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Automated composite manufacturing processes such as Automated Tape Laying (ATL) and Automated Fibre Placement (AFP) are effective methods to produce high quality, lightweight parts. Typically, preimpregnated fibres or tapes are laid side-by-side onto a tooling surface to generate the composite preform. Although these two main technologies are widely used to produce large composite components, inconsistencies such as overlapping tapes or gaps between adjacent tapes may occur during the manufacturing. Within this study, the effect of gaps and overlaps, so-called defects, has been investigated experimentally. Tensile and compressive testing has been carried out on specimens with a quasi-isotropic, symmetric layup into which artificial defects in various defined formations were introduced. Of particular interest were the strength knockdown factors and changes in the failure mode.

Z-pins have been shown to significantly improve delamination resistance and impact strength of carbon fibre reinforced (CFRP) composites. In this paper, an experimental investigation of the influence of different fatigue parameters (mean opening/sliding displacement, amplitude, frequency, number of cycles) on the through-thickness reinforcement (TTR) is presented. For mode I, it is shown that the degradation on pin behaviour during fatigue is mostly affected by the applied displacement amplitude. The degradation is primarily caused by surface wear. Due to the brittleness of the Z-pins, mode II fatigue does not have a significant effect for very small sliding displacements. Exceeding a critical displacement causes the pin to rupture within the very first cycles

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