Your requirement is a difficult one and the subject of thousands of inquiries. If you STRENGTHEN the nose this normally adds weight. Extra weight normally means that the plane flys and crashes faster. More weight plus more speed means much more damage.
Another item of consideration is that if you reinforce the nose and make it indestructible then the ENERGY of the plane hitting the ground at speed must be dissipated elsewhere. This could mean that instead of a nose repair you may find the plane fuselage is bent in half or the nose has been driven backwards into the fuselage.
The ideal method of damage reduction, (apart from not crashing), is to reduce the weight of the aircraft and the flying, (impact), speed.
Perhaps you should consider making the nose sacrificial and make a number of spares.