get the value from force:RecordData on Init handler

force:recordData handles loading the record(s) asynchronously. As such, it will not be available during the init handler (there hasn't been a chance to run asynchronous code yet), and will likely not be available in the first render/afterRender cycle either.

The official method is to use the recordUpdated event.

<aura:attribute name="record" type="Asset" />

<force:recordData layoutType="FULL"
                  recordId="{!v.recordId}"
                  targetFields="{!v.record}"
                  recordUpdated="{!c.recordUpdate}" />

---

({
    recordUpdate: function(component, event, helper) {
        alert(component.get("v.record").Name);
    }
})