Also called Tri-fold pop rivets or exploding rivets

This supplier has a video to show how they work

"El Remache Trebol Bralo es un remache ciego de rotura de vástago concebido para la unión, de una forma rápida y sencilla, de materiales rígidos con materiales blandos o de baja resistencia.
Este remache cuenta con una gran contra-cabeza formada por tres pétalos que proporciona una gran superficie de contacto por la parte trasera. Esta amplia expansión en el lado ciego distribuye la carga y la fuerza de apriete reduciendo el riesgo de aplastamiento y rotura de los materiales."

https://bralo.com/es/productos/remache-trebol/

Video here on pop/blind rivets
https://www.mech4study.com/2016/02/types-of-rivets-joints.ht...

This one has diagrams of tri-fold rivets (which are, by nature, blind and mandrel breaking)
"Bulbex® trifold rivets are a style of blind rivets that are specially designed for structural and other high-strength applications. Also called Tribex® rivets, these tri fold rivets feature a slotted sheath; when installed, the sheath splits to create three “wings” that provide a large bearing surface. "
https://www.rivetsonline.com/blind-rivets/bulbex-tribex-trif...

An American site her which calls them exploding rivets (this has diagrams to show how they work too)
http://www.greatplainsproducts.com/Exploding-Rivets--Tri-Fol...