Natural fiber composites are less expensive, can be recyclable, biodegradable and tend to have less adverse effect on human health and environment than synthetic fiber. The composites of natural fibers are mostly used in the manufacturing of automobile parts, electronic devices and also in strengthening of construction materials.
Researchers led by Professor Heow Pueh Lee from National University of Singapore proposed to use natural fiber composites in the manufacturing of automotive interiors where shock resistance is needed. They performed the shock test using a shock tube on flax/epoxy and flax/polypropylene unidirectional and cross ply laminated composites in order to compare the resistance of polypropylene and epoxy and also to check the performance of both unidirectional and cross ply. Other researchers involved in the study are Dr. Wern Sze Teo and Dr. Le Quan Ngoc Tran from Singapore Institute of Manufacturing Technology. The research work is now published in journal, Composites Part B.
There are few methods available for the impact test of the flax fibre they are, the controlled detonation of explosives, dropping weights, firing projectiles, shock tubes, etc. In his idea he had chosen a shock wave method in impact studies. The shock wave tube is made up of a long rigid cylindrical tube made of metal with gas at both high and low pressure separated by a diaphragm. The region of high and low pressure is called as driver and as driven section. Here the sensor is placed at some position in order to measure the parameters such as gas, temperature, density etc.
Here the authors had demonstrated this test flax epoxy and flax polypropylene. The flax epoxy material is manufactured by thermosetting preparation. In Thermosetting method the vacuum assisted resin infusion technique is used. Before it is cooling down to room temperature the unidirectional flax fiber was cut out with the dimensions of 270 mm x 270 mm, and dried in an oven at 80 °C for 24 h. Then this unidirectional flax fiber is kept in an aluminium plate for moulding purpose and sealed on a vacuum bag. The epoxy resin is kept at a room temperature for 15 min in order to remove the air bubbles after the oven is degassed with the resin. Before the demoulding of the resin it is kept at a room temperature for 24 h and after demoulding, it is kept at 80 °C for 16 h.
The thermoplastic method is used for the manufacturing of flax polypropylene by compression molding process. It is cut with a dimension of 450 mm x 450 mm and it is molded from stainless steel and it is subjected into a platen press. Before it is cooling down to a room temperature the polymer is placed at 180 °C under 5 bar for 10 min and also subjected to an increased pressure of 20 bar at 190 °C for 10 min.
This shock loading test is done by using a shock tube with helium as a driver gas. The length the shock tube is about 4.6 m with 1.3 m of driver section and 3.3 m of driven section. Kistler sensor is placed on the clamping plates in order to record the peak pressure at the test.
Thus the shock test was conducted successfully on both the flax epoxy and flax polypropylene composites in both unidirectional and cross ply methods. This shows that the cross ply materials have shown a better impact strength than the unidirectional materials. Particularly in cross ply materials the cross ply flax polypropylene shows better strength than cross ply flax epoxy as it has no visible cracks. Hence, the cross ply flax fiber reinforced polypropylene composites is preferable for the manufacturing of materials where shock load impacts in needed.
Kede huang1, Abhishek vishwanath Rammohan1, Umeyr Kureemun1, Wern Sze Teo2, Le Quan Ngoc Tran2, Heow Pueh Lee1 Shock wave impact behavior of flax fiber reinforced polymer composites. Composites Part B, volume 102, 2016, Pages 78-85.Show Affiliations
- Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore
- Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075, Singapore
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