Irreversibly absorbed energy and damage in GFRP laminates impacted at low velocity

• Published in: Composite structures 2011-10, Vol.93 (11), p.2853-2860
• Main Authors: Caprino, G., Lopresto, V., Langella, A., Durante, M.
• Format: Article
• Language: English
• Subjects: Absorbed energy; Applied sciences; Breakage; Composites; Damage; Delaminating; Delamination; Exact sciences and technology; Failure modes; Fibre; Forms of application and semi-finished materials; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Glass fiber reinforced plastics; Glass-fibre-reinforced plastics; Impact; Laminates; Mathematical models; Mechanical contact (friction...); Physics; Polymer industry, paints, wood; Solid mechanics; Structural and continuum mechanics; Technology of polymers; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...)
• ISSN: 0263-8223; 1879-1085
• DOI: 10.1016/j.compstruct.2011.05.019

The scope of this paper was to establish a correlation between the damage occurring in a composite as a consequence of low-velocity impact and the energy dissipated during the impact phenomenon. To this aim, instrumented impact tests were carried out on glass fabric/epoxy laminates of three different thicknesses, using different energy levels. The irreversibly absorbed energy was obtained from the force–displacement curves provided by the impact machine. To assess damage progression as a function of impact energy, ply-by-ply delamination and fibre breakages revealed by destructive tests were measured. A previous model, based on energy balance considerations, was applied to interpret the experimental results, together with an original method of data reduction, allowing for the isolation of the maximum energy portion due to indentation and vibrational effects. From the results obtained, the contribution of fibre breakage and matrix damage to the irreversibly absorbed energy is comparable at low impact energies; with increasing initial energy levels, delamination becomes predominant in determining energy dissipation. However, the critical energy-release rate required to propagate delamination, as calculated from impact data, is considerably higher than the typical values deriving from Mode II delamination tests performed under laboratory conditions.