Calaulation Of Ice Impact Force Based On Response Of Composite Laminate

Aircraft may be subjected to the impact of ice material,such as hailstone and ice particles shed from aircraft surfaces,at cruise speed.Aircraft components such as wing,empennage and engine blade will be damaged.Skin of modern aircraft is usually made of composite material,which is easily to be damaged under the impact,with appearance of delamination which is hard to inspect.The contact force of hailstone impact on the composite laminate can't be measured directly in experiments.So it is necessary to study the relationship between contact force and other parameters,such as displacement and strain,which are easy to be measured.The characters of contact force and response of composite laminate under the ice impact are investigated based on finite element method(FEM),and the method to calculate the impact force with laminate responses is studied.A strain rate dependent yield strength material is employed to establish the smoothed particle hydrodynamics(SPH)model of hailstone.The response model when composite laminate is loaded by the concentrated force is used to calculate the response of impacted site based on contact force got from FEM.The relationship between contact force and displacement coincides with that computed with FEM.The analytical result is 10% differ from the FEM result when using displacement to calculate contact force.So it is feasible to calculate impact force through measuring the displacement of impacted site.Contact force is also calculated by using the acceleration of the centroid of hailstone got from FEM.Compared with the FEM contact force,the calculated force is almost the same before the time of peak force appears.So it is possible to record the acceleration of hailstone's centroid and then to calculate the contact force.The response of delaminating of composite laminate under hailstone impact is studied.When the delamination occurs,the velocity of composite under impact site will increase suddenly,and the strain will also change,so they can be used to identify the moment of delaminating.The ice ball will crack during impact,and the contact area will increase,so the delamination threshold is larger than the threshold impacted by steel ball.