Does the Catholic Church have any explicit teaching on marital rape?

^{1 Corinthians 7:4} The wife hath not power of her own body, but the husband:
and likewise also the husband hath not power of his own body, but the wife.

Female nymphomania, seeking to satisfy her own bodily appetites at the expense of the exhausted husband, and male satyriasis, seeking to satisfy his own physical desires at the expense of the worn out spouse, are thus equally proscribed by the abstinent apostle of the celibate Christ, born to an unwed virgin.

This then naturally induces a mutual state of temperance, fertile for prayer and spirituality; however, one should wisely avoid the diametrically opposite extreme as well, of forcing unbearable chastity for unreasonable amounts of time upon the other, which is why the divine Paul promptly adds:

^{1 Corinthians 7:5} Defraud ye not one the other, except it be with consent for a time,
that ye may give yourselves to fasting and prayer;
and come together again, that Satan tempt you not for your incontinency.

Since, even though it is better to remain unmarried (provided one has been granted the gift of singleness) sexual union within marriage and the protective release that accompanies it is prescribed for those who lack self-control (the vast majority) in that area:

For I would that all men were even as I myself. But every man hath his proper gift of God, one after this manner, and another after that. I say therefore to the unmarried and widows, It is good for them if they abide even as I. But if they cannot contain, let them marry: for it is better to marry than to burn. - 1 Corinthians 7:7-9

Wherefore, "Marriage is honourable in all, and the bed undefiled. (Hebrews 13:4a)" and there is no sin in consensual sexual union within marriage for non-reproductive purposes.

St. Jerome in Contra Jovin. i.49:

Xystus in his Sentences tells us that "He who too ardently (ardentior) loves his own wife is an adulterer."
_{alternate translation: "Sixtus the Pythagorean says in his Maxims: 'He that is insatiable of his wife is an adulterer'"
Latin original, PL 23 col. 293: "Xystus in sententiis: Adulter est, inquit, in suam uxorem amator ardentior."
Greek original, Sentence #231, p. 240 (PDF p. 255): "μοιχὸς τῆς ἑαυτοῦ γυναικὸς πᾶς ὁa ἀκόλαστος."}

St. Jerome continues:

It is disgraceful to love another man’s wife at all, or one’s own too much. A wise man ought to love his wife with judgment, not with passion. Let a man govern his voluptuous impulses, and not rush headlong into intercourse. There is nothing blacker than to love a wife as if she were an adulteress.
_{Latin original, PL 23 col. 293: "In aliena quippe uxore omnis amor turpis est, in sua nimius. Sapiens vir judicio debet amare conjugem, non affectu. Regat impetus voluptatis, nec præceps feretur in coitum. Nihil est fœdius quam uxorem amare quasi adulteram."}

St. Thomas Aquinas comments on this in Summa Theologica II-II q. 154 a. 8 ad 2:

since the man who is too ardent a lover of his wife acts counter to the good of marriage if he use her indecently, although he be not unfaithful, he may in a sense be called an adulterer; and even more so than he that is too ardent a lover of another woman.
_{quia ille qui est ardentior amator uxoris, facit contra bonum matrimonii, inhoneste eo utens, licet fidem non violet; ideo aliqualiter potest adulter nominari; et magis quam ille qui est ardentior amator alterius mulieris.}

Discussing whether it is a mortal sin to have sexual intercourse solely for pleasure, for a husband to treat his wife as a woman and not as his wife, St. Thomas writes (Summa Theologica suppl. q. 49 a. 6 co.):

if pleasure be sought in such a way as to exclude the honesty of marriage, so that, to wit, it is not as a wife but as a woman that a man treats his wife, and that he is ready to use her in the same way if she were not his wife, it is a mortal sin; wherefore such a man is said to be too ardent a lover of his wife, because his ardor carries him away from the goods of marriage [sacrament, fidelity, offspring].
_{Latin original, Super Sent. lib. 4 d. 31 q. 2 a. 3 co.: "si delectatio quaeratur ultra honestatem matrimonii, ut scilicet quia aliquis in conjuge non attendat quod conjux est, sed solum quod mulier est, idem paratus facere cum ea etsi non esset conjux, est peccatum mortale; et talis dicitur ardentior amator uxoris, quia scilicet ardor ille extra bona matrimonii effertur."}

Archangel St. Gabriel advised Tobias that he wait three nights before consummating his marriage, so as not to take his wife in lust:

Tobias 6:22
when the third night [after Tobias's wedding] is past, thou [Tobias] shalt take the virgin [his bride Sara] with the fear of the Lord, moved rather for love of children than for lust, that in the seed of Abraham thou mayst obtain a blessing in children.

Rules of Married Life by 15^th century Cherubino da Siena, O.F.M., devotes an entire section to the "Peaceful rendering of the marriage debt".

As mentioned in Lucian's answer here, a husband and wife must not defraud (unjustly deprive) one another of the marriage debt they may owe to one another (1 Cor. 7:5); that'd be a sin against justice. It would be extortion (cf. 1 Cor. 6:10: "…nor extortioners, shall possess the kingdom of God.") if one forced the other to pay the marriage debt, like if a creditor used force to extract from his debtor what the debtor owes him (cf. the Parable of the Unmerciful Servant, Mt. 18:23-35, who "throttled him [his debtor], saying: Pay what thou owest.").