The influence of kenaf contents and stacking sequence on drop-weight impact properties of hybrid laminated composites reinforced polyvinyl butyral composites

Abstract

<jats:p> For the high cost of aramid fibres and the necessity for finding alternatives which are environmentally friendly, a portion of aramid was substituted by woven kenaf at various sequences and thicknesses, to identify the proper arrangement for producing helmet shell. Drop-weight impact tests were conducted on different configurations of 19 layers of kenaf and aramid reinforced polyvinyl butyral film, which were fabricated by the hot press method. Effects of fibre content, layering sequence and energy absorption of the laminated composites were studied at three different impact energies 50, 75, 100 J. Results suggested that the behaviour of hybrid laminates has a positive effect in terms of energy absorbed and impact resistance, due to lower failure strain of kenaf fibres. Additionally, placing woven kenaf layers alternate with aramid layers provides higher impact loads and absorbed energy than placing woven kenaf and aramid separately, especially at impact level 100 J. For example, the absorbed energy of the 17 Aramid/2 Kenaf Alt. (H1A) is 72.99 J, while for 17 Aramid/2 Kenaf (H1) is 66.04 J. The closed curves indicated the success of the samples in absorbing the dissipated energy at various impact energies values. It could be deduced that it is possible to replace the aramid fibre in various composites industries by kenaf fibre, to minimize harmful environmental effects and cost of petroleum products. </jats:p>

Failure mechanisms of kenaf/glass sandwich laminates subjected to low velocity impact loading

“…From the results, it is indicated that fully kenaf composite withstand lower energy than designated energy which were 5 J, 10 J and 15 J and exhibited the opened-loop curve at 5 J, 10 J and 15 J graphs. This result was similar to the results reported by Salman SD, 9 where the pure kenaf composites could not withstand higher impact energy compared to a hybrid composites. According to Majid et al, the oscillatory behaviour of the force in Figure 3(c) happened due to vibrational motions between the impactor and impacted surface.…”

“…It can be concluded that G/K/G composite can still resist the impact energy at 10 J while the G/K/K and K/K/K composites experienced penetration by the impactor. Similar to the study reported by Salman SD, 9 it was found that large amount of energy are absorbed by hybrid composites compared to pure composites made of one type of material. Also, Salman’s study had also shown that the layering sequence of alternating the natural fibre mat (kenaf mat - K) and the synthetic fibre (aramid mat – A) mat tend to have better energy absorption compared to stacking the same type of material at one end such as A/K/K.…”

“…This failure mode explained the opened-loop curve of the force against displacement graph in Figure 3(a). 9 The G/K/K hybrid exhibited indention, matrix cracking and delamination on the top surface of the composite while the bottom showed the fibre breakage failure. For the G/K/G hybrid composite, there was a small dot of delamination on the top surface of the hybrid caused by the impactor but the matrix cracking and delamination failure modes were exhibited at the bottom of the hybrid.…”

“…Also, Salman’s study had also shown that the layering sequence of alternating the natural fibre mat (kenaf mat - K) and the synthetic fibre (aramid mat – A) mat tend to have better energy absorption compared to stacking the same type of material at one end such as A/K/K. 9…”

“…As for the stacking sequence, the placement of kenaf and aramid layers alternately could withstand higher impact loads compared to stacking kenaf layers and aramid layers separately. 9…”