use este codigo en el boton
ilustracion_btn.addEventListener(MouseEvent.CLICK, cargarPel);
function cargarPel(event:MouseEvent):void {
var urlSwf:URLRequest = new URLRequest("portafolio.swf");
var cargarSwf:Loader = new Loader();
cargarSwf.load(urlSwf);
this.addChild(cargarSwf);
}
