An Air Force enlisted man was sentenced yesterday to 15 years in prison for placing a bomb in his wife's suitcase shortly before she flew from Washington National Airport to Texas.

Clutching paper tissues and weeping, Airman Martin T. Bradley told a federal judge in Alexandria that he had not intended to kill his wife, but only to frighten her. Bradley said the couple had been experiencing marital difficulties.

District Judge Albert V. Bryan Jr. ordered that Bradley, 27, a mechanic stationed at Andrews Air Force Base, also receive psychiatric counseling. The serviceman told the judge he had been a loner in high school, had always had trouble in his relationships with women and had been battered as a child.

Bradley was convicted June 23, following a brief trial, of placing a destructive device on an airplane. He offered no defense, and his lawyer said later Bradley was unable emotionally to plead guilty to the offense.

Bradley was to have received an 18 1/2-year prison term under an arrangement with federal prosecutors, but Bryan said he considered several statements made by Bradley in court yesterday as mitigating factors in imposing the lesser penalty.

U.S. Public Defender Fred Warren Bennett of Baltimore said that in talks with a probation officer after his trial, Bradley for the first time claimed he had purposely wired the device so it would not detonate.

Assistant U.S. Attorney Michael Schatzow countered that Bradley's statements came only after he had seen the remains of the bomb--partially damaged during disarming by ordnance experts--during an interview in Schatzow's office..

Schatzow also maintained Bradley, who was arrested at Andrews on March 3, had told a fellow prisoner while in the Baltimore City Jail that he had tried to kill his wife, an Air Force sergeant.

Bradley's wife, Mary Jo, was en route to Sheppard Air Force Base in Wichita Falls, Tex., for three months' temporary duty at the time of the incident. She discovered the device, which was wired to a ticking clock, while unpacking.