Research and Development of Wood/Plastic Composite Materials (II) Dynamic Viscoelasticities of Three Types of Wood Fibre/PP Composites, Spruce Wood and Particleboard

The purpose of this study was intended to investigate and evaluate the dynamic properties of three type wood fibre/PP composites, and also to com-pare them with the values obtained from sitka spruce wood and particleboard. The feasibility of using as the musical sound boards and speeker boxes for these composties was also discussed based on the property data obtained from solid wood and wooden panel of this test and the others. The materials used are those discarded wood fibres-sander dusts (SrD), wood fines (W.F.), sawdust (SwD)-and polypropylene (PP) composites. With each contained five levels of fibre content (F.C. 10, 20, 30, 40 AND 50%) and a set of pure polypropylene (PP or F. C. 0%) specimens were injection moulded. Similar size air dry sitka sprucc wood (parallel to and perpendi-cular to wood grain) and larger size particleboard (19x 1.5x 0.6cm) specimens were also prepared. ALL tests were carried out strictly in accordance with the standard method (bending vibration) developed in here institute. The results were then ananlysed and compared statistically. 1. E' values of composites, spruce wood and particleboard tended to be higher than those obtained from their static flexural elastic modulus (F.E.M. or E) values. The difference between E' and E values varied noticiablily by the percents F. C., types of composites, specific gravity and the materials. 2. F.E.M. or E values of three type composites correlated significantly with their E', loss modulus E', loss tangent (tan δ) and logarithmic decrement (λ). 3. Static maximum flexural strength (M.F.S.) of three type composites on the other hand, correlated only with their E’. 4. Three type composites seemed to the feasible for applying as the sound board or box of musical instrument since their dynamic properties are quite close to those of solid wood, particleboard as well as hardboard which have statis-factorily been applied for it. 5. It will be encouraged to see that the using of wood fibre/plastic composite materials to fabricate the musical sound boxes of any size and shape by injection moulding or other processes.