The Woodruff School

SUMMARY

The focus of this research is recycling the post-industrial prepreg waste to produce light weight polymer composites suitable for automotive industries and to understand their process-property relationships. The progression of the research was performed in three stages including employing sheet molding compound (SMC) technique for recycling the prepreg, aging condition assessment of the incoming prepreg waste and mechanical performance analysis of the CF prepreg composite. Since cutting and SMC preparation of the prepreg wastes depend on their thermal history, a systematic assessment of their aging condition was performed using differential scanning calorimetry (DSC). The DSC analysis revealed that aging helps in the advancement of cure of the prepregs resulting in non-tacky prepregs which can be cut completely in the SMC line. The non-tacky aged prepregs can be obtained either by oven aging or room temperature aging. The cure kinetic parameters such as thermal transitions, degree of cure, activation energy etc. were studied to investigate the thermal history of the prepregs. To study the mechanical performance of the recycled prepregs, composites with minimum void contents were fabricated from the tacky and the non-tacky prepregs using compression molding. The mechanical properties of the composites, including tensile modulus, tensile strength and impact strength were determined according to the ASTM standards as a function of the composite’s fabrication conditions. A micromechanical model for randomly oriented discontinuous fiber composite system was used to calculate theoretical modulus of the CF prepreg composite. The recycled CF prepreg composites are 18% lighter, and are two times higher in tensile modulus and tensile strength compared to the commercial glass fiber SMC composites which are currently used in automotive industries. Furthermore, failure analysis indicated that the recycled composites retained its integrity upon failure under tensile loading. Thus, this thesis suggests that the post-industrial prepreg composites processed by SMC technique is a promising lightweight material for applications in automotive industries.

SUBJECT:	Ph.D. Dissertation Defense

BY:	Sanzida Sultana

TIME:	Tuesday, December 11, 2018, 2:00 p.m.

PLACE:	MARC Building, 431

TITLE:	Process-Property Relation of Prerreg Trim Waste Ccomposites via Sheet Molding Compound (SMC)

COMMITTEE:	Dr. Kyriaki Kalaitzidou, Co-Chair (ME) Dr. Jonathan S. Colton, Co-Chair (ME) Dr. Suresh Sitaraman (ME) Dr. Satish Kumar (MSE) Dr. Ben Wang (MSE)

SUMMARY The focus of this research is recycling the post-industrial prepreg waste to produce light weight polymer composites suitable for automotive industries and to understand their process-property relationships. The progression of the research was performed in three stages including employing sheet molding compound (SMC) technique for recycling the prepreg, aging condition assessment of the incoming prepreg waste and mechanical performance analysis of the CF prepreg composite. Since cutting and SMC preparation of the prepreg wastes depend on their thermal history, a systematic assessment of their aging condition was performed using differential scanning calorimetry (DSC). The DSC analysis revealed that aging helps in the advancement of cure of the prepregs resulting in non-tacky prepregs which can be cut completely in the SMC line. The non-tacky aged prepregs can be obtained either by oven aging or room temperature aging. The cure kinetic parameters such as thermal transitions, degree of cure, activation energy etc. were studied to investigate the thermal history of the prepregs. To study the mechanical performance of the recycled prepregs, composites with minimum void contents were fabricated from the tacky and the non-tacky prepregs using compression molding. The mechanical properties of the composites, including tensile modulus, tensile strength and impact strength were determined according to the ASTM standards as a function of the composite’s fabrication conditions. A micromechanical model for randomly oriented discontinuous fiber composite system was used to calculate theoretical modulus of the CF prepreg composite. The recycled CF prepreg composites are 18% lighter, and are two times higher in tensile modulus and tensile strength compared to the commercial glass fiber SMC composites which are currently used in automotive industries. Furthermore, failure analysis indicated that the recycled composites retained its integrity upon failure under tensile loading. Thus, this thesis suggests that the post-industrial prepreg composites processed by SMC technique is a promising lightweight material for applications in automotive industries.