In the previous paper, the physical anchoring principle was proposed to obtain scummingless SMC moldings. When the styrene (ST)-divinyl benzene (DVB) loosely cross linked polymer is applied for the low profile additive to SMC, it is desirable to use the additive polymers having particle size under 50μm to avoid the growth of waveness at the surface of the moldings. To spread the allowable range of particle size of the polymer, it was suggested by the authors that the glass transition temperature of the polymers must be low to near the room temperature. The main purpose of this paper is to confirm the supposition. The experiments were carried out on methyl acrylate (MA), MA-ST and MA-ST-DVB. As the results, it has been revealed that the supposition is quite right, MA monomer has a property to give the loosely cross linked polymer without any cross linking agent but a cross linking one, such as DVB, for MA-ST monomer system is an essential component to obtain the scummingless additive polymers and small addition of the DVB into MA-ST mixed monomer bears an important role to prevent the growth of two types of polymer with different T_g.

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The tensile stress-strain behavior of copper matrix composites reinforced with helical tungsten fiber has been investigated using monofilamentary composite specimens. A tungsten fiber of 150μm in diameter was formed into a helix, whose helical angle was 78.4° and helical radius was 75μm. It was incorporated into copper matrix by means of electrodeposition. The volume fraction of fiber (V_f) studied ranged from 0.01 to 0.12. The composite specimens were tensiletested and the relations of stress with strain and V_f, the relations of recovery and permanent components in the total tensile strain, were examined. These results were compared with those on straight fiber reinforced composites. At the beginning of tensile deformation the flow stress of the helical fiber composite was smaller than that of the straight fiber composite at the same V_f. However, as the strain was increased, the flow stress of the helical fiber composite approached that of the straight fiber composite. The ultimate tensile stresses of the both kinds of composites at the same V_f were shown to be nearly equal. The flow stress of helical fiber composites were always larger than the values calculated by the rule of mixtures, while those of straight fiber composites well obeyed the rule. This phenomenon was considered to be due to the different deformation behavior of the helical fiber in the matrix as compared with the bare one and strong interaction between the helical fiber and the matrix during the early stage of deformation. The fracture strain decreased with increasing _f for the both kinds of com-posites. However, significantly larger fracture strains were always observed for the helical fiber composites than for the straight fiber ones at the same _f.

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Characteristics of tool wear are theoretically studied. Theoretical results agreed with experiment. The tool wear in cutting of GFRP is abrasive. As glass fiber has the flexural rigidity and is held in visco-elastic material, the contact pressure between glass fiber and tool changes with fiber orientation and cutting conditions. This causes the peculiar tool wear characteristics. (i) Dependence of the rate of tool wear on cutting speed : With increase of cutting speed, the rate of tool wear initially increases gradually (region I), then it increases proportionally to cutting speed (region II), and finally the rate is constant beyond a critical speed (region III). (ii) Dependence of the tool wear on chip thickness before cutting (t) is either one of following two cases (a) and (b) or intermediate between (a) and (b). (a) : The tool wear rate decreases in the region I and does not change in the regions II and III as “t” increases. (b) : The tool wear rate increases in the regions I and II, and does not change in the region III as “t” increases. The intermediate situation between (a) and (b) is the case where the tool wear rate decreases in the region I, and increases in the region II and does not change in the region III as “t” increases. (iii) The rate of tool wear decreases with softer matrix. This theory can be applied for cutting not only of GFRP but also of the composite materials composed of hard fiber and plastics such as CFRP.

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