The invention relates to an induction connection sleeve (1) for fusion joining of plastic pipes (2, 3). The induction connection sleeve (1) comprises a sleeve body (9) having a first (5) and a second receiving portion (7) for receiving first (4) and second connection portions (6) of the plastic pipes (2, 3) to be connected, a first induction heating element (12) and a second induction heating element (13). The sleeve body (9) comprises an inner part (10), which inner part (10) forms the two receiving portions (5, 7) and on which the induction heating elements (12, 13) are accommodated in such a way that the recesses (16) of the induction heating elements (12) are penetrated by the inner part (10) and are flush at their outer lateral surfaces (14, 15) with the inner part (10) in the area of the induction heating elements (12, 13). The sleeve body (9) further comprises an outer part (11) which is connected to the inner part (10) in a bonded manner and surrounds the outer lateral surfaces (14, 15) of the induction heating elements (12, 13).

A grooved resin molded part which when joined to another molded part, can form a composite molded product having an enhanced strength. This part contains an inorganic filler and has multiple grooves formed by partially removing the resin, such that the filler is exposed in these grooves. The depth of the grooves may be at least one-half of the length of the grooves in the shorter direction. The filler may have a fibrous shape; and the longer direction of the filler may be different from that of the grooves. The part is obtained by subjecting a resin molded part containing the filler to laser irradiation or the like to form multiple grooves in which the filler is exposed.

To connect two plastic pipes 3 together, an induction connection sleeve 1 is used, which is provided with annular recesses 5 into which the pipes 3 with the ends 3A are pushed. Subsequently, induction heating elements 9 present in the induction connecting sleeve are heated with induction hand pliers 21 and the induction connecting sleeve is pressed against the end 3A of one of the tubes 3. The induction connection sleeve fuses to the tube. Because the induction hand pliers 21 are provided with ribs 27, grooves 19 are pressed into the pipe wall 3B in order to check whether sufficient heating and pressing has taken place over the entire circumference to obtain a gastight connection.