The adhesive peel test exists in a number of forms such as the stripping, “T”,
floating roller and climbing drum tests. These are all essentially variations
of a common theme, shown schematically in Figure 1. A peel load is applied
at some angle to the adhesive through a flexible adherend. This tests the
adhesive in its weakest mode, since strengths from shear lap tests are many
times greater than those from peel tests even for high peel strength adhesives.
This is because the load, P, and more importantly, the bending moment, M,
due to the moment of the load about the bond end (see Figure 1) are reacted
over a very small region of the adhesive at the bond end, thus causing high
local stresses.
The various peel tests have only been used in a comparative manner,
largely because of the lack of information about the adhesive stress distribution. Further, small modifications of adhesive structure, such as adding Large displacement finite element analysis and subsequent experimental work has been uscd 10
investigate the adhesive peel test; at this stage, only elastic behaviour has been considered.
Both non-cracked and cracked configurations have been analysed, representing initial and
continuous failure of the peel test. Analysis of the former indicated that initial failure was
caused by the adhesive principal stresses driving a crack towards the interface with the flexible
adherend. Investigation of the cracked configuration has shown that the amount of mode I1
loading at the crack tip is significant and is essentially independent of peel angle, load and
adhesive or adherend modulus, only decreasing as the adhesive becomes incompressible. Failure
(propagation) has been shown to occur at a critical applied bending moment for a particular
adherend and adhesive, independent of peel angle. Further, the strength (IoadJ’measured by the
peel test is not proportional to the actual strength ofthe adhesive, a small increase in the adhesive
strength causing a much larger increase in the applied peel load. stigate the mechanics of the peel test in order to establish
the way in which such joints fail. This necessitates the evaluation of the
adhesive stress distribution in the peel test and subsequent application of a
failure criterion based on fracture mechanics concepts. The finite element
technique, which has already been used successfully for the analysis of adhesive joints,' has been used here. This technique provides a method of stress
analysis for geometrically complicated structures. The effects of plasticity
may well be important but, at this stage, elastic behaviour has been assumed.
Previously, the peel test has been represented either by a non-cracked, bimaterial model or by a cracked, single-material model. Among the workers
who adopt the first approach are Kaelble' and Nich~lson.~ They have
modelled the adhesive as a layer of tension and shear springs and assum
7. The laminated objects manufacturing
1. 1. Hybrid process which involves
adding and subtracting material to
create a part
2. Take-up spindle controls the
excess.
3. Layers the material with
thickness
4. ranges from 0.001 – 0.005 inches
Each layer is cut with a CO2 laser
8. MATERIALS
The most common materials used in LOM are
thermoplastics such as PVC; Paper (.002-.02inch);
Composites (Ferrous metals; Non-ferrous metals;
Ceramics)
9. Material is usually a paper sheet laminated with
adhesive on one side, but plastic and metal
laminates are appearing.
1.Layer fabrication starts with sheet being adhered
tosubstrate with the heated roller.
2. The laser then traces out the outline of the layer.
3. Non-part areas are cross-hatched to facilitate
removal of waste material.
4. Once the laser cutting is complete, the platform
moves down and out of the way so that fresh
sheet material can be rolled into position.
5.Once new material is in position, the platform
moves back up to one layer below its previous
position.
6. The process can now be repeated.
Basic Process
11. What gets made?
LOM is used primarily for creating scaled models
and conceptual prototypes that can be tested for
form or design. It can also be used to make
patterns for use in traditional manufacturing, such
as sand molded casting, a metal casting process
and for Investment casting patterns ,direct use
14. LOM layers of plastic or paper are fused or
laminated together using heat and pressure
and then cut into the desired shape using
computer.
3 D PRINTING USING LOM
16. • Ability to produce larger-scaled models
• Uses very inexpensive paper
• Fast and accurate
• Good handling strength
• Environmentally friendly
• Not health threatening
• Precision claimed to be ±0.005 in.
• Variety of material can be used such as paper ,
plastics , composites and ceramics
17. DISADVANTAGES
• Paper is cheap but is not very stable.
• Need decubing which requires a lot of labour
• Produce smoke or fumes
• Fire hazard
• Not ideal for making complex geometries .
• It is not used to create functional prototypes.
