Trans RINA, Vol 152, Part B2, Intl J Small Craft Tech, 2010 Jul-Dec
Figure 4.3: Acoustic Emission parameter Correlation for Layup 2 specimens 4.3(a) Layup 3 (Csm+Db+Ud) Experimental Results
Interestingly the third layup consisting of CSM+DB+ Uni Directional (UD) had high ultimate strength but low stiffness until the first ply failure. The process of crack initiation and progression is shown in Figure 5.1. However the
post-failure behaviour observed had
increased residual strength as shown in Fig. 5.2. Further application of load past the first failure point, the CSM fibres sheared away in tension shown as kinks in the load-displacement plot. The DB layers were more flexible, and remained intact. Upon further loading, the bend started to vanish and the specimen began to straighten up, thus behaving like a tensile specimen, as shown in Figure
carried the entire load until final collapse. Hence addition of uni-directional proved beneficial.
5.1. Only the uni-directional fibres fibres in composite curved panels
4.3(b) Layup 3 (Csm+Db+Ud) Acoustic Emission Correlation
Layup 3 had two CSM, two UD and three DB layers. The initial damage was observed at 9% of the ultimate load at 370 sec between second and third layers, as shown in Figure 5.3. Though no reduction of load was observed (due to the presence of UD fibres which carried most of the load), other AE parameters showed extensive matrix cracking and
fibre breakage – energy of 2103eu,
amplitude of 95dB and event duration of 4076μs were observed. The six peaks in the energy and event duration plots demonstrate progressive delamination until final collapse. The first major damage was observed at 438 sec at 14% of ultimate load, as the delamination between second and third layers. The energy release was 6496eu, amplitude was 100dB, rise time was 469μs and duration was 20912μs during the second stage of damage. Further delaminations were observed at 550sec (14% of ultimate
B-100 ©2010: The Royal Institution of Naval Architects
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