Effect of hybridisation on the compressive behaviour of glass/carbon fibre hybrid composites comprising different types of carbon fibres
Topic(s) : Special Sessions
Co-authors :
Aree TONGLOET (UNITED KINGDOM), Xun WU (UNITED KINGDOM), Michael R. WISNOM (FRANCE)Abstract :
Two different hybrid composites were studied to investigate their compressive behaviour and failure mechanisms using an unconventional 4-point flexural test with sandwich beam configuration to mitigate the stress concentrations in traditional direct compression tests [1]. The sandwich beam was composed of a top skin which was the tested hybrid composite configuration, a solid core, and the bottom skin made of IM7/8552, as shown in Figure 1a [2]. The top skin consisted of 913 S-glass/M55 high modulus carbon fibre (SG1/M551/SG1) and 913 S-glass/TC33 high strength carbon fibre (SG1/TC331/SG1). A 4-point flexural test fixture with a universal testing machine was used and the strain measured with unidirectional strain gauges. Figure 1b shows the experimental setup with an adjustable 4-point bending fixture to support the specimen. The load-compressive strain and calculated stress-strain responses were plotted, the failure was observed, and the experimental results were compared to the pure low-strain material from previous studies to observe the hybrid effect. It was found that the compressive failure strain of the carbon in the hybrid composites was improved for both hybrid systems, but the failure characteristics were significantly different. This study shows that the type of low-strain fibre material is a key feature controlling the failure characteristics of hybrid composites in compression.
The failure characteristics from SG1/M551/SG1 involved small carbon fibre fragmentations across the width of the beam, as shown in Figure 2a. The average compressive load-compressive strain response from SG1/M551/SG1 showed non-linearity, with a knee-point. The stiffness of the material changed and loading was carried on until reaching the final failure. The average knee-point compressive strain was 0.49% and the average final failure compressive strain was 0.78%. The experimental compressive failure strain was compared to the value from the study on pure M55 [3] which was 0.318%, showing the improvement with hybridisation.
The failure of SG1/TC331/SG1 is shown in Figure 2b, with compressive failure including fibre splitting along the length of the beam, with evidence of delamination. The compressive load–compressive strain response from SG1/TC331/SG1 also showed a non-linear response until reaching the final failure and the average final failure compressive strain was 2.609%, showing the improvement with hybridisation compared to the baseline compressive failure strain of TC33 carbon fibre which was about 1.50% [4]. The experimental results show the improvement of the compressive failure behaviour in both hybrids when compared to the baseline compressive strain of the carbon fibre in each case.
References
The failure characteristics from SG1/M551/SG1 involved small carbon fibre fragmentations across the width of the beam, as shown in Figure 2a. The average compressive load-compressive strain response from SG1/M551/SG1 showed non-linearity, with a knee-point. The stiffness of the material changed and loading was carried on until reaching the final failure. The average knee-point compressive strain was 0.49% and the average final failure compressive strain was 0.78%. The experimental compressive failure strain was compared to the value from the study on pure M55 [3] which was 0.318%, showing the improvement with hybridisation.
The failure of SG1/TC331/SG1 is shown in Figure 2b, with compressive failure including fibre splitting along the length of the beam, with evidence of delamination. The compressive load–compressive strain response from SG1/TC331/SG1 also showed a non-linear response until reaching the final failure and the average final failure compressive strain was 2.609%, showing the improvement with hybridisation compared to the baseline compressive failure strain of TC33 carbon fibre which was about 1.50% [4]. The experimental results show the improvement of the compressive failure behaviour in both hybrids when compared to the baseline compressive strain of the carbon fibre in each case.
References