All dryer vents must vent to the outside, doing so into your crawlspace is a definate no-no, a fire hazard, and a real humidity rot issue. You may certainly run your vent through your crawlspace to the outside, but do not vent into the crawlspace itself.
As far as the vent itself is concerned, you may not use duct tape to connect it, nor may you use screws, becuase they trap lint as it goes by and creates a fire hazard. The length and number of bends in the duct, which should be all metal, even between the dryer and the floor, will be published by your dryer manufacturer. GE's phone number is 1-800-626-2000. Be sure to have your model and serial number which will be just inside the door or on the back of the control panel. Good luck!