Tensile Testing

A well-known method for determining the mechanical properties of fibre reinforced composites is tensile testing; however, there is no standard protocol like in traditional fields such as metallurgy. Based on the composition and nature of the material - specific test conditions need to be applied such as wet, dry or fully swollen samples, geometry and range of applied strain (Fig. 3.2) [18, 20-25]. For example the elastic modulus of unreinforced alginate hydrogels has been shown to be 77.88 ± 18.67 kPa and the inclusion of gelatin electrospun fibres increased the tensile modulus to 0.50 ± 0.11 MPa. The failure strength increased by a factor of 17.6 times on incorporation of the gelatin electospun fibres [24]. In another study, the tensile modulus of a PCL-alginate composite increased from 30-200 kPa to 180-400 kPa depending on the level of fibre loading [25]. The effect of the fibres was high when 1 wt.% alginate gel was used, where a modulus mismatch between the gel and fibres was greatest. To evaluate the effectiveness of fibre reinforcement, tensile testing should be performed at a relatively low strain rate, which is considered as the gold standard for making comparisons between studies.

Schematic representation of various tests used for characterising the mechanical properties of fibre reinforced composites

Fig. 3.2 Schematic representation of various tests used for characterising the mechanical properties of fibre reinforced composites: (a) compression, (b) tension, (c) confined compression, (d) dynamic testing (Note arrow indicates the direction of loading. © by Elsevier - reprinted with permission)

 
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