"If it had, Hannah might have returned to her course and still be alive today."
Peter added he believed the attack was "the sole reason" for his granddaughter's depression which led to her death, and accused the university of "inadequate" support.
Hannah's mother Amanda announced her daughter's death on Facebook on 2 September in an emotional post.
A university spokesman said: "We were deeply upset to learn of [Hannah’s] tragic death. The university offers a comprehensive support service to its students and its priority lies with their welfare. These matters are without exception sensitive and confidential and we cannot comment further on particular cases and allegations."
A Staffordshire Police spokesman said: "Since we were made aware of an allegation of a rape, specially trained officers have been conducting an investigation into the incident.
"This included referring Hannah for counselling support whilst the investigation progressed.
"A suspect was questioned by detectives and a file was compiled for consideration by the Crown Prosecution Service for a charging decision.
"A report on the circumstances of Hannah’s death will be made for Her Majesty’s Coroner."
Useful websites and helplines:
Samaritans, open 24 hours a day, on 08457 90 90 90
Mind, open Monday to Friday, 9am-6pm on 0300 123 3393
Get Connected is a free advice service for people under 25. Call 0808 808 4994; email: firstname.lastname@example.org or visit the website getconnected.org.uk
Young Minds offers information to young people about mental health and emotional wellbeing
HopeLine runs a confidential advice helpline if you are a young person at risk of suicide or are worried about a young person at risk of suicide. Mon-Fri 10-5pmand 7pm-10pm. Weekends 2pm-5pm on 0800 068 41 41
HeadMeds - a straight-talking website on mental health medication