Hey! This is a rather interesting question with the give-and-take over the years (and even from Muhammad's own time) between the various Abrahamic faiths and their views on the Apocalypse. Although I don't have the time to provide an exhaustive answer, I hope this will help with an overview!

First things first, I am hesitant to use the term failed apocalyptic prophet because I feel it places undue stress upon a single facet of the complex message delivered by Muhammad; one can preach apocalyptic themes without it being the single defining feature of the movement. Obviously, as I am writing this in 2017, the apocalypse did not happen in Muhammad's lifetime and so if that is the criteria you are using than perhaps you can consider him a 'failed' apocalyptic prophet. However, I believe we can more safely talk about the relative focus on apocalyptic content within the message of early Islam, and on what many early Muslims thought regarding the immediacy of the apocalypse, without assign labels such as 'failed' or 'successful'.

All of this being said, we can indeed say that Muhammad believed the apocalypse was near. He made it abundantly clear that he was to be the last of the prophets and that the end of days - marked by wars, increasing adultery and drunkenness, and the rise of the false leader known as al-masih al-dajjal - would occur just before the return of the mahdi and the passing of judgement upon the earth. If we look at the Qur'an itself, the exact date of judgement is not mentioned. Instead, Surah 31:34 explicitly says:

With God alone rests the knowledge of the Last Hour (when it will come). He sends down rain (just at the time and place He alone knows), and He alone knows what is in the wombs. No soul knows what it will reap tomorrow, and no soul knows in what place it will die.7 Surely God is All-Knowing, All-Aware.

The Qur'an does mention, however, that the hour is near (Surahs 42:17 - 18, Surah 54:1) and definitely going to come (Surah 22:7, for example).

If we want more details on the immediacy of the apocalypse and the Day of Judgement, we instead have to examine the hadith. One hadith mentions Muhammad remarking to his compatriots that they may see the rise of this dajjal within their lifetimes (Ibn Hanbal, Musnad). Another hadith recounts Muhammad saying "God sent me with a sword, just before the Hour [of Judgment] . . ." (Ibn al Mubarak).

The hadith come together to show an overarching belief in early Muslim society that the world was in the process of being prepared for the foretold end of days. Some scholars even argue that the success of the Islamic conquests, expanding in mere decades from Arabia to as far as the Atlantic ocean and Iran, was a byproduct of a fervour to conquer as much of the world as possible before the imminent end of the world.

I unfortunately have work soon and can't take the time to flesh this out too much more. I also have to admit that there are many Muslim thinkers on this subject that I have not read or have only skimmed, as most of my knowledge on this topic comes from reading up on other facets of Islamic belief. However, I hope this starts to answer your question and if you have any follow-up questions, I can try to get back to them tomorrow!