Impact Damage Resistance and Tolerance of Stitched Carbon Epoxy Laminates

The damage resistance and tolerance of fourteen near quasi-isotropic composite laminates have been evaluated. Three different manufacturing techniques, namely the conventional prepreg lay-up, resin transfer moulding and resin film infusion, have been used to produce a series of tape, woven (both plain and five harness satin weaves) and stitched woven laminates with nominal thicknesses of 1mm and 3mm. This afforded a study to be carried out on the effects of thickness, fibre architecture, manufacturing route and stitching effects upon the impact resistance and tolerance of carbon/epoxy laminates. Results have revealed that the use of woven fabric composite laminates over tape is advantageous in obtaining a more impact damage resistant material. Although the use of stitching to further enhance damage resistance of woven fabric structures proved to be of no significant benefit, some improvement in damage tolerance was evident. This apparent superiority in terms of damage tolerance, however, was not realized due to a reduction of the undamaged compression strength as a result of fibre crimping from the stitching. The present work also demonstrated that resin transfer moulding, resin film infusion and prepreg lay-up techniques produce laminates of comparable impact performance.