PSI - Issue 17

Haibao Liu et al. / Procedia Structural Integrity 17 (2019) 992–1001 Liu H. et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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values of the predicted maximum major strain and central OOP displacement are 1.2% and 3.6 mm, respectively, which are only about 8% lower than the experimentally measured values. To further confirm the accuracy of the numerical FE model, the predicted central OOP displacement versus time trace was also compared with the corresponding experimental results, see Fig. 9b. It can be seen from the results in these figures that, although the modelling studies gave somewhat lower maximum values than the experimentally measured values, the general trend and overall response of the composite test specimen were predicted extremely well using the FE model.

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Fig. 9. The predicted and experimental results for 37 J impact: (a) the central OOP displacement versus time trace and (b) the predicted contact pressure.

Fig. 10. The experimentally measured and predicted degrees of damage resulting in the rear-face of the CF/PEEK test specimens from using a gelatine projectile with (a) 37 J and (b) 72 J impact energies.

6.3. Damage in the CF/PEEK composite

The next step is to assess the capability of the numerical FE model that has been developed to predict the impact damage created in the composite by the impact event. The impact events were modelled at two impact energies of 37 J and 72 J. The experimental and predicted degrees of damage, which resulted in the CF/PEEK composite specimens, Figs. 10a and 10b, respectively. The term “DAMAGESHR” represents the predicted shear damage in the composites. It was found that at an energ y level of 37 J (‘Test GCP - I’) that the prediction from the numerical modelling studies was ‘(a) no visible damage ’ , which is in agreement with the experimental results, Fig. 10a. When an impact energy level of 72 J (‘Test GCP - IV’) was modelled, failure was predicted to be present only in the central area of the gelatine-impacted CF/PEEK composite, Fig. 10b. The experimental results revealed that some damage had indeed occurred in this region of the composite. In addition, the extent of the damage, as determined from the post-impact experimental observations on the composite specimen, is accurately predicted by the numerical studies.

Conclusions

This paper has focussed on experimental and numerical studies of the response of polymer-matrix fibre reinforced composites under impact loading by a soft objective. A high-speed camera was used to record the deformation of the projectile during the impact event. The recorded frames showed that the gelatine projectile behaved as a viscoelastic-plastic fluid. The gas-gun tests were performed using woven carbon-fibre reinforced poly