Crack healing in infusible thermoplastic composite laminates

T. Khan, M. S. Irfan, W. J. Cantwell, Rehan Umer

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18 Scopus citations


In this research, pre-cracked carbon fiber reinforced composite laminates, based on an infusible thermoplastic resin (Elium®), were manufactured via the vacuum assisted resin transfer molding process. The opened pre-cracks were subsequently ‘repaired’ using hot press by heating the laminates above the glass transition temperature of the cured liquid thermoplastic resin. A number of well-defined healing experiments were conducted by varying the key healing parameters (i.e., temperature, time and pressure) and applying a three factor, three-level (3 × 3) factorial design of experiments based on a Taguchi analysis. The Mode I interlaminar fracture toughness (GIc) was investigated by conducting a series of double cantilever beam (DCB) tests. The precise contribution of each processing parameter towards the measured fracture toughness was determined using an analysis of variance (ANOVA) approach. The results revealed that the joining temperature was the most dominant parameter, with an 82% contribution, followed by the contact time which had a 12% influence. The specimens bonded at higher temperatures for longer times exhibited the highest fracture toughness characteristics, these being in excess of 0.74 N/mm, values that compare favorably with those measured on fully-infused reference samples (1.16 N/mm). An examination of the DCB samples during testing highlighted the presence of a fiber bridging toughening mechanism, which was more prevalent in samples joined at higher temperatures for longer periods of time. The results from this study are in agreement with previously-reported interdiffusion and crack-healing theories developed for other polymeric materials.

Original languageBritish English
Article number106896
JournalComposites Part A: Applied Science and Manufacturing
StatePublished - May 2022


  • Crack healing
  • Fracture toughness
  • Joining
  • Thermoplastics


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