MIL-HDBK-17-3F Volume 3,Chapter 12-Lessons Learned C-29.The use of interference fit fasteners Installation of interference-fit fasteners should be checked before permitting can damage laminates if a loose-fit sleeve their use in design. is not installed first. C-30.Fastener-to-hole size tolerance for pri- Tight fitting fastener promotes uniform mary structure joints must be assessed bearing stress in a single fastener hole, and controlled. and promotes proper load sharing in a multi-fastener joint. C-31.Squeeze rivets can be used if washer is Washer helps protect the hole. provided on tail side. C-32.For blind attachments to composite sub- Prevents damage to composite substruc- structure,use fastener with large blind ture by locking collars of fasteners. side footprint of titanium or A286. C-33.Tension head fasteners are preferred for Shear head fasteners most applications.Shear head fasten- ers may be used in special applications only with stress approval. C-34.Avoid putting fastener threads in bearing Fastener threads can gouge and damage against the laminate. the laminate. C-35.Tapered splice plates should be used to Multi-row bolted joints between uniformly tailor the load transfer,row by row,to thick members will have high peak bear- minimize the bearing stress at the most ing loads in outermost rows of fasteners. critical row. 12.3.1.3 Bonded joints D-1.Use secondary adhesive bonding exten- Reduces cost.Reduces the number of sively for thin,lightly loaded,composite holes in composite components.Re- structures,restricting the use of me- duces weight by eliminating build-ups for chanical fastening to thicker,more fastener countersinking and bearing heavily loaded structures. strength. D-2.Never design for an adhesive bond to Maximizes the strength of the structure. be the weak link in a structure.The The bond could act as a weak-link fuse bonds should always be stronger than and unzip catastrophically from a local the members being joined. defect. D-3.Thick bonded structures need complex Large loads require many steps to trans- stepped-lap joints to develop adequate fer the load and assure that adhesive de- efficiency. velops the strength of the adherends. D-4.Anticipate bolted repairs for thick struc- Thick structures are impractical to repair tures by reducing strain levels by bonding,except for one-shot and throwaway structures. 12-18MIL-HDBK-17-3F Volume 3, Chapter 12 - Lessons Learned 12-18 C-29. The use of interference fit fasteners should be checked before permitting their use in design. Installation of interference-fit fasteners can damage laminates if a loose-fit sleeve is not installed first. C-30. Fastener-to-hole size tolerance for pri￾mary structure joints must be assessed and controlled. Tight fitting fastener promotes uniform bearing stress in a single fastener hole, and promotes proper load sharing in a multi-fastener joint. C-31. Squeeze rivets can be used if washer is provided on tail side. Washer helps protect the hole. C-32. For blind attachments to composite sub￾structure, use fastener with large blind side footprint of titanium or A286. Prevents damage to composite substruc￾ture by locking collars of fasteners. C-33. Tension head fasteners are preferred for most applications. Shear head fasten￾ers may be used in special applications only with stress approval. Shear head fasteners. C-34. Avoid putting fastener threads in bearing against the laminate. Fastener threads can gouge and damage the laminate. C-35. Tapered splice plates should be used to tailor the load transfer, row by row, to minimize the bearing stress at the most critical row. Multi-row bolted joints between uniformly thick members will have high peak bear￾ing loads in outermost rows of fasteners. 12.3.1.3 Bonded joints D-1. Use secondary adhesive bonding exten￾sively for thin, lightly loaded, composite structures, restricting the use of me￾chanical fastening to thicker, more heavily loaded structures. Reduces cost. Reduces the number of holes in composite components. Re￾duces weight by eliminating build-ups for fastener countersinking and bearing strength. D-2. Never design for an adhesive bond to be the weak link in a structure. The bonds should always be stronger than the members being joined. Maximizes the strength of the structure. The bond could act as a weak-link fuse and unzip catastrophically from a local defect. D-3. Thick bonded structures need complex stepped-lap joints to develop adequate efficiency. Large loads require many steps to trans￾fer the load and assure that adhesive de￾velops the strength of the adherends. D-4. Anticipate bolted repairs for thick struc￾tures by reducing strain levels. Thick structures are impractical to repair by bonding, except for one-shot and throwaway structures