The function and requirement of automobile top
The structure of the car top is usually composed of skin and pad, which refers to the interior parts of the roof.
The function of the ceiling interior decoration should reflect the modeling design of the car, the heat insulation, sound insulation and absorption with the outside, and the protection of the head of the passengers. Therefore, the ceiling interior is very particular about the different injury indexes of different parts of the human body, so different interior materials should be used in different parts of the car interior and human body contact parts.
The material of the ceiling shall be selected to match the human head, which shall be determined through test and research. The undeformed materials can not absorb energy, and the materials that bear the increased force with the increase of deformation can not protect the passengers in the whole process of collision.
Although some materials meet the requirements of force and deformation, they have great resilience and poor energy absorption ability, and are not suitable for interior decoration.
In order to meet the needs of heat insulation, sound insulation, sound absorption, touch, safety and low cost of the ceiling, the interior is usually mounted on the roof by means of "foam plastic" or felt, with adhesive or mosaic.
Taking hard top cars as an example, the finishing, foam and base three layers of materials are generally combined into a certain shape component by hot pressing method. They are mounted on the roof by means of bonding or mosaic, of which the fabric is mainly made of fabric, TPO or PVC film.
The foam layer is made of rigid polyurethane foam plastic board. PU foam sheet, PP foam sheet, corrugated paper, recycled cotton or glass fiber impregnated with resin are mostly used as the base. The selection of these materials shall ensure the effective protection of human body when the head of passengers collides with the ceiling.
At present, the latest ceiling material is PP corrugated board, which is composed of PP foam sheet (buffer layer) and TPO surface layer.
In addition to energy absorption, the interior of the car ceiling also has the properties of flame retardant, noise reduction, heat insulation and easy recycling. Among them, fire-retardant, heat insulation and recycling are mainly guaranteed by the nature of the material itself, and noise reduction is guaranteed by material and design.
There are three aspects to achieve sound insulation and noise reduction
The first is that the ceiling material should have the function of isolating the noise sound wave outside the vehicle on the metal top cover to stimulate the noise generated by the vibration of the metal top cover.
The second is to reduce the vibration noise caused by the poor assembly between the metal top cover and the ceiling interior.
The third is to reduce the noise in the car.
Therefore, in the current automobile manufacturing, sound insulation and absorption are usually used to reduce the noise inside the car. The roof components and metal top cover should be firmly connected. The material of the roof base should be able to block the sound wave penetration. The roof interior should be able to absorb the sound energy radiated to it and reduce the reflected sound energy. Porous sound-absorbing materials are often used when the sound wave hits the surface of porous sound-absorbing materials Voids, which cause the vibration of tiny fibers in the air, can convert a considerable part of sound energy into heat energy.
The characteristics of this material is to keep a certain air layer at the back of the hole, which mainly absorbs medium and low frequency noise to produce resonance and consume energy.
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