A Study on the Bonding Strength of Carbon Fiber Reinforced Prepreg / Thermoplastic Injection Molding

• Main Authors: Jia-Jhu Jyu, 朱家駒
• Other Authors: Shi-Chang Tseng
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/43390344244171623426

碩士 === 國立雲林科技大學 === 機械工程系 === 102 === This study focused on the bonding strength and warpage of injection over molded thermoplastics combined with long fiber reinforced plastic composites (LFRP). First, the carbon fiber reinforced prepreg was prepared and compression molded into a long fiber reinforced plastic composites (LFRP) component. And then it was placed inside the mold. By applying injection overmolding of thermoplastic, it became a final multi-component part. Thus, this study investigated the effect of gate types and preheating LFRP on the bonding strengths of LFRPs and injection overmolded thermoplastics. Mold filling simulation and Taguchi Method were employed to carry out the experiments. Processing conditions - planned controlling factors and Orthogonal Arrays (OA) were applied to find out the factors with higher contribution and the optimum molding condition. Through this procedure, the interfacial bonding strength of the overmolded products could be improved. For bonding strength of LFRP overmolded with thermoplastic, results of Taguchi’s design of experiments showed that the fan gate has better bonding strength than the side gate. Melt temperature has the highest contribution to the interfacial bonding strength (61.94%), and the next is the mold temperature (24.33%). In addition, pre-heating LFRP helps to increase the bonding strength of the final overmolded parts. The bonding strength of combining plastics with LFRP is deeply subject to the temperature of plastic material, the mold temperature and the pre-heating temperature of LFRP. Higher temperatures will result in slower heat conduction and heat loss inside the mold and make the surface temperature of LFRP’s became higher and even over thermoplastic glass transition temperature. Thus it allows the macromolecule of bonding interface to be permeated into these internal bonding between thermoplastic resins and LFRP laminates. As a result, it can improve the bonding strength. Molding with side gate has higher pressure loss on the inlet, poorer flow and more uneven temperature distribution. This resulted in the reduction of molecule bonding. Since the inlet width of side gate is smaller, it has larger shear stresses and residual stresses and causes poorer bonding than the fan gate one.