Notched response of non-crimp fabric thin-ply laminates

This paper presents an experimental investigation of the mechanical response of a new class of advanced composite materials manufactured using thin non-crimp fabrics. Tensile and compressive tests in both unnotched and notched specimens were performed using two different lay-ups. The notched tests were based on specimens with central cracks and with circular holes, loaded in tension and compression. Digital image correlation was used to monitor the onset and propagation of damage on the surface plies. The results show that the lay-up with blocked plies and with higher differences in fiber orientation angles between consecutive plies has lower unnotched strength. However, due to the larger fracture process zone observed in the notched tests, such lay-up has marginally higher notched strengths. A size effect on the strength was observed for both the open-hole tension and compression tests. The size effect and the associated notch sensitivity of thin non-crimp fabrics were similar to those observed in typical aerospace grade unidirectional pre-impregnated composite materials. It is also concluded that the thin non-crimp fabrics exhibit an improved response to bolt-bearing loads over traditional composite materials.