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En Çok Okunanlar
Sandwich Panel Description
Sandwich panels are typically single piece, modular factory engineered units comprising
two metal faces and a fully insulating core.
The metal facings are fully bonded to
the core so that the panel acts compositely when under load, in most cases, providing
free standing panels. Facings used for insulated panels are predominantly of steel.
The
insulating core is typically bonded to the facings using a conventional adhesive
bond. If other than EP, the core material is usually a material that provides good
thermal insulation properties.
The panels are typically manufactured on a continuous
production line, as shown below.
Core Materials
The following generic core material
types are often used in Sandwich Panel:
- Expanded Polystyrene (EPS)
- Polyurethane (PUR)
- Polyisocyanurate (PIR)
- Mineral Wool / Stone Wool
- Phenolic foams
- Phenolic/EPS Composites
What Is A Sandwich - Panel ?
Now there are a large number of completely different construction materials. For
roofs and walls, there are special sandwich - panel. What kind of building material,
and what it has advantages and disadvantages, let's try look below. - Sandwich Panel
- a building material, which has a three-layered structure consisting of sheets of
metal or fiberboard, and insulation layer between them. All the details of such panels
are glued together by hot pressing.
American engineer Frank Lloyd Ryton first used
the sandwich - the panel in 1930, when the project Unsonian. They had many shortcomings,
but their primary task was a combination of aesthetics and ease. In 1950, Alden B.
Dow creates ergonomic sandwich panels, which quickly became popular in the construction
industry. Company Koppers in 1959, has already begun mass production of sandwich
- panels Board reclassified car production.
Sandwich panels have appeared in Russia
since the mid 1980's. Insulation sandwich - panels can consist of the following materials:
polyurethane foam, fiberglass, mineral wool, expanded polystyrene. Now, about every
detail. Polyurethane - characterized by a combination of strength and lightness,
has a cellular structure. His life did not envy the level of ambient humidity. Panels
with Polyurethane has a high level of insulation and are classified as nonflammable
materials. Glass fibers - bound material made from the finest glass filaments. Panel
with glass demand, primarily because of its sound-absorbing properties. Fiberglass
- nonflammable, easy to transport and install, as well as environmentally friendly.
It has good resistance to chemicals. Mineral wool - one of the the most popular heaters
for sandwich panels. Panels with mineral wool relevant in the construction of simple
buildings. Mineral wool does not support open burning, provides high levels of heat
and soundproofing. Expanded polystyrene - the most low weight material. Has a cellular
structure. Widely used in the construction of warehouses, workshops and trade pavilions.
Panels with polystyrene collected in short time. Let's talk about the pros and cons
of the panels. Let's start with the disadvantages. Sandwich panels have a high likelihood
of cosmetic damage, they can not withstand significant additional loads. Panels of
polystyrene foam and fire risk, combined with osb. Their disadvantage is the frequent
freezing of the joints. On the shortcomings of this all, now on the merits. Construction
of the use of these panels can be produced in any period of time, they have high
thermal insulation, sound insulation, hygiene and environmental protection. If their
application does not require additional finish, no extra load on the foundation of
their possible use in the food industry. In general, the use of sandwich - panels
in the building and helps to reduce construction time and save money.
The Sandwich Panels are used mostly in huge industries and companies for their internal
fixtures. These panels basically consist of two outer layers that are interconnected
by another layer called the core layer. The outer layer can be sheets, slabs of wood,
metal or paper. The inner material is made out of plywood, plastic sheeting or the
honeycomb structure. Many of the panels of this category are also formed of inner
cores made out of plastics. Placing the plastic sheet between the heated molds forms
it. This results into a definite cellular structure.
The description of how this instrument
works requires some pre-requisites, i.e. the person with little engineering experience
can understand it well. The Sandwich Panel consists of I-beam, where its flanges
are bonded to the web so as to create a structural member. The strength that is required
between the two edges of the flanges is acquired by keeping the two flanges in compression
and tension.
A sandwich panel is very similar to the I-beam. The things that correlate
between them are the skin of the panel and the core of the panel. The skin correlates
to the flanges of the I-beam where as the core relates to the I-beam Web. The panel
bears a bending strength on all the directions of the plane, the X-Y plane, and Z-X
plane, except the Y-Z plane. The core has the major functionality of the sandwich
panel, i.e. it is responsible for holding the skins together and relative to each
other. This helps in avoiding the buckle, snap, deformation or brokerage.
The core
of the sandwich panel experiences mainly the shear stress. The stiffness of the material
can be known by examining the shear properties. The cores that are more flexible
and bend easily are known to have low shear modulus. To avoid this, another material
can be bonded to the surface and creating a skin with higher tensile strength. This
leads to the construction of Composite sandwich panels.
Thus the sandwich panels
can be used where strong, stiff, lightweight panels are required. They support the
properties like the rigidity, strength, compressibility, and flexibility; also maintain
the shape, size, thickness, and weight. The main motive is to build or construct
a panel that is light weighted. They can be formed by using thin plastic sheets as
the as the core area. They should have broad bonding areas at their free ends and
also to bond with outer areas. The projections can be made out of different shapes,
heights, spacing, tilts etc. These different projections help to produce different
characteristics in the panel being made.
As many of the characteristics can be well
known at the beginning, it can be designed on the computer itself. With use of this
many useful applications such as the airplane wings and the thermal boards can be
designed. Thus the panels are widely used in many industrial and commercial applications
of the day-to-day life. Thus, each panel possessing some different characteristics
suitable for that particular environment.
What is PU sandwich panel
Description
The PU sandwich panel is a panel used as covering consisting of an insulating core
material with inner and outer matel skins. The panels are widely used for freezer,
warehouses, factories, laboratories and houses.
Features of Polyurethane Panels
Outstanding fineness and insulating efficiency
Water
and noise free
Easy installation, moving and dismantle
Economical
Good appearance
and bolt free
Physical Properties of Polyurethane:
Classification Physical Property Classification Physical Property
Compressive Strength 1kg/cm2 Temperature -190 -200
Bending Strength 2 -2.5kg/cm2 Thermal Conductivity 0.018kcal/mh
Shear Strength 2g/cm2 Density 0.04g±5/cm2
Adhesive Strength 1kg/cm Modulus of Elasticity 20kg/cm2
Absorption 1g/100cm2
What is a Sandwich Panel?
SUMMARY
This article presents sandwich panels, produced gluing the core material
between two coverings. These panels contain many positive aspects which are requested
from a construction material. The panels can be used in various applications. The
following points are very essential to achieve a good quality and meet the demands:
- the choice of the coverings and the core material
- reliable gluing technique
-
use of right montage details
A Sandwich Panel is a multiple composite of materials adhesive bonded together to create a multi-functionel product.
The most common form is a three component sandwich consisting of two thin facing materials (or coverings) and a foam plastic core (see Figure 1).
Figure 1
The theory of obtaining it’s structural characterictics comes from the T beam principal where the facings are the flanges and the core is the web (see below: Figure 2).
METHOD OF MANUFACTURE
There are two types of panels according to the manufacturing method:
1. Bonded Sandwich Panels (where the core is glued between the facings; suitable
for
all core types)
2. Injected Sandwich Panels (where the core is injected in a press
between the
facings, suitable only for polyurethane cores)
Furthermore we will discuss only about the first type of sandwich panels:
PANEL THEORY
The overall characterictics of the panel are derivated from a number of major factors being:
1. The E (Young’s) modulus of the facings
2. The thickness of facings.
3. The mechanical
properties of the core material
4. The core thickness
As you can see from Table 1, if comparing say steel and aluminium, the E-modulus of steel is approximately three times greater than that of aluminium, therefore offering far greater structural properties.
Table 1
Solids E-Modulus E (Mpa) Shear Modulus K (MPa)
Aluminium 0.71 x 105 0.71 x 105
Steel 2.00 x 105 1.60 x 105
cast iron 1.00 x 105 0.80 x 105
brass 1.00 x 105 1.00 x 105
Quarz Glass 0.69 x 105 0.32 x 105
Similarly, when comparing core materials Styrofoam IB is over three times better than polyurethane with a shear modulus of 77 Kp/cm2 as apposed to P.U. 25 Kp/ cm2.
It is therefore very critical when discussing structural performance of panels to take the above four factors into consideration which can make a significant difference to the way the panel reacts to various stresses.
In Figure 3, 6, 7 and 8 we can see some of the effects of varying the four major factors involved.
It is interesting to note that when looking at panel spans in particular, the two significant factors are the core thickness and type of facing.
In Figure 5 we can see how a bonded sandwich panel walks by the core restraining the facings in compression and in tension.
In practice, the failure of panels at normal loads is dictated by the shear strength of the core material and therefore emphasises the benefits, of using extruded polystyrenes whenever possible as they outperform most other core materials in this respect.
In summary, creating a good panel relies on the choise of materials used and using a high performance adhesive system to ensure a strong bond between the various components.
WHY A SANDWICH PANEL ?
- LIGHTWEIGHT
- STRONGER
- HIGHER IMPACT / COMPRESSION RESISTANCE
- MORE INSULATION
- IMPROVED PRODUCTION RATE / COST
- DESIGN FREEDOM
WHY EXTRUDED POLYSTYRENE ?
- STRONGER (G)
- HIGH IMPACT / COMPRESSION
- BETTER INSULATION
- NO WATER ABSORPTION (see Annex 1 at the and of this document)
- NARROW DIMENSIONAL TOLERANCE
- BETTER ADHESIVE COVERAGE
PROBLEM AREAS OF PANELS
In practical experience we have found there to be three main areas of panel failure. The first is panel delamination which should not occur if the correct bonding technique is used and all parameters are accurately controlled.
A Sandwich Panel...
...Is a composite of two or more materials bonded together to form a structural panel
...Takes advantage of the shear strength of a low density core material and
the high
compressive and tensile strengths of high density facing to obtain
high strength to
weight ratios.
...Acts like an " I " beam, with the facings carrying the compressive and tensile
loads
similar to the flanges of the beam and the core carries the shear loads
like the web.
Figure 2
Some Aplications :
- Recreational Vehicles
- Panel Truck Bodies and Doors
- Agricultural Confinement Buildings
- Cold Storage Panels
- Display Boards
- Concrete Foams
- Curtain Wall Panels
- Lightweight Insulated Doors
- Furniture
- Swimming Pools
COMMON PANEL FAILURES (See below: Figure 3)
- THERMAL BLISTERING
- STRUCTURAL DEFLECTION
- CORE SHEAR
- FACING WRINKLING
- FACING TENSION
- THERMAL OR HYGROSCOPIC BOWING
- EXPOSURE (water, heat, cold)
- IMPACT
Figure 3
HOW IS STRENGTH OBTAINED ?
If the unbonded components of the sandwich panel are supported at each end and a load is applied at the centre, the facing will slide across the core material and cause a large deflection.
Figure 4
If the facings are now bonded to the core and the same load applied, the deflection will be much lower because the facings cannot slide over the core.
Figure 5
Tension and compression in the facing oppose the deflection. The maximum stresses are being applied to the more resistant materials: the facing.
FUNCTION OF THE FACINGS
They have to resist tension and compression to prevent :
Compression
Figure 6
- buckling under compression
Figure 7
tension
- tension failure
Figure 8
- impact deformation
Normally, aluminum is used for the exterior facing and plywood for the interior.
FUNCTION OF THE CORE
The core should stabilize the facings and have a good compression and shear resistance to avoid:
Figure 9
Buckling Wrinkling of Facings Core Crushing Shear Crimping
This type of failure is very rare because plywood has a high buckling and compression resistance.
Figure 10
Impact and Compression Core Shear Failure
Usually, the core is a very light plastic foam, such as extruded polystyrene, which in addition to its structural function provides the necessary INSULATION.
PANEL SPAN CAPABILITIES
For more detailed and specific information, please contact info@catiteknik.com
INSULATION THICKNESSES
The thickness of insulation required in any particular situation depends on the value assigned to what may be called a reasonable allowable heat flow. Experience has shown that a figure between 8 an 10 Watts/m2 is acceptable.
The calculation is thus:
L x dt
D = -----------
Q
where
D = Thickness of insulation (m)
L = Lambda value of insulation (W/mK)
dt = Difference
between internal & external temperatures (K)
Q = Heat flow (W/m2) For more detailed
and specific information, please contact
PRODUCTION & MANUFACTURING TECHNIQUES & EQUIPMENT
For more detailed and specific information, please contact info@catiteknik.com
Annex1
WATER PICK - UP ( % VOL)
WATER CONTENT: 28 days by absorption
SAMPLES: Both samples Dimensions: 1000 mm x
1000 mm x 50 mm
Extruded Polystyrene (Exmpl: Styrofoam RTM; density 40 kg/m3) ~ 0.5
% vol.
Polyurethane PU 40 (Density 40 kg/m3) ~ 5 % vol.
HOW MUCH WATER HAS BEEN ABSORBED ?
RTM
VOLUME OF SAMPLE: 5 x 100 x100 cm = 50,000 cm3
WATER CONTENT: 250 cm3 ( = 0.5
% of 50,000 cm3)
PU 40
VOLUME OF SAMPLE: 50,000 cm3
WATER CONTENT: 2500 cm3 ( = 5 % of 50,000 cm3)
Add to this, water pick up by diffusion. Consider vapour permeability resistance µ - value.
Sandwich Panel definition
Sandwich panels for building applications are large prefabricated building products.
Sandwich panels generally consist of two outer metal sheets (steel, aluminium, other) with a stabilizing core of insulation sandwiched between them. The metal sheets are bonded to the insulation core with specialised adhesives. The outer surface of the sheets can be flat, slightly corrugated or with a significant profile (eg. for roofs or external façade design). A huge assortment of shapes, coatings and colours is available. Because sandwich panel installation requires only a limited number of mechanical fasteners (eg. screws), the resulting constructions avoid significant thermal bridging. To achieve distinctive architectural features, panels with hidden joints are available.
Since 2009 a new European standard EN 14509 has defined the regulation and quality of sandwich panels with insulating core materials.
At ROCKWOOL our sandwich panel specialists are trained to support sandwich panel producers and other component suppliers to achieve maximum panel performance. For many years ROCKWOOL has developed and supplied robust insulation core materials for sandwich panel solutions worldwide.
Sandwich Panel advantages
For several decades, sandwich panels with stone wool cores have been used successfully in fast track construction, conferring numerous advantages compared to ‘build on site’ systems:
- Fast installation and ease of handling
- Crane assembly therefore no scaffolding required
- No thermal bridges and good thermal insulation properties
- Design flexibility with choice of colour finishes
- Panels can be installed horizontally or vertically
- Reliable robust mechanical performance
- Outstanding non combustible and acoustic performance
Sandwich Panel production lines
In general 3 different sandwich panel production line technologies with stone wool cores are used by sandwich panel manufacturers:
- Discontinuous lines
Flexible production lines for sandwich panels which also allow for specialties with simple discontinuous press equipment. They are often used a as starter line for the production of niche panel applications - fire doors, cold stores, cabins and shelters, clean rooms, acoustic and marine panels.
Capacity up to 100,000 m² / year
- Simple continuous lines
Standardised sandwich panel production lines for rigid core materials with continuous rolls or caterpillar press equipment. These lines enable manufacturers to use low investment start up equipment for the production of large insulated sandwich panels for internal and external applications.
Capacity up to 1,000,000 m² / year
- Fully-automatic continuous lines
Sandwich panel production lines for rigid and extruding insulation core materials. The press and curing process operates continuously with up to 40m heated caterpillar systems. All the pre-packaging processes are controlled by a central control station.
Capacity up to 2,000,000 m² / year