Eloquent model between dates format d.m.Y

I have column "exp_date" with type of string, format of column is d.m.Y. I want to get records between two dates.

I am trying like with this code:

$start = '10.09.2016';
$end = '20.10.2018';

$company->records()->whereBetween('exp_date', [$start, $end])->get();

via Chebli Mohamed