Date of Award

2022-12-01

Degree Name

Master of Science

Department

Mechanical Engineering

Advisor(s)

Alejandra G. Castellanos

Abstract

Aerospace, aircraft, marine, and automobile applications are increasingly using composite materials for lighter, higher stiffness, and strength properties. Despite these advantages, composite materials have one major disadvantage. The through-thickness properties are extremely weak when subjected to impact damage. When a composite material is subjected to a low-velocity impact, there is hardly any visible damage on the surface compromising the composite material internally without any external notice. Internal damage may be delamination, which is the most common, matrix cracking, and fiber breakage. A composite material is made up of layers of fiber. The interlaminar region is located in between these layers. This region is a resin-rich area that has extremely poor mechanical properties due to no reinforcement. The arrest of delamination is essential for composite materials when they are used for impact applications. Delamination reduces the laminatesâ?? strength and stiffness, making the composite unsafe and limiting its full potential when impacted. The interlaminar region may be modified in the fiber (3D) or in the matrix (2D). An example of 3D interlaminar reinforcement is stitching and Z-pinning which increases the through-thickness mechanical properties by penetrating through the layers of fiber. For 2D interlaminar reinforcement, nanotubes and nanowires are used to strengthen the interlaminar region without perforating the layers. These modifications have proven to increase the through-thickness mechanical properties. However, it has been shown to damage or breaks the fibers. 3D interlaminar reinforcement has also been revealed to decrease the in-plane properties of a composite material. To strengthen the through-thickness mechanical properties without sacrificing the other orientationâ??s mechanical properties, Aramid pulp or Kevlar has been introduced as an interlaminar reinforcement. The main purpose of this research is to determine the ideal amount of Aramid pulp that is necessary to reinforce the interlaminar region of a carbon fiber-reinforced polymer (CFRP) composite during a low-velocity impact scenario. Three different groups of Aramid pulp to resin ratio were studied, one times reinforcement (1X), two times reinforcement (2X), and four times reinforcement (4X). After analysis, 1X is the recommended Aramid pulp-to-resin ratio, 1:15 in volume. 2X reinforcement consisted of a 2:15 by volume of Aramid pulp to resin ratio and 4X reinforcement 4:15 ratio. Data such as energy, time, displacement, and contact force were obtained and examined using the Instron CEAST 9340 for drop weight impact testing. The impacted energy used for this research was 5 Joules (J) following the standard for ASTM D7136/D7136M-20. The outcome of this investigation recorded 1X is the ideal quantity of reinforcement for a CFRP composite. A laminate that used more than 1X reinforcement exhibit a higher degree of damage, greater deformation, lower maximum force, lower impact duration, and brittle-like properties. 2X and 4X reinforcement laminates showed an increase in air pockets during manufacturing leading to a decrease in bending stiffness [1].

Language

en

Provenance

Received from ProQuest

File Size

44 p.

File Format

application/pdf

Rights Holder

Daisy Haidee Mariscal

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