EFFECT OF TUFTING ON THE RESPONSE OF NON CRIMP FABRIC COMPOSITES

Abstract. This paper examines the effectiveness of tufting in enhancing the through the thick-ness properties of non crimped fabrics. The response of tufted and untufted carbon/epoxy non crimped fabric composites produced using resin infusion is investigated in axial tension and compression and cyclic [±45] loading. The out-of-plane response is studied in mode I and mode II delamination tests. Tufted material has significantly higher delamination resistance and lower in plane properties in tension and compression. Tufted and untufted non crimp fab-ric composites have similar response in shear in terms of both plastic strain and strength. Op-tical strain measurements allowed monitoring of the two dimensional damage field in cyclic experiments. Damage tends to be localised in untufted specimens, whereas it becomes more uniform across the width of specimens with tufts. Material models for untufted and tufted non-crimped fabric composites simulating both non-linear in-plane behaviour and delamina-tion damage were developed. Material parameters were estimated from experimental results, and both material submodels were implemented in a commercial explicit finite element code which allows the incorporation of delamination behaviour using cohesive interface elements. A comparison of experiments and finite element model results simulating coupons verified the implementation of the models