Prediction of threshold impact energy for onset of delamination in quasi-isotropic carbon/epoxy composite laminates under low-velocity impact

Impact damage and CAI strength of a woven CFRP material with fire retardant properties

“…The majority of the experimental research for the predictive capability of resistance to impact damage, damage extends and residual strength after impact was mainly focused and formulated around UD laminate composite materials [18][19][20][21]. For the unidirectional composites the damage phenomena and mechanism are well understood and models based on the strength degradation and fracture mechanics have been developed for predicting the damage initiation and propagation.…”

“…The first load drop was found to be approximately at 4.2 -4.5 kN for both layup configurations. This load is often called as the threshold impact force for delamination onset or the critical impact force and is denoted as P crit [20].…”

Impact Damage Management of Composite Laminated Structures by a Probabilistic Approach

“…The probabilistic system PDS, using the Monte Carlo's method [20], chooses a set of samples defined by the deterministic variables and by values of the probabilistic variables selected from proper stochastic distribution functions. The probabilistic module calls the Davies' deterministic procedure [10,12], implemented as Ansys Design Parametric Language (APDL) script in ANSYS, which, together with a static linear analysis, is used to evaluate the impact damage resistance. This calculation is repeated for each different set of probabilistic variables values sampled from the statistical distribution functions of the input parameters according to the chosen sampling method.…”

“…Focusing on impact induced delaminations, the damage resistance of impacted composite laminated structures can be predicted by evaluating the "threshold critical impact energy" needed for the onset of impact induced delaminations [10][11][12]. According to this approach, if the impact energy is below the threshold level, the impact does not cause delaminations in the laminate.…”

“…As a matter of fact, the introduced probabilistic approach, by means of Monte Carlo based Simulations and adopting the threshold critical impact energy approach [10,12] for the assessment of the impact induced delaminations, is able to take into account simultaneously the scatter of material mechanical properties, and the randomness of the impact location when determining the impact damage resistance of composite laminated structures. The material properties stochastic distributions, used for the numerical simulations, have been taken from an experimental program, on a number of laminate samples respecting specific conditions of temperature and moisture levels.…”