Crimps on Aluminium twin and earth cable.

A proper crimp would have a copper half and an aluminium half with the joint covered.  The Al end would likely be filled with special paste to aid crimping and electrical contact and to keep water out.  The aluminium end would be heat treated to match the condition of the aluminium cable and ditto the copper.  I have never seen them other than for use on overhead lines where they can provide a high quality joint if used with the right dies and tools.  The big issues with a straight copper crimp will be the differential compression of the core and crimp and different thermal expansion.  On expansion as Al expands about 30% more than copper for the same temp rise so the joint will soon be subject to some massive stresses which will quickly loosen the copper - al crimp. The actual crimping process will be a bit indeterminate too as Aluminium has a lower modulus of elasticity than copper so initially the core will compress relatively more than the crimp when the slack is taken up.  After that the copper will probably yield before the aluminium which may never permanently deform and that could mean that the whole permanent compression ends up in the copper.  Either way these crimps are not designed for dissimilar metals and will fail if moved or thermally cycled.

A proper crimp would have a copper half and an aluminium half with the joint covered.  The Al end would likely be filled with special paste to aid crimping and electrical contact and to keep water out.  The aluminium end would be heat treated to match the condition of the aluminium cable and ditto the copper.  I have never seen them other than for use on overhead lines where they can provide a high quality joint if used with the right dies and tools.  The big issues with a straight copper crimp will be the differential compression of the core and crimp and different thermal expansion.  On expansion as Al expands about 30% more than copper for the same temp rise so the joint will soon be subject to some massive stresses which will quickly loosen the copper - al crimp. The actual crimping process will be a bit indeterminate too as Aluminium has a lower modulus of elasticity than copper so initially the core will compress relatively more than the crimp when the slack is taken up.  After that the copper will probably yield before the aluminium which may never permanently deform and that could mean that the whole permanent compression ends up in the copper.  Either way these crimps are not designed for dissimilar metals and will fail if moved or thermally cycled.