Comparison of polymer composites behavior to low-velocity impact quasi-static indentation
Jarosław Bieniaś, Patryk Jakubczak, Barbara Surowska
Quarterly No. 3, 2013 pages 155-159
DOI:
keywords: polymer composites, static and dynamic loads, failure
abstract Abstract Fibre Reinforced Polymers (composites) are widely used in the aerospace industry due to their excellent quasi- static mechanical properties in relation to density. However, it is known that polymer composites do not have good resistance to dynamic loads, especially to low-velocity impact phenomena, which is one of the most important issues for composite structures, particularly in aerospace due to the effect it has on material structures. The purpose of this study was to investigate the differences in polymer composite behavior between low-velocity impact and the similar (the same boundary conditions) quasi- static indentation. The composites used in this study were: Carbon Fibre Reinforced Polymer (CFRP) and Glass Fibre Reinforced Polymer (GFRP) manufactured by the autoclave method (materials used in aerospace technology). Impact tests were carried out according to the ASTM D7136 standard. Quasi-static indentation was performed according to the ASTM D6264 standard. After the tests, the samples were subjected to non-destructive and microscopic testing methods to investigate the damage size and failure character. It was noted that low-velocity impact causes significant damage to both kinds of composite structures, while the quasi-static indentation under the same impact force level results in some internal degradation of the laminate structures (barely visible damage). However, the size of it is extremely different to the case of low-velocity impact. The failure types of composite structures after static and dynamic loads are similar. The major failure type in composites after static and dynamic loads are matrix cracks, delaminations, and in the case of impact fibres-cracks. To obtain similar damage character and size (as in the impact effect) in the composite structure on account of quasi-static indentation, a much higher force level in comparison to dynamic loads is necessary.