axial compression exerted by a hydraulic press and a drop-hammer, respectively. The effect of specimen geometry, i.e. of thickness and axial length, and of the loading rate on the energy absorbing capability are studied in detail. Attention is directed towards the mechanics of the axial crumbling process from macroscopic and microscopic point of view for facilitating engineering design calculations of the amount of energy dissipated and for a somewhat more complete aspect on the actual fracture mechanism during the failure of the composite material tested. A theoretical analysis of the collapse mechanism of the components tested under axial compression is proposed, leading to a good approximation of the energy absorbed during crushing.

Analysis of failure mechanisms observed in axial collapse of thin-walled circular fibreglass composite tubes

Theoretical analysis of the failure mechanism of the stable mode of collapse of thin-walled fibreglass composite tubes under static axial compression, based on experimental observations and taking into account all possible energy absorbing mechanisms developed during the process, is reported. Crushing loads and the energy absorbed are theoretically predicted. The proposed theoretical model was experimentally verified for various composite materials and tube geometries and proved to be very efficient for theoretically predicting the energy absorbing capacity of the shell.

The static and dynamic axial collapse of fibreglass composite automotive frame rails

Abstract An automotive frame rail of hourglass cross-section, made of a glass fibre/ vinylester composite, was designed for use in the apron construction of the car in order to obtain a high degree of crashworthiness at this location of the car body. The crashworthy behaviour of this structural component in axial compression at various strain rates (head-on collision) was studied experimentally. The modes of collapse at macroscopic scale, the microscopic fracture patterns and the energy absorbing capability of such rail beams were examined and discussed. A theoretical analysis of the collapse mechanism of the components tested under axial compression is proposed leading to a good approximation of the energy absorbed during crushing.

Analytical modelling of the static and dynamic axial collapse of thin-walled fibreglass composite conical shells

A theoretical analysis of the observed stable collapse mechanism of thin-walled circular frusta and tubes, crushed under axial static and/or dynamic loading, for calculating crushing loads and the energy absorbed during collapse, is reported. The analysis is based on experimental observations regarding the energy-absorbing collapse mechanisms developed during the crushing process. The proposed theoretical model was experimentally verified and proved to be very efficient for theoretically predicting the energy-absorbing capability of the conical shells.

Crushing of hybrid square sandwich composite vehicle hollow bodyshells with reinforced core subjected to axial loading: numerical simulation

The present paper is dealing with the implementation of the explicit FE Code LS-DYNA to the simulation of the crash behaviour and energy absorption characteristics of thick-walled square tubular crashworthy bodyshells made of hybrid sandwich composite panels with integral FRP (fibre-reinforced plastic) hollow cylindrical inserts subjected to axial compressive loading. The obtained numerical results are compared with actual experimental data from small-scale physical models in terms of deformation modes, energy absorption capability, load/deflection history and crush zone characteristics, showing very good agreement.

On the compression of hybrid sandwich composite panels reinforced with internal tube inserts: experimental

Edgewise and flatwise compression was performed on hybrid sandwich composite specimens with internal tube reinforcements, in order to evaluate the load-carrying capacity and energy absorption capability of such composite structures and provide data related to panel design for crashworthiness applications. Extensive experimental data were recorded on the compressive properties of the tested hybrid composite panels and the failure modes were examined.

Energy absorption capability of fibreglass composite square frusta subjected to static and dynamic axial collapse

The crashworthy behaviour of square frusta of fibreglass composite material subjected to axial compression at various strain rates is reported. The effect of specimen geometry and the loading rate on the energy absorbing capability was experimentally studied. The mechanics of the axial crumbling process from macroscopic and microscopic points of view were also investigated theoretically and experimentally. The collapse modes at macroscopic and microscopic scale during the failure process were observed and analysed. A theoretical analysis of the observed stable collapse mechanism of the components crushed under axial compression, for calculating crushing loads and energy absorbed during collapse, is proposed. A good agreement between theoretical and experimental results was obtained indicating the efficiency of the theoretical model in predicting the energy absorbing capacity of the collapsed shell.