The mechanical behaviour of semi-crystalline polymers strongly depends on the initial underlying microstructure and its evolution during deformation. In polymeric composites, the interfacial region between the polymer matrix and reinforcing fiber is especially relevant for optimizing the composite’s mechanical performance since these interfacial regions often fail [1,2] by the interplay of many damage mechanisms that happen three-dimensionally. In this work, we performed a three-dimensional (3D) in-situ investigation under compressive load of a composite consisting of a polymer based on benzoxazine and polyetheramine [3] using X-ray microtomography (micro-CT), with the composite specimen having the carbon fibers orthogonally oriented to the loading z-direction. The 3D images enabled estimating the porosity change of the composite during the compression (Fig.1 a), visualising the barrelling effect in the specimen [4] and changes in the pores shape (Fig.1 b, red boxes), which almost completely collapsed at 5 kN. We used Digital Volume Correlation (DVC) [4] to track the relative movements between the 3D images after each compression state to retrieve the 3D displacement vector field and visualize the local strains changes that take place due to the applied force. The composite exhibits a heterogeneous strain field, with the largest strains observed after the first compression. 

References

[1] L. ElKhoury; J. C. Berg Journal of Adhesion Science and Technology, 2023, 37, 897-912.

[2] P. Narongdej; T Reddy; E. Barjasteh, Journal of Composite Materials, 2023, 57, 2389-2404.

[3] L. Pursche, A. Wolf, T. Urbaniak, K. Koschek, Frontiers in Soft Matter, 2023, 3.

[4] D Takano; N Lenoir; J Otani; SA Hall Soils and Foundations, 2015, 55, 906-915.