toughening fragil veneer

例句：

1. 1. The oldwooden chair was toughening with age.
   旧木椅随着岁月变得更加坚硬。
2. 2. The car's suspension system needs to be toughenedto handle the bumps on the road.
   汽车的悬挂系统需要加固以应对道路上的颠簸。
3. 3. The company is toughening itsproduct quality standards to meet new environmental regulations.
   公司正在加强其产品质量标准，以满足新的环保法规。