Architecture effects for mode I trans-laminar fracture in over-height compact tension tests: Damage propagation and fracture response

An experimental study was carried out to investigate the effect of material architecture on the damage evolution in carbon/epoxy composites through Overheight Compact Tension (OCT) tests. Four representative lay-ups were designed for both the unidirectional (UD) and woven-based laminates. Interrupted tests were carried out to characterise specimen damage using X-Ray Micro-Computed Tomography. Digital Image Correlation and Acoustic Emission were used to support measurements. Damage analysis was carried out for each architecture to determine the sequence of damage mechanisms occurring and to assess the development of the Damage Zone (DZ). It was found that in woven architectures, damage is more localized to a narrow band around the artificial crack tip and tends to propagate in a more sudden manner. In UD laminates, extensive subcritical damage occurs prior to fibre fracture, a more prolonged load bearing capability was exhibited, and the developing DZ did not reach a plateau during loading.