Damage and residual strength of laminated carbon–epoxy composite circular plates loaded at the centre

Fatigue residual strength of circular laminate graphite–epoxy composite plates damaged by transverse load

“…in vessels subject to internal pressure). In [7], Cesari et al found a significant reduction of the static tensile strength in quasi-isotropic CFRP specimens with visible damage due to transverse load.…”

“…Composite square 250 × 250 × 1.6 mm graphite/epoxy laminate plates, the same studied in [7,17], were tested. The laminates were made in an autoclave from pre-pregs by stacking eight unidirectional plies in the quasi-isotropic [0/90/+45/−45] s lay-up.…”

“…The laminates were made in an autoclave from pre-pregs by stacking eight unidirectional plies in the quasi-isotropic [0/90/+45/−45] s lay-up. In order to induce controlled damage in the material, specimens were placed in a circular clamping fixture, with an internal diameter of 200 mm, and they were loaded at the centre [7]. The indentation tool was a hardened steel sphere with a radius of 7 mm.…”

“…4 and 5. Stress intensities are expressed as percentages of the ultimate tensile strength σ uts of plain (undamaged) specimens [7]. The experimental points are drawn together with the 10%, 50% and 90% iso-failure probability curves, as calculated according to the Weibull model of Eq.…”

“…Damage monitoring was based on the definition of a "sentry" function taking into account the strain energy (E s ), which is related to the integrity of the material, and the AE events energy (E a ), which is rather related to the damage intensity. The definition of the "sentry" function as f = ln(E s /E a ) has proven to be a useful indicator of the damage progression during low velocity impact testing [7,17]. Moreover, it was found that the integral J f of the sentry function over the indenter displacement is related with the quasi-static residual ultimate tensile strength of 2 ACCEPTED MANUSCRIPT the material [17].…”