1 Peter 3:15 (ESV):
15 but in your hearts honor Christ the Lord as holy, always being prepared to make a defense [G627 apologia] to anyone who asks you for a reason for the hope that is in you; yet do it with gentleness and respect,
627 apología (from 575 /apó, "from" and 3056 /lógos, "intelligent reasoning") – properly, a well-reasoned reply; a thought-out response to adequately address the issue(s) that is raised.
627 /apología ("reasoned defense") is the term for making a legal defense in an ancient court. Today 627 /apología ("biblical apologetics") is used for supplying evidences for the Christian faith.
[An "apology" in classical times had nothing to do with saying, "I'm sorry," but rather was a reasoned argument (defense) that presented evidence (supplied compelling proof).]
In fact, the English word 'apologetics' comes from a Greek word in this verse. So a strong argument can be made that Peter is encouraging believers to train in apologetics in 1 Peter 3:15. However, I do not think this is Peter's emphasis that he encourages every Chrisitan to be formally trained in intellectual apologetics. I think he used the Greek word rather informally.
Unlike Paul, Peter himself was not trained in logical apologetic reasoning. Peter's emphasis was on actions as he himself was a man of actions. One chapter earlier, he wrote in 2:12
Live such good lives among the pagans that, though they accuse you of doing wrong, they may see your good deeds and glorify God on the day he visits us.
This is the context. This is the first line of defense: Live a good life. The 2nd line of defense is to be able to simply "give an answer to everyone who asks you to give the reason for the hope that you have" (NIV).
Jamieson-Fausset-Brown emphasizes on the hope and not on the apologetics:
This verse does not impose an obligation to bring forward a learned proof and logical defense of revelation. But as believers deny themselves, crucify the world, and brave persecution, they must be buoyed up by some strong "hope"; men of the world, having no such hope themselves, are moved by curiosity to ask the secret of this hope; the believer must be ready to give an experimental [experiencial] account "how this hope arose in him, what it contains, and on what it rests" [Steiger].
Is Peter encouraging believers to train in apologetics in 1 Peter 3:15?
I think that would be an over-interpretation of 1 Peter 3:15. Peter was thinking in more concrete terms of living the hope and be able to explain it.