Vikings are, by definition, raiders, pirates, and bandits. A lot of Norse never went viking, and joining a viking band once is often worth noting in a memorial stone. There is a slight split in the culture between the full-time warrior, usually a viking, and the full-time farmer, rarely a viking, but the difference is never hard. Often it is a matter of opportunity and economics, as well as training, age, and personality. The Norse are the last European culture to retain the concept of weapons and war-training as the right of all free men, not just an upper class of warrior-nobility. This alone marks them as a remnant of ancient, Germanic, pagan, egalitarian culture in a feudal, aristocratic, phallicist, autocratic, and Christian continent.
Personality as well as birth into warrior families accounts for most female vikings, perhaps one to five percent of the total number of raiders. Only one has a saga named after her, and that often considered but part of a king's saga, but many of the women in sagas have arms training, and fight beside brothers, husbands, or lovers. A number of female viking captains are noted by foreign chroniclers, with female, mixed, or male crews. Undoubtedly many women went unremarked as common crew. Someone being pillaged is too busy running, fighting, or dying to check to see if beardlessness is youth or femininity. Armour by its weight flattens the best curves and aids androgyny.
Breast-cup armour, as seen on opera Brunhildas, has no historicity. It would be uncomfortable, channeling the force of blows on the breast straight to the ribs; inconvenient, sticking a pair of metal bowls out in the way of your upper arm; and dangerous, as any weapon striking inboard of the tips would be immediately funneled towards the center of the chest. Women wore the same chain, splint, or scale armour as a man their size who had good chest expansion and pectoral development.
Female vikings are often of the upper classes, at least the captains mentioned, but then so are the male captains. The very concept of nobility is variable in Norse culture, both from north to south and early to late. These women warriors come from all sexual orientations, heterosexual, homosexual, and neuter. They are usually described as beautiful or at least handsome, indicating masculine admiration for their warlike qualities. Our culture, after all, assumes female warriors are "battle axes" with foul temperments, man-haters, and/or old maids too ugly to get a man.
Speaking of women and vikings, a word often connected with viking raids, "rapine," has nothing at all to do with our concept of "rape."
Rapine is best translated to contemporary English as abduction or kidnapping. It has no sexual component. Rapine is mentioned by chroniclers as practiced on communities of monks by vikings. Considering that most raids are conducted in the face of at least some opposition, there simply isn't time to safely abuse women on the spot. What happens once they are carrried off is up to the individual viking, but the rape even of slaves is not condoned nor encouraged in their culture. Rape-mentality must not be assumed simply because it is common in our culture.
After all, it is among the Norse that one hears of beautiful woman slaves being courted by the free men round about, rather than raped by any and all who take a fancy to her.
Raiding is done for the purpose of getting gold and silver, or valuables that could be turned into ready cash. This includes taking younger and stronger members of the community to sell as slaves, or important-looking ones to ransom back to their relatives. That is rapine. For foreign women worth ransoming, it would preclude sex, forced or voluntary, as their culture declared them worthless if they might be carrying an illegitimate child.
Why has this been forgotten? On the one hand, language has changed recently. Many of us nowadays are operating with a fairly small vocabulary, and guessing - badly! - at the rest rather than keeping a dictionary handy as we read. In the Bowdlerized, sex-is-never-mentioned Victorian age, the word "rape" could be used in family publications because it had no sexual component. When Bullfinch speaks of the Greek myth of "the rape of Helen," he is referring to her being abducted from her lawful home by Paris (even with her conivance), not to her being sexually forced. In Pope's pseudo-epic poem, The Rape of the Lock, any sexual reference is obviously silly, since it is about a lock of hair being stolen.
On the other hand, filling in any horrible crime fits easily in with the Medieval demonization of those terrible, pagan invaders who committed all outrages imaginable. Similar is the later creation of the Gothic witch who eats babies and kisses goats' rears, or the Jew who murders Christian children to use their blood in Passover matzoh.
In line with this demonization are infamous viking tortures, like the "blood eagle." Supposedly this involved performing various crude and unfriendly surgeries on living men to cause a prolonged and hideous death, but it has now been proved to be a complete fiction invented by a couple of Christian writers (who must have had sick sadistic imaginations). So when you read of the "blood eagle" in a novel, or a history, the author is way out of date on his or her research.
About the worst the Norse ever did is to set fire to halls that were being too stoutly defended, giving those inside the choice of burning to death or facing steel. In the sagas and reliable chronicles, death as dealt by the vikings is usually pretty quick.
So near as we can tell, the fortunate Norse simply were allowed by their culture to live such uninhibited lives that they didn't need to be sadistic, and did not tie together sex and violence. The men did not hate and fear women, and so had no need to either rape them, or keep them in weaponless subjection.