PSI - Issue 14

Kishora Shetty et al. / Procedia Structural Integrity 14 (2019) 849–854 Kishora Shetty et al. / Structural Integrity Procedia 00 (2018) 000 – 000

853

5

(a)

(b)

(c)

Figure 3. (a) Low magnification; (b) and (c) high magnification SEM micrographs of ILSS tested specimen from condition C.

As seen in SEMmicrographs for non-aged and twodifferent agingconditions, theILSS test using three-point bend test mainly resulted in inter laminar de-bonding failure. Please note that some cases we can see surface coatings breakage kind of features which is nothingbut the resin coated beforeconditioning the specimens to prevent direct exposure to moisture of cut surfaces. At higher magnification there are evidences of fibre pull-out and fibre breakage. Low magnification SEM Micrographs shown in figure 1 (a), 2 (a) and 3 (a) shows de-lamination between plies due to applied load during ILSS test. At highermagnificationwe can see de-bonding between fibre and matrix due to applied load at ILSS test as shown in figure 1 (b), 2 (b) and 3 (b). At very high magnificationwe can see some evidenceof fibre breakage as shown in figure 1 (c), 2 (c) and 3 (c). Whencompared between three conditions A, Band C, it is clearly seen that specimens undergone conditioning at ConditionBand C are shown increased de-bonding as compared to specimens of conditionA (un-aged). This clearly indicates that the absorbed moisture content plays important role in increasedde-bonding therebybringing down the ILSS. 4. Conclusions Hot-wet environmental conditions on composite materials has a very important role to play in performance and durability of compositeparts. The combined effects ofwater absorption and thermal environment havegreater effects onCFRP laminates. This indicates the importance of carrying out s tudies on moisture absorption at different hot-wet conditions on CFRP composite materials. Here from this study we have seen that moisture absorption significantly brings down the ILSS of an Aircraft grade CFRP Composite material. Moisture absorption follows Fickian behaviour. Moisture absorption depends on both temperature and amount of relative humidity in the environment. But at the end i.e., after reaching the saturation, the effect of moisture on ILSS is same. This is evident as both condition B and C shown similar ILSS strength. As specimens of both these conditions have reached saturation