Compressive properties of thin tow-based discontinuous composites

Ultra-thin tow-based discontinuous composites are an emerging class of composite materials which can be used for high performance applications in a wide range of industries. They offer significant advantages compared to continuous composites, such as reduced waste material, enhanced formability and even increased mechanical properties. However, the properties of composite materials under compression are often a limiting factor in structural design. Measuring the compressive properties of composites is also non-trivial, as premature failures are occurring often with the existing testing standards. Finally, the compressive response of discontinuous composites is currently unclear as the existing studies are limited. This work presents a full experimental campaign on the characterization of the compressive response of ultra-thin tow-based discontinuous composites. A uniaxial test is initially employed which reveals instabilities, premature failures and large experimental scatter. Afterwards, a sandwich beam bending test is employed which allows to measure the compressive properties accurately with low variability. The compressive strains measured exceed 1 %, which is also the tensile limit for this material. The agreement between the tensile and compressive strength was investigated by using scanning electron microscopy which revealed that the damage was controlled by matrix deformation in the tow interfaces. • Ultra-thin TBDCs were manufactured and tested under compressive loading using two different experimental setups. • The direct uniaxial compressive test led to bending and premature failures at about 80 % of the tensile strength. • The strain-to-failure reached with the Sandwich Beam Bending method exceeded 1 %. • Tape shear-out was a key damage mechanism which is closely connected to the tape pull-out observed during tensile testing.