Under overload beyond ultimate yield, which statement is true about metals and composites?

Under overload beyond ultimate yield, which statement is true about metals and composites?

• A. Metals crack and break; composites disbond, crack or breaks
• B. Metals bend; composites melt
• C. Metals fuse; composites corrode
• D. Metals deform elastically; composites remain intact

Answer: (A)

When a material is loaded beyond its ultimate strength, metals typically fail after plastic deformation by cracking and eventual fracture. The metal’s ductile nature allows deformation, but continued loading leads to crack initiation and propagation, resulting in fracture. In contrast, composites fail differently because they’re made of distinct materials bonded together; the weakest link is often the interface between layers. Under overload, delamination (disbonding), along with matrix cracking or fiber breakage, are common failure modes in composites. So the true statement is that metals crack and break, while composites tend to disbond, crack, or break. Other options describe phenomena that aren’t the primary failure modes under overload beyond ultimate yield: melting or fusing isn’t how these materials fail structurally, and corrosion isn’t the immediate mechanical outcome. Also, metals don’t simply deform elastically beyond yield; they undergo plastic deformation before failing.

When a material is loaded beyond its ultimate strength, metals typically fail after plastic deformation by cracking and eventual fracture. The metal’s ductile nature allows deformation, but continued loading leads to crack initiation and propagation, resulting in fracture. In contrast, composites fail differently because they’re made of distinct materials bonded together; the weakest link is often the interface between layers. Under overload, delamination (disbonding), along with matrix cracking or fiber breakage, are common failure modes in composites. So the true statement is that metals crack and break, while composites tend to disbond, crack, or break.

Other options describe phenomena that aren’t the primary failure modes under overload beyond ultimate yield: melting or fusing isn’t how these materials fail structurally, and corrosion isn’t the immediate mechanical outcome. Also, metals don’t simply deform elastically beyond yield; they undergo plastic deformation before failing.