LOW VELOCITY IMPACT OF WOVEN GFRP/ CFRP COMPOSITES: NUMERICAL ANALYSIS AND EXPERIMENTATION

Abstract

Low-velocity impact (LVI) of laminated composites is commonly used in aerospace industry certification as part of a durability and damage tolerance assessment (e.g., barely visible impact damage, compression after impact, etc.). In certain situations, the puncture resistance of an impacted composite structure is of interest. To study the behavior of composite plates near perforation, this work focusses on LVI of composites at relatively high impact energies. An experimental test campaign was conducted wherein composite laminates composed of layers of woven glass fiber-reinforced polymer (GFRP) and woven carbon fiber-reinforced polymer (CFRP) plies were impacted in a drop tower using a standard LVI setup with a hemispherical indenter tip. The stacking sequence contained blocked plies of the same material, yielding a glass-carbon-glass layup. A range of impact energies were selected to produce widespread damage, including delamination, fiber fracture, and shear failure, and to fully perforate the panels in some instances. These tests are distinguished from other such impact experiments in that substantial damage and perforation are observed at low velocities. The interface between dissimilar materials showed large delaminations, which could propagate to the edge of the plate at the highest tested impact energies. Numerical modelling was performed using the explicit transient dynamics solver of Sierra/Solid Mechanics, a finite element code developed at Sandia National Laboratories. Continuum damage mechanics (CDM) and cohesive zone modelling (CZM) were utilized for the intra- and interlaminar failure, respectively. Pseudo-ply-by-ply meshing with one element through the thickness of every two blocked plies was used, and delamination planes were modelled with cohesive zone elements (CZE) inserted between every two layers. The main quantities of interest, including the energy dissipation, force-displacement curve, peak force, and damage patterns, were used to compare the numerical simulations with the experiments. These data are useful for validating computational simulations and provide insight into the impact resistance and energy dissipation capability of hybrid GFRP/CFRP composites.