Third Day Poster Session, 17 June 2010 - NanoTR-VI
Third Day Poster Session, 17 June 2010 - NanoTR-VI
Third Day Poster Session, 17 June 2010 - NanoTR-VI
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<strong>Poster</strong> <strong>Session</strong>, Thursday, <strong>June</strong> <strong>17</strong><br />
Theme F686 - N1123<br />
Structural hybrid composites with Polymer/MWCNTs reinforced nanocomposite interlayers<br />
*<br />
Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul 34956, Turkey<br />
Abstract— The focus of this study is to investigate toughening of conventional carbon fiber/epoxy prepregs by using surface<br />
reactive nanofibers containing MWCNTs as nanocomposite interlayers. Electrospun P(St-co-GMA)/MWCNTs nanofibers<br />
with the average diameter of 500 nm are laid up between carbon fiber prepreg plies and the hybrid composites are cured by<br />
vacuum bagging. Mechanical flexural tests of the hybrid composites are carried out. The results demonstrated significant<br />
improvement in flexural modulus and strength due to reinforced nanocomposite interlayers.<br />
Interlaminar modes of failure are of concern in laminated<br />
composite applications, particularly under shear and impact<br />
loading conditions. Poor interlaminar strength is usually<br />
considered as polymer matrix dominated problem for which<br />
the toughened and reinforced nanocomposites can provide<br />
substantial improvement. As reported in our previous work,<br />
the surface reactive P(St-co-GMA)/MWCNTs nanofibers are<br />
promising materials in reinforcing and toughening the epoxy<br />
resin [1]. Moreover, it was indicated [2] that nanofibers<br />
support the load and resist crack opening and delamination.<br />
Here P(St-co-GMA)/MWCNTs composite fiber mats were<br />
incorporated as interlayer reinforcement.<br />
Inhouse P(St-co-GMA) copolymers were first dissolved in<br />
DMF at %30 wt polymer concentration. The solutions were<br />
stirred magnetically for 24 hour to obtain homogeneity and<br />
then electrospun to produce the non-woven fiber mats. Syringe<br />
pump (NewEra NE-1000 Syringe Pump) was utilized to<br />
control the solution <br />
electrospinning. Applied voltage was adjusted to 15kV while<br />
the grounded collector was placed 10 cm away from the<br />
syringe needle.<br />
The fiber mats were placed between the prepreg plies to<br />
form reinforced interlayers by two different approaches. In the<br />
first method, nanofibers were electrospun onto a collector and<br />
peeled later to be laminated between successive plies. Second,<br />
P(St-co-GMA) were directly electrospun onto the conductive<br />
carbon fiber prepregs that were later stacked. Considering the<br />
efficiency of production, first method was preferred. Curing<br />
cycle was completed 36 hours at 100°C.<br />
The laminates with and without nanofiber reinforced<br />
nanocomposite interlayers were tested using Universal Testing<br />
Machine-ASTM D790 standard in 3 point bending mode.<br />
Different ply orientations were considered. Lay-up sequences<br />
were prepared as laminates of (0/0/0), (0/90/0) and (90/0/90)<br />
and hybrid composites of (0/m/0/m/0), (0/m/90/m/0) and<br />
(90/m/0/m/90) where “m” stands for fibrous mat interlayers.<br />
Preliminary results suggested that the interlaminar strength<br />
of the laminates were improved by using the reactive<br />
nanofibrous webs as interlayer reinforcement. Significant<br />
improvement in flexural modulus up to 15% was achieved by<br />
the hybrid composites compared to laminates without the<br />
nanocomposite interlayers. Depending on the ply orientations,<br />
flexural strength and modulus values of hybrid composites<br />
differed (See Figure 1). 0/0/0 lay-up sequence did not<br />
demonstrate significant improvement, in preliminary tests.<br />
That would be related to vacuum in curing process or any<br />
experimental error while laying up. Flexural tests of 0/0/0 and<br />
0/m/0/m/0 specimens were repeated. Flexural Modulus (E y )<br />
and strength (S F ) of toughened and untoughened composites in<br />
0/0/0 lay-up were still low compared to sequences. Nanowebs<br />
enhanced the E y and S F in 0/0/0 lay-up while reinforcing the<br />
nanocomposite interlayers as in 0/90/0 and 90/0/90<br />
orientations.<br />
In order to investigate the failure mode of the composites,<br />
Scanning Electron Microscopy (SEM) was utilized. SEM<br />
micrographs revealed that failure mode in hybrid composites<br />
differ from composites without the interlayers, as shown in<br />
Figure 2.<br />
Figure 1 Flexural Strength and Flexural Modulus of reinforced<br />
and unreinforced prepregs in 0/0/0, 0/90/0, 90/0/90 sequences.<br />
Figure 2 Failure Mode of Toughened Carbon/ Epoxy Prepregs<br />
(left) and P(St-co-GMA)/MWCNTs (right-small) nanofibers and<br />
nanofibrous webs @100<br />
*Presenting author: kaanbilge@sabanciuniv.edu<br />
[1] Ozden E.; Menceloglu Y.; Papila M. "Electrospun<br />
Polymer/MWCNTs Nanofiber Reinforced Composites “Improvement<br />
of Interfacial Bonding by Surface Modified Nanofibers”" , 2009<br />
MRS Fall Meeting Symposium FF proceedings.<br />
[2] Gao Y.; Sagi S.; Zhang L.; Liao Y.; Cowles D. M.; Sun Y.; Fong<br />
H. 2008 J. App. Polym. Sci. 110, 2063–2070.<br />
6th Nanoscience and Nanotechnology Conference, zmir, <strong>2010</strong> 741
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