Introduction to Composite Materials and Processes: Unique Materials that Require Unique Processes

Introduction

Composite materials have emerged as a game-changing solution in various industries due to their unique properties, such as high strength-to-weight ratios and anisotropic behavior. This has led to increasing popularity and adoption of composites in aerospace, automotive, marine, and sports equipment industries, among others.

Basics

Laminates

Fiber, Matrix, Composites, laminate (Source: Geometry Assurance Integrating Process Variation With Simulation of Spring-In for Composite Parts and Assemblies))

laminates are continuous-fiber composites in which the individual layers, plies or laminae are oriented in directions that enhance the strength in the primary load direction. In other words, laminates are made up of multiple layers of fibers that are oriented in a specific way to optimize their strength and stiffness.

Unidirectional (0°) laminates are extremely strong and stiff in the 0° direction; however, they are also very weak in the 90° direction because the load must be carried by the much weaker polymeric matrix. While a high-strength fiber can have a tensile strength of 500 ksi or more, a typical polymeric matrix normally has a tensile strength of only 5-10 ksi.

The Crucial Role of Fibers in Composite Materials: Balancing Strength, Stiffness, and Durability

The primary function of fibers in composite materials is to provide strength and stiffness. Typically, fibers are composed of high-strength materials like carbon, glass, or aramid, and are embedded within a polymeric matrix material. In a composite, fibers bear most of the load due to their exceptional strength and stiffness, while the polymeric matrix serves to bind the fibers together and facilitate load transfer between them.

It is crucial to recognize that, in general, high-strength fibers exhibit brittle characteristics and display linear stress-strain behavior. Consequently, they may be susceptible to failure under specific conditions, such as impact or fatigue loading. To ensure composite components fulfill performance requirements while minimizing weight and cost, designers need to meticulously evaluate factors such as fiber orientation and matrix material selection. By doing so, they can strike an optimal balance between the material's strength, stiffness, and durability.