Method of producing fiber-reinforced composite material

A method of producing a fiber-reinforced composite material in which a fiber body is mounted on mounting surfaces in a mold cavity, which mounting surfaces are in fluid communication with the outside of the mold through air relief passages. A molten matrix metal is poured into the mold cavity and then subjected to a high hydrostatic pressure so as to be filled into the fiber body while expelling the air from the fiber body to the outside of the mold through the air relief passages. The molten metal is thereafter filled into the air relief passages and solidifies immediately to seal the mold cavity from the ambient atmosphere whereby the molten matrix in the mold cavity is rapidly solidified under high pressure to form a fiber-reinforced composite material of high quality with inclusion of substantially reduced voids or cavities.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method of producing a fiber-reinforced 
composite material. 
2. Description of the Prior Art 
The present inventors have already proposed a method of producing a 
fiber-reinforced composite material which comprises the steps of fixing 
fiber body in the cavity of a mold, pouring a molten light alloy as the 
matrix material into the mold cavity, applying a high hydrostatic pressure 
to the molten metal to fill the fiber body with the molten metal to form a 
composite material, and rapidly solidifying the fiber-reinforced composite 
material. 
This method, however, has the following disadvantage. During the pouring of 
the molten light alloy into the mold cavity, the fiber body is surrounded 
by the molten alloy so that the air in the fiber body is confined therein. 
Then, as the molten alloy is pressurized to penetrate into and combine 
with the fiber body, the molten alloy expels the air from the fiber body 
and disperses it thereinto. However, it is often experienced that 
depending on the timing of pressurizing the air is not expelled from the 
fiber body but remain therein to form voids which are not filled with the 
alloy. 
In order to avoid this problem, it is considered to suitably adjust the 
timing of pressurizing so as to give a preference to the expelling of the 
air to ensure good dispersion thereof into the molten alloy. Such an 
adjustment of timing of pressurizing, however, limits or complicates the 
casting condition undesirably. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the invention is to provide a method of producing 
a fiber-reinforced composite material which is capable of expelling the 
air confined in the fiber body without fail thereby to form a quality 
product with inclusion of substantially reduced voids or cavities. 
According to the present invention, there is provided a method of producing 
a fiber reinforced composite material comprising the steps of: 
(a) mounting a fiber body on mounting surfaces in a cavity of a mold, said 
mounting surfaces being in fluid communication with the outside of said 
mold through air relieving means; 
(b) pouring a molten matrix metal into said mold cavity; 
(c) filling said molten matrix metal into said fiber body under application 
of a high hydrostatic pressure while expelling the air in said fiber body 
to the outside of said mold through said air relieving means; 
(d) filling said air relieving means with said molten matrix metal; 
(e) solidifying said molten matrix in said air relieving means to seal said 
mold cavity from the ambient atmosphere; and 
(f) solidifying under high pressure said molten matrix metal in said mold 
cavity. 
The above described method of the invention offers the following 
advantages. 
The air relieving means is not filled or clogged with the molten metal 
before the fiber body is filled with the molten metal, because, when the 
molten metal is poured into the mold cavity, the air relieving means is 
sealed by the fiber body against the entry of the molten metal. It is, 
therefore, possible to expel and remove the air in the fiber body easily 
and without fail through the air relieving means in the next step of 
applying the high pressure to the molten metal for filling and combining 
the fiber body with the molten metal. Accordingly, a composite material 
having a fiber-reinforced portion of a fine structure without inclusion of 
voids or cavities can be obtained. 
In addition, the molten metal in the air relieving means solidifies earlier 
than the molten metal in the mold cavity so as to seal the mold cavity 
from the ambient atmosphere. This not only eliminates any need for 
increasing the pressure applied to the molten metal for rapid 
solidification thereof, but also any troublesome adjustment of timing for 
pressure application, which is required in the prior art for expelling and 
dispersing the air from the fiber body, thereby simplifying the casting 
condition and enabling easier and more efficient production of the 
fiber-reinforced composite material. 
The above and other objects, as well as advantageous features of the 
invention will become clear from the following description of the 
preferred embodiments taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Hereinafter, the invention will be described in detail through a preferred 
embodiment applied to the production of a connecting rod of internal 
combustion engine having a fiber-reinforced rod portion, with reference to 
the accompanying drawings. 
Referring to FIGS. 1 to 4, a horizontally split mold 1 consists of an upper 
mold part 1a and a lower mold part 1b which are adapted to be coupled with 
each other to form therebetween cavities 2a, 2b corresponding to the 
configuration of the connecting rod C as shown in FIGS. 5 and 6. Arcuate 
mounting surfaces 3a, 3b are formed to oppose to each other along both 
longitudinal edges of those portions of cavities 2a, 2b which correspond 
to the rod portion C.sub.1 of the connecting rod C. Formed in the joint 
surface of the lower mold part 1b are grooves 4 which extend over a 
predetermined length in the axial direction of the connecting rod to form 
slit-like air relief passages S with their opposite ends opening at the 
mounting surfaces 3a, 3b and to the outside of the mold 1, respectively. 
The positions of the air relief passages S are determined taking into 
account the filling path of the molten metal into the fiber body and the 
sequence of solidification. More specifically, the air relief passages S 
are so positioned as to communicate with the portion where the 
solidification takes place later than other portions. 
In production of a fiber-reinforced connecting rod, a fiber body F which is 
made by bundling unidirectional inorganic fibers is laid on the mounting 
surfaces 3b of the lower mold part 1b as illustrated in FIG. 1. Then, the 
upper mold part 1a is lowered to be jointed to the lower mold part 1b so 
that the fiber body F is clamped between the mounting surfaces 3a, 3b as 
shown in FIG. 2. Subsequently, as shown in FIG. 3, a molten matrix metal M 
such as a molten aluminum alloy is poured into the mold cavities 2a, 2b. 
In this stage, the ends of the air relief passages S opening at the 
mounting surfaces 3a, 3b are closed by the fiber body F so as to prevent 
the molten metal M from flowing into the air relief passage. 
Then, the molten metal M is pressurized to fill into the fiber body F to be 
combined with the latter while expelling air through the air relief 
passages S from the minute vacant spaces formed between adjacent fibers in 
the fiber body F to the outside of the mold. Then, the molten metal M 
fills the air relief passages S and is promptly solidified therein to 
interrupt the communication between the mold cavities 2a, 2b and the 
ambient air. Thereafter, the molten metal M in the cavities 2a, 2b is also 
solidified rapidly under the application of the high pressure. 
The aluminum alloy solidified in the air relief passages S forms fins. By 
removing these fins, a connecting rod C having a fiber-reinforced rod 
portion C.sub.1 as shown in FIGS. 5 and 6 is obtained.