Fibre Waviness Generation and Measurement and Its Effect on Compressive Strength

Abstract

Artificial fibre waviness was produced by laying up unidirectional carbon fibre-epoxy on a curved plate, and then straightening it before curing. A technique was developed for measuring out-of-plane waviness using a surface displacement transducer mounted on a traversing table. Measurements within the laminate were made by splitting it open along ply interfaces treated with release agent prior to curing. Typical maximum misalignment angles at the centre of a 2 mm thick panel were in the range 0.7 to 1 degree. In-plane waviness data was also generated by splitting the plies along the fibre direction. Tests in a pin-ended buckling rig gave compressive failures with reductions of compressive and tensile surface strain of only 17% and 26%, despite in-plane misalignments of up to 24 degrees in the surface plies.