Radial Corrugated Composite Tube

AN EXPERIMENTAL INVESTIGATION INTO CRUSHING BEHAVIOR OF RADIAL CORRUGATED COMPOSITE TUBE Elfetori F. Abdewi, Shamsuddeen Suliman, A.M.S. Hamouda, E. Mahdi Mechanical and Manufacturing Engineering Department, Faculty of Engineering, University Putra Malaysia, UPM, Serdang, Selangor, 43400, Malaysia

[email protected], Tel: (603) 89466330 and Fax (603) 86567122 Abstract This paper presents the effect of corrugation geometry on the crushing behavior, energy absorption, failure mechanism, and failure mode of woven roving glass fibre/ epoxy laminated composite tube. Experimental investigations were carried out on three geometrical different types of composite tubes subjected to compressive loading. On the addition to a radial corrugated composite tube, cylindrical composite tube, and corrugated surrounded by cylindrical tube were fabricated and tested under the same condition in order to know the effect of corrugation geometry. The results showed that, CCT and RCCT specimens crush with progressive folding forming continuous fronds, which spread radial outwards and inwards in the form of a mushrooming failure. However, RCSCT specimen crushes in interaction between upper and lower side of specimen. It exhibits lower total energy absorption than other two types. Corrugation geometry shows more stability under axial compression load than cylindrical tube. The results also show that, radial corrugated composite tube has more specific energy absorption than cylindrical composite tube. Keywords: Corrugated composite tubes; Energy absorption capability; Axial compression crushing

1. Introduction

The design of air, sea, and ground vehicles is increasingly driven by minimum weight considerations and by concerns for passenger safety. Composite structures are light, can be tailored in composition and shape, and can provide high crashworthiness when used as part of an energy-dissipating device [1]. As a part of engineering applications, composite tubes replacing metal products on many applications. High attention was given to produce composite tubes and testing it. They utilize these researches in composite crushing behavior and energy absorption. There is a considerable amount of published data on the response of composite tubes to axial crushing [2-5]. Many of these studies utilize circular cross-section tubular specimens to determine the energy absorption capability of the material. This paper focuses in studying the effect of corrugation across a cylindrical composite tube mentioned as Radial Corrugated Composite Tube RCCT on energy absorption capacity, failure mechanism, and failure mode of woven roving glass fibre/epoxy laminated composite tube. Circular Composite Tube CCT have been also fabricated and tested under the same conditions in order to maintain an effective comparison between different geometries. Radial Corrugated Surrounded by Circular composite Tube RCSCT have been fabricated and tested. RCSCT, which is a combination of CCT and RCCT specimens, contributes the research regarding the effect of the geometry on the energy absorption capability of composite material structures.

2. Experimental setup 2.1. Geometry and material Three types of specimens have been investigated, Circular Composite Tube CCT, Radial Corrugated Composite Tube RCCT, and Radial Corrugated Surrounded by Circular Tube RCSCT. The three structures are made of woven roving glass fibre/epoxy 600 g/sqm. All specimens fabricated under the same conditions with a fixed number of layers equal to six. The height (h) for both structures is same, while the diameter (d) of CCT structure is equal to mean diameter of RCCT structure (dm), where dm is the average of (dup) and (dlw), however, RCSCT is a combination of RCCT covered by CCT. Details on specimens’ geometry are given in Table 1. Table 1. Description of woven roving composite tubes specimens Type of tube

No. Wall Height Upper Lower Mean Cylinder No. of thickness diameter diameter diameter diameter of layers tested spcs. n t h dup dlw dm d (mm) (mm) (mm) (mm) (mm) (mm)

CCT

6

3.7

150

-

-

-

160

5

RCCT

6

3.5

150

182

138

160

-

5

RCSCT

6

4

150

189

138

-

189

3

2.2. Fabrication process The principle of wet winding process was used for the fabrication of all types of specimens. However, there is a difference in the details of fabrication process for each type due to the difference of the final shape need to be produced. A hand-lay-up process was used for the fabrication process. The tube was fabricated by rolling the woven roving fibreglass onto a rotating mandrel of suitable circular section. The woven roving fibre is passed through a resin bath, causing resin impregnation. 2.3. Test procedure Test was carried out under the same condition for all types of specimens. Static uniaxial compression load was applied using an Instron 8500 digital-testing machine with full scale load range of 250 KN. Load platens were set parallel to each other prior to the initiation of the test. From three to five replicate tests were conducted for each specimen. The tests were carried out at a speed of 15 mm/min. Load and displacement were recorded by an automatic data acquisition system.

3. Results and discussion 3.1. Failure modes As shown in Fig. 1, CCT tubes were crushed progressively from one end by splaying mode. In each crush test the axial load increased initially and micro-fragmentation was observed. As the load picked up, the tube wall expanded outward. With the platen moving downward the longitudinal cracks advanced by splitting the tube wall in to many segments. These segments were forced by the axial load to bend outwards in the shape of fronds. However, RCCT has a similar folding failure mode as that of the CCT. As shown in Fig. 2, the load first attains a high value then it drops to a lower level in first and second stages. However, after a small displacement, a steady fluctuating load was established. Subsequently, at the last stage load rise up rabidly due to end of crushing zone. RCCT exhibit high load carrying capacity with obviously high buckling resistance and minimum fluctuating load along RCCT crushing length was observed. RCSCT specimens exhibit more rigidity under the axial compression force. It is fractured in a form of interaction between the upper and lower parts of the specimen. These fractures propagated along the specimen forming complete crush of the specimen (see Fig. 3). Since RCSCT is a combination of CCT and RCCT with three layers each, it exhibits lower total energy absorption. 3.2 Crush Force Efficiency (CFE) CFE is the ratio between average crush load and initial crush failure load. It is useful to measure the performance of an absorber. It can be calculated as CFE =

P P max

Where Pmax and P are the maximum initial and the average crushing load, respectively. As far as the initial peak value of the load coincides with the highest peak force value, the desired value of the CFE parameter is equal to 1, which is difficult to achieve in practice, but an ideal absorber is said to exhibit a crush force efficiency of 100%. The results of crush force efficiency and other parameters were listed in Table 2. Table 2. Crashworthiness parameters of cylindrical and radial corrugated composite tubes

Pmax

P

Es

CFE

SE

(KN)

(KN)

(KJ/Kg)

(%)

(%)

CCT

56.622

49.943

10.2

88.2

65.85

RCCT

75.315

68.088

12.2

90.4

72.00

SRCCT

35.996

22.258

3.57

61.84

76.67

Specimen type

150 125

Load (KN)

100 75 50 25 0 0

25

50

75

100

125

150

Displacement (mm)

Figure 1. Load-displacement curves and deformation history of CCT specimens 150 125

Load (KN)

100 75 50 25 0 0

25

50

75

100

125

150

Displacement (mm)

Figure 2. Load-displacement curves and deformation history of RCCT specimens 150 125

Load (KN)

100 75 50 25 0 0

25

50

75

100

125

150

Displacement (mm)

Figure 3. Load-displacement curves and deformation history of RCSCT specimens

3.3. Stroke Efficiency (SE) Crushing of a tube will lead to compaction of the tube. This results in a continuously increasing load level as the deformation increases. The relative deformation of the absorber, at which compaction takes place, is referred to as the stroke efficiency (SE) of the absorber. The SE can be obtained as

SE =

u h

Where u and h represent the crush length and length of the tube, respectively.

3.4. Specific energy absorption (Es) To compare different materials, it is necessary to consider the specific energy, which is defined as the amount of energy absorbed per unit mass crushed material. Therefore, the specific energy (Es) that is dependent on the structure geometry was used for comparing the energy absorption of all three specimens. Figure 4 shows the load displacement curve of CCT, RCCT and RCSCT. Specific energy absorption (Es) can be calculated as

Es =

P Aρ

Where P is the average crush load, A is cross-sectional area of the tube, and ρ is the density of the composite tube. High values of Es indicate the lightweight absorber.

150 125

Load (KN)

100 CCT

75

RCCT RCSCT

50 25 0 0

25

50

75

100

125

150

Displacement (mm)

Figure 4. Load-displacement curve of CCT, RCCT and RCSCT

4. Conclusion 1- The quasi-static crushing behaviour of woven roving composite tubes is affected by the structural geometry. 2- Radial corrugation geometry has a high positive effect in elimination of sliding of the structure. 3- Radial corrugation composite tube exhibited better energy absorption capability than cylindrical composite tube. 4- RCCT and CCT exhibited high value of crash force efficiency. 5- RCSCT crushed at lower load than other two types of tested composite tubes. It also exhibits lower values of tested parameters except specific energy as recorded above.

Acknowledgement The authors would like to thank Universiti Putra Malaysia and staff for the financial support for this research. References Anne-Marie Hart, Norman A.F. Michael F.A (2000). Energy absorption of foam-filled circular tubes with braided composite walls. Eur. J. Mech. A/Solids 19 31-50. Hull, D (1983). Axial crushing of fiber reinforced composite tubes. In Structural Crashworthiness, T. Wierzbicki. Butterworths, London, pp. 118-35. Thornton, P. H (1986). The crush behaviour of glass fiber reinforced plastic sections. Cmp. Sci. Tech., 27 199-224. Hull, D. A (1991). Unified Approach to progressive Crushing of Fibre-Reinforced CompositeTubes. Composites Science and Technology 40 377-421. Mahdi, E., Sahari, B.B., Hamouda, A.M.S., Khalid, Y.A (2002). Crushing behaviour of cone-cylinder-cone composite system. Mech. Composite structure 2 99-117.