A material database has been developed, impact tests on plates and beams of selected has been selected materials with varying impact velocities, have been performed and a finite element (FE) computer code suited to incorporation of the proposed constitutive models has been selected. The proposed constitutive models have been developed and incorporated into FE computer code for both the shell and solid elements, and the FE computer code has been used to simulate the initial and post impact response recorded during impact testing. Full scale tests have been performed on portions of the fuselage of the Seastar plane.
A new composite constitutive model for glass fibre fabric reinforced with epoxy was developed and implemented into the DYNA3D code for both the shell and solid elements. The approach uses a damage mechanics formulation to predict matrix cracks and fibre fracture in the warp and weft directions in a woven fabric composite.
Results were compared with laboratory experiments and full scale tests. The comparisons indicated that the damage model can predict with reasonable accuracy the damage modes observed in both the laboratory and full scale experiments. Based on the numerical simulations of the laboratory tests and the industrial component testing, the following conclusions and recommendations can be made:
The composite damage model can predict correctly the matrix microcracks in the weft and warp fibre directions (within the transverse fibre bundles) of the composite beams and plates being simulated. The matrix crack evolution relationship together with the evolution rate limit, which can be related loosely to the speed of sound in the matrix, appears to characterize correctly the extent of observed cracks. These cracks are an important energy dissipation mechanism during an impact event.
The predicted fibre fracture in the numerical simulations shows very good agreement with the experimentally observed fracture for complete laminate failure, and for nucleation and part growth of fibre damage. At present the model cannot predict accurately part failure of a laminate.
The damage model formulation predicts correctly the strain rate enhancement of the glass based composite under various impact strain rates.
Enhancements to the fibre evolution relationship are required to include the in plane shear stresses and the in plane strengths as the thresholds for nucleation or growth of damage.
THE OBJECTIVE OF THE R&D PROGRAMME IS TO PRODUCE AND DEVELOP A MATHEMATICAL MODELLING TECHNIQUE FOR SIMULATING THE HIGHLY NON-LINEAR BEHAVIOUR OF COMPOSITES UNDER IMPULSIVE LOADINGS.
COMPOSITE MATERIALS WILL BE SUBJECTED TO IMPACT, EITHER BY DROPPING OR FIRING PROJECTILES INTO STATIONARY TARGETS OR BY SLAMMING PANELS INTO WATER OR SOLID SURFACES.
SUCH IMPULSIVE LOADS CAUSE EXTREME STRESSES IN THE MATERIAL, LEADING TO FRACTURE, DELAMINATION, PENETRATION AND OTHER COMPLEX PHENOMENA.
THE EXPERIMENTAL WORK OF THIS PROGRAMME WILL RESULT IN THE DEVELOPMENT OF CONSTITUTIVE MODELS THAT DEFINE DEFORMATION AND DAMAGE AS A FUNCTION OF STRESS LEVEL, STRAIN RATE AND MATERIAL PARAMETERS. THESE MODELS WILL BE INCORPORATED WITHIN A PREDICTIVE TOOL DEVELOPED TO SIMULATE THE BEHAVIOUR OF SELECTED COMPOSITES UNDER IMPULSIVE LOADING.
THE COMBINATION OF DETAILED NUMERICAL SIMULATION WITH AN EXTENSIVE DATA BASE ON THE PERFORMANCE OF THESE MATERIALS, UNDER A RANGE OF CONDITIONS, WILL PROVIDE A RELIABLE TOOL TO BE USED FOR IMPROVED DESIGN AND MANUFACTURE.
Funding SchemeCSC - Cost-sharing contracts
6401 JH Heerlen