Toray announced that it succeeded in developing a new fabrication technology for CFRP that it says enables both improved dimensional accuracy and energy savings. Going forward, Toray will further mature this new technology and broadly deploy it to mainly aircraft applications that continuously demand higher productivity and more energy savings. Moreover, this technology is anticipated to benefit automobile and general industrial applications as well, and will contribute to the development of CFRP materials.
As Toray explains, CFRP is usually fabricated using an autoclave (high temperature and high-pressure furnace) or an oven where prepreg (intermediate material in sheet form) is placed on a mold of predetermined shape and the resin in the prepreg is cured using heated air for fabrication. The conventional fabrication technology has a disadvantage that requires long time for heating up and curing due to inefficient heat transfer of heated air and large heat capacity of the mold.
Toray notes there is also dimensional accuracy problem of the part to be resolved particularly for a large, complex-shaped one with variable thickness from location to location. This is due to the difficulty in control of temperature distribution in the part, which could, in turn, generate variable residual stresses and sometimes significantly deform the part. Due to this, extensive labor work is required during final assembly of multiple parts such as aircraft’s main wing by manually inserting filler materials called shims resulting in a longer assembly time than that for fabrication.
The newly developed fabrication technology, according to the company, provides a solution to the problem with a number of embedded sheet heaters on the mod’s surface such that each heater is individually controlled. The part under vacuum is heated effectively from direct contacts with the heaters, which could achieve energy savings. Controlling individual heaters and allowing optimum heat distribution at each location provides even residual stress throughout the fabricated part. As a result, the part can be fabricated as close to the original design with minimal dimensional inconsistencies and dimensions solving the aforementioned problem, and it is expected to reduce labor cost and duration of part assembly.
In order to effectively control this heating system, Toray carried out a joint research program with Ehime University and Tokyo University of Science to establish simulation technologies to predict part deformation and optimize heater temperature. Toray combined them into a program for designing heating conditions that would effectively minimize fabrication time and dimensional errors of the parts. Toray installed a prototype fabrication device and is currently conducting demonstration trials.