Design of Laminates/Joints

Question 1

How are laminates determined

Answer 1

Determined the
angle relative to this main direction for each layer, from bottom to top

Question 2

List mechanical failure mechanisms

Answer 2

Splitting
Delamination
Buckling
Fatigue
Impact damage
Creep and stress relaxation
Osmosis
UV-damage
Erosion
Temperature and fire damage

Question 3

Joints can be classified on the basis of different criteria

Answer 3

-Detachable ↔ non-detachable
-Bonding of non-cured laminates (primary, wet-on-wet) ↔ cured laminates
(Secondary)
-Between similar ↔ different types of materials
-Mechanical ↔ adhesive

Question 4

How to prepare to make adhesive joints

Answer 4

sanding, cleaning, conditions

Question 5

Types of adhesive joints

Answer 5

Single lap joint 1
Beveled lap joint 1.25
Double lap joint 1.4
Stepped lap joint 2
Scarf joint 2.25

Question 5

Describe adhesive failure

Answer 5

failure occurs at the place of the bonding between the adhesive and the
component to be bonded

Question 6

How can adhesive failure be prevented

Answer 6

Adhesive failure can be prevented
-by proper pre-treatment
(cleaning and drying, degreasing). -by ensuring that the
components have a correct roughness. Correct surface roughness provides a larger
contact surface. Excessive roughness causes air inclusions (voids).
-Adhesive failure
occurs less readily if the parts to be bonded are porous. This is due to the mechanical
anchoring effect of the adhesive in the pores

Question 7

Where does cohesive fracture occur

Answer 7

A cohesive (‘cohesion’) fracture occurs in the
adhesive.

Question 8

Cohesion strength is determined by?

Answer 8

determined by the
*type of adhesive,
*possible curing shrinkage,
*the porosity of the adhesive layer due to solvent evaporation (when
bonding with solvent),
*any entrapped air,
*the
homogeneity
*correct ratio of the components (for
mixed ‘two-component’ adhesives)

Question 9

Types of adhesive

Answer 9

*thermoplastic (‘hot melt’) adhesives
*mixed or two-component adhesives (polymerisation adhesives)
*adhesive solutions (which cure under emission of a volatile solvent)

Question 10

Failure in mechanical joints

Answer 10

 Tensile fracture
 Failure due to bearing pressure.
 Fatigue fracture.
 Shear fracture.
 Creep.