b0=rbind(letters[1:10],LETTERS[1:10])
b1=as.list.data.frame(data.frame(b0,stringsAsFactors = F))
b2=Reduce(function(v1,v2){
  Reduce(rbind,lapply(v2,function(x){
    cbind(v1,x)
  }))
},b1)
dim(b2)
head(b2)
tail(b2)