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Rifeng PMI foam cores used in loudspeaker
Rifeng PMI Structural Foam Cores For Bicycle Carbon Rim
In order to improve the structure of hollow carbon fiber rim heat-resistant temperature, there are several ways:
(1) Improve the dip of the glass transition temperature of epoxy resin system for carbon fiber, so as to improve its heat resistance. Can choose good heat resistance of epoxy resin, curing agent and accelerator. Epoxy resins such as alicyclic epoxy resin, bisphenol S epoxy resin, phenolic epoxy resin, epoxy resin, silicone epoxy resin. High temperature curing agent such as aromatic curing agent. At the same time cure ratio should be reasonable, curing temperature increasing temperature step by step, after curing temperature high, long time, heat resistance will be increased.
(2) In order to improve the braking area high temperature performance, the common market is the rim brake zone peripheral surface with a layer of wear-resistant, low thermal conductivity and thermal express characteristics of aluminum metal rims or protective film, so that the brake, brake pads directly and the protection plate contact, they will not directly contact, and the friction generated heat can not be directly transferred to the wheel rim. But for the game players must frequently replace the brake pads, is not the best method of use. In addition to the braking area coated with high temperature ceramic.
Increase the stiffness of hollow structure of carbon fiber rim structure, improve the structural stability of another kind of way is filled with lightweight foam core material of low density in the middle.
Rifeng® PMI foam sandwich structure of carbon fiber rim
Foam sandwich structure is a kind of structural material is composed of high strength and low density light skin core material. Join the core purpose is to maintain the distance between the two panels, can increase a few premise in weight, make the sandwich panel section moment of inertia and flexural stiffness increase, greatly improve the stiffness of the structure.
Referred to as the half hollow sandwich structure of carbon fiber and carbon fiber structure for sandwich foam sandwich structure of carbon fiber rim. Half hollow sandwich structure of carbon fiber in brake area filled with foam enhancement, process by using a combination of air bag method and moulding. By moulding the sandwich structure of carbon fiber, the rigid structure of the best.
Foam sandwich bicycle rims in the core material for the hard foam and polyurethane foam, density in the range of 29-52kg/m3. Polyurethane foam by in-mold foaming process, density of about 30kg/m3, the price is cheap, but difficult to foam density uniform, center of low density, high density of epidermis, internal defects is also large, mechanical properties is also poor, with long lead to internal cracks, bubbles break, wheel rotation time can hear the squeak.
Rifeng® PMI foam core material is a 100% closed-cell rigid foam, it has the highest specific strength and stiffness, high thermal deformation temperature of 180-240 ℃.foam
i. In the rim design stage, the PMI foam is a kind of structural core material, can be used as a stress unit in the sandwich structures to improve the stability of structure and function, the rim of carbon fiber skin, reduce the prepreg layer 1-2 carbon fiber rim, reduce weight, improve the added value of products.
ii. In the paving process, after the foam core machine or hot forming plays a core role, so that the carbon fiber prepreg ply smoothly, improve the mechanical properties of carbon fiber skin.
iii. In the curing stage, the PMI foam cores be able to withstand high temperatures. PMI foam core has a certain magnitude of interference, that is to say the core size slightly larger than the cavity size, curing time, the foam core can provide sufficient back pressure, the curing of carbon fiber composite skin more compact.
iiii. Rifeng® PMI foam cores have good fatigue resistance performance, in the process of using, it and CFRP panel can be long-term firm combination, is an ideal structural core material to making a bicycle rim.