Magento 2 - Get custom attribute of child products of a configurable

I tried to get value of my custom attribute of child products in product details of a configurable but without success.

This is my code but not work:

$simple_collection = $_product->getTypeInstance()->getUsedProducts($_product);
foreach($simple_collection as $simple_product){
echo $simple_product->getResource()->getAttribute('my_custom_attribute')->getFrontend()->getValue($simple_product);
}

Thanks for any help