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Damage modes of the carbon/epoxy were investigated under low velocity

impact and the damages induced were observed using ultrasonic C-scan and optical
microscopy. Both devices show a good agreement on the damages result. Low velocity

impact was conducted with range velocities from 1.42 m/s to 2.42 m/s using 15.9 mm
diameter of hemispherical indenter. It was found that the damage size of the impact

test was slightly larger than the static test. Sudden drop occurring at 1.8 kN with large
deflection was observed in comparison with static test [93].

Wang et al. [100] studied the 3D woven basalt/aramid hybrid composites with

different samples configurations between interplay and intraply sequences in resisting
low velocity impact. It was found that the interplay hybrid composite had higher

ductile indices, lower peak load, and higher specific energy absorption in both warp
and weft directions than those of the intraply hybrid composite.

For the large part, the amount of energy dissipated during fibre pull-out
represents the impact strength of the tested specimen. The surficial adhesion between

fibre and matrix influenced the impact strength. A laminate with good bonding results

in shorter average of fibre pull-out lengths and cause lower impact strength. The fibre
pull-out is governed by the fibre breakage and bonding failure which depends on the

fibre tensile strength and interfacial shear strength, respectively. Impact problem can

be divided into two separate conditions: low velocity impact by a large mass (dropped
tool) and high velocity impact by a small mass (runway debris, small arms fire, etc.).

Izod, charpy and drop weigh can be classified as a low velocity impact test while split
Hopkinson pressure bar (SHPB) and gas gun can be categorized as a high-velocity

impact [101].

Low velocity impact test was done to investigate the impact energy absorption

characteristics of glass fibre hybridisation with kevlar fibre. The effect of stacking

sequences was also discussed with the variation of kevlar position either at front, rear
or middle surface of glass/kevlar hybrid composite. It was found that glass/kevlar

revealed the best energy absorption capacity with an increase of 80 % in comparison
to pure glass at the optimum volume fraction of Kevlar up to 3.4 % as depicted in

Figure 2.28 [102].

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